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-rw-r--r--lib/std/compress/flate/Compress.zig2740
1 files changed, 2479 insertions, 261 deletions
diff --git a/lib/std/compress/flate/Compress.zig b/lib/std/compress/flate/Compress.zig
index 2249ece4c0..d97053befd 100644
--- a/lib/std/compress/flate/Compress.zig
+++ b/lib/std/compress/flate/Compress.zig
@@ -1,332 +1,2550 @@
-//! Default compression algorithm. Has two steps: tokenization and token
-//! encoding.
+//! Allocates statically ~224K (128K lookup, 96K tokens).
//!
-//! Tokenization takes uncompressed input stream and produces list of tokens.
-//! Each token can be literal (byte of data) or match (backrefernce to previous
-//! data with length and distance). Tokenization accumulators 32K tokens, when
-//! full or `flush` is called tokens are passed to the `block_writer`. Level
-//! defines how hard (how slow) it tries to find match.
-//!
-//! Block writer will decide which type of deflate block to write (stored, fixed,
-//! dynamic) and encode tokens to the output byte stream. Client has to call
-//! `finish` to write block with the final bit set.
-//!
-//! Container defines type of header and footer which can be gzip, zlib or raw.
-//! They all share same deflate body. Raw has no header or footer just deflate
-//! body.
-//!
-//! Compression algorithm explained in rfc-1951 (slightly edited for this case):
-//!
-//! The compressor uses a chained hash table `lookup` to find duplicated
-//! strings, using a hash function that operates on 4-byte sequences. At any
-//! given point during compression, let XYZW be the next 4 input bytes
-//! (lookahead) to be examined (not necessarily all different, of course).
-//! First, the compressor examines the hash chain for XYZW. If the chain is
-//! empty, the compressor simply writes out X as a literal byte and advances
-//! one byte in the input. If the hash chain is not empty, indicating that the
-//! sequence XYZW (or, if we are unlucky, some other 4 bytes with the same
-//! hash function value) has occurred recently, the compressor compares all
-//! strings on the XYZW hash chain with the actual input data sequence
-//! starting at the current point, and selects the longest match.
-//!
-//! To improve overall compression, the compressor defers the selection of
-//! matches ("lazy matching"): after a match of length N has been found, the
-//! compressor searches for a longer match starting at the next input byte. If
-//! it finds a longer match, it truncates the previous match to a length of
-//! one (thus producing a single literal byte) and then emits the longer
-//! match. Otherwise, it emits the original match, and, as described above,
-//! advances N bytes before continuing.
-//!
-//!
-//! Allocates statically ~400K (192K lookup, 128K tokens, 64K window).
+//! The source of an `error.WriteFailed` is always the backing writer. After an
+//! `error.WriteFailed`, the `.writer` becomes `.failing` and is unrecoverable.
+//! After a `flush`, the writer also becomes `.failing` since the stream has
+//! been finished. This behavior also applies to `Raw` and `Huffman`.
+
+// Implementation details:
+// A chained hash table is used to find matches. `drain` always preserves `flate.history_len`
+// bytes to use as a history and avoids tokenizing the final bytes since they can be part of
+// a longer match with unwritten bytes (unless it is a `flush`). The minimum match searched
+// for is of length `seq_bytes`. If a match is made, a longer match is also checked for at
+// the next byte (lazy matching) if the last match does not meet the `Options.lazy` threshold.
+//
+// Up to `block_token` tokens are accumalated in `buffered_tokens` and are outputted in
+// `write_block` which determines the optimal block type and frequencies.
const builtin = @import("builtin");
const std = @import("std");
-const assert = std.debug.assert;
-const testing = std.testing;
-const expect = testing.expect;
const mem = std.mem;
const math = std.math;
-const Writer = std.Io.Writer;
+const assert = std.debug.assert;
+const Io = std.Io;
+const Writer = Io.Writer;
const Compress = @This();
-const Token = @import("Token.zig");
-const BlockWriter = @import("BlockWriter.zig");
+const token = @import("token.zig");
const flate = @import("../flate.zig");
-const Container = flate.Container;
-const Lookup = @import("Lookup.zig");
-const HuffmanEncoder = flate.HuffmanEncoder;
-const LiteralNode = HuffmanEncoder.LiteralNode;
-
-lookup: Lookup = .{},
-tokens: Tokens = .{},
-block_writer: BlockWriter,
-level: LevelArgs,
-hasher: Container.Hasher,
-writer: Writer,
-state: State,
-// Match and literal at the previous position.
-// Used for lazy match finding in processWindow.
-prev_match: ?Token = null,
-prev_literal: ?u8 = null,
+/// Until #104 is implemented, a ?u15 takes 4 bytes, which is unacceptable
+/// as it doubles the size of this already massive structure.
+///
+/// Also, there are no `to` / `from` methods because LLVM 21 does not
+/// optimize away the conversion from and to `?u15`.
+const PackedOptionalU15 = packed struct(u16) {
+ value: u15,
+ is_null: bool,
-pub const State = enum { header, middle, ended };
+ pub fn int(p: PackedOptionalU15) u16 {
+ return @bitCast(p);
+ }
-/// Trades between speed and compression size.
-/// Starts with level 4: in [zlib](https://github.com/madler/zlib/blob/abd3d1a28930f89375d4b41408b39f6c1be157b2/deflate.c#L115C1-L117C43)
-/// levels 1-3 are using different algorithm to perform faster but with less
-/// compression. That is not implemented here.
-pub const Level = enum(u4) {
- level_4 = 4,
- level_5 = 5,
- level_6 = 6,
- level_7 = 7,
- level_8 = 8,
- level_9 = 9,
-
- fast = 0xb,
- default = 0xc,
- best = 0xd,
+ pub const null_bit: PackedOptionalU15 = .{ .value = 0, .is_null = true };
};
-/// Number of tokens to accumulate in deflate before starting block encoding.
-///
-/// In zlib this depends on memlevel: 6 + memlevel, where default memlevel is
-/// 8 and max 9 that gives 14 or 15 bits.
-pub const n_tokens = 1 << 15;
-
-/// Algorithm knobs for each level.
-const LevelArgs = struct {
- good: u16, // Do less lookups if we already have match of this length.
- nice: u16, // Stop looking for better match if we found match with at least this length.
- lazy: u16, // Don't do lazy match find if got match with at least this length.
- chain: u16, // How many lookups for previous match to perform.
-
- pub fn get(level: Level) LevelArgs {
- return switch (level) {
- .fast, .level_4 => .{ .good = 4, .lazy = 4, .nice = 16, .chain = 16 },
- .level_5 => .{ .good = 8, .lazy = 16, .nice = 32, .chain = 32 },
- .default, .level_6 => .{ .good = 8, .lazy = 16, .nice = 128, .chain = 128 },
- .level_7 => .{ .good = 8, .lazy = 32, .nice = 128, .chain = 256 },
- .level_8 => .{ .good = 32, .lazy = 128, .nice = 258, .chain = 1024 },
- .best, .level_9 => .{ .good = 32, .lazy = 258, .nice = 258, .chain = 4096 },
+/// After `flush` is called, all vtable calls with result in `error.WriteFailed.`
+writer: Writer,
+has_history: bool,
+bit_writer: BitWriter,
+buffered_tokens: struct {
+ /// List of `TokenBufferEntryHeader`s and their trailing data.
+ list: [@as(usize, block_tokens) * 3]u8,
+ pos: u32,
+ n: u16,
+ lit_freqs: [286]u16,
+ dist_freqs: [30]u16,
+
+ pub const empty: @This() = .{
+ .list = undefined,
+ .pos = 0,
+ .n = 0,
+ .lit_freqs = @splat(0),
+ .dist_freqs = @splat(0),
+ };
+},
+lookup: struct {
+ /// Indexes are the hashes of four-bytes sequences.
+ ///
+ /// Values are the positions in `chain` of the previous four bytes with the same hash.
+ head: [1 << lookup_hash_bits]PackedOptionalU15,
+ /// Values are the non-zero number of bytes backwards in the history with the same hash.
+ ///
+ /// The relationship of chain indexes and bytes relative to the latest history byte is
+ /// `chain_pos -% chain_index = history_index`.
+ chain: [32768]PackedOptionalU15,
+ /// The index in `chain` which is of the newest byte of the history.
+ chain_pos: u15,
+},
+container: flate.Container,
+hasher: flate.Container.Hasher,
+opts: Options,
+
+const BitWriter = struct {
+ output: *Writer,
+ buffered: u7,
+ buffered_n: u3,
+
+ pub fn init(w: *Writer) BitWriter {
+ return .{
+ .output = w,
+ .buffered = 0,
+ .buffered_n = 0,
};
}
+
+ /// Asserts `bits` is zero-extended
+ pub fn write(b: *BitWriter, bits: u56, n: u6) Writer.Error!void {
+ assert(@as(u8, b.buffered) >> b.buffered_n == 0);
+ assert(@as(u57, bits) >> n == 0); // n may be 56 so u57 is needed
+ const combined = @shlExact(@as(u64, bits), b.buffered_n) | b.buffered;
+ const combined_bits = @as(u6, b.buffered_n) + n;
+
+ const out = try b.output.writableSliceGreedy(8);
+ mem.writeInt(u64, out[0..8], combined, .little);
+ b.output.advance(combined_bits / 8);
+
+ b.buffered_n = @truncate(combined_bits);
+ b.buffered = @intCast(combined >> (combined_bits - b.buffered_n));
+ }
+
+ /// Assserts one byte can be written to `b.otuput` without rebasing.
+ pub fn byteAlign(b: *BitWriter) void {
+ b.output.unusedCapacitySlice()[0] = b.buffered;
+ b.output.advance(@intFromBool(b.buffered_n != 0));
+ b.buffered = 0;
+ b.buffered_n = 0;
+ }
+
+ pub fn writeClen(
+ b: *BitWriter,
+ hclen: u4,
+ clen_values: []u8,
+ clen_extra: []u8,
+ clen_codes: [19]u16,
+ clen_bits: [19]u4,
+ ) Writer.Error!void {
+ // Write the first four clen entries seperately since they are always present,
+ // and writing them all at once takes too many bits.
+ try b.write(clen_bits[token.codegen_order[0]] |
+ @shlExact(@as(u6, clen_bits[token.codegen_order[1]]), 3) |
+ @shlExact(@as(u9, clen_bits[token.codegen_order[2]]), 6) |
+ @shlExact(@as(u12, clen_bits[token.codegen_order[3]]), 9), 12);
+
+ var i = hclen;
+ var clen_bits_table: u45 = 0;
+ while (i != 0) {
+ i -= 1;
+ clen_bits_table <<= 3;
+ clen_bits_table |= clen_bits[token.codegen_order[4..][i]];
+ }
+ try b.write(clen_bits_table, @as(u6, hclen) * 3);
+
+ for (clen_values, clen_extra) |value, extra| {
+ try b.write(
+ clen_codes[value] | @shlExact(@as(u16, extra), clen_bits[value]),
+ clen_bits[value] + @as(u3, switch (value) {
+ 0...15 => 0,
+ 16 => 2,
+ 17 => 3,
+ 18 => 7,
+ else => unreachable,
+ }),
+ );
+ }
+ }
+};
+
+/// Number of tokens to accumulate before outputing as a block.
+/// The maximum value is `math.maxInt(u16) - 1` since one token is reserved for end-of-block.
+const block_tokens: u16 = 1 << 15;
+const lookup_hash_bits = 15;
+const Hash = u16; // `u[lookup_hash_bits]` is not used due to worse optimization (with LLVM 21)
+const seq_bytes = 3; // not intended to be changed
+const Seq = std.meta.Int(.unsigned, seq_bytes * 8);
+
+const TokenBufferEntryHeader = packed struct(u16) {
+ kind: enum(u1) {
+ /// Followed by non-zero `data` byte literals.
+ bytes,
+ /// Followed by the length as a byte
+ match,
+ },
+ data: u15,
+};
+
+const BlockHeader = packed struct(u3) {
+ final: bool,
+ kind: enum(u2) { stored, fixed, dynamic, _ },
+
+ pub fn int(h: BlockHeader) u3 {
+ return @bitCast(h);
+ }
+
+ pub const Dynamic = packed struct(u17) {
+ regular: BlockHeader,
+ hlit: u5,
+ hdist: u5,
+ hclen: u4,
+
+ pub fn int(h: Dynamic) u17 {
+ return @bitCast(h);
+ }
+ };
};
+fn outputMatch(c: *Compress, dist: u15, len: u8) Writer.Error!void {
+ // This must come first. Instead of ensuring a full block is never left buffered,
+ // draining it is defered to allow end of stream to be indicated.
+ if (c.buffered_tokens.n == block_tokens) {
+ @branchHint(.unlikely); // LLVM 21 optimizes this branch as the more likely without
+ try c.writeBlock(false);
+ }
+ const header: TokenBufferEntryHeader = .{ .kind = .match, .data = dist };
+ c.buffered_tokens.list[c.buffered_tokens.pos..][0..2].* = @bitCast(header);
+ c.buffered_tokens.list[c.buffered_tokens.pos + 2] = len;
+ c.buffered_tokens.pos += 3;
+ c.buffered_tokens.n += 1;
+
+ c.buffered_tokens.lit_freqs[@as(usize, 257) + token.LenCode.fromVal(len).toInt()] += 1;
+ c.buffered_tokens.dist_freqs[token.DistCode.fromVal(dist).toInt()] += 1;
+}
+
+fn outputBytes(c: *Compress, bytes: []const u8) Writer.Error!void {
+ var remaining = bytes;
+ while (remaining.len != 0) {
+ if (c.buffered_tokens.n == block_tokens) {
+ @branchHint(.unlikely); // LLVM 21 optimizes this branch as the more likely without
+ try c.writeBlock(false);
+ }
+
+ const n = @min(remaining.len, block_tokens - c.buffered_tokens.n, math.maxInt(u15));
+ assert(n != 0);
+ const header: TokenBufferEntryHeader = .{ .kind = .bytes, .data = n };
+ c.buffered_tokens.list[c.buffered_tokens.pos..][0..2].* = @bitCast(header);
+ @memcpy(c.buffered_tokens.list[c.buffered_tokens.pos + 2 ..][0..n], remaining[0..n]);
+ c.buffered_tokens.pos += @as(u32, 2) + n;
+ c.buffered_tokens.n += n;
+
+ for (remaining[0..n]) |b| {
+ c.buffered_tokens.lit_freqs[b] += 1;
+ }
+ remaining = remaining[n..];
+ }
+}
+
+fn hash(x: u32) Hash {
+ return @intCast((x *% 0x9E3779B1) >> (32 - lookup_hash_bits));
+}
+
+/// Trades between speed and compression size.
