librocksdb-sys 6.20.3

Native bindings to librocksdb
Documentation 
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/*
 * 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, exit
#include <stdio.h>     // printf
#include <string.h>    // strerror
#include <errno.h>     // errno
#include <sys/stat.h>  // stat
#include <zstd.h>      // presumes zstd library is installed


static off_t fsize_orDie(const char *filename)
{
    struct stat st;
    if (stat(filename, &st) == 0) return st.st_size;
    /* error */
    perror(filename);
    exit(1);
}

static FILE* fopen_orDie(const char *filename, const char *instruction)
{
    FILE* const inFile = fopen(filename, instruction);
    if (inFile) return inFile;
    /* error */
    perror(filename);
    exit(2);
}

static void* malloc_orDie(size_t size)
{
    void* const buff = malloc(size);
    if (buff) return buff;
    /* error */
    perror("malloc");
    exit(3);
}

static void* loadFile_orDie(const char* fileName, size_t* size)
{
    off_t const buffSize = fsize_orDie(fileName);
    FILE* const inFile = fopen_orDie(fileName, "rb");
    void* const buffer = malloc_orDie(buffSize);
    size_t const readSize = fread(buffer, 1, buffSize, inFile);
    if (readSize != (size_t)buffSize) {
        fprintf(stderr, "fread: %s : %s \n", fileName, strerror(errno));
        exit(4);
    }
    fclose(inFile);
    *size = buffSize;
    return buffer;
}

static void saveFile_orDie(const char* fileName, const void* buff, size_t buffSize)
{
    FILE* const oFile = fopen_orDie(fileName, "wb");
    size_t const wSize = fwrite(buff, 1, buffSize, oFile);
    if (wSize != (size_t)buffSize) {
        fprintf(stderr, "fwrite: %s : %s \n", fileName, strerror(errno));
        exit(5);
    }
    if (fclose(oFile)) {
        perror(fileName);
        exit(6);
    }
}

/* createDict() :
   `dictFileName` is supposed to have been created using `zstd --train` */
static ZSTD_CDict* createCDict_orDie(const char* dictFileName, int cLevel)
{
    size_t dictSize;
    printf("loading dictionary %s \n", dictFileName);
    void* const dictBuffer = loadFile_orDie(dictFileName, &dictSize);
    ZSTD_CDict* const cdict = ZSTD_createCDict(dictBuffer, dictSize, cLevel);
    if (!cdict) {
        fprintf(stderr, "ZSTD_createCDict error \n");
        exit(7);
    }
    free(dictBuffer);
    return cdict;
}


static void compress(const char* fname, const char* oname, const ZSTD_CDict* cdict)
{
    size_t fSize;
    void* const fBuff = loadFile_orDie(fname, &fSize);
    size_t const cBuffSize = ZSTD_compressBound(fSize);
    void* const cBuff = malloc_orDie(cBuffSize);

    ZSTD_CCtx* const cctx = ZSTD_createCCtx();
    if (cctx==NULL) { fprintf(stderr, "ZSTD_createCCtx() error \n"); exit(10); }
    size_t const cSize = ZSTD_compress_usingCDict(cctx, cBuff, cBuffSize, fBuff, fSize, cdict);
    if (ZSTD_isError(cSize)) {
        fprintf(stderr, "error compressing %s : %s \n", fname, ZSTD_getErrorName(cSize));
        exit(7);
    }

    saveFile_orDie(oname, cBuff, cSize);

    /* success */
    printf("%25s : %6u -> %7u - %s \n", fname, (unsigned)fSize, (unsigned)cSize, oname);

    ZSTD_freeCCtx(cctx);   /* never fails */
    free(fBuff);
    free(cBuff);
}


static char* createOutFilename_orDie(const char* filename)
{
    size_t const inL = strlen(filename);
    size_t const outL = inL + 5;
    void* 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];
    int const cLevel = 3;

    if (argc<3) {
        fprintf(stderr, "wrong arguments\n");
        fprintf(stderr, "usage:\n");
        fprintf(stderr, "%s [FILES] dictionary\n", exeName);
        return 1;
    }

    /* load dictionary only once */
    const char* const dictName = argv[argc-1];
    ZSTD_CDict* const dictPtr = createCDict_orDie(dictName, cLevel);

    int u;
    for (u=1; u<argc-1; u++) {
        const char* inFilename = argv[u];
        char* const outFilename = createOutFilename_orDie(inFilename);
        compress(inFilename, outFilename, dictPtr);
        free(outFilename);
    }

    ZSTD_freeCDict(dictPtr);
    printf("All %u files compressed. \n", argc-2);
    return 0;
}