static int mpjpeg_read_packet(AVFormatContext *s, AVPacket *pkt) { int size; int ret; MPJPEGDemuxContext *mpjpeg = s->priv_data; if (mpjpeg->boundary == NULL) { mpjpeg->boundary = av_strdup("--"); mpjpeg->searchstr = av_strdup("\r\n--"); if (!mpjpeg->boundary || !mpjpeg->searchstr) { av_freep(&mpjpeg->boundary); av_freep(&mpjpeg->searchstr); return AVERROR(ENOMEM); } mpjpeg->searchstr_len = strlen(mpjpeg->searchstr); } ret = parse_multipart_header(s->pb, &size, mpjpeg->boundary, s); if (ret < 0) return ret; if (size > 0) { /* size has been provided to us in MIME header */ ret = av_get_packet(s->pb, pkt, size); } else { /* no size was given -- we read until the next boundary or end-of-file */ int remaining = 0, len; const int read_chunk = 2048; av_init_packet(pkt); pkt->data = NULL; pkt->size = 0; pkt->pos = avio_tell(s->pb); /* we may need to return as much as all we've read back to the buffer */ ffio_ensure_seekback(s->pb, read_chunk); while ((ret = av_append_packet(s->pb, pkt, read_chunk - remaining)) >= 0) { /* scan the new data */ len = ret + remaining; char *start = pkt->data + pkt->size - len; do { if (!memcmp(start, mpjpeg->searchstr, mpjpeg->searchstr_len)) { // got the boundary! rewind the stream avio_seek(s->pb, -(len-2), SEEK_CUR); pkt->size -= (len-2); return pkt->size; } len--; start++; } while (len >= mpjpeg->searchstr_len); remaining = len; } /* error or EOF occurred */ if (ret == AVERROR_EOF) { ret = pkt->size > 0 ? pkt->size : AVERROR_EOF; } else { av_packet_unref(pkt); } } return ret; }