ppapi: examples: audio_encode: reduce array buffer reallocations

ppapi/examples/audio_encode/audio_encode.html

Index: ppapi/examples/audio_encode/audio_encode.html
diff --git a/ppapi/examples/audio_encode/audio_encode.html b/ppapi/examples/audio_encode/audio_encode.html
index 36b322a54d1e8d236a68a4d86867a3bd94a477c0..14cab7b3a2f8d8553532fe2736c74e8dd02f1e6e 100644
--- a/ppapi/examples/audio_encode/audio_encode.html
+++ b/ppapi/examples/audio_encode/audio_encode.html
@@ -14,71 +14,126 @@
     var profiles;
 
     function writeString(array, offset, string) {
-      var out = new Uint8Array(array);
       for (var i = 0; i < string.length; i++)
-        out.set([string.charCodeAt(i)], i + offset);
+        array.set([string.charCodeAt(i)], i + offset);
       return string.length;
     }
     function writeValue(array, bytes, offset, value) {
-      var out = new Uint8Array(array);
       for (var i = 0; i < bytes; i++)
-        out.set([((value >>> (i * 8)) & 0xff)], offset + i);
+        array.set([((value >>> (i * 8)) & 0xff)], offset + i);
       return bytes;
     }
-    // Writes way data.
+
+    var BufferArray = function() {
+      this._arrays = [ this._createBuffer() ];
+    };
+    BufferArray.prototype = {
+      _createBuffer: function() {
+        var buffer = new Uint8Array(100 * 1024);
+        buffer.dataLength = 0;
+        return buffer;
+      },
+      appendData: function(data) {
+        var currentBuffer = this._arrays[this._arrays.length - 1];
+        if (currentBuffer.byteLength < (currentBuffer.dataLength + data.byteLength)) {
+          this._arrays.push(this._createBuffer());
+          currentBuffer = this._arrays[this._arrays.length - 1];
+        }
+        currentBuffer.set(new Uint8Array(data), currentBuffer.dataLength);
+        currentBuffer.dataLength += data.byteLength;
+      },
+      getByte: function(offset) {
+        var bufferOffset = 0;
+        for (var i = 0; i < this._arrays.length; i++) {
+          var buffer = this._arrays[i];
+          if (offset < (bufferOffset + buffer.dataLength)) {
+            return buffer[offset - bufferOffset];
+          }
+          bufferOffset += buffer.dataLength;
+        }
+        throw new Error('Out of range access');
+      },
+      getSize: function() {
+        var size = 0;
+        for (var i = 0; i < this._arrays.length; i++)
+          size += this._arrays[i].dataLength;
+        return size;
+      },
+      writeValue: function(bytes, offset, value) {
+        var bufferOffset = 0;
+        for (var i = 0; i < this._arrays.length; i++) {
+          var buffer = this._arrays[i];
+          if (offset < (bufferOffset + buffer.dataLength)) {
+            writeValue(buffer, bytes, offset - bufferOffset, value);
+            return;
+          }
+          bufferOffset += buffer.dataLength;
+        }
+        throw new Error('Out of range access');
+      },
+      toBlob: function() {
+        var result = new Uint8Array(this.getSize());
+        var offset = 0;
+        for (var i = 0; i < this._arrays.length; i++) {
+          var buffer = this._arrays[i];
+          result.set(buffer.subarray(0, buffer.dataLength), offset);
+          offset += buffer.dataLength;
+        }
+        return new Blob([result]);
+      },
+    };
+
+    // Writes wav data.
     var WavWriter = function() {
       this.chunkSizeOffset = 0;
-      this.arrayBuffer = new ArrayBuffer();
+      this.buffer = new BufferArray();
     };
     WavWriter.prototype = {
       writeHeader: function(format) {
-        this.arrayBuffer =
-          new ArrayBuffer(4 + 4 + 4 + 4 + 4 + 2 + 2 + 4 + 4 + 2 + 2 + 4 + 4);
+        var buffer =
+          new Uint8Array(4 + 4 + 4 + 4 + 4 + 2 + 2 + 4 + 4 + 2 + 2 + 4 + 4);
         var i = 0;
         // File header
-        i += writeString(this.arrayBuffer, i, 'RIFF');
+        i += writeString(buffer, i, 'RIFF');
         i += 4; // Gap for final size.
-        i += writeString(this.arrayBuffer, i, 'WAVE');
+        i += writeString(buffer, i, 'WAVE');
         // Chunk ID.
-        i += writeString(this.arrayBuffer, i, 'fmt ');
+        i += writeString(buffer, i, 'fmt ');
         // Chunk length.
-        i += writeValue(this.arrayBuffer, 4, i, 16);
+        i += writeValue(buffer, 4, i, 16);
         // Codec (uncompressed LPCM).
-        i += writeValue(this.arrayBuffer, 2, i, 1);
+        i += writeValue(buffer, 2, i, 1);
         // Number of channels.
-        i += writeValue(this.arrayBuffer, 2, i, format.channels);
+        i += writeValue(buffer, 2, i, format.channels);
         // Sample rate.
-        i += writeValue(this.arrayBuffer, 4, i, format.sample_rate);
+        i += writeValue(buffer, 4, i, format.sample_rate);
         // Average bytes per seconds (sample rate * bytes per sample)
-        i += writeValue(this.arrayBuffer, 4, i,
+        i += writeValue(buffer, 4, i,
                         format.sample_rate * format.sample_size);
         // Bytes per sample.
-        i += writeValue(this.arrayBuffer, 2, i,
+        i += writeValue(buffer, 2, i,
                         format.sample_size * format.channels);
         // Bits per sample.
-        i += writeValue(this.arrayBuffer, 2, i, format.sample_size * 8);
+        i += writeValue(buffer, 2, i, format.sample_size * 8);
 
         // Data chunk
-        i += writeString(this.arrayBuffer, i, 'data');
+        i += writeString(buffer, i, 'data');
         this.chunkSizeOffset = i; // Location of the chunk's size
+        this.buffer.appendData(buffer);
       },
       writeData: function(data) {
-        var tmp = new Uint8Array(this.arrayBuffer.byteLength + data.byteLength);
-        tmp.set(new Uint8Array(this.arrayBuffer), 0);
-        tmp.set(new Uint8Array(data), this.arrayBuffer.byteLength);
-        this.arrayBuffer = tmp.buffer;
+        this.buffer.appendData(data);
       },
       end: function() {
-        var out = new Uint32Array(this.arrayBuffer);
-        out.set([this.arrayBuffer.byteLength - 8], 1);
-        out.set([this.arrayBuffer.byteLength - this.chunkSizeOffset],
-                this.chunkSizeOffset / 4);
+        this.buffer.writeValue(4, 4, this.buffer.getSize() - 8);
+        this.buffer.writeValue(4, this.chunkSizeOffset,
+                               this.buffer.getSize() - this.chunkSizeOffset);
       },
       getSize: function() {
-        return this.arrayBuffer.byteLength;
+        return this.buffer.getSize();
       },
       getData: function() {
-        return this.arrayBuffer;
+        return this.buffer;
       },
       getExtension: function() {
         return 'wav';
@@ -88,7 +143,7 @@
     // Writes ogg data.
     var OggWriter = function(profile) {
       this.writeHeader = this._writeOpusHeader;
-      this.arrayBuffer = new ArrayBuffer();
+      this.buffer = new BufferArray();
       this.pageSequence = 0;
       this.bitstreamNumber = 0;
       this.position = 0;
@@ -98,12 +153,6 @@
       _Start: 0x2,
       _Continue: 0x1,
       _Stop: 0x4,
-      _append: function(data) {
-        var tmp = new Uint8Array(this.arrayBuffer.byteLength + data.byteLength);
-        tmp.set(new Uint8Array(this.arrayBuffer), 0);
-        tmp.set(new Uint8Array(data), this.arrayBuffer.byteLength);
-        this.arrayBuffer = tmp.buffer;
-      },
       _makeCRCTable: function() {
         var crcTable = [];
         for (var n = 0; n < 256; n++) {
@@ -120,15 +169,14 @@
       },
       _crc32: function(data, start, end) {
         var crc = 0;
-        var u8data = new Uint8Array(data)
         var crcTable = this._crcTable || (this._crcTable = this._makeCRCTable());
         for (var i = start; i < end; i++)
-          crc = (crc << 8) ^ crcTable[((crc >> 24) & 0xff) ^ u8data[i]];
+          crc = (crc << 8) ^ crcTable[((crc >> 24) & 0xff) ^ data.getByte(i)];
         return crc;
       },
       _writePage: function(flag, size, position) {
         var pages = 1 + Math.floor(size / 255);
-        var buffer = new ArrayBuffer(27 + pages), i = 0;
+        var buffer = new Uint8Array(27 + pages), i = 0;
         // capture_pattern.
         i += writeString(buffer, i, 'OggS');
         // stream_structure_version.
@@ -154,17 +202,17 @@
           i += writeValue(buffer, 1, i, 255);
         i += writeValue(buffer, 1, i, size % 255);
 
