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const std = @import("../std.zig");
const assert = std.debug.assert;
pub const Decompress = @import("zstd/Decompress.zig");
/// Recommended amount by the standard. Lower than this may result in inability
/// to decompress common streams.
pub const default_window_len = 8 * 1024 * 1024;
pub const block_size_max = 1 << 17;
pub const literals_length_default_distribution = [36]i16{
4, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1,
2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 1, 1, 1, 1, 1,
-1, -1, -1, -1,
};
pub const match_lengths_default_distribution = [53]i16{
1, 4, 3, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, -1, -1,
-1, -1, -1, -1, -1,
};
pub const offset_codes_default_distribution = [29]i16{
1, 1, 1, 1, 1, 1, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, -1, -1, -1, -1, -1,
};
pub const start_repeated_offset_1 = 1;
pub const start_repeated_offset_2 = 4;
pub const start_repeated_offset_3 = 8;
pub const literals_length_code_table = [36]struct { u32, u5 }{
.{ 0, 0 }, .{ 1, 0 }, .{ 2, 0 }, .{ 3, 0 },
.{ 4, 0 }, .{ 5, 0 }, .{ 6, 0 }, .{ 7, 0 },
.{ 8, 0 }, .{ 9, 0 }, .{ 10, 0 }, .{ 11, 0 },
.{ 12, 0 }, .{ 13, 0 }, .{ 14, 0 }, .{ 15, 0 },
.{ 16, 1 }, .{ 18, 1 }, .{ 20, 1 }, .{ 22, 1 },
.{ 24, 2 }, .{ 28, 2 }, .{ 32, 3 }, .{ 40, 3 },
.{ 48, 4 }, .{ 64, 6 }, .{ 128, 7 }, .{ 256, 8 },
.{ 512, 9 }, .{ 1024, 10 }, .{ 2048, 11 }, .{ 4096, 12 },
.{ 8192, 13 }, .{ 16384, 14 }, .{ 32768, 15 }, .{ 65536, 16 },
};
pub const match_length_code_table = [53]struct { u32, u5 }{
.{ 3, 0 }, .{ 4, 0 }, .{ 5, 0 }, .{ 6, 0 }, .{ 7, 0 }, .{ 8, 0 },
.{ 9, 0 }, .{ 10, 0 }, .{ 11, 0 }, .{ 12, 0 }, .{ 13, 0 }, .{ 14, 0 },
.{ 15, 0 }, .{ 16, 0 }, .{ 17, 0 }, .{ 18, 0 }, .{ 19, 0 }, .{ 20, 0 },
.{ 21, 0 }, .{ 22, 0 }, .{ 23, 0 }, .{ 24, 0 }, .{ 25, 0 }, .{ 26, 0 },
.{ 27, 0 }, .{ 28, 0 }, .{ 29, 0 }, .{ 30, 0 }, .{ 31, 0 }, .{ 32, 0 },
.{ 33, 0 }, .{ 34, 0 }, .{ 35, 1 }, .{ 37, 1 }, .{ 39, 1 }, .{ 41, 1 },
.{ 43, 2 }, .{ 47, 2 }, .{ 51, 3 }, .{ 59, 3 }, .{ 67, 4 }, .{ 83, 4 },
.{ 99, 5 }, .{ 131, 7 }, .{ 259, 8 }, .{ 515, 9 }, .{ 1027, 10 }, .{ 2051, 11 },
.{ 4099, 12 }, .{ 8195, 13 }, .{ 16387, 14 }, .{ 32771, 15 }, .{ 65539, 16 },
};
pub const table_accuracy_log_max = struct {
pub const literal = 9;
pub const match = 9;
pub const offset = 8;
};
pub const table_symbol_count_max = struct {
pub const literal = 36;
pub const match = 53;
pub const offset = 32;
};
pub const default_accuracy_log = struct {
pub const literal = 6;
pub const match = 6;
pub const offset = 5;
};
pub const table_size_max = struct {
pub const literal = 1 << table_accuracy_log_max.literal;
pub const match = 1 << table_accuracy_log_max.match;
pub const offset = 1 << table_accuracy_log_max.offset;
};
fn testDecompress(gpa: std.mem.Allocator, compressed: []const u8) ![]u8 {
var out: std.Io.Writer.Allocating = .init(gpa);
defer out.deinit();
var in: std.Io.Reader = .fixed(compressed);
var zstd_stream: Decompress = .init(&in, &.{}, .{});
_ = try zstd_stream.reader.streamRemaining(&out.writer);
return out.toOwnedSlice();
}
fn testExpectDecompress(uncompressed: []const u8, compressed: []const u8) !void {
const gpa = std.testing.allocator;
const result = try testDecompress(gpa, compressed);
defer gpa.free(result);
try std.testing.expectEqualSlices(u8, uncompressed, result);
}
fn testExpectDecompressError(err: anyerror, compressed: []const u8) !void {
const gpa = std.testing.allocator;
var out: std.Io.Writer.Allocating = .init(gpa);
defer out.deinit();
var in: std.Io.Reader = .fixed(compressed);
var zstd_stream: Decompress = .init(&in, &.{}, .{});
try std.testing.expectError(
error.ReadFailed,
zstd_stream.reader.streamRemaining(&out.writer),
);
try std.testing.expectError(err, zstd_stream.err orelse {});
}
test Decompress {
const uncompressed = @embedFile("testdata/rfc8478.txt");
const compressed3 = @embedFile("testdata/rfc8478.txt.zst.3");
const compressed19 = @embedFile("testdata/rfc8478.txt.zst.19");
try testExpectDecompress(uncompressed, compressed3);
try testExpectDecompress(uncompressed, compressed19);
}
test "partial magic number" {
const input_raw =
"\x28\xb5\x2f"; // 3 bytes of the 4-byte zstandard frame magic number
try testExpectDecompressError(error.BadMagic, input_raw);
}
test "zero sized raw block" {
const input_raw =
"\x28\xb5\x2f\xfd" ++ // zstandard frame magic number
"\x20\x00" ++ // frame header: only single_segment_flag set, frame_content_size zero
"\x01\x00\x00"; // block header with: last_block set, block_type raw, block_size zero
try testExpectDecompress("", input_raw);
}
test "zero sized rle block" {
const input_rle =
"\x28\xb5\x2f\xfd" ++ // zstandard frame magic number
"\x20\x00" ++ // frame header: only single_segment_flag set, frame_content_size zero
"\x03\x00\x00" ++ // block header with: last_block set, block_type rle, block_size zero
"\xaa"; // block_content
try testExpectDecompress("", input_rle);
}
test "declared raw literals size too large" {
const input_raw =
"\x28\xb5\x2f\xfd" ++ // zstandard frame magic number
"\x00\x00" ++ // frame header: everything unset, window descriptor zero
"\x95\x00\x00" ++ // block header with: last_block set, block_type compressed, block_size 18
"\xbc\xf3\xae" ++ // literals section header with: type raw, size_format 3, regenerated_size 716603
"\xa5\x9f\xe3"; // some bytes of literal content - the content is shorter than regenerated_size
// Note that the regenerated_size in the above input is larger than block maximum size, so the
// block can't be valid as it is a raw literals block.
try testExpectDecompressError(error.MalformedLiteralsSection, input_raw);
}
test "skippable frame" {
const input_raw =
"\x50\x2a\x4d\x18" ++ // min magic number for a skippable frame
"\x02\x00\x00\x00" ++ // number of bytes to skip
"\xFF\xFF"; // the bytes that are skipped
try testExpectDecompress("", input_raw);
}
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