init

    pub fn init(input: *File.Reader) !Iterator {
        const end_record = try EndRecord.findFile(input);

        if (!isMaxInt(end_record.record_count_disk) and end_record.record_count_disk > end_record.record_count_total)
            return error.ZipDiskRecordCountTooLarge;

        if (end_record.disk_number != 0 or end_record.central_directory_disk_number != 0)
            return error.ZipMultiDiskUnsupported;

        {
            const counts_valid = !isMaxInt(end_record.record_count_disk) and !isMaxInt(end_record.record_count_total);
            if (counts_valid and end_record.record_count_disk != end_record.record_count_total)
                return error.ZipMultiDiskUnsupported;
        }

        var result: Iterator = .{
            .input = input,
            .cd_record_count = end_record.record_count_total,
            .cd_zip_offset = end_record.central_directory_offset,
            .cd_size = end_record.central_directory_size,
        };
        if (!end_record.need_zip64()) return result;

        const locator_end_offset: u64 = @as(u64, end_record.comment_len) + @sizeOf(EndRecord) + @sizeOf(EndLocator64);
        const stream_len = try input.getSize();

        if (locator_end_offset > stream_len)
            return error.ZipTruncated;
        try input.seekTo(stream_len - locator_end_offset);
        const locator = input.interface.takeStruct(EndLocator64, .little) catch |err| switch (err) {
            error.ReadFailed => return input.err.?,
            error.EndOfStream => |e| return e,
        };
        if (!std.mem.eql(u8, &locator.signature, &end_locator64_sig))
            return error.ZipBadLocatorSig;
        if (locator.zip64_disk_count != 0)
            return error.ZipUnsupportedZip64DiskCount;
        if (locator.total_disk_count != 1)
            return error.ZipMultiDiskUnsupported;

        try input.seekTo(locator.record_file_offset);

        const record64 = input.interface.takeStruct(EndRecord64, .little) catch |err| switch (err) {
            error.ReadFailed => return input.err.?,
            error.EndOfStream => |e| return e,
        };

        if (!std.mem.eql(u8, &record64.signature, &end_record64_sig))
            return error.ZipBadEndRecord64Sig;

        if (record64.end_record_size < @sizeOf(EndRecord64) - 12)
            return error.ZipEndRecord64SizeTooSmall;
        if (record64.end_record_size > @sizeOf(EndRecord64) - 12)
            return error.ZipEndRecord64UnhandledExtraData;

        if (record64.version_needed_to_extract > 45)
            return error.ZipUnsupportedVersion;

        {
            const is_multidisk = record64.disk_number != 0 or
                record64.central_directory_disk_number != 0 or
                record64.record_count_disk != record64.record_count_total;
            if (is_multidisk)
                return error.ZipMultiDiskUnsupported;
        }

        if (isMaxInt(end_record.record_count_total)) {
            result.cd_record_count = record64.record_count_total;
        } else if (end_record.record_count_total != record64.record_count_total)
            return error.Zip64RecordCountTotalMismatch;

        if (isMaxInt(end_record.central_directory_offset)) {
            result.cd_zip_offset = record64.central_directory_offset;
        } else if (end_record.central_directory_offset != record64.central_directory_offset)
            return error.Zip64CentralDirectoryOffsetMismatch;

        if (isMaxInt(end_record.central_directory_size)) {
            result.cd_size = record64.central_directory_size;
        } else if (end_record.central_directory_size != record64.central_directory_size)
            return error.Zip64CentralDirectorySizeMismatch;

        return result;
    }