Add BGM Preview Functionality

Some code adapted from Themely. Thanks to ErmanSayin

source/music.c

@@ -0,0 +1,121 @@
+/*
+*   This file is part of Anemone3DS
+*   Copyright (C) 2016-2018 Contributors in CONTRIBUTORS.md
+*
+*   This program is free software: you can redistribute it and/or modify
+*   it under the terms of the GNU General Public License as published by
+*   the Free Software Foundation, either version 3 of the License, or
+*   (at your option) any later version.
+*
+*   This program is distributed in the hope that it will be useful,
+*   but WITHOUT ANY WARRANTY; without even the implied warranty of
+*   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*   GNU General Public License for more details.
+*
+*   You should have received a copy of the GNU General Public License
+*   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*
+*   Additional Terms 7.b and 7.c of GPLv3 apply to this file:
+*       * Requiring preservation of specified reasonable legal notices or
+*         author attributions in that material or in the Appropriate Legal
+*         Notices displayed by works containing it.
+*       * Prohibiting misrepresentation of the origin of that material,
+*         or requiring that modified versions of such material be marked in
+*         reasonable ways as different from the original version.
+*/
+
+#include "music.h"
+
+// Play a given audio struct
+Result play_audio(audio_s *audio) 
+{
+    long size = audio->wave_buf[audio->buf_pos].nsamples * 4 - audio->data_read;
+    char size_info[50] = {0};
+    sprintf(size_info, "Audio Size: %ld\n", size);
+    DEBUG(size_info);
+    if (audio->wave_buf[audio->buf_pos].status == NDSP_WBUF_DONE) // only run if the current selected buffer has already finished playing
+    { 
+        size_t read = ov_read(&audio->vf, (char*)audio->wave_buf[audio->buf_pos].data_vaddr + audio->data_read, size, NULL); // read 1 vorbis packet into wave buffer
+
+        if (read <= 0) // EoF or error
+        { 
+            ov_clear(&audio->vf);
+            if (read == 0) // EoF
+            { 
+                ov_open(fopen(audio->filename, "rb"), &audio->vf, NULL, 0); // Reopen file. Don't need to reinit channel stuff since it's all the same as before
+            } else // Error :(
+            { 
+                char error[100] = {0};
+                sprintf(error, "Vorbis play error: %d\n", read);
+                DEBUG(error);
+                ndspChnReset(0);
+                return MAKERESULT(RL_FATAL, RS_INVALIDARG, RM_APPLICATION, RD_NO_DATA);
+            }
+        } else 
+        {
+            audio->data_read += read;
+            if (read == size) {
+                audio->data_read = 0;
+                ndspChnWaveBufAdd(0, &audio->wave_buf[audio->buf_pos]); // Add buffer to ndsp 
+                audio->buf_pos = 1 - audio->buf_pos; // switch to other buffer to load and prepare it while the current one is playing
+            }
+        }
+    }
+    return MAKERESULT(RL_SUCCESS, RS_SUCCESS, RM_APPLICATION, RD_SUCCESS);
+}
+
+void thread_audio(void* data) {
+    audio_s *audio = (audio_s*)data;
+    DEBUG(audio->filename);
+    while(!audio->stop) {
+        play_audio(audio);
+    }
+    free(audio);
+}
+
+// Initialize the audio struct
+Result load_audio(u16 *entry_path, audio_s *audio) 
+{
+    u16 path[0x106] = {0};
+    strucat(path, entry_path);
+    struacat(path, "/bgm.ogg");
+    
+    ssize_t len = strulen(path, 0x106);
+    char *cpath = calloc(sizeof(char), len*sizeof(u16));
+    utf16_to_utf8((u8*)cpath, path, len*sizeof(u16));
+    audio->filename = cpath;
+
+    audio->mix[0] = audio->mix[1] = 1.0f; // Determines volume for the 12 (?) different outputs. See http://smealum.github.io/ctrulib/channel_8h.html#a30eb26f1972cc3ec28370263796c0444
+
+    ndspChnSetInterp(0, NDSP_INTERP_LINEAR); 
+    ndspChnSetRate(0, 44100);
+    ndspChnSetFormat(0, NDSP_FORMAT_STEREO_PCM16); // Tremor outputs ogg files in 16 bit PCM stereo
+	ndspChnSetMix(0, audio->mix); // See mix comment above
+
+    FILE *file = fopen(cpath, "rb");
+    if(file != NULL) 
+    {
+        int e = ov_open(file, &audio->vf, NULL, 0);
+        if (e < 0) 
+        {
+            char error[50];
+            sprintf(error, "Vorbis: %d\n", e);
+            DEBUG(error);
+            return MAKERESULT(RL_FATAL, RS_INVALIDARG, RM_APPLICATION, RD_NO_DATA);
+        }
+
+        vorbis_info *vi = ov_info(&audio->vf, -1);
+        ndspChnSetRate(0, vi->rate);// Set sample rate to what's read from the ogg file
+
+        audio->wave_buf[0].nsamples = audio->wave_buf[1].nsamples = vi->rate / 4; // 4 bytes per sample, samples = rate (bytes) / 4
+        audio->wave_buf[0].status = audio->wave_buf[1].status = NDSP_WBUF_DONE; // Used in play to stop from writing to current buffer
+        audio->wave_buf[0].data_vaddr = linearAlloc(BUF_TO_READ); // Most vorbis packets should only be 4 KB at most (?) Possibly dangerous assumption
+        audio->wave_buf[1].data_vaddr = linearAlloc(BUF_TO_READ);
+        DEBUG("Success!");
+        threadCreate(thread_audio, audio, 0x1000, 0x3F, 1, true);
+        return MAKERESULT(RL_SUCCESS, RS_SUCCESS, RM_APPLICATION, RD_SUCCESS);
+    } else {
+        DEBUG("File not found!\n");
+        return MAKERESULT(RL_FATAL, RS_NOTFOUND, RM_APPLICATION, RD_NOT_FOUND);
+    }
+}