Added .pos support for .vgmstream (FFmpeg) files not directly supported

The format is LE 4+4 [loop_start loop_end], or LE 4+4+4 [loop_start
loop_end num_samples] when FFmpeg can't determine correctly num_samples

src/meta/ffmpeg.c

@@ -43,23 +43,52 @@ VGMSTREAM * init_vgmstream_ffmpeg(STREAMFILE *streamFile) {
 
 VGMSTREAM * init_vgmstream_ffmpeg_offset(STREAMFILE *streamFile, uint64_t start, uint64_t size) {
     VGMSTREAM *vgmstream = NULL;
+    int loop_flag = 0;
+    int32_t loop_start = 0, loop_end = 0, num_samples = 0;
 
+    /* init ffmpeg */
     ffmpeg_codec_data *data = init_ffmpeg_offset(streamFile, start, size);
     if (!data) return NULL;
-    
-    vgmstream = allocate_vgmstream(data->channels, 0);
+
+
+    /* try to get .pos data */
+    {
+        uint8_t posbuf[4+4+4];
+
+        if ( read_pos_file(posbuf, 4+4+4, streamFile) ) {
+            loop_start = get_32bitLE(posbuf+0);
+            loop_end = get_32bitLE(posbuf+4);
+            loop_flag = 1; /* incorrect looping will be validated outside */
+            /* FFmpeg can't always determine totalSamples correctly so optionally load it (can be 0/NULL)
+             * won't crash and will output silence if no loop points and bigger than actual stream's samples */
+            num_samples = get_32bitLE(posbuf+8);
+        }
+    }
+
+
+    /* build VGMSTREAM */
+    vgmstream = allocate_vgmstream(data->channels, loop_flag);
     if (!vgmstream) goto fail;
     
-    vgmstream->loop_flag = 0;
+    vgmstream->loop_flag = loop_flag;
     vgmstream->codec_data = data;
     vgmstream->channels = data->channels;
     vgmstream->sample_rate = data->sampleRate;
-    vgmstream->num_samples = data->totalSamples;
     vgmstream->coding_type = coding_FFmpeg;
     vgmstream->layout_type = layout_none;
     vgmstream->meta_type = meta_FFmpeg;
 
-    /* this may happen for some streams */
+    if (!num_samples) {
+        num_samples = data->totalSamples;
+    }
+    vgmstream->num_samples = num_samples;
+
+    if (loop_flag) {
+        vgmstream->loop_start_sample = loop_start;
+        vgmstream->loop_end_sample = loop_end;
+    }
+
+    /* this may happen for some streams if FFmpeg can't determine it */
     if (vgmstream->num_samples <= 0)
         goto fail;
 

src/streamfile.c

@@ -350,3 +350,44 @@ fail:
     return 0;
 }
 
+/**
+ * open file containing looping data and copy to buffer
+ *
+ * returns true if found and copied
+ */
+int read_pos_file(uint8_t * buf, size_t bufsize, STREAMFILE *streamFile) {
+    char posname[PATH_LIMIT];
+    char filename[PATH_LIMIT];
+    /*size_t bytes_read;*/
+    STREAMFILE * streamFilePos= NULL;
+
+    streamFile->get_name(streamFile,filename,sizeof(filename));
+
+    if (strlen(filename)+4 > sizeof(posname)) goto fail;
+
+    /* try to open a posfile using variations: "(name.ext).pos" */
+    {
+        strcpy(posname, filename);
+        strcat(posname, ".pos");
+        streamFilePos = streamFile->open(streamFile,posname,STREAMFILE_DEFAULT_BUFFER_SIZE);
+        if (streamFilePos) goto found;
+
+        goto fail;
+    }
+
+found:
+    //if (get_streamfile_size(streamFilePos) != bufsize) goto fail;
+
+    /* allow pos files to be of different sizes in case of new features, just fill all we can */
+    memset(buf, 0, bufsize);
+    read_streamfile(buf, 0, bufsize, streamFilePos);
+
+    close_streamfile(streamFilePos);
+
+    return 1;
+
+fail:
+    if (streamFilePos) close_streamfile(streamFilePos);
+
+    return 0;
+}

src/streamfile.h

@@ -151,5 +151,6 @@ size_t get_streamfile_dos_line(int dst_length, char * dst, off_t offset,
 
 int read_key_file(uint8_t * buf, size_t bufsize, STREAMFILE *streamFile);
 
+int read_pos_file(uint8_t * buf, size_t bufsize, STREAMFILE *streamFile);
 
 #endif