+///
+/// Default paramaters are [taken from zlib]
+/// (https://github.com/madler/zlib/blob/v1.3.1/deflate.c#L112)
pub const Options = struct {
- level: Level = .default,
- container: Container = .raw,
+ /// Perform less lookups when a match of at least this length has been found.
+ good: u16,
+ /// Stop when a match of at least this length has been found.
+ nice: u16,
+ /// Don't attempt a lazy match find when a match of at least this length has been found.
+ lazy: u16,
+ /// Check this many previous locations with the same hash for longer matches.
+ chain: u16,
+
+ // zig fmt: off
+ pub const level_1: Options = .{ .good = 4, .nice = 8, .lazy = 0, .chain = 4 };
+ pub const level_2: Options = .{ .good = 4, .nice = 16, .lazy = 0, .chain = 8 };
+ pub const level_3: Options = .{ .good = 4, .nice = 32, .lazy = 0, .chain = 32 };
+ pub const level_4: Options = .{ .good = 4, .nice = 16, .lazy = 4, .chain = 16 };
+ pub const level_5: Options = .{ .good = 8, .nice = 32, .lazy = 16, .chain = 32 };
+ pub const level_6: Options = .{ .good = 8, .nice = 128, .lazy = 16, .chain = 128 };
+ pub const level_7: Options = .{ .good = 8, .nice = 128, .lazy = 32, .chain = 256 };
+ pub const level_8: Options = .{ .good = 32, .nice = 258, .lazy = 128, .chain = 1024 };
+ pub const level_9: Options = .{ .good = 32, .nice = 258, .lazy = 258, .chain = 4096 };
+ // zig fmt: on
+ pub const fastest = level_1;
+ pub const default = level_6;
+ pub const best = level_9;
};
-pub fn init(output: *Writer, buffer: []u8, options: Options) Compress {
+/// It is asserted `buffer` is least `flate.max_history_len` bytes.
+/// It is asserted `output` has a capacity of at least 8 bytes.
+pub fn init(
+ output: *Writer,
+ buffer: []u8,
+ container: flate.Container,
+ opts: Options,
+) Writer.Error!Compress {
+ assert(output.buffer.len > 8);
+ assert(buffer.len >= flate.max_window_len);
+
+ // note that disallowing some of these simplifies matching logic
+ assert(opts.chain != 0); // use `Huffman`, disallowing this simplies matching
+ assert(opts.good >= 3 and opts.nice >= 3); // a match will (usually) not be found
+ assert(opts.good <= 258 and opts.nice <= 258); // a longer match will not be found
+ assert(opts.lazy <= opts.nice); // a longer match will (usually) not be found
+ if (opts.good <= opts.lazy) assert(opts.chain >= 1 << 2); // chain can be reduced to zero
+
+ try output.writeAll(container.header());
return .{
- .block_writer = .init(output),
- .level = .get(options.level),
- .hasher = .init(options.container),
- .state = .header,
.writer = .{
.buffer = buffer,
- .vtable = &.{ .drain = drain },
+ .vtable = &.{
+ .drain = drain,
+ .flush = flush,
+ .rebase = rebase,
+ },
+ },
+ .has_history = false,
+ .bit_writer = .init(output),
+ .buffered_tokens = .empty,
+ .lookup = .{
+ // init `value` is max so there is 0xff pattern
+ .head = @splat(.{ .value = math.maxInt(u15), .is_null = true }),
+ .chain = undefined,
+ .chain_pos = math.maxInt(u15),
},
+ .container = container,
+ .opts = opts,
+ .hasher = .init(container),
};
}
-// Tokens store
-const Tokens = struct {
- list: [n_tokens]Token = undefined,
- pos: usize = 0,
+fn drain(w: *Writer, data: []const []const u8, splat: usize) Writer.Error!usize {
+ errdefer w.* = .failing;
+ // There may have not been enough space in the buffer and the write was sent directly here.
+ // However, it is required that all data goes through the buffer to keep a history.
+ //
+ // Additionally, ensuring the buffer is always full ensures there is always a full history
+ // after.
+ const data_n = w.buffer.len - w.end;
+ _ = w.fixedDrain(data, splat) catch {};
+ assert(w.end == w.buffer.len);
+ try rebaseInner(w, 0, 1, false);
+ return data_n;
+}
+
+fn flush(w: *Writer) Writer.Error!void {
+ defer w.* = .failing;
+ const c: *Compress = @fieldParentPtr("writer", w);
+ try rebaseInner(w, 0, w.buffer.len - flate.history_len, true);
+ try c.bit_writer.output.rebase(0, 1);
+ c.bit_writer.byteAlign();
+ try c.hasher.writeFooter(c.bit_writer.output);
+}
+
+fn rebase(w: *Writer, preserve: usize, capacity: usize) Writer.Error!void {
+ return rebaseInner(w, preserve, capacity, false);
+}
+
+pub const rebase_min_preserve = flate.history_len;
+pub const rebase_reserved_capacity = (token.max_length + 1) + seq_bytes;
+
+fn rebaseInner(w: *Writer, preserve: usize, capacity: usize, eos: bool) Writer.Error!void {
+ if (!eos) {
+ assert(@max(preserve, rebase_min_preserve) + (capacity + rebase_reserved_capacity) <= w.buffer.len);
+ assert(w.end >= flate.history_len + rebase_reserved_capacity); // Above assert should
+ // fail since rebase is only called when `capacity` is not present. This assertion is
+ // important because a full history is required at the end.
+ } else {
+ assert(preserve == 0 and capacity == w.buffer.len - flate.history_len);
+ }
+
+ const c: *Compress = @fieldParentPtr("writer", w);
+ const buffered = w.buffered();
+
+ const start = @as(usize, flate.history_len) * @intFromBool(c.has_history);
+ const lit_end: usize = if (!eos)
+ buffered.len - rebase_reserved_capacity - (preserve -| flate.history_len)
+ else
+ buffered.len -| (seq_bytes - 1);
+
+ var i = start;
+ var last_unmatched = i;
+ // Read from `w.buffer` instead of `buffered` since the latter may not
+ // have enough bytes. If this is the case, this variable is not used.
+ var seq: Seq = mem.readInt(
+ std.meta.Int(.unsigned, (seq_bytes - 1) * 8),
+ w.buffer[i..][0 .. seq_bytes - 1],
+ .big,
+ );
+ if (buffered[i..].len < seq_bytes - 1) {
+ @branchHint(.unlikely);
+ assert(eos);
+ seq = undefined;
+ assert(i >= lit_end);
+ }
+
+ while (i < lit_end) {
+ var match_start = i;
+ seq <<= 8;
+ seq |= buffered[i + (seq_bytes - 1)];
+ var match = c.matchAndAddHash(i, hash(seq), token.min_length - 1, c.opts.chain, c.opts.good);
+ i += 1;
+ if (match.len < token.min_length) continue;
+
+ var match_unadded = match.len - 1;
+ lazy: {
+ if (match.len >= c.opts.lazy) break :lazy;
+ if (match.len >= c.writer.buffered()[i..].len) {
+ @branchHint(.unlikely); // Only end of stream
+ break :lazy;
+ }
- fn add(self: *Tokens, t: Token) void {
- self.list[self.pos] = t;
- self.pos += 1;
+ var chain = c.opts.chain;
+ var good = c.opts.good;
+ if (match.len >= good) {
+ chain >>= 2;
+ good = math.maxInt(u8); // Reduce only once
+ }
+
+ seq <<= 8;
+ seq |= buffered[i + (seq_bytes - 1)];
+ const lazy = c.matchAndAddHash(i, hash(seq), match.len, chain, good);
+ match_unadded -= 1;
+ i += 1;
+
+ if (lazy.len > match.len) {
+ match_start += 1;
+ match = lazy;
+ match_unadded = match.len - 1;
+ }
+ }
+
+ assert(i + match_unadded == match_start + match.len);
+ assert(mem.eql(
+ u8,
+ buffered[match_start..][0..match.len],
+ buffered[match_start - 1 - match.dist ..][0..match.len],
+ )); // This assert also seems to help codegen.
+
+ try c.outputBytes(buffered[last_unmatched..match_start]);
+ try c.outputMatch(@intCast(match.dist), @intCast(match.len - 3));
+
+ last_unmatched = match_start + match.len;
+ if (last_unmatched + seq_bytes >= w.end) {
+ @branchHint(.unlikely);
+ assert(eos);
+ i = undefined;
+ break;
+ }
+
+ while (true) {
+ seq <<= 8;
+ seq |= buffered[i + (seq_bytes - 1)];
+ _ = c.addHash(i, hash(seq));
+ i += 1;
+
+ match_unadded -= 1;
+ if (match_unadded == 0) break;
+ }
+ assert(i == match_start + match.len);
}
- fn full(self: *Tokens) bool {
- return self.pos == self.list.len;
+ if (eos) {
+ i = undefined; // (from match hashing logic)
+ try c.outputBytes(buffered[last_unmatched..]);
+ c.hasher.update(buffered[start..]);
+ try c.writeBlock(true);
+ return;
}
- fn reset(self: *Tokens) void {
- self.pos = 0;
+ try c.outputBytes(buffered[last_unmatched..i]);
+ c.hasher.update(buffered[start..i]);
+
+ const preserved = buffered[i - flate.history_len ..];
+ assert(preserved.len > @max(rebase_min_preserve, preserve));
+ @memmove(w.buffer[0..preserved.len], preserved);
+ w.end = preserved.len;
+ c.has_history = true;
+}
+
+fn addHash(c: *Compress, i: usize, h: Hash) void {
+ assert(h == hash(mem.readInt(Seq, c.writer.buffer[i..][0..seq_bytes], .big)));
+
+ const l = &c.lookup;
+ l.chain_pos +%= 1;
+
+ // Equivilent to the below, however LLVM 21 does not optimize `@subWithOverflow` well at all.
+ // const replaced_i, const no_replace = @subWithOverflow(i, flate.history_len);
+ // if (no_replace == 0) {
+ if (i >= flate.history_len) {
+ @branchHint(.likely);
+ const replaced_i = i - flate.history_len;
+ // The following is the same as the below except uses a 32-bit load to help optimizations
+ // const replaced_seq = mem.readInt(Seq, c.writer.buffer[replaced_i..][0..seq_bytes], .big);
+ comptime assert(@sizeOf(Seq) <= @sizeOf(u32));
+ const replaced_u32 = mem.readInt(u32, c.writer.buffered()[replaced_i..][0..4], .big);
+ const replaced_seq: Seq = @intCast(replaced_u32 >> (32 - @bitSizeOf(Seq)));
+
+ const replaced_h = hash(replaced_seq);
+ // The following is equivilent to the below since LLVM 21 doesn't optimize it well.
+ // l.head[replaced_h].is_null = l.head[replaced_h].is_null or
+ // l.head[replaced_h].int() == l.chain_pos;
+ const empty_head = l.head[replaced_h].int() == l.chain_pos;
+ const null_flag = PackedOptionalU15.int(.{ .is_null = empty_head, .value = 0 });
+ l.head[replaced_h] = @bitCast(l.head[replaced_h].int() | null_flag);
}
- fn tokens(self: *Tokens) []const Token {
- return self.list[0..self.pos];
+ const prev_chain_index = l.head[h];
+ l.chain[l.chain_pos] = @bitCast((l.chain_pos -% prev_chain_index.value) |
+ (prev_chain_index.int() & PackedOptionalU15.null_bit.int())); // Preserves null
+ l.head[h] = .{ .value = l.chain_pos, .is_null = false };
+}
+
+/// If the match is shorter, the returned value can be any value `<= old`.
