FreeBSD/Linux Kernel Cross Reference
sys/contrib/zstd/examples/streaming_compression.c

     /*
      * Copyright (c) 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>     // printf
    #include <stdlib.h>    // free
    #include <string.h>    // memset, strcat, strlen
    #include <zstd.h>      // presumes zstd library is installed
    #include "common.h"    // Helper functions, CHECK(), and CHECK_ZSTD()
    
    static void compressFile_orDie(const char* fname, const char* outName, int cLevel,
                                   int nbThreads)
    {
        fprintf (stderr, "Starting compression of %s with level %d, using %d threads\n",
                 fname, cLevel, nbThreads);
    
        /* Open the input and output files. */
        FILE* const fin  = fopen_orDie(fname, "rb");
        FILE* const fout = fopen_orDie(outName, "wb");
        /* Create the input and output buffers.
         * They may be any size, but we recommend using these functions to size them.
         * Performance will only suffer significantly for very tiny buffers.
         */
        size_t const buffInSize = ZSTD_CStreamInSize();
        void*  const buffIn  = malloc_orDie(buffInSize);
        size_t const buffOutSize = ZSTD_CStreamOutSize();
        void*  const buffOut = malloc_orDie(buffOutSize);
    
        /* Create the context. */
        ZSTD_CCtx* const cctx = ZSTD_createCCtx();
        CHECK(cctx != NULL, "ZSTD_createCCtx() failed!");
    
        /* Set any parameters you want.
         * Here we set the compression level, and enable the checksum.
         */
        CHECK_ZSTD( ZSTD_CCtx_setParameter(cctx, ZSTD_c_compressionLevel, cLevel) );
        CHECK_ZSTD( ZSTD_CCtx_setParameter(cctx, ZSTD_c_checksumFlag, 1) );
        ZSTD_CCtx_setParameter(cctx, ZSTD_c_nbWorkers, nbThreads);
    
        /* This loop read from the input file, compresses that entire chunk,
         * and writes all output produced to the output file.
         */
        size_t const toRead = buffInSize;
        for (;;) {
            size_t read = fread_orDie(buffIn, toRead, fin);
            /* Select the flush mode.
             * If the read may not be finished (read == toRead) we use
             * ZSTD_e_continue. If this is the last chunk, we use ZSTD_e_end.
             * Zstd optimizes the case where the first flush mode is ZSTD_e_end,
             * since it knows it is compressing the entire source in one pass.
             */
            int const lastChunk = (read < toRead);
            ZSTD_EndDirective const mode = lastChunk ? ZSTD_e_end : ZSTD_e_continue;
            /* Set the input buffer to what we just read.
             * We compress until the input buffer is empty, each time flushing the
             * output.
             */
            ZSTD_inBuffer input = { buffIn, read, 0 };
            int finished;
            do {
                /* Compress into the output buffer and write all of the output to
                 * the file so we can reuse the buffer next iteration.
                 */
                ZSTD_outBuffer output = { buffOut, buffOutSize, 0 };
                size_t const remaining = ZSTD_compressStream2(cctx, &output , &input, mode);
                CHECK_ZSTD(remaining);
                fwrite_orDie(buffOut, output.pos, fout);
                /* If we're on the last chunk we're finished when zstd returns 0,
                 * which means its consumed all the input AND finished the frame.
                 * Otherwise, we're finished when we've consumed all the input.
                 */
                finished = lastChunk ? (remaining == 0) : (input.pos == input.size);
            } while (!finished);
            CHECK(input.pos == input.size,
                  "Impossible: zstd only returns 0 when the input is completely consumed!");
    
            if (lastChunk) {
                break;
            }
        }
    
        ZSTD_freeCCtx(cctx);
        fclose_orDie(fout);
        fclose_orDie(fin);
        free(buffIn);
        free(buffOut);
    }
    
    
    static char* createOutFilename_orDie(const char* filename)
    {
        size_t const inL = strlen(filename);
       size_t const outL = inL + 5;
       void* const outSpace = malloc_orDie(outL);
       memset(outSpace, 0, outL);
       strcat(outSpace, filename);
       strcat(outSpace, ".zst");
       return (char*)outSpace;
   }
   
   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 [LEVEL] [THREADS]\n", exeName);
           return 1;
       }
   
       int cLevel = 1;
       int nbThreads = 4;
   
       if (argc >= 3) {
         cLevel = atoi (argv[2]);
         CHECK(cLevel != 0, "can't parse LEVEL!");
       }
   
       if (argc >= 4) {
         nbThreads = atoi (argv[3]);
         CHECK(nbThreads != 0, "can't parse THREADS!");
       }
   
       const char* const inFilename = argv[1];
   
       char* const outFilename = createOutFilename_orDie(inFilename);
       compressFile_orDie(inFilename, outFilename, cLevel, nbThreads);
   
       free(outFilename);   /* not strictly required, since program execution stops there,
                             * but some static analyzer may complain otherwise */
       return 0;
   }

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