diff --git a/lib/common/huf.h b/lib/common/huf.h index 73d1ee56543..99bf85d6f4e 100644 --- a/lib/common/huf.h +++ b/lib/common/huf.h @@ -197,9 +197,22 @@ size_t HUF_readCTable (HUF_CElt* CTable, unsigned* maxSymbolValuePtr, const void /** HUF_getNbBitsFromCTable() : * Read nbBits from CTable symbolTable, for symbol `symbolValue` presumed <= HUF_SYMBOLVALUE_MAX - * Note 1 : is not inlined, as HUF_CElt definition is private */ + * Note 1 : If symbolValue > HUF_readCTableHeader(symbolTable).maxSymbolValue, returns 0 + * Note 2 : is not inlined, as HUF_CElt definition is private + */ U32 HUF_getNbBitsFromCTable(const HUF_CElt* symbolTable, U32 symbolValue); +typedef struct { + BYTE tableLog; + BYTE maxSymbolValue; + BYTE unused[sizeof(size_t) - 2]; +} HUF_CTableHeader; + +/** HUF_readCTableHeader() : + * @returns The header from the CTable specifying the tableLog and the maxSymbolValue. + */ +HUF_CTableHeader HUF_readCTableHeader(HUF_CElt const* ctable); + /* * HUF_decompress() does the following: * 1. select the decompression algorithm (X1, X2) based on pre-computed heuristics diff --git a/lib/compress/huf_compress.c b/lib/compress/huf_compress.c index 29871877a7f..3fe25789603 100644 --- a/lib/compress/huf_compress.c +++ b/lib/compress/huf_compress.c @@ -220,6 +220,25 @@ static void HUF_setValue(HUF_CElt* elt, size_t value) } } +HUF_CTableHeader HUF_readCTableHeader(HUF_CElt const* ctable) +{ + HUF_CTableHeader header; + ZSTD_memcpy(&header, ctable, sizeof(header)); + return header; +} + +static void HUF_writeCTableHeader(HUF_CElt* ctable, U32 tableLog, U32 maxSymbolValue) +{ + HUF_CTableHeader header; + HUF_STATIC_ASSERT(sizeof(ctable[0]) == sizeof(header)); + ZSTD_memset(&header, 0, sizeof(header)); + assert(tableLog < 256); + header.tableLog = (BYTE)tableLog; + assert(maxSymbolValue < 256); + header.maxSymbolValue = (BYTE)maxSymbolValue; + ZSTD_memcpy(ctable, &header, sizeof(header)); +} + typedef struct { HUF_CompressWeightsWksp wksp; BYTE bitsToWeight[HUF_TABLELOG_MAX + 1]; /* precomputed conversion table */ @@ -237,6 +256,9 @@ size_t HUF_writeCTable_wksp(void* dst, size_t maxDstSize, HUF_STATIC_ASSERT(HUF_CTABLE_WORKSPACE_SIZE >= sizeof(HUF_WriteCTableWksp)); + assert(HUF_readCTableHeader(CTable).maxSymbolValue == maxSymbolValue); + assert(HUF_readCTableHeader(CTable).tableLog == huffLog); + /* check conditions */ if (workspaceSize < sizeof(HUF_WriteCTableWksp)) return ERROR(GENERIC); if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge); @@ -283,7 +305,9 @@ size_t HUF_readCTable (HUF_CElt* CTable, unsigned* maxSymbolValuePtr, const void if (tableLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge); if (nbSymbols > *maxSymbolValuePtr+1) return ERROR(maxSymbolValue_tooSmall); - CTable[0] = tableLog; + *maxSymbolValuePtr = nbSymbols - 1; + + HUF_writeCTableHeader(CTable, tableLog, *maxSymbolValuePtr); /* Prepare base value per rank */ { U32 n, nextRankStart = 0; @@ -315,7 +339,6 @@ size_t HUF_readCTable (HUF_CElt* CTable, unsigned* maxSymbolValuePtr, const void { U32 n; for (n=0; n HUF_readCTableHeader(CTable).maxSymbolValue) + return 0; return (U32)HUF_getNbBits(ct[symbolValue]); } @@ -723,7 +748,8 @@ static void HUF_buildCTableFromTree(HUF_CElt* CTable, nodeElt const* huffNode, i HUF_setNbBits(ct + huffNode[n].byte, huffNode[n].nbBits); /* push nbBits per symbol, symbol order */ for (n=0; nCTable + 1, maxSymbolValue+1)); } - /* Zero unused symbols in CTable, so we can check it for validity */ - { - size_t const ctableSize = HUF_CTABLE_SIZE_ST(maxSymbolValue); - size_t const unusedSize = sizeof(table->CTable) - ctableSize * sizeof(HUF_CElt); - ZSTD_memset(table->CTable + ctableSize, 0, unusedSize); - } /* Write table description header */ { CHECK_V_F(hSize, HUF_writeCTable_wksp(op, dstSize, table->CTable, maxSymbolValue, huffLog,