[Octave-bug-tracker] [bug #60450] load fails to read MAT file

[John W. Eaton]

Follow-up Comment #13, bug #60450 (project octave):

The uncompress2 function is just the following.


/*
===========================================================================
     Decompresses the source buffer into the destination buffer.  *sourceLen
is
   the byte length of the source buffer. Upon entry, *destLen is the total
size
   of the destination buffer, which must be large enough to hold the entire
   uncompressed data. (The size of the uncompressed data must have been saved
   previously by the compressor and transmitted to the decompressor by some
   mechanism outside the scope of this compression library.) Upon exit,
   *destLen is the size of the decompressed data and *sourceLen is the number
   of source bytes consumed. Upon return, source + *sourceLen points to the
   first unused input byte.

     uncompress returns Z_OK if success, Z_MEM_ERROR if there was not enough
   memory, Z_BUF_ERROR if there was not enough room in the output buffer, or
   Z_DATA_ERROR if the input data was corrupted, including if the input data
is
   an incomplete zlib stream.
*/
int ZEXPORT uncompress2 (dest, destLen, source, sourceLen)
    Bytef *dest;
    uLongf *destLen;
    const Bytef *source;
    uLong *sourceLen;
{
    z_stream stream;
    int err;
    const uInt max = (uInt)-1;
    uLong len, left;
    Byte buf[1];    /* for detection of incomplete stream when *destLen == 0
*/

    len = *sourceLen;
    if (*destLen) {
        left = *destLen;
        *destLen = 0;
    }
    else {
        left = 1;
        dest = buf;
    }

    stream.next_in = (z_const Bytef *)source;
    stream.avail_in = 0;
    stream.zalloc = (alloc_func)0;
    stream.zfree = (free_func)0;
    stream.opaque = (voidpf)0;

    err = inflateInit(&stream);
    if (err != Z_OK) return err;

    stream.next_out = dest;
    stream.avail_out = 0;

    do {
        if (stream.avail_out == 0) {
            stream.avail_out = left > (uLong)max ? max : (uInt)left;
            left -= stream.avail_out;
        }
        if (stream.avail_in == 0) {
            stream.avail_in = len > (uLong)max ? max : (uInt)len;
            len -= stream.avail_in;
        }
        err = inflate(&stream, Z_NO_FLUSH);
    } while (err == Z_OK);

    *sourceLen -= len + stream.avail_in;
    if (dest != buf)
        *destLen = stream.total_out;
    else if (stream.total_out && err == Z_BUF_ERROR)
        left = 1;

    inflateEnd(&stream);
    return err == Z_STREAM_END ? Z_OK :
           err == Z_NEED_DICT ? Z_DATA_ERROR  :
           err == Z_BUF_ERROR && left + stream.avail_out ? Z_DATA_ERROR :
           err;
}


It only requires a few typedefs and the inflate function.  But the logic is
apparently wrong because the Z_BUF_ERROR or Z_DATA_ERROR status can escape the
function when the uncompress action appears to actually be correct and the
buffer limit is not actually exceeded.  So if someone could figure out how to
use inflate correctly, we could just avoid the missing function problem.

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