make stableSrc compatible with regular streaming API

including flushStream().

Now the only condition is for `input.size` to continuously grow.

lib/compress/zstd_compress.c

@@ -5338,7 +5338,7 @@ static size_t ZSTD_compressStream_generic(ZSTD_CStream* zcs,
     U32 someMoreWork = 1;
 
     /* check expectations */
-    DEBUGLOG(5, "ZSTD_compressStream_generic, flush=%u", (unsigned)flushMode);
+    DEBUGLOG(5, "ZSTD_compressStream_generic, flush=%i", (int)flushMode);
     if (zcs->appliedParams.inBufferMode == ZSTD_bm_buffered) {
         assert(zcs->inBuff != NULL);
         assert(zcs->inBuffSize > 0);
@@ -5424,9 +5424,8 @@ static size_t ZSTD_compressStream_generic(ZSTD_CStream* zcs,
                     if (!lastBlock)
                         assert(zcs->inBuffTarget <= zcs->inBuffSize);
                     zcs->inToCompress = zcs->inBuffPos;
-                } else {
+                } else { /* !inputBuffered, hence ZSTD_bm_stable */
                     unsigned const lastBlock = (ip + iSize == iend);
-                    assert(flushMode == ZSTD_e_end /* Already validated */);
                     cSize = lastBlock ?
                             ZSTD_compressEnd(zcs, cDst, oSize, ip, iSize) :
                             ZSTD_compressContinue(zcs, cDst, oSize, ip, iSize);
@@ -5533,11 +5532,10 @@ static size_t ZSTD_checkBufferStability(ZSTD_CCtx const* cctx,
 {
     if (cctx->appliedParams.inBufferMode == ZSTD_bm_stable) {
         ZSTD_inBuffer const expect = cctx->expectedInBuffer;
-        if (expect.src != input->src || expect.pos != input->pos || expect.size != input->size)
+        if (expect.src != input->src || expect.pos != input->pos)
             RETURN_ERROR(srcBuffer_wrong, "ZSTD_c_stableInBuffer enabled but input differs!");
-        if (endOp != ZSTD_e_end)
-            RETURN_ERROR(srcBuffer_wrong, "ZSTD_c_stableInBuffer can only be used with ZSTD_e_end!");
     }
+    (void)endOp;
     if (cctx->appliedParams.outBufferMode == ZSTD_bm_stable) {
         size_t const outBufferSize = output->size - output->pos;
         if (cctx->expectedOutBufferSize != outBufferSize)
@@ -5650,7 +5648,7 @@ size_t ZSTD_compressStream2( ZSTD_CCtx* cctx,
           && (endOp == ZSTD_e_continue)                             /* more to come */
           && (input->pos < ZSTD_BLOCKSIZE_MAX) ) {                  /* not even reached one block yet */
             cctx->expectedInBuffer = *input;
-            return (ZSTD_BLOCKSIZE_MAX - input->pos);               /* don't do anything : allows lazy compression parameters adaptation */
+            return (ZSTD_BLOCKSIZE_MAX - input->pos);               /* don't do anything : allows lazy adaptation of compression parameters */
         }
         FORWARD_IF_ERROR(ZSTD_CCtx_init_compressStream2(cctx, endOp, input->size), "CompressStream2 initialization failed");
         ZSTD_setBufferExpectations(cctx, output, input);    /* Set initial buffer expectations now that we've initialized */
@@ -6167,7 +6165,10 @@ size_t ZSTD_compressSequences(ZSTD_CCtx* const cctx, void* dst, size_t dstCapaci
  * @return : amount of data remaining to flush */
 size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output)
 {
-    ZSTD_inBuffer input = { NULL, 0, 0 };
+    ZSTD_inBuffer const nullInput = { NULL, 0, 0 };
+    int const stableInput = (zcs->appliedParams.inBufferMode == ZSTD_bm_stable);
+    ZSTD_inBuffer input = stableInput ? zcs->expectedInBuffer : nullInput;
+    input.size = input.pos; /* do not ingest more input during flush */
     return ZSTD_compressStream2(zcs, output, &input, ZSTD_e_flush);
 }
 

