add multiple_simple_compression.c

examples/multiple_simple_compression.c

@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 2016-present, 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 <stdlib.h>    // malloc, free, exit
+#include <stdio.h>     // fprintf, perror, fopen, etc.
+#include <string.h>    // strlen, strcat, memset, strerror
+#include <errno.h>     // errno
+#include <sys/stat.h>  // stat
+#include <zstd.h>      // presumes zstd library is installed
+#include "utils.h"
+
+typedef struct {
+    void* fBuffer;
+    void* cBuffer;
+    size_t fBufferSize;
+    size_t cBufferSize;
+    ZSTD_CCtx* cctx;
+} resources;
+
+/*
+ * allocate memory for buffers big enough to compress all files
+ * as well as memory for output file name (outFilename)
+ */
+static resources createResources_orDie(int argc, const char** argv, char **outFilename)
+{
+    size_t maxFilenameLength=0;
+    size_t maxFileSize = 0;
+
+    int argNb;
+    for (argNb = 1; argNb < argc; argNb++) {
+      const char* const filename = argv[argNb];
+      size_t const filenameLength = strlen(filename);
+      size_t const fileSize = fsize_orDie(filename);
+
+      if (filenameLength > maxFilenameLength) maxFilenameLength = filenameLength;
+      if (fileSize > maxFileSize) maxFileSize = fileSize;
+    }
+
+    resources ress;
+    ress.fBufferSize = maxFileSize;
+    ress.cBufferSize = ZSTD_compressBound(maxFileSize);
+
+    *outFilename = (char*)malloc_orDie(maxFilenameLength + 5);
+    ress.fBuffer = malloc_orDie(ress.fBufferSize);
+    ress.cBuffer = malloc_orDie(ress.cBufferSize);
+    ress.cctx = ZSTD_createCCtx();
+    if (ress.cctx==NULL) { fprintf(stderr, "ZSTD_createCCtx() error \n"); exit(10); }
+    return ress;
+}
+
+static void freeResources(resources ress, char *outFilename)
+{
+    free(ress.fBuffer);
+    free(ress.cBuffer);
+    ZSTD_freeCCtx(ress.cctx);   /* never fails */
+    free(outFilename);
+}
+
+/* compress with pre-allocated context (ZSTD_CCtx) and input/output buffers*/
+static void compressFile_orDie(resources ress, const char* fname, const char* oname)
+{
+    size_t fSize;
+    loadFile_orDie(fname, &fSize, ress.fBuffer, ress.fBufferSize);
+
+    size_t const cSize = ZSTD_compressCCtx(ress.cctx, ress.cBuffer, ress.cBufferSize, ress.fBuffer, fSize, 1);
+    if (ZSTD_isError(cSize)) {
+        fprintf(stderr, "error compressing %s : %s \n", fname, ZSTD_getErrorName(cSize));
+        exit(8);
+    }
+
+    saveFile_orDie(oname, ress.cBuffer, cSize);
+
+    /* success */
+    printf("%25s : %6u -> %7u - %s \n", fname, (unsigned)fSize, (unsigned)cSize, oname);
+}
+
+int main(int argc, const char** argv)
+{
+    const char* const exeName = argv[0];
+
+    if (argc<2) {
+        printf("wrong arguments\n");
+        printf("usage:\n");
+        printf("%s FILE(s)\n", exeName);
+        return 1;
+    }
+
+    /* memory allocation for outFilename and resources */
+    char* outFilename;
+    resources ress = createResources_orDie(argc, argv, &outFilename); 
+
+    /* compress files with shared context, input and output buffers */
+    int argNb;
+    for (argNb = 1; argNb < argc; argNb++) {
+        const char* const inFilename = argv[argNb];
+        memset(outFilename, 0, 1);
+        strcat(outFilename, inFilename);
+        strcat(outFilename, ".zst");
+        compressFile_orDie(ress, inFilename, outFilename);
+    }
+
+    /* free momery */
+    freeResources(ress,outFilename);
+
+    printf("compressed %i files \n", argc-1);
+
+    return 0;
+}

examples/utils.h

@@ -51,10 +51,11 @@ static size_t fsize_orDie(const char *filename)
 
     off_t const fileSize = st.st_size;
     size_t const size = (size_t)fileSize;
-    /* if off_t -> size_t type conversion results in discrepancy,
+    /* 1. fileSize should be non-negative,
-     * the file size is too big for at least one type to handle.
+     * 2. if off_t -> size_t type conversion results in discrepancy,
+     *    the file size is too large for type size_t.
      */
-    if (size != fileSize) {   /* narrowcast overflow */
+    if ((fileSize < 0) || (fileSize != (off_t)size)) { 
         fprintf(stderr, "%s : filesize too large \n", filename);
         exit(ERROR_largeFile);
     }