+fn betterMatchLen(old: u16, prev: []const u8, bytes: []const u8) u16 {
+ assert(old < @min(bytes.len, token.max_length));
+ assert(prev.len >= bytes.len);
+ assert(bytes.len >= token.min_length);
+
+ var i: u16 = 0;
+ const Block = std.meta.Int(.unsigned, @min(math.divCeil(
+ comptime_int,
+ math.ceilPowerOfTwoAssert(usize, @bitSizeOf(usize)),
+ 8,
+ ) catch unreachable, 256) * 8);
+
+ if (bytes.len < token.max_length) {
+ @branchHint(.unlikely); // Only end of stream
+
+ while (bytes[i..].len >= @sizeOf(Block)) {
+ const a = mem.readInt(Block, prev[i..][0..@sizeOf(Block)], .little);
+ const b = mem.readInt(Block, bytes[i..][0..@sizeOf(Block)], .little);
+ const diff = a ^ b;
+ if (diff != 0) {
+ @branchHint(.likely);
+ i += @ctz(diff) / 8;
+ return i;
+ }
+ i += @sizeOf(Block);
+ }
+
+ while (i != bytes.len and prev[i] == bytes[i]) {
+ i += 1;
+ }
+ assert(i < token.max_length);
+ return i;
}
-};
-fn drain(me: *Writer, data: []const []const u8, splat: usize) Writer.Error!usize {
- _ = data;
- _ = splat;
- const c: *Compress = @fieldParentPtr("writer", me);
- const out = c.block_writer.output;
- switch (c.state) {
- .header => {
- c.state = .middle;
- const header = c.hasher.container().header();
- try out.writeAll(header);
- return header.len;
- },
- .middle => {},
- .ended => unreachable,
+ if (old >= @sizeOf(Block)) {
+ // Check that a longer end is present, otherwise the match is always worse
+ const a = mem.readInt(Block, prev[old + 1 - @sizeOf(Block) ..][0..@sizeOf(Block)], .little);
+ const b = mem.readInt(Block, bytes[old + 1 - @sizeOf(Block) ..][0..@sizeOf(Block)], .little);
+ if (a != b) return i;
+ }
+
+ while (true) {
+ const a = mem.readInt(Block, prev[i..][0..@sizeOf(Block)], .little);
+ const b = mem.readInt(Block, bytes[i..][0..@sizeOf(Block)], .little);
+ const diff = a ^ b;
+ if (diff != 0) {
+ i += @ctz(diff) / 8;
+ return i;
+ }
+ i += @sizeOf(Block);
+ if (i == 256) break;
+ }
+
+ const a = mem.readInt(u16, prev[i..][0..2], .little);
+ const b = mem.readInt(u16, bytes[i..][0..2], .little);
+ const diff = a ^ b;
+ i += @ctz(diff) / 8;
+ assert(i <= token.max_length);
+ return i;
+}
+
+test betterMatchLen {
+ try std.testing.fuzz({}, testFuzzedMatchLen, .{});
+}
+
+fn testFuzzedMatchLen(_: void, input: []const u8) !void {
+ @disableInstrumentation();
+ var r: Io.Reader = .fixed(input);
+ var buf: [1024]u8 = undefined;
+ var w: Writer = .fixed(&buf);
+ var old = r.takeLeb128(u9) catch 0;
+ var bytes_off = @max(1, r.takeLeb128(u10) catch 258);
+ const prev_back = @max(1, r.takeLeb128(u10) catch 258);
+
+ while (r.takeByte()) |byte| {
+ const op: packed struct(u8) {
+ kind: enum(u2) { splat, copy, insert_imm, insert },
+ imm: u6,
+
+ pub fn immOrByte(op_s: @This(), r_s: *Io.Reader) usize {
+ return if (op_s.imm == 0) op_s.imm else @as(usize, r_s.takeByte() catch 0) + 64;
+ }
+ } = @bitCast(byte);
+ (switch (op.kind) {
+ .splat => w.splatByteAll(r.takeByte() catch 0, op.immOrByte(&r)),
+ .copy => write: {
+ const start = w.buffered().len -| op.immOrByte(&r);
+ const len = @min(w.buffered().len - start, r.takeByte() catch 3);
+ break :write w.writeAll(w.buffered()[start..][0..len]);
+ },
+ .insert_imm => w.writeByte(op.imm),
+ .insert => w.writeAll(r.take(
+ @min(r.bufferedLen(), @as(usize, op.imm) + 1),
+ ) catch unreachable),
+ }) catch break;
+ } else |_| {}
+
+ w.splatByteAll(0, (1 + 3) -| w.buffered().len) catch unreachable;
+ bytes_off = @min(bytes_off, @as(u10, @intCast(w.buffered().len - 3)));
+ const prev_off = bytes_off -| prev_back;
+ assert(prev_off < bytes_off);
+ const prev = w.buffered()[prev_off..];
+ const bytes = w.buffered()[bytes_off..];
+ old = @min(old, bytes.len - 1, token.max_length - 1);
+
+ const diff_index = mem.indexOfDiff(u8, prev, bytes).?; // unwrap since lengths are not same
+ const expected_len = @min(diff_index, 258);
+ errdefer std.debug.print(
+ \\prev : '{any}'
+ \\bytes: '{any}'
+ \\old : {}
+ \\expected: {?}
+ \\actual : {}
+ ++ "\n", .{
+ prev, bytes, old,
+ if (old < expected_len) expected_len else null, betterMatchLen(old, prev, bytes),
+ });
+ if (old < expected_len) {
+ try std.testing.expectEqual(expected_len, betterMatchLen(old, prev, bytes));
+ } else {
+ try std.testing.expect(betterMatchLen(old, prev, bytes) <= old);
+ }
+}
+
+fn matchAndAddHash(c: *Compress, i: usize, h: Hash, gt: u16, max_chain: u16, good_: u16) struct {
+ dist: u16,
+ len: u16,
+} {
+ const l = &c.lookup;
+ const buffered = c.writer.buffered();
+
+ var chain_limit = max_chain;
+ var best_dist: u16 = undefined;
+ var best_len = gt;
+ const nice = @min(c.opts.nice, buffered[i..].len);
+ var good = good_;
+
+ search: {
+ if (l.head[h].is_null) break :search;
+ // Actually a u15, but LLVM 21 does not optimize that as well (it truncates it each use).
+ var dist: u16 = l.chain_pos -% l.head[h].value;
+ while (true) {
+ chain_limit -= 1;
+
+ const match_len = betterMatchLen(best_len, buffered[i - 1 - dist ..], buffered[i..]);
+ if (match_len > best_len) {
+ best_dist = dist;
+ best_len = match_len;
+ if (best_len >= nice) break;
+ if (best_len >= good) {
+ chain_limit >>= 2;
+ good = math.maxInt(u8); // Reduce only once
+ }
+ }
+
+ if (chain_limit == 0) break;
+ const next_chain_index = l.chain_pos -% @as(u15, @intCast(dist));
+ // Equivilent to the below, however LLVM 21 optimizes the below worse.
+ // if (l.chain[next_chain_index].is_null) break;
+ // dist, const out_of_window = @addWithOverflow(dist, l.chain[next_chain_index].value);
+ // if (out_of_window == 1) break;
+ dist +%= l.chain[next_chain_index].int(); // wrapping for potential null bit
+ comptime assert(flate.history_len == PackedOptionalU15.int(.null_bit));
+ // Also, doing >= flate.history_len gives worse codegen with LLVM 21.
+ if ((dist | l.chain[next_chain_index].int()) & flate.history_len != 0) break;
+ }
+ }
+
+ c.addHash(i, h);
+ return .{ .dist = best_dist, .len = best_len };
+}
+
+fn clenHlen(freqs: [19]u16) u4 {
+ // Note that the first four codes (16, 17, 18, and 0) are always present.
+ if (builtin.mode != .ReleaseSmall and (std.simd.suggestVectorLength(u16) orelse 1) >= 8) {
+ const V = @Vector(16, u16);
+ const hlen_mul: V = comptime m: {
+ var hlen_mul: [16]u16 = undefined;
+ for (token.codegen_order[3..], 0..) |i, hlen| {
+ hlen_mul[i] = hlen;
+ }
+ break :m hlen_mul;
+ };
+ const encoded = freqs[0..16].* != @as(V, @splat(0));
+ return @intCast(@reduce(.Max, @intFromBool(encoded) * hlen_mul));
+ } else {
+ var max: u4 = 0;
+ for (token.codegen_order[4..], 1..) |i, len| {
+ max = if (freqs[i] == 0) max else @intCast(len);
+ }
+ return max;
+ }
+}
+
+test clenHlen {
+ var freqs: [19]u16 = @splat(0);
+ try std.testing.expectEqual(0, clenHlen(freqs));
+ for (token.codegen_order, 1..) |i, len| {
+ freqs[i] = 1;
+ try std.testing.expectEqual(len -| 4, clenHlen(freqs));
+ freqs[i] = 0;
+ }
+}
+
+/// Returns the number of values followed by the bitsize of the extra bits.
+fn buildClen(
+ dyn_bits: []const u4,
+ out_values: []u8,
+ out_extra: []u8,
+ out_freqs: *[19]u16,
+) struct { u16, u16 } {
+ assert(dyn_bits.len <= out_values.len);
+ assert(out_values.len == out_extra.len);
+
+ var len: u16 = 0;
+ var extra_bitsize: u16 = 0;
+
+ var remaining_bits = dyn_bits;
+ var prev: u4 = 0;
+ while (true) {
+ const b = remaining_bits[0];
+ const n_max = @min(@as(u8, if (b != 0)
+ if (b != prev) 1 else 6
+ else
+ 138), remaining_bits.len);
+ prev = b;
+
+ var n: u8 = 0;
+ while (true) {
+ remaining_bits = remaining_bits[1..];
+ n += 1;
+ if (n == n_max or remaining_bits[0] != b) break;
+ }
+ const code, const extra, const xsize = switch (n) {
+ 0 => unreachable,
+ 1...2 => .{ b, 0, 0 },
+ 3...10 => .{
+ @as(u8, 16) + @intFromBool(b == 0),
+ n - 3,
+ @as(u8, 2) + @intFromBool(b == 0),
+ },
+ 11...138 => .{ 18, n - 11, 7 },
+ else => unreachable,
+ };
+ while (true) {
+ out_values[len] = code;
+ out_extra[len] = extra;
+ out_freqs[code] += 1;
+ extra_bitsize += xsize;
+ len += 1;
+ if (n != 2) {
+ @branchHint(.likely);
+ break;
+ }
+ // Code needs outputted once more
+ n = 1;
+ }
+ if (remaining_bits.len == 0) break;
+ }
+
+ return .{ len, extra_bitsize };
+}
+
+test buildClen {
+ //dyn_bits: []u4,
+ //out_values: *[288 + 30]u8,
+ //out_extra: *[288 + 30]u8,
+ //out_freqs: *[19]u16,
+ //struct { u16, u16 }
+ var out_values: [288 + 30]u8 = undefined;
+ var out_extra: [288 + 30]u8 = undefined;
+ var out_freqs: [19]u16 = @splat(0);
+ const len, const extra_bitsize = buildClen(&([_]u4{
+ 1, // A
+ 2, 2, // B
+ 3, 3, 3, // C
+ 4, 4, 4, 4, // D
+ 5, // E
+ 5, 5, 5, 5, 5, 5, //
+ 5, 5, 5, 5, 5, 5,
+ 5, 5,
+ 0, 1, // F
+ 0, 0, 1, // G
+ } ++ @as([138 + 10]u4, @splat(0)) // H
+ ), &out_values, &out_extra, &out_freqs);
+ try std.testing.expectEqualSlices(u8, &.{
+ 1, // A
+ 2, 2, // B
+ 3, 3, 3, // C
+ 4, 16, // D
+ 5, 16, 16, 5, 5, // E
+ 0, 1, // F
+ 0, 0, 1, // G
+ 18, 17, // H
+ }, out_values[0..len]);
+ try std.testing.expectEqualSlices(u8, &.{
+ 0, // A
+ 0, 0, // B
+ 0, 0, 0, // C
+ 0, (0), // D
+ 0, (3), (3), 0, 0, // E
+ 0, 0, // F
+ 0, 0, 0, // G
+ (127), (7), // H
+ }, out_extra[0..len]);
+ try std.testing.expectEqual(2 + 2 + 2 + 7 + 3, extra_bitsize);
+ try std.testing.expectEqualSlices(u16, &.{
+ 3, 3, 2, 3, 1, 3, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0,
+ 3, 1, 1,
+ }, &out_freqs);
+}
+
+fn writeBlock(c: *Compress, eos: bool) Writer.Error!void {
+ const toks = &c.buffered_tokens;
+ if (!eos) assert(toks.n == block_tokens);
+ assert(toks.lit_freqs[256] == 0);
+ toks.lit_freqs[256] = 1;
+
+ var dyn_codes_buf: [286 + 30]u16 = undefined;
+ var dyn_bits_buf: [286 + 30]u4 = @splat(0);
+
+ const dyn_lit_codes_bitsize, const dyn_last_lit = huffman.build(
+ &toks.lit_freqs,
+ dyn_codes_buf[0..286],
+ dyn_bits_buf[0..286],
+ 15,
+ true,
+ );
+ const dyn_lit_len = @max(257, dyn_last_lit + 1);
+
+ const dyn_dist_codes_bitsize, const dyn_last_dist = huffman.build(
+ &toks.dist_freqs,
+ dyn_codes_buf[dyn_lit_len..][0..30],
+ dyn_bits_buf[dyn_lit_len..][0..30],
+ 15,
+ true,
+ );
+ const dyn_dist_len = @max(1, dyn_last_dist + 1);
+
+ var clen_values: [288 + 30]u8 = undefined;
+ var clen_extra: [288 + 30]u8 = undefined;
+ var clen_freqs: [19]u16 = @splat(0);
+ const clen_len, const clen_extra_bitsize = buildClen(
+ dyn_bits_buf[0 .. dyn_lit_len + dyn_dist_len],
+ &clen_values,
+ &clen_extra,
+ &clen_freqs,
+ );
+
+ var clen_codes: [19]u16 = undefined;
+ var clen_bits: [19]u4 = @splat(0);
+ const clen_codes_bitsize, _ = huffman.build(
+ &clen_freqs,
+ &clen_codes,
+ &clen_bits,
+ 7,
+ false,
+ );
+ const hclen = clenHlen(clen_freqs);
+
+ const dynamic_bitsize = @as(u32, 14) +
+ (4 + @as(u6, hclen)) * 3 + clen_codes_bitsize + clen_extra_bitsize +
+ dyn_lit_codes_bitsize + dyn_dist_codes_bitsize;
+ const fixed_bitsize = n: {
+ const freq7 = 1; // eos
+ var freq8: u16 = 0;
+ var freq9: u16 = 0;
+ var freq12: u16 = 0; // 7 + 5 - match freqs always have corresponding 5-bit dist freq
+ var freq13: u16 = 0; // 8 + 5
+ for (toks.lit_freqs[0..144]) |f| freq8 += f;
+ for (toks.lit_freqs[144..256]) |f| freq9 += f;
+ assert(toks.lit_freqs[256] == 1);
+ for (toks.lit_freqs[257..280]) |f| freq12 += f;
+ for (toks.lit_freqs[280..286]) |f| freq13 += f;
+ break :n @as(u32, freq7) * 7 +
+ @as(u32, freq8) * 8 + @as(u32, freq9) * 9 +
+ @as(u32, freq12) * 12 + @as(u32, freq13) * 13;
+ };
+
+ stored: {
+ for (toks.dist_freqs) |n| if (n != 0) break :stored;
+ // No need to check len frequencies since they each have a corresponding dist frequency
+ assert(for (toks.lit_freqs[257..]) |f| (if (f != 0) break false) else true);
+
+ // No matches. If the stored size is smaller than the huffman-encoded version, it will be
+ // outputed in a store block. This is not done with matches since the original input would
+ // need to be stored since the window may slid, and it may also exceed 65535 bytes. This
+ // should be OK since most inputs with matches should be more compressable anyways.
+ const stored_align_bits = -%(c.bit_writer.buffered_n +% 3);
+ const stored_bitsize = stored_align_bits + @as(u32, 32) + @as(u32, toks.n) * 8;
+ if (@min(dynamic_bitsize, fixed_bitsize) < stored_bitsize) break :stored;
+
+ try c.bit_writer.write(BlockHeader.int(.{ .kind = .stored, .final = eos }), 3);
+ try c.bit_writer.output.rebase(0, 5);
+ c.bit_writer.byteAlign();
+ c.bit_writer.output.writeInt(u16, c.buffered_tokens.n, .little) catch unreachable;
+ c.bit_writer.output.writeInt(u16, ~c.buffered_tokens.n, .little) catch unreachable;
+
+ // Relatively small buffer since regular draining will
+ // always consume slightly less than 2 << 15 bytes.
