/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
* 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 <zstd.h>      // presumes zstd library is installed
#include "common.h"    // Helper functions, CHECK(), and CHECK_ZSTD()

/* createDict() :
  `dictFileName` is supposed to have been created using `zstd --train` */
static ZSTD_DDict* createDict_orDie(const char* dictFileName)
{
   size_t dictSize;
   printf("loading dictionary %s \n", dictFileName);
   void* const dictBuffer = mallocAndLoadFile_orDie(dictFileName, &dictSize);
   ZSTD_DDict* const ddict = ZSTD_createDDict(dictBuffer, dictSize);
   CHECK(ddict != NULL, "ZSTD_createDDict() failed!");
   free(dictBuffer);
   return ddict;
}

static void decompress(const char* fname, const ZSTD_DDict* ddict)
{
   size_t cSize;
   void* const cBuff = mallocAndLoadFile_orDie(fname, &cSize);
   /* Read the content size from the frame header. For simplicity we require
    * that it is always present. By default, zstd will write the content size
    * in the header when it is known. If you can't guarantee that the frame
    * content size is always written into the header, either use streaming
    * decompression, or ZSTD_decompressBound().
    */
   unsigned long long const rSize = ZSTD_getFrameContentSize(cBuff, cSize);
   CHECK(rSize != ZSTD_CONTENTSIZE_ERROR, "%s: not compressed by zstd!", fname);
   CHECK(rSize != ZSTD_CONTENTSIZE_UNKNOWN, "%s: original size unknown!", fname);
   void* const rBuff = malloc_orDie((size_t)rSize);

   /* Check that the dictionary ID matches.
    * If a non-zstd dictionary is used, then both will be zero.
    * By default zstd always writes the dictionary ID into the frame.
    * Zstd will check if there is a dictionary ID mismatch as well.
    */
   unsigned const expectedDictID = ZSTD_getDictID_fromDDict(ddict);
   unsigned const actualDictID = ZSTD_getDictID_fromFrame(cBuff, cSize);
   CHECK(actualDictID == expectedDictID,
         "DictID mismatch: expected %u got %u",
         expectedDictID,
         actualDictID);

   /* Decompress using the dictionary.
    * If you need to control the decompression parameters, then use the
    * advanced API: ZSTD_DCtx_setParameter(), ZSTD_DCtx_refDDict(), and
    * ZSTD_decompressDCtx().
    */
   ZSTD_DCtx* const dctx = ZSTD_createDCtx();
   CHECK(dctx != NULL, "ZSTD_createDCtx() failed!");
   size_t const dSize = ZSTD_decompress_usingDDict(dctx, rBuff, rSize, cBuff, cSize, ddict);
   CHECK_ZSTD(dSize);
   /* When zstd knows the content size, it will error if it doesn't match. */
   CHECK(dSize == rSize, "Impossible because zstd will check this condition!");

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

   ZSTD_freeDCtx(dctx);
   free(rBuff);
   free(cBuff);
}


int main(int argc, const char** argv)
{
   const char* const exeName = argv[0];

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

   /* load dictionary only once */
   const char* const dictName = argv[argc-1];
   ZSTD_DDict* const dictPtr = createDict_orDie(dictName);

   int u;
   for (u=1; u<argc-1; u++) decompress(argv[u], dictPtr);

   ZSTD_freeDDict(dictPtr);
   printf("All %u files correctly decoded (in memory) \n", argc-2);
   return 0;
}