int FAST_FUNC read_bunzip(bunzip_data *bd, char *outbuf, int len)
{
	const uint32_t *dbuf;
	int pos, current, previous;
	uint32_t CRC;

	/* If we already have error/end indicator, return it */
	if (bd->writeCount < 0)
		return bd->writeCount;

	dbuf = bd->dbuf;

	/* Register-cached state (hopefully): */
	pos = bd->writePos;
	current = bd->writeCurrent;
	CRC = bd->writeCRC; /* small loss on x86-32 (not enough regs), win on x86-64 */

	/* We will always have pending decoded data to write into the output
	   buffer unless this is the very first call (in which case we haven't
	   Huffman-decoded a block into the intermediate buffer yet). */
	if (bd->writeCopies) {

 dec_writeCopies:
		/* Inside the loop, writeCopies means extra copies (beyond 1) */
		--bd->writeCopies;

		/* Loop outputting bytes */
		for (;;) {

			/* If the output buffer is full, save cached state and return */
			if (--len < 0) {
				/* Unlikely branch.
				 * Use of "goto" instead of keeping code here
				 * helps compiler to realize this. */
				goto outbuf_full;
			}

			/* Write next byte into output buffer, updating CRC */
			*outbuf++ = current;
			CRC = (CRC << 8) ^ bd->crc32Table[(CRC >> 24) ^ current];

			/* Loop now if we're outputting multiple copies of this byte */
			if (bd->writeCopies) {
				/* Unlikely branch */
				/*--bd->writeCopies;*/
				/*continue;*/
				/* Same, but (ab)using other existing --writeCopies operation
				 * (and this if() compiles into just test+branch pair): */
				goto dec_writeCopies;
			}
 decode_next_byte:
			if (--bd->writeCount < 0)
				break; /* input block is fully consumed, need next one */

			/* Follow sequence vector to undo Burrows-Wheeler transform */
			previous = current;
			pos = dbuf[pos];
			current = (uint8_t)pos;
			pos >>= 8;

			/* After 3 consecutive copies of the same byte, the 4th
			 * is a repeat count.  We count down from 4 instead
			 * of counting up because testing for non-zero is faster */
			if (--bd->writeRunCountdown != 0) {
				if (current != previous)
					bd->writeRunCountdown = 4;
			} else {
				/* Unlikely branch */
				/* We have a repeated run, this byte indicates the count */
				bd->writeCopies = current;
				current = previous;
				bd->writeRunCountdown = 5;

				/* Sometimes there are just 3 bytes (run length 0) */
				if (!bd->writeCopies) goto decode_next_byte;

				/* Subtract the 1 copy we'd output anyway to get extras */
				--bd->writeCopies;
			}
		} /* for(;;) */

		/* Decompression of this input block completed successfully */
		bd->writeCRC = CRC = ~CRC;
		bd->totalCRC = ((bd->totalCRC << 1) | (bd->totalCRC >> 31)) ^ CRC;

		/* If this block had a CRC error, force file level CRC error */
		if (CRC != bd->headerCRC) {
			bd->totalCRC = bd->headerCRC + 1;
			return RETVAL_LAST_BLOCK;
		}
	}

	/* Refill the intermediate buffer by Huffman-decoding next block of input */
	{
		int r = get_next_block(bd);
		if (r) { /* error/end */
			bd->writeCount = r;
			return (r != RETVAL_LAST_BLOCK) ? r : len;
		}
	}

	CRC = ~0;
	pos = bd->writePos;
	current = bd->writeCurrent;
	goto decode_next_byte;

 outbuf_full:
	/* Output buffer is full, save cached state and return */
	bd->writePos = pos;
	bd->writeCurrent = current;
	bd->writeCRC = CRC;

	bd->writeCopies++;

	return 0;
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.