Update Comment on `ZSTD_estimateCCtxSize()`

diff --git a/lib/zstd.h b/lib/zstd.h
index 52266ab56ebe0b67265b5814c92bcec81d03dd51..c2fbc3c9bea83f5d544c0dc0414f7d917c9a6c17 100644 (file)
--- a/lib/zstd.h
+++ b/lib/zstd.h
@@ -1221,14 +1221,23 @@ ZSTDLIB_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
 ***************************************/
 
 /*! ZSTD_estimate*() :
- *  These functions make it possible to estimate memory usage
- *  of a future {D,C}Ctx, before its creation.
- *  ZSTD_estimateCCtxSize() will provide a budget large enough for any compression level up to selected one.
- *  It will also consider src size to be arbitrarily "large", which is worst case.
- *  If srcSize is known to always be small, ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation.
- *  ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
- *  ZSTD_estimateCCtxSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1.
- *  Note : CCtx size estimation is only correct for single-threaded compression. */
+ *  These functions make it possible to estimate memory usage of a future
+ *  {D,C}Ctx, before its creation.
+ *
+ *  ZSTD_estimateCCtxSize() will provide a budget large enough for any
+ *  compression level up to selected one. Unlike ZSTD_estimateCStreamSize*(),
+ *  this estimate does not include space for a window buffer, so this estimate
+ *  is guaranteed to be enough for single-shot compressions, but not streaming
+ *  compressions. It will however assume the input may be arbitrarily large,
+ *  which is the worst case. If srcSize is known to always be small,
+ *  ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation.
+ *  ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with
+ *  ZSTD_getCParams() to create cParams from compressionLevel.
+ *  ZSTD_estimateCCtxSize_usingCCtxParams() can be used in tandem with
+ *  ZSTD_CCtxParams_setParameter().
+ *
+ *  Note: only single-threaded compression is supported. This function will
+ *  return an error code if ZSTD_c_nbWorkers is >= 1. */
 ZSTDLIB_API size_t ZSTD_estimateCCtxSize(int compressionLevel);
 ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
 ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);

diff --git a/tests/fuzzer.c b/tests/fuzzer.c
index 0ae0b39434c78776269d708733c6cfaafae4a304..3baa9b0793e642b1ed43a55e5de5f9ee5363b8f3 100644 (file)
--- a/tests/fuzzer.c
+++ b/tests/fuzzer.c
@@ -2156,9 +2156,9 @@ static int basicUnitTests(U32 const seed, double compressibility)
         size_t approxIndex = 0;
         size_t maxIndex = ((3U << 29) + (1U << ZSTD_WINDOWLOG_MAX)); /* ZSTD_CURRENT_MAX from zstd_compress_internal.h */
 
-        /* vastly overprovision space in a static context so that we can do all
-         * this without ever reallocating, which would reset the indices */
-        size_t const staticCCtxSize = 2 * ZSTD_estimateCCtxSize(22);
+        /* Provision enough space in a static context so that we can do all
+         * this without ever reallocating, which would reset the indices. */
+        size_t const staticCCtxSize = ZSTD_estimateCStreamSize(22);
         void* const staticCCtxBuffer = malloc(staticCCtxSize);
         ZSTD_CCtx* cctx = ZSTD_initStaticCCtx(staticCCtxBuffer, staticCCtxSize);