+ var vec_buf: [4][]const u8 = undefined;
+ var vec_n: usize = 0;
+ var i: usize = 0;
+
+ assert(c.buffered_tokens.pos != 0);
+ while (i != c.buffered_tokens.pos) {
+ const h: TokenBufferEntryHeader = @bitCast(toks.list[i..][0..2].*);
+ assert(h.kind == .bytes);
+
+ i += 2;
+ vec_buf[vec_n] = toks.list[i..][0..h.data];
+ i += h.data;
+
+ vec_n += 1;
+ if (i == c.buffered_tokens.pos or vec_n == vec_buf.len) {
+ try c.bit_writer.output.writeVecAll(vec_buf[0..vec_n]);
+ vec_n = 0;
+ }
+ }
+
+ toks.* = .empty;
+ return;
+ }
+
+ const lit_codes, const lit_bits, const dist_codes, const dist_bits =
+ if (dynamic_bitsize < fixed_bitsize) codes: {
+ try c.bit_writer.write(BlockHeader.Dynamic.int(.{
+ .regular = .{ .final = eos, .kind = .dynamic },
+ .hlit = @intCast(dyn_lit_len - 257),
+ .hdist = @intCast(dyn_dist_len - 1),
+ .hclen = hclen,
+ }), 17);
+ try c.bit_writer.writeClen(
+ hclen,
+ clen_values[0..clen_len],
+ clen_extra[0..clen_len],
+ clen_codes,
+ clen_bits,
+ );
+ break :codes .{
+ dyn_codes_buf[0..dyn_lit_len],
+ dyn_bits_buf[0..dyn_lit_len],
+ dyn_codes_buf[dyn_lit_len..][0..dyn_dist_len],
+ dyn_bits_buf[dyn_lit_len..][0..dyn_dist_len],
+ };
+ } else codes: {
+ try c.bit_writer.write(BlockHeader.int(.{ .final = eos, .kind = .fixed }), 3);
+ break :codes .{
+ &token.fixed_lit_codes,
+ &token.fixed_lit_bits,
+ &token.fixed_dist_codes,
+ &token.fixed_dist_bits,
+ };
+ };
+
+ var i: usize = 0;
+ while (i != toks.pos) {
+ const h: TokenBufferEntryHeader = @bitCast(toks.list[i..][0..2].*);
+ i += 2;
+ if (h.kind == .bytes) {
+ for (toks.list[i..][0..h.data]) |b| {
+ try c.bit_writer.write(lit_codes[b], lit_bits[b]);
+ }
+ i += h.data;
+ } else {
+ const dist = h.data;
+ const len = toks.list[i];
+ i += 1;
+ const dist_code = token.DistCode.fromVal(dist);
+ const len_code = token.LenCode.fromVal(len);
+ const dist_val = dist_code.toInt();
+ const lit_val = @as(u16, 257) + len_code.toInt();
+
+ var out: u48 = lit_codes[lit_val];
+ var out_bits: u6 = lit_bits[lit_val];
+ out |= @shlExact(@as(u20, len - len_code.base()), @intCast(out_bits));
+ out_bits += len_code.extraBits();
+
+ out |= @shlExact(@as(u35, dist_codes[dist_val]), out_bits);
+ out_bits += dist_bits[dist_val];
+ out |= @shlExact(@as(u48, dist - dist_code.base()), out_bits);
+ out_bits += dist_code.extraBits();
+
+ try c.bit_writer.write(out, out_bits);
+ }
+ }
+ try c.bit_writer.write(lit_codes[256], lit_bits[256]);
+
+ toks.* = .empty;
+}
+
+/// Huffman tree construction.
+///
+/// The approach for building the huffman tree is [taken from zlib]
+/// (https://github.com/madler/zlib/blob/v1.3.1/trees.c#L625) with some modifications.
+const huffman = struct {
+ const max_leafs = 286;
+ const max_nodes = max_leafs * 2;
+
+ const Node = struct {
+ freq: u16,
+ depth: u16,
+
+ pub const Index = u16;
+
+ pub fn smaller(a: Node, b: Node) bool {
+ return if (a.freq != b.freq) a.freq < b.freq else a.depth < b.depth;
+ }
+ };
+
+ fn heapSiftDown(nodes: []Node, heap: []Node.Index, start: usize) void {
+ var i = start;
+ while (true) {
+ var min = i;
+ const l = i * 2 + 1;
+ const r = l + 1;
+ min = if (l < heap.len and nodes[heap[l]].smaller(nodes[heap[min]])) l else min;
+ min = if (r < heap.len and nodes[heap[r]].smaller(nodes[heap[min]])) r else min;
+ if (i == min) break;
+ mem.swap(Node.Index, &heap[i], &heap[min]);
+ i = min;
+ }
+ }
+
+ fn heapRemoveRoot(nodes: []Node, heap: []Node.Index) void {
+ heap[0] = heap[heap.len - 1];
+ heapSiftDown(nodes, heap[0 .. heap.len - 1], 0);
+ }
+
+ /// Returns the total bits to encode `freqs` followed by the index of the last non-zero bits.
+ /// For `freqs[i]` == 0, `out_codes[i]` will be undefined.
+ /// It is asserted `out_bits` is zero-filled.
+ /// It is asserted `out_bits.len` is at least a length of
+ /// one if ncomplete trees are allowed and two otherwise.
+ pub fn build(
+ freqs: []const u16,
+ out_codes: []u16,
+ out_bits: []u4,
+ max_bits: u4,
+ incomplete_allowed: bool,
+ ) struct { u32, u16 } {
+ assert(out_codes.len - 1 >= @intFromBool(incomplete_allowed));
+ // freqs and out_codes are in the loop to assert they are all the same length
+ for (freqs, out_codes, out_bits) |_, _, n| assert(n == 0);
+ assert(out_codes.len <= @as(u16, 1) << max_bits);
+
+ // Indexes 0..freqs are leafs, indexes max_leafs.. are internal nodes.
+ var tree_nodes: [max_nodes]Node = undefined;
+ var tree_parent_nodes: [max_nodes]Node.Index = undefined;
+ var nodes_end: u16 = max_leafs;
+ // Dual-purpose buffer. Nodes are ordered by least frequency or when equal, least depth.
+ // The start is a min heap of level-zero nodes.
+ // The end is a sorted buffer of nodes with the greatest first.
+ var node_buf: [max_nodes]Node.Index = undefined;
+ var heap_end: u16 = 0;
+ var sorted_start: u16 = node_buf.len;
+
+ for (0.., freqs) |n, freq| {
+ tree_nodes[n] = .{ .freq = freq, .depth = 0 };
+ node_buf[heap_end] = @intCast(n);
+ heap_end += @intFromBool(freq != 0);
+ }
+
+ // There must be at least one code at minimum,
+ node_buf[heap_end] = 0;
+ heap_end += @intFromBool(heap_end == 0);
+ // and at least two if incomplete must be avoided.
+ if (heap_end == 1 and incomplete_allowed) {
+ @branchHint(.unlikely); // LLVM 21 optimizes this branch as the more likely without
+
+ // Codes must have at least one-bit, so this is a special case.
+ out_bits[node_buf[0]] = 1;
+ out_codes[node_buf[0]] = 0;
+ return .{ freqs[node_buf[0]], node_buf[0] };
+ }
+ const last_nonzero = @max(node_buf[heap_end - 1], 1); // For heap_end > 1, last is not be 0
+ node_buf[heap_end] = @intFromBool(node_buf[0] == 0);
+ heap_end += @intFromBool(heap_end == 1);
+
+ // Heapify the array of frequencies
+ const heapify_final = heap_end - 1;
+ const heapify_start = (heapify_final - 1) / 2; // Parent of final node
+ var heapify_i = heapify_start;
+ while (true) {
+ heapSiftDown(&tree_nodes, node_buf[0..heap_end], heapify_i);
+ if (heapify_i == 0) break;
+ heapify_i -= 1;
+ }
+
+ // Build optimal tree. `max_bits` is not enforced yet.
+ while (heap_end > 1) {
+ const a = node_buf[0];
+ heapRemoveRoot(&tree_nodes, node_buf[0..heap_end]);
+ heap_end -= 1;
+ const b = node_buf[0];
+
+ sorted_start -= 2;
+ node_buf[sorted_start..][0..2].* = .{ b, a };
+
+ tree_nodes[nodes_end] = .{
+ .freq = tree_nodes[a].freq + tree_nodes[b].freq,
+ .depth = @max(tree_nodes[a].depth, tree_nodes[b].depth) + 1,
+ };
+ defer nodes_end += 1;
+ tree_parent_nodes[a] = nodes_end;
+ tree_parent_nodes[b] = nodes_end;
+
+ node_buf[0] = nodes_end;
+ heapSiftDown(&tree_nodes, node_buf[0..heap_end], 0);
+ }
+ sorted_start -= 1;
+ node_buf[sorted_start] = node_buf[0];
+
+ var bit_counts: [16]u16 = @splat(0);
+ buildBits(out_bits, &bit_counts, &tree_parent_nodes, node_buf[sorted_start..], max_bits);
+ return .{ buildValues(freqs, out_codes, out_bits, bit_counts), last_nonzero };
+ }
+
+ fn buildBits(
+ out_bits: []u4,
+ bit_counts: *[16]u16,
+ parent_nodes: *[max_nodes]Node.Index,
+ sorted: []Node.Index,
+ max_bits: u4,
+ ) void {
+ var internal_node_bits: [max_nodes - max_leafs]u4 = undefined;
+ var overflowed: u16 = 0;
+
+ internal_node_bits[sorted[0] - max_leafs] = 0; // root
+ for (sorted[1..]) |i| {
+ const parent_bits = internal_node_bits[parent_nodes[i] - max_leafs];
+ overflowed += @intFromBool(parent_bits == max_bits);
+ const bits = parent_bits + @intFromBool(parent_bits != max_bits);
+ bit_counts[bits] += @intFromBool(i < max_leafs);
+ (if (i >= max_leafs) &internal_node_bits[i - max_leafs] else &out_bits[i]).* = bits;
+ }
+
+ if (overflowed == 0) {
+ @branchHint(.likely);
+ return;
+ }
+
+ outer: while (true) {
+ var deepest: u4 = max_bits - 1;
+ while (bit_counts[deepest] == 0) deepest -= 1;
+ while (overflowed != 0) {
+ // Insert an internal node under the leaf and move an overflow as its sibling
+ bit_counts[deepest] -= 1;
+ bit_counts[deepest + 1] += 2;
+ // Only overflow moved. Its sibling's depth is one less, however is still >= depth.
+ bit_counts[max_bits] -= 1;
+ overflowed -= 2;
+
+ if (overflowed == 0) break :outer;
+ deepest += 1;
+ if (deepest == max_bits) continue :outer;
+ }
+ }
+
+ // Reassign bit lengths
+ assert(bit_counts[0] == 0);
+ var i: usize = 0;
+ for (1.., bit_counts[1..]) |bits, all| {
+ var remaining = all;
+ while (remaining != 0) {
+ defer i += 1;
+ if (sorted[i] >= max_leafs) continue;
+ out_bits[sorted[i]] = @intCast(bits);
+ remaining -= 1;
+ }
+ }
+ assert(for (sorted[i..]) |n| { // all leafs consumed
+ if (n < max_leafs) break false;
+ } else true);
+ }
+
+ fn buildValues(freqs: []const u16, out_codes: []u16, bits: []u4, bit_counts: [16]u16) u32 {
+ var code: u16 = 0;
+ var base: [16]u16 = undefined;
+ assert(bit_counts[0] == 0);
+ for (bit_counts[1..], base[1..]) |c, *b| {
+ b.* = code;
+ code +%= c;
+ code <<= 1;
+ }
+ var freq_sums: [16]u16 = @splat(0);
+ for (out_codes, bits, freqs) |*c, b, f| {
+ c.* = @bitReverse(base[b]) >> -%b;
+ base[b] += 1; // For `b == 0` this is fine since v is specified to be undefined.
