static FASTLZ_INLINE int FASTLZ_DECOMPRESSOR()

in fastlz/fastlz.c [420:549]

• 113 lines of code
• 20 McCabe index (conditional complexity)

static FASTLZ_INLINE int FASTLZ_DECOMPRESSOR(const void* input, int length, void* output, int maxout)
{
  const flzuint8* ip = (const flzuint8*) input;
  const flzuint8* ip_limit  = ip + length;
  flzuint8* op = (flzuint8*) output;
  flzuint8* op_limit = op + maxout;
  flzuint32 ctrl = (*ip++) & 31;
  int loop = 1;

  do
  {
    const flzuint8* ref = op;
    flzuint32 len = ctrl >> 5;
    flzuint32 ofs = (ctrl & 31) << 8;

    if(ctrl >= 32)
    {
#if FASTLZ_LEVEL==2
      flzuint8 code;
#endif
      len--;
      ref -= ofs;
      if (len == 7-1)
#if FASTLZ_LEVEL==1
        len += *ip++;
      ref -= *ip++;
#else
        do
        {
          code = *ip++;
          len += code;
        } while (code==255);
      code = *ip++;
      ref -= code;

      /* match from 16-bit distance */
      if(FASTLZ_UNEXPECT_CONDITIONAL(code==255))
      if(FASTLZ_EXPECT_CONDITIONAL(ofs==(31 << 8)))
      {
        ofs = (*ip++) << 8;
        ofs += *ip++;
        ref = op - ofs - MAX_DISTANCE;
      }
#endif
      
#ifdef FASTLZ_SAFE
      if (FASTLZ_UNEXPECT_CONDITIONAL(op + len + 3 > op_limit))
        return 0;

      if (FASTLZ_UNEXPECT_CONDITIONAL(ref-1 < (flzuint8 *)output))
        return 0;
#endif

      if(FASTLZ_EXPECT_CONDITIONAL(ip < ip_limit))
        ctrl = *ip++;
      else
        loop = 0;

      if(ref == op)
      {
        /* optimize copy for a run */
        flzuint8 b = ref[-1];
        *op++ = b;
        *op++ = b;
        *op++ = b;
        for(; len; --len)
          *op++ = b;
      }
      else
      {
#if !defined(FASTLZ_STRICT_ALIGN)
        const flzuint16* p;
        flzuint16* q;
#endif
        /* copy from reference */
        ref--;
        *op++ = *ref++;
        *op++ = *ref++;
        *op++ = *ref++;

#if !defined(FASTLZ_STRICT_ALIGN)
        /* copy a byte, so that now it's word aligned */
        if(len & 1)
        {
          *op++ = *ref++;
          len--;
        }

        /* copy 16-bit at once */
        q = (flzuint16*) op;
        op += len;
        p = (const flzuint16*) ref;
        for(len>>=1; len > 4; len-=4)
        {
          *q++ = *p++;
          *q++ = *p++;
          *q++ = *p++;
          *q++ = *p++;
        }
        for(; len; --len)
          *q++ = *p++;
#else
        for(; len; --len)
          *op++ = *ref++;
#endif
      }
    }
    else
    {
      ctrl++;
#ifdef FASTLZ_SAFE
      if (FASTLZ_UNEXPECT_CONDITIONAL(op + ctrl > op_limit))
        return 0;
      if (FASTLZ_UNEXPECT_CONDITIONAL(ip + ctrl > ip_limit))
        return 0;
#endif

      *op++ = *ip++; 
      for(--ctrl; ctrl; ctrl--)
        *op++ = *ip++;

      loop = FASTLZ_EXPECT_CONDITIONAL(ip < ip_limit);
      if(loop)
        ctrl = *ip++;
    }
  }
  while(FASTLZ_EXPECT_CONDITIONAL(loop));

  return op - (flzuint8*)output;
}