parse

pub fn parse(allocator: std.mem.Allocator, reader: anytype) !Tz {
    var legacy_header = try reader.readStruct(Header);
    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 (builtin.target.cpu.arch.endian() != std.builtin.Endian.big) {
        std.mem.byteSwapAllFields(@TypeOf(legacy_header.counts), &legacy_header.counts);
    }

    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.skipBytes(skipv, .{});

        var 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;
        if (builtin.target.cpu.arch.endian() != std.builtin.Endian.big) {
            std.mem.byteSwapAllFields(@TypeOf(header.counts), &header.counts);
        }

        return parseBlock(allocator, reader, header, false);
    }
}