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[examples] Update streaming_decompression.c 

Update to use the new streaming API. Making progress on Issue #1548.

Tested that it can decompress files produced by `streaming_compression`.
Tested that it can decompress two frames concatenated together.
Tested that it fails on corrupted data.
dev
Nick Terrell 2019-04-01 17:25:26 -07:00
parent 425ce5547c
commit de58910b5a
1 changed files with 25 additions and 11 deletions
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36
examples/streaming_decompression.c
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@ -25,26 +25,40 @@ static void decompressFile_orDie(const char* fname)
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_DStream* const dstream = ZSTD_createDStream();
if (dstream==NULL) { fprintf(stderr, "ZSTD_createDStream() error \n"); exit(10); }
ZSTD_DCtx* const dctx = ZSTD_createDCtx();
CHECK(dctx != NULL, "ZSTD_createDCtx() failed!");
/* In more complex scenarios, a file may consist of multiple appended frames (ex : pzstd).
* The following example decompresses only the first frame.
* It is compatible with other provided streaming examples */
size_t const initResult = ZSTD_initDStream(dstream);
if (ZSTD_isError(initResult)) { fprintf(stderr, "ZSTD_initDStream() error : %s \n", ZSTD_getErrorName(initResult)); exit(11); }
size_t read, toRead = initResult;
/* 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;
while ( (read = fread_orDie(buffIn, toRead, fin)) ) {
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 };
toRead = ZSTD_decompressStream(dstream, &output , &input); /* toRead : size of next compressed block */
if (ZSTD_isError(toRead)) { fprintf(stderr, "ZSTD_decompressStream() error : %s \n", ZSTD_getErrorName(toRead)); exit(12); }
/* 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);
}
}
ZSTD_freeDStream(dstream);
ZSTD_freeDCtx(dctx);
fclose_orDie(fin);
fclose_orDie(fout);
free(buffIn);