From d2eb771eea8bb4e5ff775f23e3c28168fb768c9b Mon Sep 17 00:00:00 2001
From: Eric Rosenbaum <eric.rosenbaum@gmail.com>
Date: Sat, 19 Nov 2016 14:17:43 -0500
Subject: [PATCH] cleanup and return a promise

---
 src/ADPCMSoundLoader.js | 138 ++++++++++++++++++++++------------------
 1 file changed, 75 insertions(+), 63 deletions(-)

diff --git a/src/ADPCMSoundLoader.js b/src/ADPCMSoundLoader.js
index b4ea9ba..198b7bb 100644
--- a/src/ADPCMSoundLoader.js
+++ b/src/ADPCMSoundLoader.js
@@ -5,77 +5,89 @@ ADPCMSoundLoader loads wav files that have been compressed with the ADPCM format
 based on code from Scratch-Flash:
 https://github.com/LLK/scratch-flash/blob/master/src/sound/WAVFile.as
 
+to do: I think this will ultimately need to run in a web worker
+
 */
 
 var ArrayBufferStream = require('./ArrayBufferStream');
 var Tone = require('tone');
 var log = require('./log');
 
-function ADPCMSoundLoader (url) {
-    var request = new XMLHttpRequest();
-    request.open('GET', url, true);
-    request.responseType = 'arraybuffer';
-
-    request.onload = function () {
-        var audioData = request.response;
-        var stream = new ArrayBufferStream(audioData);
-
-        var riffStr = stream.readUint8String(4);
-        if (riffStr != 'RIFF') {
-            log.warn('incorrect adpcm wav header');
-        }
-
-        var lengthInHeader = stream.readInt32();
-        if ((lengthInHeader + 8) != audioData.byteLength) {
-            log.warn('adpcm wav length in header: ' + length + 'is incorrect');
-        }
-
-        var wavStr = stream.readUint8String(4);
-        if (wavStr != 'WAVE') {
-            log.warn('incorrect adpcm wav header');
-        }
-
-        var formatChunk = this.extractChunk('fmt ', stream);
-        this.encoding = formatChunk.readUint16();
-        this.channels = formatChunk.readUint16();
-        this.samplesPerSecond = formatChunk.readUint32();
-        this.bytesPerSecond = formatChunk.readUint32();
-        this.blockAlignment = formatChunk.readUint16();
-        this.bitsPerSample = formatChunk.readUint16();
-        formatChunk.position += 2;  // skip extra header byte count
-        this.samplesPerBlock = formatChunk.readUint16();
-        this.adpcmBlockSize = ((this.samplesPerBlock - 1) / 2) + 4; // block size in bytes
-
-        var samples = this.imaDecompress(this.extractChunk('data', stream), this.adpcmBlockSize);
-        var buffer = Tone.context.createBuffer(1, samples.length, this.samplesPerSecond);
-
-        // todo: optimize this?
-        for (var i=0; i<samples.length; i++) {
-            buffer.getChannelData(0)[i] = samples[i] / 32768;
-        }
-
-        var source = Tone.context.createBufferSource();
-        source.buffer = buffer;
-        source.connect(Tone.Master);
-        source.start();
-
-
-    }.bind(this);
-    request.send();
-
-    this.stepTable = [
-        7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
-        50, 55, 60, 66, 73, 80, 88, 97, 107, 118, 130, 143, 157, 173, 190, 209, 230,
-        253, 279, 307, 337, 371, 408, 449, 494, 544, 598, 658, 724, 796, 876, 963,
-        1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024, 3327,
-        3660, 4026, 4428, 4871, 5358, 5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487,
-        12635, 13899, 15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767];
-
-    this.indexTable = [
-        -1, -1, -1, -1, 2, 4, 6, 8,
-        -1, -1, -1, -1, 2, 4, 6, 8];
+function ADPCMSoundLoader () {
 }
 
+ADPCMSoundLoader.prototype.load = function (url) {
+
+    return new Promise(function (resolve, reject) {
+
+        var request = new XMLHttpRequest();
+        request.open('GET', url, true);
+        request.responseType = 'arraybuffer';
+
+        request.onload = function () {
+            var audioData = request.response;
+            var stream = new ArrayBufferStream(audioData);
+
+            var riffStr = stream.readUint8String(4);
+            if (riffStr != 'RIFF') {
+                log.warn('incorrect adpcm wav header');
+                reject();
+            }
+
+            var lengthInHeader = stream.readInt32();
+            if ((lengthInHeader + 8) != audioData.byteLength) {
+                log.warn('adpcm wav length in header: ' + lengthInHeader + ' is incorrect');
+            }
+
+            var wavStr = stream.readUint8String(4);
+            if (wavStr != 'WAVE') {
+                log.warn('incorrect adpcm wav header');
+                reject();
+            }
+
+            var formatChunk = this.extractChunk('fmt ', stream);
+            this.encoding = formatChunk.readUint16();
+            this.channels = formatChunk.readUint16();
+            this.samplesPerSecond = formatChunk.readUint32();
+            this.bytesPerSecond = formatChunk.readUint32();
+            this.blockAlignment = formatChunk.readUint16();
+            this.bitsPerSample = formatChunk.readUint16();
+            formatChunk.position += 2;  // skip extra header byte count
+            this.samplesPerBlock = formatChunk.readUint16();
+            this.adpcmBlockSize = ((this.samplesPerBlock - 1) / 2) + 4; // block size in bytes
+
+            var samples = this.imaDecompress(this.extractChunk('data', stream), this.adpcmBlockSize);
+
+            // this line is the only place Tone is used here, should be possible to remove
+            var buffer = Tone.context.createBuffer(1, samples.length, this.samplesPerSecond);
+
+            // todo: optimize this? e.g. replace the divide by storing 1/32768 and multiply?
+            for (var i=0; i<samples.length; i++) {
+                buffer.getChannelData(0)[i] = samples[i] / 32768;
+            }
+
+            resolve(buffer);
+
+        }.bind(this);
+
+        request.send();
+
+    }.bind(this));
+};
+
+
+ADPCMSoundLoader.prototype.stepTable = [
+    7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
+    50, 55, 60, 66, 73, 80, 88, 97, 107, 118, 130, 143, 157, 173, 190, 209, 230,
+    253, 279, 307, 337, 371, 408, 449, 494, 544, 598, 658, 724, 796, 876, 963,
+    1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024, 3327,
+    3660, 4026, 4428, 4871, 5358, 5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487,
+    12635, 13899, 15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767];
+
+ADPCMSoundLoader.prototype.indexTable = [
+    -1, -1, -1, -1, 2, 4, 6, 8,
+    -1, -1, -1, -1, 2, 4, 6, 8];
+
 ADPCMSoundLoader.prototype.extractChunk = function (chunkType, stream) {
     stream.position = 12;
     while (stream.position < (stream.getLength() - 8)) {