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std.tz: fix redundant endian handling

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I didn't notice the check+swap before.
This commit is contained in:
Andrew Kelley 2025-08-28 18:30:32 -07:00
parent 530cc2c111
commit 7da9e4b35e
1 changed files with 18 additions and 19 deletions
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31
lib/std/tz.zig
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@ -1,3 +1,6 @@
//! The Time Zone Information Format (TZif)
//! https://datatracker.ietf.org/doc/html/rfc8536
const builtin = @import("builtin");
const std = @import("std.zig");
@ -58,31 +61,27 @@ pub const Tz = struct {
};
pub fn parse(allocator: Allocator, reader: *Reader) !Tz {
var legacy_header = try reader.takeStruct(Header, .little);
const legacy_header = try reader.takeStruct(Header, .big);
if (!std.mem.eql(u8, &legacy_header.magic, "TZif")) return error.BadHeader;
if (legacy_header.version != 0 and legacy_header.version != '2' and legacy_header.version != '3') return error.BadVersion;
if (legacy_header.version != 0 and legacy_header.version != '2' and legacy_header.version != '3')
return error.BadVersion;
if (builtin.target.cpu.arch.endian() != std.builtin.Endian.big) {
std.mem.byteSwapAllFields(@TypeOf(legacy_header.counts), &legacy_header.counts);
}
if (legacy_header.version == 0) {
if (legacy_header.version == 0)
return parseBlock(allocator, reader, legacy_header, true);
} else {
// If the format is modern, just skip over the legacy data
const skipv = legacy_header.counts.timecnt * 5 + legacy_header.counts.typecnt * 6 + legacy_header.counts.charcnt + legacy_header.counts.leapcnt * 8 + legacy_header.counts.isstdcnt + legacy_header.counts.isutcnt;
try reader.discardAll(skipv);
var header = try reader.takeStruct(Header, .little);
// If the format is modern, just skip over the legacy data
const skip_n = legacy_header.counts.timecnt * 5 +
legacy_header.counts.typecnt * 6 +
legacy_header.counts.charcnt + legacy_header.counts.leapcnt * 8 +
legacy_header.counts.isstdcnt + legacy_header.counts.isutcnt;
try reader.discardAll(skip_n);
var header = try reader.takeStruct(Header, .big);
if (!std.mem.eql(u8, &header.magic, "TZif")) return error.BadHeader;
if (header.version != '2' and header.version != '3') return error.BadVersion;
if (builtin.target.cpu.arch.endian() != std.builtin.Endian.big) {
std.mem.byteSwapAllFields(@TypeOf(header.counts), &header.counts);
}
return parseBlock(allocator, reader, header, false);
}
}
fn parseBlock(allocator: Allocator, reader: *Reader, header: Header, legacy: bool) !Tz {
if (header.counts.isstdcnt != 0 and header.counts.isstdcnt != header.counts.typecnt) return error.Malformed; // rfc8536: isstdcnt [...] MUST either be zero or equal to "typecnt"