Aegisub/FFmpegSource/stdiostream.cpp

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/* first we need to create an I/O object that the parser will use to read the
* source file
*/
struct StdIoStream {
struct InputStream base;
FILE *fp;
int error;
};
typedef struct StdIoStream StdIoStream;
#define CACHESIZE 65536
/* StdIoStream methods */
/* read count bytes into buffer starting at file position pos
* return the number of bytes read, -1 on error or 0 on EOF
*/
int StdIoRead(StdIoStream *st, ulonglong pos, void *buffer, int count) {
size_t rd;
if (fseek(st->fp, pos, SEEK_SET)) {
st->error = errno;
return -1;
}
rd = fread(buffer, 1, count, st->fp);
if (rd == 0) {
if (feof(st->fp))
return 0;
st->error = errno;
return -1;
}
return rd;
}
/* scan for a signature sig(big-endian) starting at file position pos
* return position of the first byte of signature or -1 if error/not found
*/
longlong StdIoScan(StdIoStream *st, ulonglong start, unsigned signature) {
int c;
unsigned cmp = 0;
FILE *fp = st->fp;
if (fseek(fp, start, SEEK_SET))
return -1;
while ((c = getc(fp)) != EOF) {
cmp = ((cmp << 8) | c) & 0xffffffff;
if (cmp == signature)
return ftell(fp) - 4;
}
return -1;
}
/* return cache size, this is used to limit readahead */
unsigned StdIoGetCacheSize(StdIoStream *st) {
return CACHESIZE;
}
/* return last error message */
const char *StdIoGetLastError(StdIoStream *st) {
return strerror(st->error);
}
/* memory allocation, this is done via stdlib */
void *StdIoMalloc(StdIoStream *st, size_t size) {
return malloc(size);
}
void *StdIoRealloc(StdIoStream *st, void *mem, size_t size) {
return realloc(mem,size);
}
void StdIoFree(StdIoStream *st, void *mem) {
free(mem);
}
/* progress report handler for lengthy operations
* returns 0 to abort operation, nonzero to continue
*/
int StdIoProgress(StdIoStream *st, ulonglong cur, ulonglong max) {
return 1;
}