tz parsing reader interface, test thicc files, and exclude tzif

1 files changed, 112 insertions, 96 deletions

diff --git a/lib/std/tz.zig b/lib/std/tz.zig
index 2680a8d48c..528150d1a2 100644
--- a/lib/std/tz.zig
+++ b/lib/std/tz.zig
@@ -40,160 +40,163 @@ pub const Tz = struct {
     leapseconds: []const Leapsecond,
     footer: []const u8,
 
-    pub fn parse(allocator: std.mem.Allocator, data: []const u8) !Tz {
-        const header_size = 4 + 1 + 15 + 6 * 4;
-        if (data.len < header_size) return error.BadSize;
-
-        const magic_l = data[0..4];
-        const version_l = data[4];
-        if (!std.mem.eql(u8, magic_l, "TZif")) return error.BadHeader;
-        if (version_l != '2' and version_l != '3') return error.BadVersion;
-
-        // Parse the legacy header and skip the entire thing
-        const isutcnt_l = std.mem.readIntBig(u32, data[20..24]);
-        const isstdcnt_l = std.mem.readIntBig(u32, data[24..28]);
-        const leapcnt_l = std.mem.readIntBig(u32, data[28..32]);
-        const timecnt_l = std.mem.readIntBig(u32, data[32..36]);
-        const typecnt_l = std.mem.readIntBig(u32, data[36..40]);
-        const charcnt_l = std.mem.readIntBig(u32, data[40..44]);
-        const data_block_size_legacy = timecnt_l * 5 + typecnt_l * 6 + charcnt_l + leapcnt_l * 8 + isstdcnt_l + isutcnt_l;
-        if (data.len < header_size + data_block_size_legacy) return error.BadSize;
-
-        const data2 = data[header_size + data_block_size_legacy ..];
-        if (data2.len < header_size) return error.BadSize;
-
-        const magic = data2[0..4];
-        const version = data2[4];
-        if (!std.mem.eql(u8, magic, "TZif")) return error.BadHeader;
-        if (version != '2' and version != '3') return error.BadVersion;
-
-        const isutcnt = std.mem.readIntBig(u32, data2[20..24]);
-        const isstdcnt = std.mem.readIntBig(u32, data2[24..28]);
-        const leapcnt = std.mem.readIntBig(u32, data2[28..32]);
-        const timecnt = std.mem.readIntBig(u32, data2[32..36]);
-        const typecnt = std.mem.readIntBig(u32, data2[36..40]);
-        const charcnt = std.mem.readIntBig(u32, data2[40..44]);
-
-        if (isstdcnt != 0 and isstdcnt != typecnt) return error.Malformed; // rfc8536: isstdcnt [...] MUST either be zero or equal to "typecnt"
-        if (isutcnt != 0 and isutcnt != typecnt) return error.Malformed; // rfc8536: isutcnt [...] MUST either be zero or equal to "typecnt"
-        if (typecnt == 0) return error.Malformed; // rfc8536: typecnt [...] MUST NOT be zero
-        if (charcnt == 0) return error.Malformed; // rfc8536: charcnt [...] MUST NOT be zero
-
-        const data_block_size = timecnt * 9 + typecnt * 6 + charcnt + leapcnt * 12 + isstdcnt + isutcnt;
-        if (data2.len < header_size + data_block_size) return error.BadSize;
-
