1 files changed, 100 insertions, 0 deletions
diff --git a/src/zstd/examples/streaming_decompression.c b/src/zstd/examples/streaming_decompression.c
new file mode 100644
index 000000000..26eda3441
--- /dev/null
+++ b/src/zstd/examples/streaming_decompression.c
@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2016-2020, Yann Collet, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ * You may select, at your option, one of the above-listed licenses.
+ */
+
+
+#include <stdio.h>     // fprintf
+#include <stdlib.h>    // free
+#include <zstd.h>      // presumes zstd library is installed
+#include "common.h"    // Helper functions, CHECK(), and CHECK_ZSTD()
+
+static void decompressFile_orDie(const char* fname)
+{
+    FILE* const fin  = fopen_orDie(fname, "rb");
+    size_t const buffInSize = ZSTD_DStreamInSize();
+    void*  const buffIn  = malloc_orDie(buffInSize);
+    FILE* const fout = stdout;
+    size_t const buffOutSize = ZSTD_DStreamOutSize();  /* Guarantee to successfully flush at least one complete compressed block in all circumstances. */
+    void*  const buffOut = malloc_orDie(buffOutSize);
+
+    ZSTD_DCtx* const dctx = ZSTD_createDCtx();
+    CHECK(dctx != NULL, "ZSTD_createDCtx() failed!");
+
+    /* This loop assumes that the input file is one or more concatenated zstd
+     * streams. This example won't work if there is trailing non-zstd data at
+     * the end, but streaming decompression in general handles this case.
+     * ZSTD_decompressStream() returns 0 exactly when the frame is completed,
+     * and doesn't consume input after the frame.
+     */
+    size_t const toRead = buffInSize;
+    size_t read;
+    size_t lastRet = 0;
+    int isEmpty = 1;
+    while ( (read = fread_orDie(buffIn, toRead, fin)) ) {
+        isEmpty = 0;
+        ZSTD_inBuffer input = { buffIn, read, 0 };
+        /* Given a valid frame, zstd won't consume the last byte of the frame
+         * until it has flushed all of the decompressed data of the frame.
+         * Therefore, instead of checking if the return code is 0, we can
+         * decompress just check if input.pos < input.size.
+         */
+        while (input.pos < input.size) {
+            ZSTD_outBuffer output = { buffOut, buffOutSize, 0 };
+            /* The return code is zero if the frame is complete, but there may
+             * be multiple frames concatenated together. Zstd will automatically
+             * reset the context when a frame is complete. Still, calling
+             * ZSTD_DCtx_reset() can be useful to reset the context to a clean
+             * state, for instance if the last decompression call returned an
+             * error.
+             */
+            size_t const ret = ZSTD_decompressStream(dctx, &output , &input);
+            CHECK_ZSTD(ret);
+            fwrite_orDie(buffOut, output.pos, fout);
+            lastRet = ret;
+        }
+    }
+
+    if (isEmpty) {
+        fprintf(stderr, "input is empty\n");
+        exit(1);
+    }
+
+    if (lastRet != 0) {
+        /* The last return value from ZSTD_decompressStream did not end on a
+         * frame, but we reached the end of the file! We assume this is an
+         * error, and the input was truncated.
+         */
+        fprintf(stderr, "EOF before end of stream: %zu\n", lastRet);
+        exit(1);
+    }
+
+    ZSTD_freeDCtx(dctx);
+    fclose_orDie(fin);
+    fclose_orDie(fout);
+    free(buffIn);
+    free(buffOut);
+}
+
+
+int main(int argc, const char** argv)
+{
+    const char* const exeName = argv[0];
+
+    if (argc!=2) {
+        fprintf(stderr, "wrong arguments\n");
+        fprintf(stderr, "usage:\n");
+        fprintf(stderr, "%s FILE\n", exeName);
+        return 1;
+    }
+
+    const char* const inFilename = argv[1];
+
+    decompressFile_orDie(inFilename);
+    return 0;
+}