wip on loading adpcm wav files

src/ArrayBufferStream.js

@@ -0,0 +1,71 @@
+/*
+
+ArrayBufferStream wraps the built-in javascript ArrayBuffer, adding the ability to access
+data in it like a stream. You can request to read a value from the front of the array,
+such as an 8 bit unsigned int, a 16 bit int, etc, and it will keep track of the position
+within the byte array, so that successive reads are consecutive.
+
+*/
+function ArrayBufferStream (arrayBuffer) {
+    this.arrayBuffer = arrayBuffer;
+    this.position = 0;
+}
+
+// return a new ArrayBufferStream that is a slice of the existing one
+ArrayBufferStream.prototype.extract = function (length) {
+    var slicedArrayBuffer = this.arrayBuffer.slice(this.position, this.position+length);
+    var newStream = new ArrayBufferStream(slicedArrayBuffer);
+    return newStream;
+};
+
+ArrayBufferStream.prototype.getLength = function () {
+    return this.arrayBuffer.byteLength;
+};
+
+ArrayBufferStream.prototype.getBytesAvailable = function () {
+    return (this.arrayBuffer.byteLength - this.position);
+};
+
+ArrayBufferStream.prototype.readUint8 = function () {
+    var val = new Uint8Array(this.arrayBuffer, this.position, 1)[0];
+    this.position += 1;
+    return val;
+};
+
+// convert a sequence of bytes of the given length to a string
+// for small length strings only
+ArrayBufferStream.prototype.readUint8String = function (length) {
+    var arr = new Uint8Array(this.arrayBuffer, this.position, length);
+    this.position += length;
+    var str = '';
+    for (var i=0; i<arr.length; i++) {
+        str += String.fromCharCode(arr[i]);
+    }
+    return str;
+};
+
+ArrayBufferStream.prototype.readInt16 = function () {
+    var val = new Int16Array(this.arrayBuffer, this.position, 1)[0];
+    this.position += 2; // one 16 bit int is 2 bytes
+    return val;
+};
+
+ArrayBufferStream.prototype.readUint16 = function () {
+    var val = new Uint16Array(this.arrayBuffer, this.position, 1)[0];
+    this.position += 2; // one 16 bit int is 2 bytes
+    return val;
+};
+
+ArrayBufferStream.prototype.readInt32 = function () {
+    var val = new Int32Array(this.arrayBuffer, this.position, 1)[0];
+    this.position += 4; // one 32 bit int is 4 bytes
+    return val;
+};
+
+ArrayBufferStream.prototype.readUint32 = function () {
+    var val = new Uint32Array(this.arrayBuffer, this.position, 1)[0];
+    this.position += 4; // one 32 bit int is 4 bytes
+    return val;
+};
+
+module.exports = ArrayBufferStream;