-        var leapseconds = try allocator.alloc(Leapsecond, leapcnt);
+    pub fn parse(allocator: std.mem.Allocator, reader: anytype) !Tz {
+        _ = allocator;
+        const Header = extern struct {
+            magic: [4]u8,
+            version: u8,
+            reserved: [15]u8,
+        };
+
+        const Counts = extern struct {
+            isutcnt: u32,
+            isstdcnt: u32,
+            leapcnt: u32,
+            timecnt: u32,
+            typecnt: u32,
+            charcnt: u32,
+        };
+
+        // Parse and skip the legacy header and data
+        {
+            const header = try reader.readStruct(Header);
+            if (!std.mem.eql(u8, &header.magic, "TZif")) return error.BadHeader;
+            if (header.version == 0) return error.UnsupportedLegacyFormat;
+            if (header.version != '2' and header.version != '3') return error.BadVersion;
+
+            var counts = try reader.readStruct(Counts);
+            if (builtin.target.cpu.arch.endian() != std.builtin.Endian.Big) {
+                std.mem.bswapAllFields(Counts, &counts);
+            }
+
+            const skipv = counts.timecnt * 5 + counts.typecnt * 6 + counts.charcnt + counts.leapcnt * 8 + counts.isstdcnt + counts.isutcnt;
+            try reader.skipBytes(skipv, .{});
+        }
+
+        const header = try reader.readStruct(Header);
+        if (!std.mem.eql(u8, &header.magic, "TZif")) return error.BadHeader;
+        if (header.version != '2' and header.version != '3') return error.BadVersion;
+
+        var counts = try reader.readStruct(Counts);
+        if (builtin.target.cpu.arch.endian() != std.builtin.Endian.Big) {
+            std.mem.bswapAllFields(Counts, &counts);
+        }
+
+        if (counts.isstdcnt != 0 and counts.isstdcnt != counts.typecnt) return error.Malformed; // rfc8536: isstdcnt [...] MUST either be zero or equal to "typecnt"
+        if (counts.isutcnt != 0 and counts.isutcnt != counts.typecnt) return error.Malformed; // rfc8536: isutcnt [...] MUST either be zero or equal to "typecnt"
+        if (counts.typecnt == 0) return error.Malformed; // rfc8536: typecnt [...] MUST NOT be zero
+        if (counts.charcnt == 0) return error.Malformed; // rfc8536: charcnt [...] MUST NOT be zero
+        if (counts.charcnt > 256 + 6) return error.Malformed; // Not explicitly banned by rfc8536 but nonsensical
+
+        var leapseconds = try allocator.alloc(Leapsecond, counts.leapcnt);
         errdefer allocator.free(leapseconds);
-        var transitions = try allocator.alloc(Transition, timecnt);
+        var transitions = try allocator.alloc(Transition, counts.timecnt);
         errdefer allocator.free(transitions);
-        var timetypes = try allocator.alloc(Timetype, typecnt);
+        var timetypes = try allocator.alloc(Timetype, counts.typecnt);
         errdefer allocator.free(timetypes);
 
