EndRecord

pub const EndRecord = extern struct

File

Code

pub const EndRecord = extern struct {
    signature: [4]u8 align(1),
    disk_number: u16 align(1),
    central_directory_disk_number: u16 align(1),
    record_count_disk: u16 align(1),
    record_count_total: u16 align(1),
    central_directory_size: u32 align(1),
    central_directory_offset: u32 align(1),
    comment_len: u16 align(1),

    pub fn need_zip64(self: EndRecord) bool {
        return isMaxInt(self.record_count_disk) or
            isMaxInt(self.record_count_total) or
            isMaxInt(self.central_directory_size) or
            isMaxInt(self.central_directory_offset);
    }

    pub const FindBufferError = error{ ZipNoEndRecord, ZipTruncated };

    /// TODO audit this logic
    pub fn findBuffer(buffer: []const u8) FindBufferError!EndRecord {
        const pos = std.mem.lastIndexOf(u8, buffer, &end_record_sig) orelse return error.ZipNoEndRecord;
        if (pos + @sizeOf(EndRecord) > buffer.len) return error.EndOfStream;
        const record_ptr: *EndRecord = @ptrCast(buffer[pos..][0..@sizeOf(EndRecord)]);
        var record = record_ptr.*;
        if (!is_le) std.mem.byteSwapAllFields(EndRecord, &record);
        return record;
    }

    pub const FindFileError = File.Reader.SizeError || File.SeekError || File.Reader.Error || error{
        ZipNoEndRecord,
        EndOfStream,
        ReadFailed,
    };

    pub fn findFile(fr: *File.Reader) FindFileError!EndRecord {
        const end_pos = try fr.getSize();

        var buf: [@sizeOf(EndRecord) + std.math.maxInt(u16)]u8 = undefined;
        const record_len_max = @min(end_pos, buf.len);
        var loaded_len: u32 = 0;
        var comment_len: u16 = 0;
        while (true) {
            const record_len: u32 = @as(u32, comment_len) + @sizeOf(EndRecord);
            if (record_len > record_len_max)
                return error.ZipNoEndRecord;

            if (record_len > loaded_len) {
                const new_loaded_len = @min(loaded_len + 300, record_len_max);
                const read_len = new_loaded_len - loaded_len;

                try fr.seekTo(end_pos - @as(u64, new_loaded_len));
                const read_buf: []u8 = buf[buf.len - new_loaded_len ..][0..read_len];
                fr.interface.readSliceAll(read_buf) catch |err| switch (err) {
                    error.ReadFailed => return fr.err.?,
                    error.EndOfStream => |e| return e,
                };
                loaded_len = new_loaded_len;
            }

            const record_bytes = buf[buf.len - record_len ..][0..@sizeOf(EndRecord)];
            if (std.mem.eql(u8, record_bytes[0..4], &end_record_sig) and
                std.mem.readInt(u16, record_bytes[20..22], .little) == comment_len)
            {
                const record: *align(1) EndRecord = @ptrCast(record_bytes.ptr);
                if (!is_le) std.mem.byteSwapAllFields(EndRecord, record);
                return record.*;
            }

            if (comment_len == std.math.maxInt(u16))
                return error.ZipNoEndRecord;
            comment_len += 1;
        }
    }
}