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ext/zstd/contrib/linux-kernel/lib/zstd/entropy_common.c  view on Meta::CPAN

				threshold >>= 1;
			}

			if ((ip <= iend - 7) || (ip + (bitCount >> 3) <= iend - 4)) {
				ip += bitCount >> 3;
				bitCount &= 7;
			} else {
				bitCount -= (int)(8 * (iend - 4 - ip));
				ip = iend - 4;
			}
			bitStream = ZSTD_readLE32(ip) >> (bitCount & 31);
		}
	} /* while ((remaining>1) & (charnum<=*maxSVPtr)) */
	if (remaining != 1)
		return ERROR(corruption_detected);
	if (bitCount > 32)
		return ERROR(corruption_detected);
	*maxSVPtr = charnum - 1;

	ip += (bitCount + 7) >> 3;
	return ip - istart;
}

/*! HUF_readStats() :
	Read compact Huffman tree, saved by HUF_writeCTable().
	`huffWeight` is destination buffer.
	`rankStats` is assumed to be a table of at least HUF_TABLELOG_MAX U32.
	@return : size read from `src` , or an error Code .
	Note : Needed by HUF_readCTable() and HUF_readDTableX?() .
*/
size_t HUF_readStats_wksp(BYTE *huffWeight, size_t hwSize, U32 *rankStats, U32 *nbSymbolsPtr, U32 *tableLogPtr, const void *src, size_t srcSize, void *workspace, size_t workspaceSize)
{
	U32 weightTotal;
	const BYTE *ip = (const BYTE *)src;
	size_t iSize;
	size_t oSize;

	if (!srcSize)
		return ERROR(srcSize_wrong);
	iSize = ip[0];
	/* memset(huffWeight, 0, hwSize);   */ /* is not necessary, even though some analyzer complain ... */

	if (iSize >= 128) { /* special header */
		oSize = iSize - 127;
		iSize = ((oSize + 1) / 2);
		if (iSize + 1 > srcSize)
			return ERROR(srcSize_wrong);
		if (oSize >= hwSize)
			return ERROR(corruption_detected);
		ip += 1;
		{
			U32 n;
			for (n = 0; n < oSize; n += 2) {
				huffWeight[n] = ip[n / 2] >> 4;
				huffWeight[n + 1] = ip[n / 2] & 15;
			}
		}
	} else {						 /* header compressed with FSE (normal case) */
		if (iSize + 1 > srcSize)
			return ERROR(srcSize_wrong);
		oSize = FSE_decompress_wksp(huffWeight, hwSize - 1, ip + 1, iSize, 6, workspace, workspaceSize); /* max (hwSize-1) values decoded, as last one is implied */
		if (FSE_isError(oSize))
			return oSize;
	}

	/* collect weight stats */
	memset(rankStats, 0, (HUF_TABLELOG_MAX + 1) * sizeof(U32));
	weightTotal = 0;
	{
		U32 n;
		for (n = 0; n < oSize; n++) {
			if (huffWeight[n] >= HUF_TABLELOG_MAX)
				return ERROR(corruption_detected);
			rankStats[huffWeight[n]]++;
			weightTotal += (1 << huffWeight[n]) >> 1;
		}
	}
	if (weightTotal == 0)
		return ERROR(corruption_detected);

	/* get last non-null symbol weight (implied, total must be 2^n) */
	{
		U32 const tableLog = BIT_highbit32(weightTotal) + 1;
		if (tableLog > HUF_TABLELOG_MAX)
			return ERROR(corruption_detected);
		*tableLogPtr = tableLog;
		/* determine last weight */
		{
			U32 const total = 1 << tableLog;
			U32 const rest = total - weightTotal;
			U32 const verif = 1 << BIT_highbit32(rest);
			U32 const lastWeight = BIT_highbit32(rest) + 1;
			if (verif != rest)
				return ERROR(corruption_detected); /* last value must be a clean power of 2 */
			huffWeight[oSize] = (BYTE)lastWeight;
			rankStats[lastWeight]++;
		}
	}

	/* check tree construction validity */
	if ((rankStats[1] < 2) || (rankStats[1] & 1))
		return ERROR(corruption_detected); /* by construction : at least 2 elts of rank 1, must be even */

	/* results */
	*nbSymbolsPtr = (U32)(oSize + 1);
	return iSize + 1;
}