+ freq_sums[b] += f;
+ }
+ return @reduce(.Add, @as(@Vector(16, u32), freq_sums) * std.simd.iota(u32, 16));
+ }
+
+ test build {
+ var codes: [8]u16 = undefined;
+ var bits: [8]u4 = undefined;
+
+ const regular_freqs: [8]u16 = .{ 1, 1, 0, 8, 8, 0, 2, 4 };
+ // The optimal tree for the above frequencies is
+ // 4 1 1
+ // \ /
+ // 3 2 #
+ // \ /
+ // 2 8 8 4 #
+ // \ / \ /
+ // 1 # #
+ // \ /
+ // 0 #
+ bits = @splat(0);
+ var n, var lnz = build(&regular_freqs, &codes, &bits, 15, true);
+ codes[2] = 0;
+ codes[5] = 0;
+ try std.testing.expectEqualSlices(u4, &.{ 4, 4, 0, 2, 2, 0, 3, 2 }, &bits);
+ try std.testing.expectEqualSlices(u16, &.{
+ 0b0111, 0b1111, 0, 0b00, 0b10, 0, 0b011, 0b01,
+ }, &codes);
+ try std.testing.expectEqual(54, n);
+ try std.testing.expectEqual(7, lnz);
+ // When constrained to 3 bits, it becomes
+ // 3 1 1 2 4
+ // \ / \ /
+ // 2 8 8 # #
+ // \ / \ /
+ // 1 # #
+ // \ /
+ // 0 #
+ bits = @splat(0);
+ n, lnz = build(&regular_freqs, &codes, &bits, 3, true);
+ codes[2] = 0;
+ codes[5] = 0;
+ try std.testing.expectEqualSlices(u4, &.{ 3, 3, 0, 2, 2, 0, 3, 3 }, &bits);
+ try std.testing.expectEqualSlices(u16, &.{
+ 0b001, 0b101, 0, 0b00, 0b10, 0, 0b011, 0b111,
+ }, &codes);
+ try std.testing.expectEqual(56, n);
+ try std.testing.expectEqual(7, lnz);
+
+ // Empty tree. At least one code should be present
+ bits = @splat(0);
+ n, lnz = build(&.{ 0, 0 }, codes[0..2], bits[0..2], 15, true);
+ try std.testing.expectEqualSlices(u4, &.{ 1, 0 }, bits[0..2]);
+ try std.testing.expectEqual(0b0, codes[0]);
+ try std.testing.expectEqual(0, n);
+ try std.testing.expectEqual(0, lnz);
+
+ // Check all incompletable frequencies are completed
+ for ([_][2]u16{ .{ 0, 0 }, .{ 0, 1 }, .{ 1, 0 } }) |incomplete| {
+ // Empty tree. Both codes should be present to prevent incomplete trees
+ bits = @splat(0);
+ n, lnz = build(&incomplete, codes[0..2], bits[0..2], 15, false);
+ try std.testing.expectEqualSlices(u4, &.{ 1, 1 }, bits[0..2]);
+ try std.testing.expectEqualSlices(u16, &.{ 0b0, 0b1 }, codes[0..2]);
+ try std.testing.expectEqual(incomplete[0] + incomplete[1], n);
+ try std.testing.expectEqual(1, lnz);
+ }
+
+ try std.testing.fuzz({}, checkFuzzedBuildFreqs, .{});
}
- const buffered = me.buffered();
- const min_lookahead = Token.min_length + Token.max_length;
- const history_plus_lookahead_len = flate.history_len + min_lookahead;
- if (buffered.len < history_plus_lookahead_len) return 0;
- const lookahead = buffered[flate.history_len..];
+ fn checkFuzzedBuildFreqs(_: void, freqs: []const u8) !void {
+ @disableInstrumentation();
+ var r: Io.Reader = .fixed(freqs);
+ var freqs_limit: u16 = 65535;
+ var freqs_buf: [max_leafs]u16 = undefined;
+ var nfreqs: u15 = 0;
+
+ const params: packed struct(u8) {
+ max_bits: u4,
+ _: u3,
+ incomplete_allowed: bool,
+ } = @bitCast(r.takeByte() catch 255);
+ while (nfreqs != freqs_buf.len) {
+ const leb = r.takeLeb128(u16);
+ const f = if (leb) |f| @min(f, freqs_limit) else |e| switch (e) {
+ error.ReadFailed => unreachable,
+ error.EndOfStream => 0,
+ error.Overflow => freqs_limit,
+ };
+ freqs_buf[nfreqs] = f;
+ nfreqs += 1;
+ freqs_limit -= f;
+ if (leb == error.EndOfStream and nfreqs - 1 > @intFromBool(params.incomplete_allowed))
+ break;
+ }
+
+ var codes_buf: [max_leafs]u16 = undefined;
+ var bits_buf: [max_leafs]u4 = @splat(0);
+ const total_bits, const last_nonzero = build(
+ freqs_buf[0..nfreqs],
+ codes_buf[0..nfreqs],
+ bits_buf[0..nfreqs],
+ @max(math.log2_int_ceil(u15, nfreqs), params.max_bits),
+ params.incomplete_allowed,
+ );
+
+ var has_bitlen_one: bool = false;
+ var expected_total_bits: u32 = 0;
+ var expected_last_nonzero: ?u16 = null;
+ var weighted_sum: u32 = 0;
+ for (freqs_buf[0..nfreqs], bits_buf[0..nfreqs], 0..) |f, nb, i| {
+ has_bitlen_one = has_bitlen_one or nb == 1;
+ weighted_sum += @shlExact(@as(u16, 1), 15 - nb) & ((1 << 15) - 1);
+ expected_total_bits += @as(u32, f) * nb;
+ if (nb != 0) expected_last_nonzero = @intCast(i);
+ }
+
+ errdefer std.log.err(
+ \\ params: {}
+ \\ freqs: {any}
+ \\ bits: {any}
+ \\ # freqs: {}
+ \\ max bits: {}
+ \\ weighted sum: {}
+ \\ has_bitlen_one: {}
+ \\ expected/actual total bits: {}/{}
+ \\ expected/actual last nonzero: {?}/{}
+ ++ "\n", .{
+ params,
+ freqs_buf[0..nfreqs],
+ bits_buf[0..nfreqs],
+ nfreqs,
+ @max(math.log2_int_ceil(u15, nfreqs), params.max_bits),
+ weighted_sum,
+ has_bitlen_one,
+ expected_total_bits,
+ total_bits,
+ expected_last_nonzero,
+ last_nonzero,
+ });
+
+ try std.testing.expectEqual(expected_total_bits, total_bits);
+ try std.testing.expectEqual(expected_last_nonzero, last_nonzero);
+ if (weighted_sum > 1 << 15)
+ return error.OversubscribedHuffmanTree;
+ if (weighted_sum < 1 << 15 and
+ !(params.incomplete_allowed and has_bitlen_one and weighted_sum == 1 << 14))
+ return error.IncompleteHuffmanTree;
+ }
+};
- // TODO tokenize
- _ = lookahead;
- //c.hasher.update(lookahead[0..n]);
- @panic("TODO");
+test {
+ _ = huffman;
}
-pub fn end(c: *Compress) !void {
- try endUnflushed(c);
- const out = c.block_writer.output;
- try out.flush();
+/// [0] is a gradient where the probability of lower values decreases across it
+/// [1] is completely random and hence uncompressable
+fn testingFreqBufs() !*[2][65536]u8 {
+ const fbufs = try std.testing.allocator.create([2][65536]u8);
+ var prng: std.Random.DefaultPrng = .init(std.testing.random_seed);
+ prng.random().bytes(&fbufs[0]);
+ prng.random().bytes(&fbufs[1]);
+ for (0.., &fbufs[0], fbufs[1]) |i, *grad, rand| {
+ const prob = @as(u8, @intCast(255 - i / (fbufs[0].len * 256)));
+ grad.* /= @max(1, rand / @max(1, prob));
+ }
+ return fbufs;
}
-pub fn endUnflushed(c: *Compress) !void {
- while (c.writer.end != 0) _ = try drain(&c.writer, &.{""}, 1);
- c.state = .ended;
+fn testingCheckDecompressedMatches(
+ flate_bytes: []const u8,
+ expected_size: u32,
+ expected_hash: flate.Container.Hasher,
+) !void {
+ const container: flate.Container = expected_hash;
+ var data_hash: flate.Container.Hasher = .init(container);
+ var data_size: u32 = 0;
+ var flate_r: Io.Reader = .fixed(flate_bytes);
+ var deflate_buf: [flate.max_window_len]u8 = undefined;
+ var deflate: flate.Decompress = .init(&flate_r, container, &deflate_buf);
- const out = c.block_writer.output;
+ while (deflate.reader.peekGreedy(1)) |bytes| {
+ data_size += @intCast(bytes.len);
+ data_hash.update(bytes);
+ deflate.reader.toss(bytes.len);
+ } else |e| switch (e) {
+ error.ReadFailed => return deflate.err.?,
+ error.EndOfStream => {},
+ }
- // TODO flush tokens
+ try testingCheckContainerHash(
+ expected_size,
+ expected_hash,
+ data_hash,
+ data_size,
+ deflate.container_metadata,
+ );
+}
- switch (c.hasher) {
- .gzip => |*gzip| {
- // GZIP 8 bytes footer
- // - 4 bytes, CRC32 (CRC-32)
- // - 4 bytes, ISIZE (Input SIZE) - size of the original (uncompressed) input data modulo 2^32
- const footer = try out.writableArray(8);
- std.mem.writeInt(u32, footer[0..4], gzip.crc.final(), .little);
- std.mem.writeInt(u32, footer[4..8], @truncate(gzip.count), .little);
+fn testingCheckContainerHash(
+ expected_size: u32,
+ expected_hash: flate.Container.Hasher,
+ actual_hash: flate.Container.Hasher,
+ actual_size: u32,
+ actual_meta: flate.Container.Metadata,
+) !void {
+ try std.testing.expectEqual(expected_size, actual_size);
+ switch (actual_hash) {
+ .raw => {},
+ .gzip => |gz| {
+ const expected_crc = expected_hash.gzip.crc.final();
+ try std.testing.expectEqual(expected_size, actual_meta.gzip.count);
+ try std.testing.expectEqual(expected_crc, gz.crc.final());
+ try std.testing.expectEqual(expected_crc, actual_meta.gzip.crc);
},
- .zlib => |*zlib| {
- // ZLIB (RFC 1950) is big-endian, unlike GZIP (RFC 1952).
- // 4 bytes of ADLER32 (Adler-32 checksum)
- // Checksum value of the uncompressed data (excluding any
- // dictionary data) computed according to Adler-32
- // algorithm.
- std.mem.writeInt(u32, try out.writableArray(4), zlib.adler, .big);
+ .zlib => |zl| {
+ const expected_adler = expected_hash.zlib.adler;
+ try std.testing.expectEqual(expected_adler, zl.adler);
+ try std.testing.expectEqual(expected_adler, actual_meta.zlib.adler);
},
- .raw => {},
}
}
-pub const Simple = struct {
- /// Note that store blocks are limited to 65535 bytes.
- buffer: []u8,
- wp: usize,
- block_writer: BlockWriter,
- hasher: Container.Hasher,
- strategy: Strategy,
+const PackedContainer = packed struct(u2) {
+ raw: bool,
+ other: enum(u1) { gzip, zlib },
+
+ pub fn val(c: @This()) flate.Container {
+ return if (c.raw) .raw else switch (c.other) {
+ .gzip => .gzip,
+ .zlib => .zlib,
+ };
+ }
+};
+
+test Compress {
+ const fbufs = try testingFreqBufs();
+ defer if (!builtin.fuzz) std.testing.allocator.destroy(fbufs);
+ try std.testing.fuzz(fbufs, testFuzzedCompressInput, .{});
+}
+
+fn testFuzzedCompressInput(fbufs: *const [2][65536]u8, input: []const u8) !void {
+ var in: Io.Reader = .fixed(input);
+ var opts: packed struct(u51) {
+ container: PackedContainer,
+ buf_size: u16,
+ good: u8,
+ nice: u8,
+ lazy: u8,
+ /// Not a `u16` to limit it for performance
+ chain: u9,
+ } = @bitCast(in.takeLeb128(u51) catch 0);
+ var expected_hash: flate.Container.Hasher = .init(opts.container.val());
+ var expected_size: u32 = 0;
+
+ var flate_buf: [128 * 1024]u8 = undefined;
+ var flate_w: Writer = .fixed(&flate_buf);
+ var deflate_buf: [flate.max_window_len * 2]u8 = undefined;
+ var deflate_w = try Compress.init(
+ &flate_w,
+ deflate_buf[0 .. flate.max_window_len + @as(usize, opts.buf_size)],
+ opts.container.val(),
+ .{
+ .good = @as(u16, opts.good) + 3,
+ .nice = @as(u16, opts.nice) + 3,
+ .lazy = @as(u16, @min(opts.lazy, opts.nice)) + 3,
+ .chain = @max(1, opts.chain, @as(u8, 4) * @intFromBool(opts.good <= opts.lazy)),
+ },
+ );
+
+ // It is ensured that more bytes are not written then this to ensure this run
+ // does not take too long and that `flate_buf` does not run out of space.
+ const flate_buf_blocks = flate_buf.len / block_tokens;
+ // Allow a max overhead of 64 bytes per block since the implementation does not gaurauntee it
+ // writes store blocks when optimal. This comes from taking less than 32 bytes to write an
+ // optimal dynamic block header of mostly bitlen 8 codes and the end of block literal plus
+ // `(65536 / 256) / 8`, which is is the maximum number of extra bytes from bitlen 9 codes. An
+ // extra 32 bytes is reserved on top of that for container headers and footers.
+ const max_size = flate_buf.len - (flate_buf_blocks * 64 + 32);
+
+ while (true) {
+ const data: packed struct(u36) {
+ is_rebase: bool,
+ is_bytes: bool,
+ params: packed union {
+ copy: packed struct(u34) {
+ len_lo: u5,
+ dist: u15,
+ len_hi: u4,
+ _: u10,
+ },
+ bytes: packed struct(u34) {
+ kind: enum(u1) { gradient, random },
+ off_hi: u4,
+ len_lo: u10,
+ off_mi: u4,
+ len_hi: u5,
+ off_lo: u8,
+ _: u2,
+ },
+ rebase: packed struct(u34) {
+ preserve: u17,
+ capacity: u17,
+ },
+ },
+ } = @bitCast(in.takeLeb128(u36) catch |e| switch (e) {
+ error.ReadFailed => unreachable,
+ error.Overflow => 0,
+ error.EndOfStream => break,
+ });
+
+ const buffered = deflate_w.writer.buffered();
+ // Required for repeating patterns and since writing from `buffered` is illegal
+ var copy_buf: [512]u8 = undefined;
+
+ if (data.is_rebase) {
+ const usable_capacity = deflate_w.writer.buffer.len - rebase_reserved_capacity;
+ const preserve = @min(data.params.rebase.preserve, usable_capacity);
+ const capacity = @min(data.params.rebase.capacity, usable_capacity -
+ @max(rebase_min_preserve, preserve));
+ try deflate_w.writer.rebase(preserve, capacity);
+ continue;
+ }
+
+ const max_bytes = max_size -| expected_size;
+ const bytes = if (!data.is_bytes and buffered.len != 0) bytes: {
+ const dist = @min(buffered.len, @as(u32, data.params.copy.dist) + 1);
+ const len = @min(
+ @max(@shlExact(@as(u9, data.params.copy.len_hi), 5) | data.params.copy.len_lo, 1),
+ max_bytes,
+ );
+ // Reuse the implementation's history. Otherwise our own would need maintained.
+ const bytes_start = buffered[buffered.len - dist ..];
+ const history_bytes = bytes_start[0..@min(bytes_start.len, len)];
+
+ @memcpy(copy_buf[0..history_bytes.len], history_bytes);
+ const new_history = len - history_bytes.len;
+ if (history_bytes.len != len) for ( // check needed for `- dist`
+ copy_buf[history_bytes.len..][0..new_history],
+ copy_buf[history_bytes.len - dist ..][0..new_history],
+ ) |*next, prev| {
+ next.* = prev;
+ };
+ break :bytes copy_buf[0..len];
+ } else bytes: {
+ const off = @shlExact(@as(u16, data.params.bytes.off_hi), 12) |
+ @shlExact(@as(u16, data.params.bytes.off_mi), 8) |
+ data.params.bytes.off_lo;
+ const len = @shlExact(@as(u16, data.params.bytes.len_hi), 10) |
+ data.params.bytes.len_lo;
+ const fbuf = &fbufs[@intFromEnum(data.params.bytes.kind)];
+ break :bytes fbuf[off..][0..@min(len, fbuf.len - off, max_bytes)];
+ };
+ assert(bytes.len <= max_bytes);
+ try deflate_w.writer.writeAll(bytes);
+ expected_hash.update(bytes);
+ expected_size += @intCast(bytes.len);
+ }
+
+ try deflate_w.writer.flush();
+ try testingCheckDecompressedMatches(flate_w.buffered(), expected_size, expected_hash);
+}
+
+/// Does not compress data
+pub const Raw = struct {
+ /// After `flush` is called, all vtable calls with result in `error.WriteFailed.`
+ writer: Writer,
+ output: *Writer,
+ hasher: flate.Container.Hasher,
- pub const Strategy = enum { huffman, store };
+ const max_block_size: u16 = 65535;
+ const full_header: [5]u8 = .{
+ BlockHeader.int(.{ .final = false, .kind = .stored }),
+ 255,
+ 255,
+ 0,
+ 0,
+ };
- pub fn init(output: *Writer, buffer: []u8, container: Container, strategy: Strategy) !Simple {
- const header = container.header();
- try output.writeAll(header);
+ /// While there is no minimum buffer size, it is recommended
+ /// to be at least `flate.max_window_len` for optimal output.
