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Update seekable API to simplify IO

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This commit is contained in:
Sean Purcell
2017-04-18 16:47:28 -07:00
parent 9626cf1ac6
commit 0f7bd772e6
5 changed files with 397 additions and 326 deletions
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72
contrib/seekable_format/examples/seekable_decompression.c
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@ -17,6 +17,7 @@
#include "zstd_seekable.h"
#define MIN(a, b) ((a) < (b) ? (a) : (b))
static void* malloc_orDie(size_t size)
{
@ -85,74 +86,31 @@ static void fseek_orDie(FILE* file, long int offset, int origin) {
static void decompressFile_orDie(const char* fname, unsigned startOffset, unsigned endOffset)
{
FILE* const fin = fopen_orDie(fname, "rb");
size_t const buffInSize = ZSTD_DStreamInSize();
void* const buffIn = malloc_orDie(buffInSize);
FILE* const fout = stdout;
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_seekable_DStream* const dstream = ZSTD_seekable_createDStream();
if (dstream==NULL) { fprintf(stderr, "ZSTD_seekable_createDStream() error \n"); exit(10); }
ZSTD_seekable* const seekable = ZSTD_seekable_create();
if (seekable==NULL) { fprintf(stderr, "ZSTD_seekable_create() error \n"); exit(10); }
{ size_t sizeNeeded = 0;
void* buffSeekTable = NULL;
size_t const initResult = ZSTD_seekable_initFile(seekable, fin);
if (ZSTD_isError(initResult)) { fprintf(stderr, "ZSTD_seekable_init() error : %s \n", ZSTD_getErrorName(initResult)); exit(11); }
do {
sizeNeeded = ZSTD_seekable_loadSeekTable(dstream, buffSeekTable, sizeNeeded);
if (!sizeNeeded) break;
while (startOffset < endOffset) {
size_t const result = ZSTD_seekable_decompress(seekable, buffOut, MIN(endOffset - startOffset, buffOutSize), startOffset);
if (ZSTD_isError(sizeNeeded)) {
fprintf(stderr, "ZSTD_seekable_loadSeekTable() error : %s \n",
ZSTD_getErrorName(sizeNeeded));
exit(11);
}
fseek_orDie(fin, -(long) sizeNeeded, SEEK_END);
buffSeekTable = realloc_orDie(buffSeekTable, sizeNeeded);
fread_orDie(buffSeekTable, sizeNeeded, fin);
} while (sizeNeeded > 0);
free(buffSeekTable);
if (ZSTD_isError(result)) {
fprintf(stderr, "ZSTD_seekable_decompress() error : %s \n",
ZSTD_getErrorName(result));
exit(12);
}
fwrite_orDie(buffOut, result, fout);
startOffset += result;
}
/* 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_seekable_initDStream(dstream, startOffset, endOffset);
if (ZSTD_isError(initResult)) { fprintf(stderr, "ZSTD_seekable_initDStream() error : %s \n", ZSTD_getErrorName(initResult)); exit(11); }
size_t result, read, toRead = 0;
do {
read = fread_orDie(buffIn, toRead, fin);
{ ZSTD_inBuffer input = { buffIn, read, 0 };
ZSTD_outBuffer output = { buffOut, buffOutSize, 0 };
result = ZSTD_seekable_decompressStream(dstream, &output, &input);
if (ZSTD_isError(result)) {
if (ZSTD_getErrorCode(result) == ZSTD_error_needSeek) {
unsigned long long const offset = ZSTD_seekable_getSeekOffset(dstream);
fseek_orDie(fin, offset, SEEK_SET);
ZSTD_seekable_updateOffset(dstream, offset);
toRead = 0;
} else {
fprintf(stderr,
"ZSTD_seekable_decompressStream() error : %s \n",
ZSTD_getErrorName(result));
exit(12);
}
} else {
toRead = result;
}
fwrite_orDie(buffOut, output.pos, fout);
if (toRead > buffInSize) toRead = buffInSize;
}
} while (result > 0);
ZSTD_seekable_freeDStream(dstream);
ZSTD_seekable_free(seekable);
fclose_orDie(fin);
fclose_orDie(fout);
free(buffIn);
free(buffOut);
}