First working pass at refactor of loadZstdDictionary()

lib/compress/zstd_compress.c

@@ -2768,37 +2768,12 @@ static size_t ZSTD_checkDictNCount(short* normalizedCounter, unsigned dictMaxSym
     return 0;
 }
 
-
+size_t ZSTD_loadCEntropy(ZSTD_compressedBlockState_t* bs, void* workspace,
-/* Dictionary format :
+                         short* offcodeNCount, unsigned* offcodeMaxValue,
- * See :
+                         const void* const dict, size_t dictSize) 
- * https://github.com/facebook/zstd/blob/master/doc/zstd_compression_format.md#dictionary-format
- */
-/*! ZSTD_loadZstdDictionary() :
- * @return : dictID, or an error code
- *  assumptions : magic number supposed already checked
- *                dictSize supposed >= 8
- */
-static size_t ZSTD_loadZstdDictionary(ZSTD_compressedBlockState_t* bs,
-                                      ZSTD_matchState_t* ms,
-                                      ZSTD_cwksp* ws,
-                                      ZSTD_CCtx_params const* params,
-                                      const void* dict, size_t dictSize,
-                                      ZSTD_dictTableLoadMethod_e dtlm,
-                                      void* workspace)
 {
     const BYTE* dictPtr = (const BYTE*)dict;
-    const BYTE* const dictEnd = dictPtr + dictSize;
+    const BYTE* const dictEnd = dictPtr + dictSize - 8;
-    short offcodeNCount[MaxOff+1];
-    unsigned offcodeMaxValue = MaxOff;
-    size_t dictID;
-
-    ZSTD_STATIC_ASSERT(HUF_WORKSPACE_SIZE >= (1<<MAX(MLFSELog,LLFSELog)));
-    assert(dictSize >= 8);
-    assert(MEM_readLE32(dictPtr) == ZSTD_MAGIC_DICTIONARY);
-
-    dictPtr += 4;   /* skip magic number */
-    dictID = params->fParams.noDictIDFlag ? 0 :  MEM_readLE32(dictPtr);
-    dictPtr += 4;
 
     {   unsigned maxSymbolValue = 255;
         size_t const hufHeaderSize = HUF_readCTable((HUF_CElt*)bs->entropy.huf.CTable, &maxSymbolValue, dictPtr, dictEnd-dictPtr);
@@ -2808,7 +2783,7 @@ static size_t ZSTD_loadZstdDictionary(ZSTD_compressedBlockState_t* bs,
     }
 
     {   unsigned offcodeLog;
-        size_t const offcodeHeaderSize = FSE_readNCount(offcodeNCount, &offcodeMaxValue, &offcodeLog, dictPtr, dictEnd-dictPtr);
+        size_t const offcodeHeaderSize = FSE_readNCount(offcodeNCount, offcodeMaxValue, &offcodeLog, dictPtr, dictEnd-dictPtr);
         RETURN_ERROR_IF(FSE_isError(offcodeHeaderSize), dictionary_corrupted);
         RETURN_ERROR_IF(offcodeLog > OffFSELog, dictionary_corrupted);
         /* Defer checking offcodeMaxValue because we need to know the size of the dictionary content */
@@ -2856,6 +2831,43 @@ static size_t ZSTD_loadZstdDictionary(ZSTD_compressedBlockState_t* bs,
     bs->rep[1] = MEM_readLE32(dictPtr+4);
     bs->rep[2] = MEM_readLE32(dictPtr+8);
     dictPtr += 12;
+    DEBUGLOG(1, "size %u)", (unsigned)(dictPtr - (const BYTE*)dict));
+    return dictPtr - (const BYTE*)dict;
+}
+
+/* Dictionary format :
+ * See :
+ * https://github.com/facebook/zstd/blob/master/doc/zstd_compression_format.md#dictionary-format
+ */
+/*! ZSTD_loadZstdDictionary() :
+ * @return : dictID, or an error code
+ *  assumptions : magic number supposed already checked
+ *                dictSize supposed > 8
+ */
+static size_t ZSTD_loadZstdDictionary(ZSTD_compressedBlockState_t* bs,
+                                      ZSTD_matchState_t* ms,
+                                      ZSTD_cwksp* ws,
+                                      ZSTD_CCtx_params const* params,
+                                      const void* dict, size_t dictSize,
+                                      ZSTD_dictTableLoadMethod_e dtlm,
+                                      void* workspace)
+{
+    size_t dictID;
+    size_t eSize;
+    const BYTE* dictPtr = (const BYTE*)dict;
+    const BYTE* const dictEnd = dictPtr + dictSize;
+    short offcodeNCount[MaxOff+1];
+    unsigned offcodeMaxValue = MaxOff;
+    ZSTD_STATIC_ASSERT(HUF_WORKSPACE_SIZE >= (1<<MAX(MLFSELog,LLFSELog)));
+    assert(dictSize > 8);
+    assert(MEM_readLE32(dictPtr) == ZSTD_MAGIC_DICTIONARY);
+    eSize = ZSTD_loadCEntropy(bs, workspace, offcodeNCount, &offcodeMaxValue, dict, dictSize);
+
+    dictPtr += 4;   /* skip magic number */
+    dictID = params->fParams.noDictIDFlag ? 0 :  MEM_readLE32(dictPtr);
+    dictPtr += 4;
+
+    dictPtr += eSize - 8;   /* size of header + magic number already accounted for */
 
     {   size_t const dictContentSize = (size_t)(dictEnd - dictPtr);
         U32 offcodeMax = MaxOff;

lib/compress/zstd_compress_internal.h

@@ -930,7 +930,17 @@ MEM_STATIC void ZSTD_debugTable(const U32* table, U32 max)
 #if defined (__cplusplus)
 }
 #endif
+/* ===============================================================
+ * Public declarations
+ * These prototypes may be called from sources not in lib/compress
+ * =============================================================== */
 
+/* ZSTD_loadCEntropy() :
+ * dict : must point at beginning of a valid zstd dictionary.
+ * return : size of entropy tables read */
+size_t ZSTD_loadCEntropy(ZSTD_compressedBlockState_t* bs, void* workspace,
+                         short* offcodeNCount, unsigned* offcodeMaxValue,
+                         const void* const dict, size_t dictSize);
 
 /* ==============================================================
  * Private declarations