DecodeHuffmanQuads()

static int fl::third_party::DecodeHuffmanQuads ( int32_t * vwxy, int nVals, int tabIdx, int bitsLeft, const unsigned char * buf, int bitOffset )

static

Definition at line 292 of file huffman.hpp.

{
    int i, v, w, x, y;
    int len, maxBits, cachedBits, padBits;
    unsigned int cache;
    unsigned char cw, *tBase;
 
    if (bitsLeft <= 0)
        return 0;
 
    tBase = (unsigned char *)quadTable + quadTabOffset[tabIdx];
    maxBits = quadTabMaxBits[tabIdx];
 
    /* initially fill cache with any partial byte */
    cache = 0;
    cachedBits = (8 - bitOffset) & 0x07;
    if (cachedBits)
        cache = (unsigned int)(*buf++) << (32 - cachedBits);
    bitsLeft -= cachedBits;
 
    i = padBits = 0;
    while (i < (nVals - 3)) {
        /* refill cache - assumes cachedBits <= 16 */
        if (bitsLeft >= 16) {
            /* load 2 new bytes into left-justified cache */
            cache |= (unsigned int)(*buf++) << (24 - cachedBits);
            cache |= (unsigned int)(*buf++) << (16 - cachedBits);
            cachedBits += 16;
            bitsLeft -= 16;
        } else {
            /* last time through, pad cache with zeros and drain cache */
            if (cachedBits + bitsLeft <= 0) return i;
            if (bitsLeft > 0)   cache |= (unsigned int)(*buf++) << (24 - cachedBits);
            if (bitsLeft > 8)   cache |= (unsigned int)(*buf++) << (16 - cachedBits);
            cachedBits += bitsLeft;
            bitsLeft = 0;
 
            cache &= (signed int)(int32_t)0x80000000 >> (cachedBits - 1);
            padBits = 10;
            cachedBits += padBits;  /* okay if this is > 32 (0's automatically shifted in from right) */
        }
 
        /* largest maxBits = 6, plus 4 for sign bits, so make sure cache has at least 10 bits */
        while (i < (nVals - 3) && cachedBits >= 10 ) {
            cw = tBase[cache >> (32 - maxBits)];
            len = GetHLenQ(cw);
            cachedBits -= len;
            cache <<= len;
 
            v = GetCWVQ(cw); if(v) {ApplySign(v, cache); cache <<= 1; cachedBits--;}
            w = GetCWWQ(cw); if(w) {ApplySign(w, cache); cache <<= 1; cachedBits--;}
            x = GetCWXQ(cw);    if(x) {ApplySign(x, cache); cache <<= 1; cachedBits--;}
            y = GetCWYQ(cw);    if(y) {ApplySign(y, cache); cache <<= 1; cachedBits--;}
 
            /* ran out of bits - okay (means we're done) */
            if (cachedBits < padBits)
                return i;
 
            *vwxy++ = v;
            *vwxy++ = w;
            *vwxy++ = x;
            *vwxy++ = y;
            i += 4;
        }
    }
 
    /* decoded max number of quad values */
    return i;
}

References ApplySign, FL_NOEXCEPT, GetCWVQ, GetCWWQ, GetCWXQ, GetCWYQ, GetHLenQ, quadTable, quadTabMaxBits, quadTabOffset, fl::x, and fl::y.

Referenced by DecodeHuffman().

Here is the caller graph for this function: