mp3 test

assets/disk0/tvdos/include/js-mp3/bits.js

@@ -0,0 +1,84 @@
+var Bits = {
+    createNew: function (vec) {
+        var bits = {
+            vec: vec, // ArrayBuffer
+            bitPos: 0,
+            bytePos: 0
+        };
+
+        /**
+         * @return {number}
+         */
+        bits.Bit = function () {
+            if (bits.vec.byteLength <= bits.bytePos) {
+                // TODO: Should this return error?
+                return 0;
+            }
+            var dv = new DataView(bits.vec, bits.bytePos);
+            var tmp = (dv.getUint8(0) >>> (7 - bits.bitPos)) >>> 0;
+            tmp &= 0x01;
+            bits.bytePos += ((bits.bitPos + 1) >>> 3) >>> 0;
+            bits.bitPos = (bits.bitPos + 1) & 0x07;
+            return tmp;
+        };
+
+        /**
+         * @return {number}
+         */
+        bits.Bits = function (num) {
+            if (num === 0) {
+                return 0;
+            }
+            if (bits.vec.byteLength <= bits.bytePos) {
+                // TODO: Should this return error?
+                return 0;
+            }
+            var bb = new DataView(bits.vec, bits.bytePos);
+            // always end bit wise ops with >>> 0 so the result gets interpreted as unsigned.
+            // don't use >>. If the left-most bit is 1 it will try to preseve the sign and thus will introduce 1's to the left. Always use >>>.
+            // see https://stackoverflow.com/a/6798829
+            var tmp = (((getValue(bb, 0) << 24) >>> 0) | ((getValue(bb, 1) << 16) >>> 0) | ((getValue(bb, 2) << 8) >>> 0) | (getValue(bb, 3) >>> 0)) >>> 0;
+            tmp = (tmp << bits.bitPos) >>> 0;
+            tmp = (tmp >>> (32 - num)) >>> 0;
+            bits.bytePos += ((bits.bitPos + num) >>> 3) >>> 0;
+            bits.bitPos = (bits.bitPos + num) & 0x07;
+            return tmp;
+        };
+
+        bits.Tail = function (offset) {
+            var a = new Uint8Array(bits.vec);
+            return a.slice(bits.vec.byteLength - offset).buffer;
+            // return new Uint8Array(bits.vec, bits.vec.byteLength - offset).buffer;
+        };
+
+        bits.LenInBytes = function () {
+            return bits.vec.byteLength;
+        };
+
+        /**
+         * @return {number}
+         */
+        bits.BitPos = function () {
+            return ((bits.bytePos << 3) >>> 0) + bits.bitPos;
+        };
+
+        bits.SetPos = function (pos) {
+            bits.bytePos = (pos >>> 3) >>> 0;
+            bits.bitPos = (pos & 0x7) >>> 0;
+        };
+
+        return bits;
+    },
+    append: function (bits, buf) {
+        return Bits.createNew(bits.vec.concat(buf));
+    },
+};
+
+var getValue = function (dv, index) {
+    if (index >= dv.byteLength) {
+        return 0;
+    }
+    return dv.getUint8(index);
+};
+
+exports = Bits;