int64_t ff_ape_parse_tag(AVFormatContext *s) { AVIOContext *pb = s->pb; int file_size = avio_size(pb); uint32_t val, fields, tag_bytes; uint8_t buf[8]; int64_t tag_start; int i; if (file_size < APE_TAG_FOOTER_BYTES) return 0; avio_seek(pb, file_size - APE_TAG_FOOTER_BYTES, SEEK_SET); avio_read(pb, buf, 8); /* APETAGEX */ if (strncmp(buf, "APETAGEX", 8)) { return 0; } val = avio_rl32(pb); /* APE tag version */ if (val > APE_TAG_VERSION) { av_log(s, AV_LOG_ERROR, "Unsupported tag version. (>=%d)\n", APE_TAG_VERSION); return 0; } tag_bytes = avio_rl32(pb); /* tag size */ if (tag_bytes - APE_TAG_FOOTER_BYTES > (1024 * 1024 * 16)) { av_log(s, AV_LOG_ERROR, "Tag size is way too big\n"); return 0; } tag_start = file_size - tag_bytes - APE_TAG_FOOTER_BYTES; if (tag_start < 0) { av_log(s, AV_LOG_ERROR, "Invalid tag size %u.\n", tag_bytes); return 0; } fields = avio_rl32(pb); /* number of fields */ if (fields > 65536) { av_log(s, AV_LOG_ERROR, "Too many tag fields (%d)\n", fields); return 0; } val = avio_rl32(pb); /* flags */ if (val & APE_TAG_FLAG_IS_HEADER) { av_log(s, AV_LOG_ERROR, "APE Tag is a header\n"); return 0; } avio_seek(pb, file_size - tag_bytes, SEEK_SET); for (i=0; i<fields; i++) if (ape_tag_read_field(s) < 0) break; return tag_start; }