[libzstd] Allow compression parameters to be set with a cdict

The order you set parameters in the advanced API is not supposed to matter.
However, once you call `ZSTD_CCtx_refCDict()` the compression parameters
cannot be changed. Remove that restriction, and document what parameters
are used when using a CDict.

If the CCtx is in dictionary mode, then the CDict's parameters are used.
If the CCtx is not in dictionary mode, then its requested parameters are
used.

diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index 8de58b709649e9da6652dae56b115f8e18756a0d..987c7b90aa683e47b9d255950165b71f057a68a0 100644 (file)
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -450,11 +450,12 @@ size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value)
 
     switch(param)
     {
-    case ZSTD_c_compressionLevel:
-        RETURN_ERROR_IF(cctx->cdict, stage_wrong,
-                        "compression level is configured in cdict");
+    case ZSTD_c_nbWorkers:
+        RETURN_ERROR_IF((value!=0) && cctx->staticSize, parameter_unsupported,
+                        "MT not compatible with static alloc");
         break;
 
+    case ZSTD_c_compressionLevel:
     case ZSTD_c_windowLog:
     case ZSTD_c_hashLog:
     case ZSTD_c_chainLog:
@@ -462,20 +463,7 @@ size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value)
     case ZSTD_c_minMatch:
     case ZSTD_c_targetLength:
     case ZSTD_c_strategy:
-        RETURN_ERROR_IF(cctx->cdict, stage_wrong,
-                        "cparams are configured in cdict");
-        break;
-
-    case ZSTD_c_nbWorkers:
-        RETURN_ERROR_IF((value!=0) && cctx->staticSize, parameter_unsupported,
-                        "MT not compatible with static alloc");
-        break;
-
     case ZSTD_c_ldmHashRateLog:
-        RETURN_ERROR_IF(cctx->cdict, stage_wrong,
-                        "LDM hash rate log is configured in cdict");
-        break;
-
     case ZSTD_c_format:
     case ZSTD_c_contentSizeFlag:
     case ZSTD_c_checksumFlag:

diff --git a/lib/zstd.h b/lib/zstd.h
index a29c9669a11c95160dfd134442336ecbc77cd160..4373d6dfd3658cae03df0497af29f7ec85bde7dc 100644 (file)
--- a/lib/zstd.h
+++ b/lib/zstd.h
@@ -503,7 +503,10 @@ typedef enum { ZSTD_fast=1,
 
 typedef enum {
 
-    /* compression parameters */
+    /* compression parameters
+     * Note: When compressing with a ZSTD_CDict these parameters are superseded
+     * by the parameters used to construct the ZSTD_CDict. See ZSTD_CCtx_refCDict()
+     * for more info (superseded-by-cdict). */
     ZSTD_c_compressionLevel=100, /* Update all compression parameters according to pre-defined cLevel table
                               * Default level is ZSTD_CLEVEL_DEFAULT==3.
                               * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
@@ -705,7 +708,9 @@ ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, s
 /*! ZSTD_CCtx_refCDict() :
  *  Reference a prepared dictionary, to be used for all next compressed frames.
  *  Note that compression parameters are enforced from within CDict,
- *  and supercede any compression parameter previously set within CCtx.
+ *  and supersede any compression parameter previously set within CCtx.
+ *  The parameters ignored are labled as "superseded-by-cdict" in the ZSTD_cParameter enum docs.
+ *  The ignored parameters will be used again if the CCtx is returned to no-dictionary mode.
  *  The dictionary will remain valid for future compressed frames using same CCtx.
  * @result : 0, or an error code (which can be tested with ZSTD_isError()).
  *  Special : Referencing a NULL CDict means "return to no-dictionary mode".

diff --git a/tests/fuzzer.c b/tests/fuzzer.c
index 37531379516380cfd61adbbd03a00cd8f4068879..feb16c8061d6edb63477da24e8e1bfd5c7f5c120 100644 (file)
--- a/tests/fuzzer.c
+++ b/tests/fuzzer.c
@@ -1294,6 +1294,17 @@ static int basicUnitTests(U32 seed, double compressibility)
         }
         DISPLAYLEVEL(3, "OK \n");
 
+        DISPLAYLEVEL(3, "test%3i : ZSTD_CCtx_refCDict() then set parameters : ", testNb++);
+        {   ZSTD_CDict* const cdict = ZSTD_createCDict(CNBuffer, dictSize, 1);
+            CHECK_Z( ZSTD_CCtx_setParameter(cctx, ZSTD_c_compressionLevel, 1) );
+            CHECK_Z( ZSTD_CCtx_setParameter(cctx, ZSTD_c_hashLog, 12 ));
+            CHECK_Z( ZSTD_CCtx_refCDict(cctx, cdict) );
+            CHECK_Z( ZSTD_CCtx_setParameter(cctx, ZSTD_c_compressionLevel, 1) );
+            CHECK_Z( ZSTD_CCtx_setParameter(cctx, ZSTD_c_hashLog, 12 ));
+            ZSTD_freeCDict(cdict);
+        }
+        DISPLAYLEVEL(3, "OK \n");
+
         DISPLAYLEVEL(3, "test%3i : Dictionary with non-default repcodes : ", testNb++);
         { U32 u; for (u=0; u<nbSamples; u++) samplesSizes[u] = sampleUnitSize; }
         dictSize = ZDICT_trainFromBuffer(dictBuffer, dictSize,