next

    pub fn next(self: *Iterator) !?Entry {
        if (self.cd_record_index == self.cd_record_count) {
            if (self.cd_record_offset != self.cd_size)
                return if (self.cd_size > self.cd_record_offset)
                    error.ZipCdOversized
                else
                    error.ZipCdUndersized;

            return null;
        }

        const header_zip_offset = self.cd_zip_offset + self.cd_record_offset;
        const input = self.input;
        try input.seekTo(header_zip_offset);
        const header = input.interface.takeStruct(CentralDirectoryFileHeader, .little) catch |err| switch (err) {
            error.ReadFailed => return input.err.?,
            error.EndOfStream => |e| return e,
        };
        if (!std.mem.eql(u8, &header.signature, &central_file_header_sig))
            return error.ZipBadCdOffset;

        self.cd_record_index += 1;
        self.cd_record_offset += @sizeOf(CentralDirectoryFileHeader) + header.filename_len + header.extra_len + header.comment_len;

        // Note: checking the version_needed_to_extract doesn't seem to be helpful, i.e. the zip file
        // at https://github.com/ninja-build/ninja/releases/download/v1.12.0/ninja-linux.zip
        // has an undocumented version 788 but extracts just fine.

        if (header.flags.encrypted)
            return error.ZipEncryptionUnsupported;
        // TODO: check/verify more flags
        if (header.disk_number != 0)
            return error.ZipMultiDiskUnsupported;

        var extents: FileExtents = .{
            .uncompressed_size = header.uncompressed_size,
            .compressed_size = header.compressed_size,
            .local_file_header_offset = header.local_file_header_offset,
        };

        if (header.extra_len > 0) {
            var extra_buf: [std.math.maxInt(u16)]u8 = undefined;
            const extra = extra_buf[0..header.extra_len];

            try input.seekTo(header_zip_offset + @sizeOf(CentralDirectoryFileHeader) + header.filename_len);
            input.interface.readSliceAll(extra) catch |err| switch (err) {
                error.ReadFailed => return input.err.?,
                error.EndOfStream => |e| return e,
            };

            var extra_offset: usize = 0;
            while (extra_offset + 4 <= extra.len) {
                const header_id = std.mem.readInt(u16, extra[extra_offset..][0..2], .little);
                const data_size = std.mem.readInt(u16, extra[extra_offset..][2..4], .little);
                const end = extra_offset + 4 + data_size;
                if (end > extra.len)
                    return error.ZipBadExtraFieldSize;
                const data = extra[extra_offset + 4 .. end];
                switch (@as(ExtraHeader, @fromBackingInt(@intCast(header_id)))) {
                    .zip64_info => try readZip64FileExtents(CentralDirectoryFileHeader, header, &extents, data),
                    else => {}, // ignore
                }
                extra_offset = end;
            }
        }

        return .{
            .version_needed_to_extract = header.version_needed_to_extract,
            .flags = header.flags,
            .compression_method = header.compression_method,
            .last_modification_time = header.last_modification_time,
            .last_modification_date = header.last_modification_date,
            .header_zip_offset = header_zip_offset,
            .crc32 = header.crc32,
            .filename_len = header.filename_len,
            .compressed_size = extents.compressed_size,
            .uncompressed_size = extents.uncompressed_size,
            .file_offset = extents.local_file_header_offset,
        };
    }