-        var p: usize = header_size;
-
-        // First, parse timezone designators ahead of time so that we can reject malformed files early
-        const designators = data2[header_size + timecnt * 9 + typecnt * 6 .. header_size + timecnt * 9 + typecnt * 6 + charcnt];
-        if (designators[designators.len - 1] != 0) return error.Malformed; // rfc8536: charcnt [...] includes the trailing NUL (0x00) octet
-
         // Parse transition types
         var i: usize = 0;
-        while (i < timecnt) : (i += 1) {
-            transitions[i].ts = std.mem.readIntSliceBig(i64, data2[p .. p + 8]);
-            p += 8;
+        while (i < counts.timecnt) : (i += 1) {
+            transitions[i].ts = try reader.readIntBig(i64);
         }
 
         i = 0;
-        while (i < timecnt) : (i += 1) {
-            const tt = data2[p];
+        while (i < counts.timecnt) : (i += 1) {
+            const tt = try reader.readByte();
             if (tt >= timetypes.len) return error.Malformed; // rfc8536: Each type index MUST be in the range [0, "typecnt" - 1]
             transitions[i].timetype = &timetypes[tt];
-            p += 1;
         }
 
         // Parse time types
         i = 0;
-        while (i < typecnt) : (i += 1) {
-            const offset = std.mem.readIntSliceBig(i32, data2[p .. p + 4]);
+        while (i < counts.typecnt) : (i += 1) {
+            const offset = try reader.readIntBig(i32);
             if (offset < -2147483648) return error.Malformed; // rfc8536: utoff [...] MUST NOT be -2**31
-            const dst = data2[p + 4];
+            const dst = try reader.readByte();
             if (dst != 0 and dst != 1) return error.Malformed; // rfc8536: (is)dst [...] The value MUST be 0 or 1.
-            const idx = data2[p + 5];
-            if (idx > designators.len - 1) return error.Malformed; // rfc8536: (desig)idx [...] Each index MUST be in the range [0, "charcnt" - 1]
-
-            const name = std.mem.sliceTo(designators[idx..], 0);
-
-            // We are mandating the "SHOULD" 6-character limit so we can pack the struct better, and to conform to POSIX.
-            if (name.len > 6) return error.Malformed; // rfc8536: Time zone designations SHOULD consist of at least three (3) and no more than six (6) ASCII characters.
-
+            const idx = try reader.readByte();
+            if (idx > counts.charcnt - 1) return error.Malformed; // rfc8536: (desig)idx [...] Each index MUST be in the range [0, "charcnt" - 1]
             timetypes[i] = .{
                 .offset = offset,
                 .flags = dst,
                 .name_data = undefined,
             };
 
-            std.mem.copy(u8, timetypes[i].name_data[0..], name);
-            timetypes[i].name_data[name.len] = 0;
-
-            p += 6;
+            // Temporarily cache idx in name_data to be processed after we've read the designator names below
+            timetypes[i].name_data[0] = idx;
         }
 
-        // Skip the designators we got earlier
-        p += charcnt;
+        var designators_data: [256 + 6]u8 = undefined;
+        try reader.readNoEof(designators_data[0..counts.charcnt]);
+        const designators = designators_data[0..counts.charcnt];
+        if (designators[designators.len - 1] != 0) return error.Malformed; // rfc8536: charcnt [...] includes the trailing NUL (0x00) octet
+
+        // Iterate through the timetypes again, setting the designator names
+        for (timetypes) |*tt| {
+            const name = std.mem.sliceTo(designators[tt.name_data[0]..], 0);
+            // We are mandating the "SHOULD" 6-character limit so we can pack the struct better, and to conform to POSIX.
+            if (name.len > 6) return error.Malformed; // rfc8536: Time zone designations SHOULD consist of at least three (3) and no more than six (6) ASCII characters.
+            std.mem.copy(u8, tt.name_data[0..], name);
+            tt.name_data[name.len] = 0;
+        }
 
         // Parse leap seconds
         i = 0;
-        while (i < leapcnt) : (i += 1) {
-            const occur = std.mem.readIntSliceBig(i64, data2[p .. p + 8]);
+        while (i < counts.leapcnt) : (i += 1) {
+            const occur = try reader.readIntBig(i64);
             if (occur < 0) return error.Malformed; // rfc8536: occur [...] MUST be nonnegative
             if (i > 0 and leapseconds[i - 1].occurrence + 2419199 > occur) return error.Malformed; // rfc8536: occur [...] each later value MUST be at least 2419199 greater than the previous value
             if (occur > std.math.maxInt(i48)) return error.Malformed; // Unreasonably far into the future
 
-            const corr = std.mem.readIntSliceBig(i32, data2[p + 8 .. p + 12]);
+            const corr = try reader.readIntBig(i32);
             if (i == 0 and corr != -1 and corr != 1) return error.Malformed; // rfc8536: The correction value in the first leap-second record, if present, MUST be either one (1) or minus one (-1)
-            if (i > 0 and leapseconds[i - 1].correction != corr + 1 and leapseconds[i - 1].correction != corr - 1) return error.Malformed; // rfc8536: The correction values in adjacent leap- second records MUST differ by exactly one (1)
+            if (i > 0 and leapseconds[i - 1].correction != corr + 1 and leapseconds[i - 1].correction != corr - 1) return error.Malformed; // rfc8536: The correction values in adjacent leap-second records MUST differ by exactly one (1)
             if (corr > std.math.maxInt(i16)) return error.Malformed; // Unreasonably large correction
 
             leapseconds[i] = .{
                 .occurrence = @intCast(i48, occur),
                 .correction = @intCast(i16, corr),
             };
-            p += 12;
         }
 