lib/zstd.h

@@ -1829,13 +1829,16 @@ ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const vo
  * Experimental parameter.
  * Default is 0 == disabled. Set to 1 to enable.
  *
- * Tells the compressor that the ZSTD_inBuffer will ALWAYS be the same
+ * Tells the compressor that input data presented with ZSTD_inBuffer
- * between calls, except for the modifications that zstd makes to pos (the
+ * will ALWAYS be the same between calls.
- * caller must not modify pos). This is checked by the compressor, and
+ * Technically, the @src pointer must never be changed,
- * compression will fail if it ever changes. This means the only flush
+ * and the @pos field can only be updated by zstd.
- * mode that makes sense is ZSTD_e_end, so zstd will error if ZSTD_e_end
+ * However, it's possible to increase the @size field,
- * is not used. The data in the ZSTD_inBuffer in the range [src, src + pos)
+ * allowing scenarios where more data can be appended after compressions starts.
- * MUST not be modified during compression or you will get data corruption.
+ * These conditions are checked by the compressor,
+ * and compression will fail if they are not respected.
+ * Also, data in the ZSTD_inBuffer within the range [src, src + pos)
+ * MUST not be modified during compression or it will result in data corruption.
  *
  * When this flag is enabled zstd won't allocate an input window buffer,
  * because the user guarantees it can reference the ZSTD_inBuffer until
@@ -1843,18 +1846,15 @@ ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const vo
  * large enough to fit a block (see ZSTD_c_stableOutBuffer). This will also
  * avoid the memcpy() from the input buffer to the input window buffer.
  *
- * NOTE: ZSTD_compressStream2() will error if ZSTD_e_flush is used.
- * That means this flag cannot be used with ZSTD_flushStream().
- *
  * NOTE: So long as the ZSTD_inBuffer always points to valid memory, using
  * this flag is ALWAYS memory safe, and will never access out-of-bounds
- * memory. However, compression WILL fail if you violate the preconditions.
+ * memory. However, compression WILL fail if conditions are not respected.
  *
  * WARNING: The data in the ZSTD_inBuffer in the range [src, src + pos) MUST
- * not be modified during compression or you will get data corruption. This
+ * not be modified during compression or it sill result in data corruption.
- * is because zstd needs to reference data in the ZSTD_inBuffer to find
+ * This is because zstd needs to reference data in the ZSTD_inBuffer to find
  * matches. Normally zstd maintains its own window buffer for this purpose,
- * but passing this flag tells zstd to use the user provided buffer.
+ * but passing this flag tells zstd to rely on user provided buffer instead.
  */
 #define ZSTD_c_stableInBuffer ZSTD_c_experimentalParam9
 

tests/zstreamtest.c

@@ -613,7 +613,7 @@ static int basicUnitTests(U32 seed, double compressibility)
             DISPLAYLEVEL(3, "OK (error detected : %s) \n", ZSTD_getErrorName(r));
     }   }
 
-    /* Complex context re-use scenario */
+    /* Compression state re-use scenario */
     DISPLAYLEVEL(3, "test%3i : context re-use : ", testNb++);
     ZSTD_freeCStream(zc);
     zc = ZSTD_createCStream();
@@ -634,8 +634,7 @@ static int basicUnitTests(U32 seed, double compressibility)
         CHECK_Z( ZSTD_compressStream(zc, &outBuff, &inBuff) );
         if (inBuff.pos != inBuff.size) goto _output_error;   /* entire input should be consumed */
         DISPLAYLEVEL(5, "end1 ");
-        { size_t const r = ZSTD_endStream(zc, &outBuff);
+        if (ZSTD_endStream(zc, &outBuff) != 0) goto _output_error;  /* error, or some data not flushed */
-            if (r != 0) goto _output_error; }  /* error, or some data not flushed */
     }
     /* use 2 */
     {   size_t const inSize = 1025;   /* will not continue, because tables auto-adjust and are therefore different size */
@@ -653,8 +652,7 @@ static int basicUnitTests(U32 seed, double compressibility)
         CHECK_Z( ZSTD_compressStream(zc, &outBuff, &inBuff) );
         if (inBuff.pos != inBuff.size) goto _output_error;   /* entire input should be consumed */
         DISPLAYLEVEL(5, "end2 ");
-        { size_t const r = ZSTD_endStream(zc, &outBuff);
+        if (ZSTD_endStream(zc, &outBuff) != 0) goto _output_error;   /* error, or some data not flushed */
-            if (r != 0) goto _output_error; }  /* error, or some data not flushed */
     }
     DISPLAYLEVEL(3, "OK \n");
 