-        this._append(buffer);
+        this.buffer.appendData(buffer);
       },
       _writePageChecksum: function(pageOffset) {
-        var crc = this._crc32(this.arrayBuffer, pageOffset,
-                              this.arrayBuffer.byteLength);
-        writeValue(this.arrayBuffer, 4, pageOffset + 22, crc);
+        var crc = this._crc32(this.buffer, pageOffset,
+                              this.buffer.getSize());
+        this.buffer.writeValue(4, pageOffset + 22, crc);
       },
       _writeOpusHeader: function(format) {
         this.format = format;
-        var start = this.getSize();
-        var buffer = new ArrayBuffer(8 + 1 + 1 + 2 + 4 + 2 + 1), i = 0;
+        var start = this.buffer.getSize();
+        var buffer = new Uint8Array(8 + 1 + 1 + 2 + 4 + 2 + 1), i = 0;
         // Opus header.
         i += writeString(buffer, i, 'OpusHead');
         // version.
@@ -181,13 +229,13 @@
         i += writeValue(buffer, 1, i, 0);
 
         this._writePage(this._Start, buffer.byteLength);
-        this._append(buffer);
+        this.buffer.appendData(buffer);
         this._writePageChecksum(start);
         this._writeCommentHeader('OpusTags');
       },
       _writeCommentHeader: function(name) {
-        var start = this.getSize();
-        var buffer = new ArrayBuffer(8 + 4 + 8 + 4 + 4 + 13), i = 0;
+        var start = this.buffer.getSize();
+        var buffer = new Uint8Array(8 + 4 + 8 + 4 + 4 + 13), i = 0;
         // Opus comment header.
         i += writeString(buffer, i, name);
         // Vendor string.
@@ -198,7 +246,7 @@
         i += this._writeLengthString(buffer, i, 'TITLE=example');
 
         this._writePage(this._Continue, buffer.byteLength);
-        this._append(buffer);
+        this.buffer.appendData(buffer);
         this._writePageChecksum(start);
       },
       _writeLengthString: function(buffer, offset, str) {
@@ -207,20 +255,17 @@
       },
       writeData: function(data) {
         this.position += this.format.sample_per_frame / this.format.channels;
-        var start = this.getSize();
+        var start = this.buffer.getSize();
         this._writePage(0, data.byteLength, this.position);
-        this._append(data);
+        this.buffer.appendData(data);
         this._writePageChecksum(start);
         this.dataWritten = true;
       },
       end: function() {
         this._writePage(this._Stop, 0);
       },
-      getSize: function() {
-        return this.arrayBuffer.byteLength;
-      },
       getData: function() {
-        return this.arrayBuffer;
+        return this.buffer;
       },
       getExtension: function() {
         return 'ogg';
@@ -255,9 +300,8 @@
       download.parentNode.removeChild(download);
     }
 
-    function setDownload(data, filename) {
+    function setDownload(blob, filename) {
       var mimeType = 'application/octet-stream';
-      var blob = new Blob([data], { type: mimeType });
       var a = document.createElement('a');
       a.id = "download";
       a.download = filename;
@@ -297,12 +341,8 @@
       });
       track.stop();
       writer.end();
-      setDownload(writer.getData(), 'Capture.' + writer.getExtension());
-    }
-
-    function saveBlob(blob) {
-      var blobUrl = URL.createObjectURL(blob);
-      window.location = blobUrl;
+      setDownload(writer.getData().toBlob(),
+                  'Capture.' + writer.getExtension());
     }
 
     function handleMessage(msg) {
@@ -312,10 +352,10 @@
         console.error(msg.data.message);
       } else if (msg.data.command == 'data') {
         writer.writeData(msg.data.buffer);
-        $('length').textContent = ' Size: ' + writer.getSize() + ' bytes';
+        $('length').textContent = ' Size: ' + writer.getData().getSize() + ' bytes';
       } else if (msg.data.command == 'format') {
         writer.writeHeader(msg.data);
-        $('length').textContent = ' Size: ' + writer.getSize() + ' bytes';
+        $('length').textContent = ' Size: ' + writer.getData().getSize() + ' bytes';
       } else if (msg.data.command == 'supportedProfiles') {
         profiles = [];
         var profileList = $('profileList');
@@ -342,7 +382,7 @@
 
     function resetData() {
       writer = new WavWriter();
-      $('length').textContent = ' Size: ' + writer.getSize() + ' bytes';
+      $('length').textContent = ' Size: ' + writer.getData().getSize() + ' bytes';
     }
 
     function initialize() {