         // Parse standard/wall indicators
         i = 0;
-        while (i < isstdcnt) : (i += 1) {
-            const stdtime = data2[p];
+        while (i < counts.isstdcnt) : (i += 1) {
+            const stdtime = try reader.readByte();
             if (stdtime == 1) {
                 timetypes[i].flags |= 0x02;
             }
-            p += 1;
         }
 
         // Parse UT/local indicators
         i = 0;
-        while (i < isutcnt) : (i += 1) {
-            const ut = data2[p];
+        while (i < counts.isutcnt) : (i += 1) {
+            const ut = try reader.readByte();
             if (ut == 1) {
                 timetypes[i].flags |= 0x04;
                 if (!timetypes[i].standardTimeIndicator()) return error.Malformed; // rfc8536: standard/wall value MUST be one (1) if the UT/local value is one (1)
             }
-            p += 1;
         }
 
+        if ((try reader.readByte()) != '\n') return error.Malformed; // An rfc8536 footer must start with a newline
+
         // Footer
-        if (data2[p..].len < 2) return error.Malformed; // rfc8536 requires at least 2 newlines
-        if (data2[p] != '\n') return error.Malformed; // Not a rfc8536 footer
-        const footer_end = std.mem.indexOfScalar(u8, data2[p + 1 ..], '\n') orelse return error.Malformed; // No 2nd rfc8536 newline
-        const footer = try allocator.dupe(u8, data2[p + 1 .. p + 1 + footer_end]);
-        errdefer allocator.free(footer);
+        var footerdata_buf: [128]u8 = undefined;
+        const footer = reader.readUntilDelimiter(&footerdata_buf, '\n') catch |err| switch (err) {
+            error.StreamTooLong => return error.OverlargeFooter, // Read more than 128 bytes, much larger than any reasonable POSIX TZ string
+            else => return err,
+        };
+
+        const footer_dup = try allocator.dupe(u8, footer);
+        errdefer allocator.free(footer_dup);
 
         return Tz{
             .allocator = allocator,
             .transitions = transitions,
             .timetypes = timetypes,
             .leapseconds = leapseconds,
-            .footer = footer,
+            .footer = footer_dup,
         };
     }
 
@@ -205,14 +208,27 @@ pub const Tz = struct {
     }
 };
 
-test "parse" {
-    // Asia/Tokyo is good for embedding, as Japan only had DST for a short while during the US occupation
+test "slim" {
     const data = @embedFile("tz/asia_tokyo.tzif");
-    var tz = try Tz.parse(std.testing.allocator, data);
+    var in_stream = std.io.fixedBufferStream(data);
+
+    var tz = try std.Tz.parse(std.testing.allocator, in_stream.reader());
     defer tz.deinit();
 
     try std.testing.expectEqual(tz.transitions.len, 9);
     try std.testing.expect(std.mem.eql(u8, tz.transitions[3].timetype.name(), "JDT"));
-    try std.testing.expectEqual(tz.transitions[5].ts, -620298000); // 1950-05-06 15:00:00 (UTC)
-    try std.testing.expectEqual(tz.leapseconds[13].occurrence, 567993613); // 1988-01-01 00:00:13 (IAT)
+    try std.testing.expectEqual(tz.transitions[5].ts, -620298000); // 1950-05-06 15:00:00 UTC
+    try std.testing.expectEqual(tz.leapseconds[13].occurrence, 567993613); // 1988-01-01 00:00:00 UTC (+23s in TAI, and +13 in the data since it doesn't store the initial 10 second offset)
+}
+
+test "fat" {
+    const data = @embedFile("tz/antarctica_davis.tzif");
+    var in_stream = std.io.fixedBufferStream(data);
+
+    var tz = try std.Tz.parse(std.testing.allocator, in_stream.reader());
+    defer tz.deinit();
+
+    try std.testing.expectEqual(tz.transitions.len, 8);
+    try std.testing.expect(std.mem.eql(u8, tz.transitions[3].timetype.name(), "+05"));
+    try std.testing.expectEqual(tz.transitions[4].ts, 1268251224); // 2010-03-10 20:00:00 UTC
 }