@@ -786,16 +784,18 @@ static int basicUnitTests(U32 seed, double compressibility)
         CHECK(!(cSize < ZSTD_compressBound(CNBufferSize)), "cSize too large for test");
         CHECK_Z(cSize = ZSTD_compress2(cctx, compressedBuffer, cSize + 4, CNBuffer, CNBufferSize));
         CHECK_Z(cctxSize1 = ZSTD_sizeof_CCtx(cctx));
-        {   ZSTD_CCtx* cctx2 = ZSTD_createCCtx();
+        {   ZSTD_CCtx* const cctx2 = ZSTD_createCCtx();
+            assert(cctx2 != NULL);
             in.pos = out.pos = 0;
             CHECK_Z(ZSTD_compressStream2(cctx2, &out, &in, ZSTD_e_continue));
             CHECK(!(ZSTD_compressStream2(cctx2, &out, &in, ZSTD_e_end) == 0), "Not finished");
             CHECK_Z(cctxSize2 = ZSTD_sizeof_CCtx(cctx2));
             ZSTD_freeCCtx(cctx2);
         }
-        {   ZSTD_CCtx* cctx3 = ZSTD_createCCtx();
+        {   ZSTD_CCtx* const cctx3 = ZSTD_createCCtx();
             ZSTD_parameters params = ZSTD_getParams(0, CNBufferSize, 0);
             size_t cSize3;
+            assert(cctx3 != NULL);
             params.fParams.checksumFlag = 1;
             cSize3 = ZSTD_compress_advanced(cctx3, compressedBuffer, compressedBufferSize, CNBuffer, CNBufferSize, NULL, 0, params);
             CHECK_Z(cSize3);
@@ -808,8 +808,7 @@ static int basicUnitTests(U32 seed, double compressibility)
         DISPLAYLEVEL(3, "OK \n");
 
         DISPLAYLEVEL(3, "test%3i : ZSTD_compress2() doesn't modify user parameters : ", testNb++);
-        {
+        {   int stableInBuffer;
-            int stableInBuffer;
             int stableOutBuffer;
             CHECK_Z(ZSTD_CCtx_getParameter(cctx, ZSTD_c_stableInBuffer, &stableInBuffer));
             CHECK_Z(ZSTD_CCtx_getParameter(cctx, ZSTD_c_stableOutBuffer, &stableOutBuffer));
@@ -870,21 +869,24 @@ static int basicUnitTests(U32 seed, double compressibility)
         }
         DISPLAYLEVEL(3, "OK \n");
 
-        DISPLAYLEVEL(3, "test%3i : ZSTD_compressStream2() ZSTD_c_stableInBuffer with continue and flush : ", testNb++);
+        /* stableSrc + streaming */
+        DISPLAYLEVEL(3, "test%3i : ZSTD_c_stableInBuffer compatibility with compressStream, flushStream and endStream : ", testNb++);
+        CHECK_Z( ZSTD_initCStream(cctx, 1) );
+        CHECK_Z( ZSTD_CCtx_setParameter(cctx, ZSTD_c_stableInBuffer, 1) );
         in.src = CNBuffer;
-        in.size = CNBufferSize;
+        in.size = 100;
         in.pos = 0;
-        out.pos = 0;
+        {   ZSTD_outBuffer outBuf;
-        out.size = compressedBufferSize;
+            outBuf.dst = (char*)(compressedBuffer)+cSize;
-        CHECK_Z(ZSTD_CCtx_reset(cctx, ZSTD_reset_session_only));
+            outBuf.size = ZSTD_compressBound(500);
-        {   size_t const ret = ZSTD_compressStream2(cctx, &out, &in, ZSTD_e_continue);
+            outBuf.pos = 0;
-            CHECK(!ZSTD_isError(ret), "Must error");
+            CHECK_Z( ZSTD_compressStream(cctx, &outBuf, &in) );
-            CHECK(!(ZSTD_getErrorCode(ret) == ZSTD_error_srcBuffer_wrong), "Must be this error");
+            in.size = 200;
-        }
+            CHECK_Z( ZSTD_compressStream(cctx, &outBuf, &in) );
-        CHECK_Z(ZSTD_CCtx_reset(cctx, ZSTD_reset_session_only));
+            CHECK_Z( ZSTD_flushStream(cctx, &outBuf) );
-        {   size_t const ret = ZSTD_compressStream2(cctx, &out, &in, ZSTD_e_flush);
+            in.size = 300;
-            CHECK(!ZSTD_isError(ret), "Must error");
+            CHECK_Z( ZSTD_compressStream(cctx, &outBuf, &in) );
-            CHECK(!(ZSTD_getErrorCode(ret) == ZSTD_error_srcBuffer_wrong), "Must be this error");
+            if (ZSTD_endStream(cctx, &outBuf) != 0) goto _output_error;  /* error, or some data not flushed */
         }
         DISPLAYLEVEL(3, "OK \n");
 
@@ -902,6 +904,7 @@ static int basicUnitTests(U32 seed, double compressibility)
         CHECK_Z(ZSTD_CCtx_setParameter(cctx, ZSTD_c_stableOutBuffer, 1));
         in.pos = out.pos = 0;
         in.size = MIN(CNBufferSize, 10);
+        out.size = compressedBufferSize;
         CHECK_Z(ZSTD_compressStream2(cctx, &out, &in, ZSTD_e_flush));
         in.pos = 0;
         in.size = CNBufferSize - in.size;