+ pub fn init(output: *Writer, buffer: []u8, container: flate.Container) Writer.Error!Raw {
+ try output.writeAll(container.header());
return .{
- .buffer = buffer,
- .wp = 0,
- .block_writer = .init(output),
+ .writer = .{
+ .buffer = buffer,
+ .vtable = &.{
+ .drain = Raw.drain,
+ .flush = Raw.flush,
+ .rebase = Raw.rebase,
+ },
+ },
+ .output = output,
.hasher = .init(container),
- .strategy = strategy,
};
}
- pub fn flush(self: *Simple) !void {
- try self.flushBuffer(false);
- try self.block_writer.storedBlock("", false);
- try self.block_writer.flush();
+ fn drain(w: *Writer, data: []const []const u8, splat: usize) Writer.Error!usize {
+ errdefer w.* = .failing;
+ const r: *Raw = @fieldParentPtr("writer", w);
+ const min_block = @min(w.buffer.len, max_block_size);
+ const pattern = data[data.len - 1];
+ var partial_header: [5]u8 = undefined;
+
+ var vecs: [16][]const u8 = undefined;
+ var vecs_n: usize = 0;
+ const data_bytes = Writer.countSplat(data, splat);
+ const total_bytes = w.end + data_bytes;
+ var rem_bytes = total_bytes;
+ var rem_splat = splat;
+ var rem_data = data;
+ var rem_data_elem: []const u8 = w.buffered();
+
+ assert(rem_bytes > min_block);
+ while (rem_bytes > min_block) { // not >= to allow `min_block` blocks to be marked as final
+ // also, it handles the case of `min_block` being zero (no buffer)
+ const block_size: u16 = @min(rem_bytes, max_block_size);
+ rem_bytes -= block_size;
+
+ if (vecs_n == vecs.len) {
+ try r.output.writeVecAll(&vecs);
+ vecs_n = 0;
+ }
+ vecs[vecs_n] = if (block_size == 65535)
+ &full_header
+ else header: {
+ partial_header[0] = BlockHeader.int(.{ .final = false, .kind = .stored });
+ mem.writeInt(u16, partial_header[1..3], block_size, .little);
+ mem.writeInt(u16, partial_header[3..5], ~block_size, .little);
+ break :header &partial_header;
+ };
+ vecs_n += 1;
+
+ var block_limit: Io.Limit = .limited(block_size);
+ while (true) {
+ if (vecs_n == vecs.len) {
+ try r.output.writeVecAll(&vecs);
+ vecs_n = 0;
+ }
+
+ const vec = block_limit.sliceConst(rem_data_elem);
+ vecs[vecs_n] = vec;
+ vecs_n += 1;
+ r.hasher.update(vec);
+
+ const is_pattern = rem_splat != splat and vec.len == pattern.len;
+ if (is_pattern) assert(pattern.len != 0); // exceeded countSplat
+
+ if (!is_pattern or rem_splat == 0 or pattern.len > @intFromEnum(block_limit) / 2) {
+ rem_data_elem = rem_data_elem[vec.len..];
+ block_limit = block_limit.subtract(vec.len).?;
+
+ if (rem_data_elem.len == 0) {
+ rem_data_elem = rem_data[0];
+ if (rem_data.len != 1) {
+ rem_data = rem_data[1..];
+ } else if (rem_splat != 0) {
+ rem_splat -= 1;
+ } else {
+ // All of `data` has been consumed.
+ assert(block_limit == .nothing);
+ assert(rem_bytes == 0);
+ // Since `rem_bytes` and `block_limit` are zero, these won't be used.
+ rem_data = undefined;
+ rem_data_elem = undefined;
+ rem_splat = undefined;
+ }
+ }
+ if (block_limit == .nothing) break;
+ } else {
+ const out_splat = @intFromEnum(block_limit) / pattern.len;
+ assert(out_splat >= 2);
+
+ try r.output.writeSplatAll(vecs[0..vecs_n], out_splat);
+ for (1..out_splat) |_| r.hasher.update(vec);
+
+ vecs_n = 0;
+ block_limit = block_limit.subtract(pattern.len * out_splat).?;
+ if (rem_splat >= out_splat) {
+ // `out_splat` contains `rem_data`, however one more needs subtracted
+ // anyways since the next pattern is also being taken.
+ rem_splat -= out_splat;
+ } else {
+ // All of `data` has been consumed.
+ assert(block_limit == .nothing);
+ assert(rem_bytes == 0);
+ // Since `rem_bytes` and `block_limit` are zero, these won't be used.
+ rem_data = undefined;
+ rem_data_elem = undefined;
+ rem_splat = undefined;
+ }
+ if (block_limit == .nothing) break;
+ }
+ }
+ }
+
+ if (vecs_n != 0) { // can be the case if a splat was sent
+ try r.output.writeVecAll(vecs[0..vecs_n]);
+ }
+
+ if (rem_bytes > data_bytes) {
+ assert(rem_bytes - data_bytes == rem_data_elem.len);
+ assert(&rem_data_elem[0] == &w.buffer[total_bytes - rem_bytes]);
+ }
+ return w.consume(total_bytes - rem_bytes);
+ }
+
+ fn flush(w: *Writer) Writer.Error!void {
+ defer w.* = .failing;
+ try Raw.rebaseInner(w, 0, w.buffer.len, true);
}
- pub fn finish(self: *Simple) !void {
- try self.flushBuffer(true);
- try self.block_writer.flush();
- try self.hasher.container().writeFooter(&self.hasher, self.block_writer.output);
+ fn rebase(w: *Writer, preserve: usize, capacity: usize) Writer.Error!void {
+ errdefer w.* = .failing;
+ try Raw.rebaseInner(w, preserve, capacity, false);
}
- fn flushBuffer(self: *Simple, final: bool) !void {
- const buf = self.buffer[0..self.wp];
- switch (self.strategy) {
- .huffman => try self.block_writer.huffmanBlock(buf, final),
- .store => try self.block_writer.storedBlock(buf, final),
+ fn rebaseInner(w: *Writer, preserve: usize, capacity: usize, eos: bool) Writer.Error!void {
+ const r: *Raw = @fieldParentPtr("writer", w);
+ assert(preserve + capacity <= w.buffer.len);
+ if (eos) assert(capacity == w.buffer.len);
+
+ var partial_header: [5]u8 = undefined;
+ var footer_buf: [8]u8 = undefined;
+ const preserved = @min(w.end, preserve);
+ var remaining = w.buffer[0 .. w.end - preserved];
+
+ var vecs: [16][]const u8 = undefined;
+ var vecs_n: usize = 0;
+ while (remaining.len > max_block_size) { // not >= so there is always a block down below
+ if (vecs_n == vecs.len) {
+ try r.output.writeVecAll(&vecs);
+ vecs_n = 0;
+ }
+ vecs[vecs_n + 0] = &full_header;
+ vecs[vecs_n + 1] = remaining[0..max_block_size];
+ r.hasher.update(vecs[vecs_n + 1]);
+ vecs_n += 2;
+ remaining = remaining[max_block_size..];
+ }
+
+ // eos check required for empty block
+ if (w.buffer.len - (remaining.len + preserved) < capacity or eos) {
+ // A partial write is necessary to reclaim enough buffer space
+ const block_size: u16 = @intCast(remaining.len);
+ partial_header[0] = BlockHeader.int(.{ .final = eos, .kind = .stored });
+ mem.writeInt(u16, partial_header[1..3], block_size, .little);
+ mem.writeInt(u16, partial_header[3..5], ~block_size, .little);
+
+ if (vecs_n == vecs.len) {
+ try r.output.writeVecAll(&vecs);
+ vecs_n = 0;
+ }
+ vecs[vecs_n + 0] = &partial_header;
+ vecs[vecs_n + 1] = remaining[0..block_size];
+ r.hasher.update(vecs[vecs_n + 1]);
+ vecs_n += 2;
+ remaining = remaining[block_size..];
+ assert(remaining.len == 0);
+
+ if (eos and r.hasher != .raw) {
+ // the footer is done here instead of `flush` so it can be included in the vector
+ var footer_w: Writer = .fixed(&footer_buf);
+ r.hasher.writeFooter(&footer_w) catch unreachable;
+ assert(footer_w.end != 0);
+
+ if (vecs_n == vecs.len) {
+ try r.output.writeVecAll(&vecs);
+ return r.output.writeAll(footer_w.buffered());
+ } else {
+ vecs[vecs_n] = footer_w.buffered();
+ vecs_n += 1;
+ }
+ }
}
- self.wp = 0;
+
+ try r.output.writeVecAll(vecs[0..vecs_n]);
+ _ = w.consume(w.end - preserved - remaining.len);
}
};
-test "generate a Huffman code from an array of frequencies" {
- var freqs: [19]u16 = [_]u16{
- 8, // 0
- 1, // 1
- 1, // 2
- 2, // 3
- 5, // 4
- 10, // 5
- 9, // 6
- 1, // 7
- 0, // 8
- 0, // 9
- 0, // 10
- 0, // 11
- 0, // 12
- 0, // 13
- 0, // 14
- 0, // 15
- 1, // 16
- 3, // 17
- 5, // 18
+test Raw {
+ const data_buf = try std.testing.allocator.create([4 * 65536]u8);
+ defer if (!builtin.fuzz) std.testing.allocator.destroy(data_buf);
+ var prng: std.Random.DefaultPrng = .init(std.testing.random_seed);
+ prng.random().bytes(data_buf);
+ try std.testing.fuzz(data_buf, testFuzzedRawInput, .{});
+}
+
+fn countVec(data: []const []const u8) usize {
+ var bytes: usize = 0;
+ for (data) |d| bytes += d.len;
+ return bytes;
+}
+
+fn testFuzzedRawInput(data_buf: *const [4 * 65536]u8, input: []const u8) !void {
+ const HashedStoreWriter = struct {
+ writer: Writer,
+ state: enum {
+ header,
+ block_header,
+ block_body,
+ final_block_body,
+ footer,
+ end,
+ },
+ block_remaining: u16,
+ container: flate.Container,
+ data_hash: flate.Container.Hasher,
+ data_size: usize,
+ footer_hash: u32,
+ footer_size: u32,
+
+ pub fn init(buf: []u8, container: flate.Container) @This() {
+ return .{
+ .writer = .{
+ .vtable = &.{
+ .drain = @This().drain,
+ .flush = @This().flush,
+ },
+ .buffer = buf,
+ },
+ .state = .header,
+ .block_remaining = 0,
+ .container = container,
+ .data_hash = .init(container),
+ .data_size = 0,
+ .footer_hash = undefined,
+ .footer_size = undefined,
+ };
+ }
+
+ /// Note that this implementation is somewhat dependent on the implementation of
+ /// `Raw` by expecting headers / footers to be continous in data elements. It
+ /// also expects the header to be the same as `flate.Container.header` and not
+ /// for multiple streams to be concatenated.
+ fn drain(w: *Writer, data: []const []const u8, splat: usize) Writer.Error!usize {
+ errdefer w.* = .failing;
+ var h: *@This() = @fieldParentPtr("writer", w);
+
+ var rem_splat = splat;
+ var rem_data = data;
+ var rem_data_elem: []const u8 = w.buffered();
+
+ data_loop: while (true) {
+ const wanted = switch (h.state) {
+ .header => h.container.headerSize(),
+ .block_header => 5,
+ .block_body, .final_block_body => h.block_remaining,
+ .footer => h.container.footerSize(),
+ .end => 1,
+ };
+
+ if (wanted != 0) {
+ while (rem_data_elem.len == 0) {
+ rem_data_elem = rem_data[0];
+ if (rem_data.len != 1) {
+ rem_data = rem_data[1..];
+ } else {
+ if (rem_splat == 0) {
+ break :data_loop;
+ } else {
+ rem_splat -= 1;
+ }
+ }
+ }
+ }
+
+ const bytes = Io.Limit.limited(wanted).sliceConst(rem_data_elem);
+ rem_data_elem = rem_data_elem[bytes.len..];
+
+ switch (h.state) {
+ .header => {
+ if (bytes.len < wanted)
+ return error.WriteFailed; // header eos
+ if (!mem.eql(u8, bytes, h.container.header()))
+ return error.WriteFailed; // wrong header
+ h.state = .block_header;
+ },
+ .block_header => {
+ if (bytes.len < wanted)
+ return error.WriteFailed; // store block header eos
+ const header: BlockHeader = @bitCast(@as(u3, @truncate(bytes[0])));
+ if (header.kind != .stored)
+ return error.WriteFailed; // non-store block
+ const len = mem.readInt(u16, bytes[1..3], .little);
+ const nlen = mem.readInt(u16, bytes[3..5], .little);
+ if (nlen != ~len)
+ return error.WriteFailed; // wrong nlen
+ h.block_remaining = len;
+ h.state = if (!header.final) .block_body else .final_block_body;
+ },
+ .block_body, .final_block_body => {
+ h.data_hash.update(bytes);
+ h.data_size += bytes.len;
+ h.block_remaining -= @intCast(bytes.len);
+ if (h.block_remaining == 0) {
+ h.state = if (h.state != .final_block_body) .block_header else .footer;
+ }
+ },
+ .footer => {
+ if (bytes.len < wanted)
+ return error.WriteFailed; // footer eos
+ switch (h.container) {
+ .raw => {},
+ .gzip => {
+ h.footer_hash = mem.readInt(u32, bytes[0..4], .little);
+ h.footer_size = mem.readInt(u32, bytes[4..8], .little);
+ },
+ .zlib => {
+ h.footer_hash = mem.readInt(u32, bytes[0..4], .big);
+ },
+ }
+ h.state = .end;
+ },
+ .end => return error.WriteFailed, // data past end
+ }
+ }
+
+ w.end = 0;
+ return Writer.countSplat(data, splat);
+ }
+
+ fn flush(w: *Writer) Writer.Error!void {
+ defer w.* = .failing; // Clears buffer even if state hasn't reached `end`
+ _ = try @This().drain(w, &.{""}, 0);
+ }
};
- var codes: [19]HuffmanEncoder.Code = undefined;
- var enc: HuffmanEncoder = .{
- .codes = &codes,
- .freq_cache = undefined,
- .bit_count = undefined,
- .lns = undefined,
- .lfs = undefined,
+ var in: Io.Reader = .fixed(input);
+ const opts: packed struct(u19) {
+ container: PackedContainer,
+ buf_len: u17,
+ } = @bitCast(in.takeLeb128(u19) catch 0);
+ var output: HashedStoreWriter = .init(&.{}, opts.container.val());
+ var r_buf: [2 * 65536]u8 = undefined;
+ var r: Raw = try .init(
+ &output.writer,
+ r_buf[0 .. opts.buf_len +% flate.max_window_len],
+ opts.container.val(),
+ );
+
+ var data_base: u18 = 0;
+ var expected_hash: flate.Container.Hasher = .init(opts.container.val());
+ var expected_size: u32 = 0;
+ var vecs: [32][]const u8 = undefined;
+ var vecs_n: usize = 0;
+
+ while (in.seek != in.end) {
+ const VecInfo = packed struct(u58) {
+ output: bool,
+ /// If set, `data_len` and `splat` are reinterpreted as `capacity`
+ /// and `preserve_len` respectively and `output` is treated as set.
+ rebase: bool,
+ block_aligning_len: bool,
+ block_aligning_splat: bool,
+ data_len: u18,
+ splat: u18,
+ data_off: u18,
+ };
+ var vec_info: VecInfo = @bitCast(in.takeLeb128(u58) catch |e| switch (e) {
+ error.ReadFailed => unreachable,
+ error.Overflow, error.EndOfStream => 0,
+ });
+
+ {
+ const buffered = r.writer.buffered().len + countVec(vecs[0..vecs_n]);
+ const to_align = mem.alignForwardAnyAlign(usize, buffered, Raw.max_block_size) - buffered;
+ assert((buffered + to_align) % Raw.max_block_size == 0);
+
+ if (vec_info.block_aligning_len) {
+ vec_info.data_len = @intCast(to_align);
+ } else if (vec_info.block_aligning_splat and vec_info.data_len != 0 and
+ to_align % vec_info.data_len == 0)
+ {
+ vec_info.splat = @divExact(@as(u18, @intCast(to_align)), vec_info.data_len) -% 1;
+ }
+ }
+
+ var splat = if (vec_info.output and !vec_info.rebase) vec_info.splat +% 1 else 1;
+ add_vec: {
+ if (vec_info.rebase) break :add_vec;
+ if (expected_size +| math.mulWide(u18, vec_info.data_len, splat) >
+ 10 * (1 << 16))
+ {
+ // Skip this vector to avoid this test taking too long.
+ // 10 maximum sized blocks is choosen as the limit since it is two more
+ // than the maximum the implementation can output in one drain.
+ splat = 1;
+ break :add_vec;
+ }
+
+ vecs[vecs_n] = data_buf[@min(
+ data_base +% vec_info.data_off,
+ data_buf.len - vec_info.data_len,
+ )..][0..vec_info.data_len];
+
+ data_base +%= vec_info.data_len +% 3; // extra 3 to help catch aliasing bugs
+
+ for (0..splat) |_| expected_hash.update(vecs[vecs_n]);
+ expected_size += @as(u32, @intCast(vecs[vecs_n].len)) * splat;
+ vecs_n += 1;
+ }
+
+ const want_drain = vecs_n == vecs.len or vec_info.output or vec_info.rebase or
+ in.seek == in.end;
+ if (want_drain and vecs_n != 0) {
+ try r.writer.writeSplatAll(vecs[0..vecs_n], splat);
+ vecs_n = 0;
+ } else assert(splat == 1);
+
+ if (vec_info.rebase) {
+ try r.writer.rebase(vec_info.data_len, @min(
+ r.writer.buffer.len -| vec_info.data_len,
+ vec_info.splat,
+ ));
+ }
+ }
+
+ try r.writer.flush();
+ try output.writer.flush();
+
+ try std.testing.expectEqual(.end, output.state);
+ try std.testing.expectEqual(expected_size, output.data_size);
+ switch (output.data_hash) {
+ .raw => {},
+ .gzip => |gz| {
+ const expected_crc = expected_hash.gzip.crc.final();
+ try std.testing.expectEqual(expected_crc, gz.crc.final());
+ try std.testing.expectEqual(expected_crc, output.footer_hash);
+ try std.testing.expectEqual(expected_size, output.footer_size);
+ },
+ .zlib => |zl| {
+ const expected_adler = expected_hash.zlib.adler;
+ try std.testing.expectEqual(expected_adler, zl.adler);
+ try std.testing.expectEqual(expected_adler, output.footer_hash);
+ },
+ }
+}
+
+/// Only performs huffman compression on data, does no matching.
+pub const Huffman = struct {
+ writer: Writer,
+ bit_writer: BitWriter,
+ hasher: flate.Container.Hasher,
+
+ const max_tokens: u16 = 65535 - 1; // one is reserved for EOF
+
+ /// While there is no minimum buffer size, it is recommended
+ /// to be at least `flate.max_window_len` to improve compression.
+ ///
+ /// It is asserted `output` has a capacity of at least 8 bytes.
+ pub fn init(output: *Writer, buffer: []u8, container: flate.Container) Writer.Error!Huffman {
+ assert(output.buffer.len > 8);
+
+ try output.writeAll(container.header());
+ return .{
+ .writer = .{
+ .buffer = buffer,
+ .vtable = &.{
+ .drain = Huffman.drain,
+ .flush = Huffman.flush,
+ .rebase = Huffman.rebase,
+ },
+ },
+ .bit_writer = .init(output),
+ .hasher = .init(container),
+ };
+ }
+
+ fn drain(w: *Writer, data: []const []const u8, splat: usize) Writer.Error!usize {
+ {
+ //std.debug.print("drain {} (buffered)", .{w.buffered().len});
+ //for (data) |d| std.debug.print("\n\t+ {}", .{d.len});
+ //std.debug.print(" x {}\n\n", .{splat});
+ }
+
+ const h: *Huffman = @fieldParentPtr("writer", w);
+ const min_block = @min(w.buffer.len, max_tokens);
+ const pattern = data[data.len - 1];
+
+ const data_bytes = Writer.countSplat(data, splat);
+ const total_bytes = w.end + data_bytes;
+ var rem_bytes = total_bytes;
+ var rem_splat = splat;
+ var rem_data = data;
+ var rem_data_elem: []const u8 = w.buffered();
+
+ assert(rem_bytes > min_block);
+ while (rem_bytes > min_block) { // not >= to allow `min_block` blocks to be marked as final
+ // also, it handles the case of `min_block` being zero (no buffer)
+ const block_size: u16 = @min(rem_bytes, max_tokens);
+ rem_bytes -= block_size;
+
+ // Count frequencies
+ comptime assert(max_tokens != 65535);
+ var freqs: [257]u16 = @splat(0);
+ freqs[256] = 1;
+
+ const start_splat = rem_splat;
+ const start_data = rem_data;
+ const start_data_elem = rem_data_elem;
+
+ var block_limit: Io.Limit = .limited(block_size);
+ while (true) {
+ const bytes = block_limit.sliceConst(rem_data_elem);
+ const is_pattern = rem_splat != splat and bytes.len == pattern.len;
+
+ const mul = if (!is_pattern) 1 else @intFromEnum(block_limit) / pattern.len;
+ assert(mul != 0);
+ if (is_pattern) assert(mul <= rem_splat + 1); // one more for `rem_data`
+
+ for (bytes) |b| freqs[b] += @intCast(mul);
+ rem_data_elem = rem_data_elem[bytes.len..];
+ block_limit = block_limit.subtract(bytes.len * mul).?;
+
+ if (rem_data_elem.len == 0) {
+ rem_data_elem = rem_data[0];
+ if (rem_data.len != 1) {
+ rem_data = rem_data[1..];
+ } else if (rem_splat >= mul) {
+ // if the counter was not the pattern, `mul` is always one, otherwise,
+ // `mul` contains `rem_data`, however one more needs subtracted anyways
+ // since the next pattern is also being taken.
+ rem_splat -= mul;
+ } else {
+ // All of `data` has been consumed.
+ assert(block_limit == .nothing);
+ assert(rem_bytes == 0);
+ // Since `rem_bytes` and `block_limit` are zero, these won't be used.
+ rem_data = undefined;
+ rem_data_elem = undefined;
+ rem_splat = undefined;
+ }
+ }
+ if (block_limit == .nothing) break;
+ }
+
+ // Output block
+ rem_splat = start_splat;
+ rem_data = start_data;
+ rem_data_elem = start_data_elem;
+ block_limit = .limited(block_size);
+
+ var codes_buf: CodesBuf = .init;
+ if (try h.outputHeader(&freqs, &codes_buf, block_size, false)) |table| {
+ while (true) {
+ const bytes = block_limit.sliceConst(rem_data_elem);
+ rem_data_elem = rem_data_elem[bytes.len..];
+ block_limit = block_limit.subtract(bytes.len).?;
+
+ h.hasher.update(bytes);
+ for (bytes) |b| {
+ try h.bit_writer.write(table.codes[b], table.bits[b]);
+ }
+
+ if (rem_data_elem.len == 0) {
+ rem_data_elem = rem_data[0];
+ if (rem_data.len != 1) {
+ rem_data = rem_data[1..];
+ } else if (rem_splat != 0) {
+ rem_splat -= 1;
+ } else {
+ // All of `data` has been consumed.
+ assert(block_limit == .nothing);
+ assert(rem_bytes == 0);
+ // Since `rem_bytes` and `block_limit` are zero, these won't be used.
+ rem_data = undefined;
+ rem_data_elem = undefined;
+ rem_splat = undefined;
+ }
+ }
+ if (block_limit == .nothing) break;
+ }
+ try h.bit_writer.write(table.codes[256], table.bits[256]);
+ } else while (true) {
+ // Store block
+
+ // Write data that is not a full vector element
+ const in_pattern = rem_splat != splat;
+ const vec_elem_i, const in_data =
+ @subWithOverflow(data.len - (rem_data.len - @intFromBool(in_pattern)), 1);
+ const is_elem = in_data == 0 and data[vec_elem_i].len == rem_data_elem.len;
+
+ if (!is_elem or rem_data_elem.len > @intFromEnum(block_limit)) {
+ block_limit = block_limit.subtract(rem_data_elem.len) orelse {
+ try h.bit_writer.output.writeAll(rem_data_elem[0..@intFromEnum(block_limit)]);
+ h.hasher.update(rem_data_elem[0..@intFromEnum(block_limit)]);
+ rem_data_elem = rem_data_elem[@intFromEnum(block_limit)..];
+ assert(rem_data_elem.len != 0);
+ break;
+ };
+ try h.bit_writer.output.writeAll(rem_data_elem);
+ h.hasher.update(rem_data_elem);
+ } else {
+ // Put `rem_data_elem` back in `rem_data`
+ if (!in_pattern) {
+ rem_data = data[vec_elem_i..];
+ } else {
+ rem_splat += 1;
+ }
+ }
+ rem_data_elem = undefined; // it is always updated below
+
+ // Send through as much of the original vector as possible
+ var vec_n: usize = 0;
+ var vlimit = block_limit;
+ const vec_splat = while (rem_data[vec_n..].len != 1) {
+ vlimit = vlimit.subtract(rem_data[vec_n].len) orelse break 1;
+ vec_n += 1;
+ } else vec_splat: {
+ // For `pattern.len == 0`, the value of `vec_splat` does not matter.
+ const vec_splat = @intFromEnum(vlimit) / @max(1, pattern.len);
+ if (pattern.len != 0) assert(vec_splat <= rem_splat + 1);
+ vlimit = vlimit.subtract(pattern.len * vec_splat).?;
+ vec_n += 1;
+ break :vec_splat vec_splat;
+ };
+
+ const n = if (vec_n != 0) n: {
+ assert(@intFromEnum(block_limit) - @intFromEnum(vlimit) ==
+ Writer.countSplat(rem_data[0..vec_n], vec_splat));
+ break :n try h.bit_writer.output.writeSplat(rem_data[0..vec_n], vec_splat);
+ } else 0; // Still go into the case below to advance the vector
+ block_limit = block_limit.subtract(n).?;
+ var consumed: Io.Limit = .limited(n);
+
+ while (rem_data.len != 1) {
+ const elem = rem_data[0];
+ rem_data = rem_data[1..];
+ consumed = consumed.subtract(elem.len) orelse {
+ h.hasher.update(elem[0..@intFromEnum(consumed)]);
+ rem_data_elem = elem[@intFromEnum(consumed)..];
+ break;
+ };
+ h.hasher.update(elem);
+ } else {
+ if (pattern.len == 0) {
+ // All of `data` has been consumed. However, the general
+ // case below does not work since it divides by zero.
+ assert(consumed == .nothing);
+ assert(block_limit == .nothing);
+ assert(rem_bytes == 0);
+ // Since `rem_bytes` and `block_limit` are zero, these won't be used.
+ rem_splat = undefined;
+ rem_data = undefined;
+ rem_data_elem = undefined;
+ break;
+ }
+
+ const splatted = @intFromEnum(consumed) / pattern.len;
+ const partial = @intFromEnum(consumed) % pattern.len;
+ for (0..splatted) |_| h.hasher.update(pattern);
+ h.hasher.update(pattern[0..partial]);
+
+ const taken_splat = splatted + 1;
+ if (rem_splat >= taken_splat) {
+ rem_splat -= taken_splat;
+ rem_data_elem = pattern[partial..];
+ } else {
+ // All of `data` has been consumed.
+ assert(partial == 0);
+ assert(block_limit == .nothing);
+ assert(rem_bytes == 0);
+ // Since `rem_bytes` and `block_limit` are zero, these won't be used.
+ rem_data = undefined;
+ rem_data_elem = undefined;
+ rem_splat = undefined;
+ }
+ }
+
+ if (block_limit == .nothing) break;
+ }
+ }
+
+ if (rem_bytes > data_bytes) {
+ assert(rem_bytes - data_bytes == rem_data_elem.len);
+ assert(&rem_data_elem[0] == &w.buffer[total_bytes - rem_bytes]);
+ }
+ return w.consume(total_bytes - rem_bytes);
+ }
+
+ fn flush(w: *Writer) Writer.Error!void {
+ defer w.* = .failing;
+ const h: *Huffman = @fieldParentPtr("writer", w);
+ try Huffman.rebaseInner(w, 0, w.buffer.len, true);
+ try h.bit_writer.output.rebase(0, 1);
+ h.bit_writer.byteAlign();
+ try h.hasher.writeFooter(h.bit_writer.output);
+ }
+
+ fn rebase(w: *Writer, preserve: usize, capacity: usize) Writer.Error!void {
+ errdefer w.* = .failing;
+ try Huffman.rebaseInner(w, preserve, capacity, false);
+ }
+
+ fn rebaseInner(w: *Writer, preserve: usize, capacity: usize, eos: bool) Writer.Error!void {
+ const h: *Huffman = @fieldParentPtr("writer", w);
+ assert(preserve + capacity <= w.buffer.len);
+ if (eos) assert(capacity == w.buffer.len);
+
+ const preserved = @min(w.end, preserve);
+ var remaining = w.buffer[0 .. w.end - preserved];
+ while (remaining.len > max_tokens) { // not >= so there is always a block down below
+ const bytes = remaining[0..max_tokens];
+ remaining = remaining[max_tokens..];
+ try h.outputBytes(bytes, false);
+ }
+
+ // eos check required for empty block
+ if (w.buffer.len - (remaining.len + preserved) < capacity or eos) {
+ const bytes = remaining;
+ remaining = &.{};
+ try h.outputBytes(bytes, eos);
+ }
+
+ _ = w.consume(w.end - preserved - remaining.len);
+ }
+
+ fn outputBytes(h: *Huffman, bytes: []const u8, eos: bool) Writer.Error!void {
+ comptime assert(max_tokens != 65535);
+ assert(bytes.len <= max_tokens);
+ var freqs: [257]u16 = @splat(0);
+ freqs[256] = 1;
+ for (bytes) |b| freqs[b] += 1;
+ h.hasher.update(bytes);
+
+ var codes_buf: CodesBuf = .init;
+ if (try h.outputHeader(&freqs, &codes_buf, @intCast(bytes.len), eos)) |table| {
+ for (bytes) |b| {
+ try h.bit_writer.write(table.codes[b], table.bits[b]);
+ }
+ try h.bit_writer.write(table.codes[256], table.bits[256]);
+ } else {
+ try h.bit_writer.output.writeAll(bytes);
+ }
+ }
+
+ const CodesBuf = struct {
+ dyn_codes: [258]u16,
+ dyn_bits: [258]u4,
+
+ pub const init: CodesBuf = .{
+ .dyn_codes = @as([257]u16, undefined) ++ .{0},
+ .dyn_bits = @as([257]u4, @splat(0)) ++ .{1},
+ };
};
- enc.generate(freqs[0..], 7);
-
- try testing.expectEqual(@as(u32, 141), enc.bitLength(freqs[0..]));
-
- try testing.expectEqual(@as(usize, 3), enc.codes[0].len);
- try testing.expectEqual(@as(usize, 6), enc.codes[1].len);
- try testing.expectEqual(@as(usize, 6), enc.codes[2].len);
- try testing.expectEqual(@as(usize, 5), enc.codes[3].len);
- try testing.expectEqual(@as(usize, 3), enc.codes[4].len);
- try testing.expectEqual(@as(usize, 2), enc.codes[5].len);
- try testing.expectEqual(@as(usize, 2), enc.codes[6].len);
- try testing.expectEqual(@as(usize, 6), enc.codes[7].len);
- try testing.expectEqual(@as(usize, 0), enc.codes[8].len);
- try testing.expectEqual(@as(usize, 0), enc.codes[9].len);
- try testing.expectEqual(@as(usize, 0), enc.codes[10].len);
- try testing.expectEqual(@as(usize, 0), enc.codes[11].len);
- try testing.expectEqual(@as(usize, 0), enc.codes[12].len);
- try testing.expectEqual(@as(usize, 0), enc.codes[13].len);
- try testing.expectEqual(@as(usize, 0), enc.codes[14].len);
- try testing.expectEqual(@as(usize, 0), enc.codes[15].len);
- try testing.expectEqual(@as(usize, 6), enc.codes[16].len);
- try testing.expectEqual(@as(usize, 5), enc.codes[17].len);
- try testing.expectEqual(@as(usize, 3), enc.codes[18].len);
-
- try testing.expectEqual(@as(u16, 0x0), enc.codes[5].code);
- try testing.expectEqual(@as(u16, 0x2), enc.codes[6].code);
- try testing.expectEqual(@as(u16, 0x1), enc.codes[0].code);
- try testing.expectEqual(@as(u16, 0x5), enc.codes[4].code);
- try testing.expectEqual(@as(u16, 0x3), enc.codes[18].code);
- try testing.expectEqual(@as(u16, 0x7), enc.codes[3].code);
- try testing.expectEqual(@as(u16, 0x17), enc.codes[17].code);
- try testing.expectEqual(@as(u16, 0x0f), enc.codes[1].code);
- try testing.expectEqual(@as(u16, 0x2f), enc.codes[2].code);
- try testing.expectEqual(@as(u16, 0x1f), enc.codes[7].code);
- try testing.expectEqual(@as(u16, 0x3f), enc.codes[16].code);
+
+ /// Returns null if the block is stored.
+ fn outputHeader(
+ h: *Huffman,
+ freqs: *const [257]u16,
+ buf: *CodesBuf,
+ bytes: u16,
+ eos: bool,
+ ) Writer.Error!?struct {
+ codes: *const [257]u16,
+ bits: *const [257]u4,
+ } {
+ assert(freqs[256] == 1);
+ const dyn_codes_bitsize, _ = huffman.build(
+ freqs,
+ buf.dyn_codes[0..257],
+ buf.dyn_bits[0..257],
+ 15,
+ true,
+ );
+
+ var clen_values: [258]u8 = undefined;
+ var clen_extra: [258]u8 = undefined;
+ var clen_freqs: [19]u16 = @splat(0);
+ const clen_len, const clen_extra_bitsize = buildClen(
+ &buf.dyn_bits,
+ &clen_values,
+ &clen_extra,
+ &clen_freqs,
+ );
+
+ var clen_codes: [19]u16 = undefined;
+ var clen_bits: [19]u4 = @splat(0);
+ const clen_codes_bitsize, _ = huffman.build(
+ &clen_freqs,
+ &clen_codes,
+ &clen_bits,
+ 7,
+ false,
+ );
+ const hclen = clenHlen(clen_freqs);
+
+ const dynamic_bitsize = @as(u32, 14) +
+ (4 + @as(u6, hclen)) * 3 + clen_codes_bitsize + clen_extra_bitsize +
+ dyn_codes_bitsize;
+ const fixed_bitsize = n: {
+ const freq7 = 1; // eos
+ var freq9: u16 = 0;
+ for (freqs[144..256]) |f| freq9 += f;
+ const freq8: u16 = bytes - freq9;
+ break :n @as(u32, freq7) * 7 + @as(u32, freq8) * 8 + @as(u32, freq9) * 9;
+ };
+ const stored_bitsize = n: {
+ const stored_align_bits = -%(h.bit_writer.buffered_n +% 3);
+ break :n stored_align_bits + @as(u32, 32) + @as(u32, bytes) * 8;
+ };
+
+ //std.debug.print("@ {}{{{}}} ", .{ h.bit_writer.output.end, h.bit_writer.buffered_n });
+ //std.debug.print("#{} -> s {} f {} d {}\n", .{ bytes, stored_bitsize, fixed_bitsize, dynamic_bitsize });
+
+ if (stored_bitsize <= @min(dynamic_bitsize, fixed_bitsize)) {
+ try h.bit_writer.write(BlockHeader.int(.{ .kind = .stored, .final = eos }), 3);
+ try h.bit_writer.output.rebase(0, 5);
+ h.bit_writer.byteAlign();
+ h.bit_writer.output.writeInt(u16, bytes, .little) catch unreachable;
+ h.bit_writer.output.writeInt(u16, ~bytes, .little) catch unreachable;
+ return null;
+ }
+
+ if (fixed_bitsize <= dynamic_bitsize) {
+ try h.bit_writer.write(BlockHeader.int(.{ .final = eos, .kind = .fixed }), 3);
+ return .{
+ .codes = token.fixed_lit_codes[0..257],
+ .bits = token.fixed_lit_bits[0..257],
+ };
+ } else {
+ try h.bit_writer.write(BlockHeader.Dynamic.int(.{
+ .regular = .{ .final = eos, .kind = .dynamic },
+ .hlit = 0,
+ .hdist = 0,
+ .hclen = hclen,
+ }), 17);
+ try h.bit_writer.writeClen(
+ hclen,
+ clen_values[0..clen_len],
+ clen_extra[0..clen_len],
+ clen_codes,
+ clen_bits,
+ );
+ return .{ .codes = buf.dyn_codes[0..257], .bits = buf.dyn_bits[0..257] };
+ }
+ }
+};
+
+test Huffman {
+ const fbufs = try testingFreqBufs();
+ defer if (!builtin.fuzz) std.testing.allocator.destroy(fbufs);
+ try std.testing.fuzz(fbufs, testFuzzedHuffmanInput, .{});
+}
+
+/// This function is derived from `testFuzzedRawInput` with a few changes for fuzzing `Huffman`.
+fn testFuzzedHuffmanInput(fbufs: *const [2][65536]u8, input: []const u8) !void {
+ var in: Io.Reader = .fixed(input);
+ const opts: packed struct(u19) {
+ container: PackedContainer,
+ buf_len: u17,
+ } = @bitCast(in.takeLeb128(u19) catch 0);
+ var flate_buf: [2 * 65536]u8 = undefined;
+ var flate_w: Writer = .fixed(&flate_buf);
+ var h_buf: [2 * 65536]u8 = undefined;
+ var h: Huffman = try .init(
+ &flate_w,
+ h_buf[0 .. opts.buf_len +% flate.max_window_len],
+ opts.container.val(),
+ );
+
+ var expected_hash: flate.Container.Hasher = .init(opts.container.val());
+ var expected_size: u32 = 0;
+ var vecs: [32][]const u8 = undefined;
+ var vecs_n: usize = 0;
+
+ while (in.seek != in.end) {
+ const VecInfo = packed struct(u55) {
+ output: bool,
+ /// If set, `data_len` and `splat` are reinterpreted as `capacity`
+ /// and `preserve_len` respectively and `output` is treated as set.
+ rebase: bool,
+ block_aligning_len: bool,
+ block_aligning_splat: bool,
+ data_off_hi: u8,
+ random_data: u1,
+ data_len: u16,
+ splat: u18,
+ /// This is less useful as each value is part of the same gradient 'step'
+ data_off_lo: u8,
+ };
+ var vec_info: VecInfo = @bitCast(in.takeLeb128(u55) catch |e| switch (e) {
+ error.ReadFailed => unreachable,
+ error.Overflow, error.EndOfStream => 0,
+ });
+
+ {
+ const buffered = h.writer.buffered().len + countVec(vecs[0..vecs_n]);
+ const to_align = mem.alignForwardAnyAlign(usize, buffered, Huffman.max_tokens) - buffered;
+ assert((buffered + to_align) % Huffman.max_tokens == 0);
+
+ if (vec_info.block_aligning_len) {
+ vec_info.data_len = @intCast(to_align);
+ } else if (vec_info.block_aligning_splat and vec_info.data_len != 0 and
+ to_align % vec_info.data_len == 0)
+ {
+ vec_info.splat = @divExact(@as(u18, @intCast(to_align)), vec_info.data_len) -% 1;
+ }
+ }
+
+ var splat = if (vec_info.output and !vec_info.rebase) vec_info.splat +% 1 else 1;
+ add_vec: {
+ if (vec_info.rebase) break :add_vec;
+ if (expected_size +| math.mulWide(u18, vec_info.data_len, splat) > 4 * (1 << 16)) {
+ // Skip this vector to avoid this test taking too long.
+ splat = 1;
+ break :add_vec;
+ }
+
+ const data_buf = &fbufs[vec_info.random_data];
+ vecs[vecs_n] = data_buf[@min(
+ (@as(u16, vec_info.data_off_hi) << 8) | vec_info.data_off_lo,
+ data_buf.len - vec_info.data_len,
+ )..][0..vec_info.data_len];
+
+ for (0..splat) |_| expected_hash.update(vecs[vecs_n]);
+ expected_size += @as(u32, @intCast(vecs[vecs_n].len)) * splat;
+ vecs_n += 1;
+ }
+
+ const want_drain = vecs_n == vecs.len or vec_info.output or vec_info.rebase or
+ in.seek == in.end;
+ if (want_drain and vecs_n != 0) {
+ var n = h.writer.buffered().len + Writer.countSplat(vecs[0..vecs_n], splat);
+ const oos = h.writer.writeSplatAll(vecs[0..vecs_n], splat) == error.WriteFailed;
+ n -= h.writer.buffered().len;
+ const block_lim = math.divCeil(usize, n, Huffman.max_tokens) catch unreachable;
+ const lim = flate_w.end + 6 * block_lim + n; // 6 since block header may span two bytes
+ if (flate_w.end > lim) return error.OverheadTooLarge;
+ if (oos) return;
+
+ vecs_n = 0;
+ } else assert(splat == 1);
+
+ if (vec_info.rebase) {
+ const old_end = flate_w.end;
+ var n = h.writer.buffered().len;
+ const oos = h.writer.rebase(vec_info.data_len, @min(
+ h.writer.buffer.len -| vec_info.data_len,
+ vec_info.splat,
+ )) == error.WriteFailed;
+ n -= h.writer.buffered().len;
+ const block_lim = math.divCeil(usize, n, Huffman.max_tokens) catch unreachable;
+ const lim = old_end + 6 * block_lim + n; // 6 since block header may span two bytes
+ if (flate_w.end > lim) return error.OverheadTooLarge;
+ if (oos) return;
+ }
+ }
+
+ {
+ const old_end = flate_w.end;
+ const n = h.writer.buffered().len;
+ const oos = h.writer.flush() == error.WriteFailed;
+ assert(h.writer.buffered().len == 0);
+ const block_lim = @max(1, math.divCeil(usize, n, Huffman.max_tokens) catch unreachable);
+ const lim = old_end + 6 * block_lim + n + opts.container.val().footerSize();
+ if (flate_w.end > lim) return error.OverheadTooLarge;
+ if (oos) return;
+ }
+
+ try testingCheckDecompressedMatches(flate_w.buffered(), expected_size, expected_hash);
}
generated by cgit v1.2.3 (git 2.39.1) at 2025-12-27 22:32:00 +0000