From 6b3bcb2026d31300b269b314a6f440f25efb4b80 Mon Sep 17 00:00:00 2001
From: raphaklaus <raphaklaus@gmail.com>
Date: Wed, 10 Jan 2018 00:38:00 -0200
Subject: [PATCH] feat: add parser and sampler

---
 src/parser.js  | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++
 src/sampler.js | 22 ++++++++++++++++
 2 files changed, 92 insertions(+)
 create mode 100644 src/parser.js
 create mode 100644 src/sampler.js

diff --git a/src/parser.js b/src/parser.js
new file mode 100644
index 0000000..df0c5da
--- /dev/null
+++ b/src/parser.js
@@ -0,0 +1,70 @@
+import { play } from './sampler.js';
+
+const load = () => {
+  let reader = new FileReader();
+  
+  reader.onload = (loadedFile) => {
+    let binary = new Uint8Array(loadedFile.srcElement.result, 0, loadedFile.srcElement.result.byteLength);
+    parse(binary);
+  };
+
+  document.querySelector('[type="file"]').files[0] |> reader.readAsArrayBuffer;
+};
+
+const parse = (binary) => {
+  var sound = {
+    channelNumber: toLittleEndian(binary.slice(22, 23)),
+    sampleRate: toLittleEndian(binary.slice(24, 27)),
+    bitsPerSample: toLittleEndian(binary.slice(34, 35)),
+    dataLength: toLittleEndian(binary.slice(40, 43))
+  };
+  
+  sound.data = Array.from(binary.slice(44, binary.length));
+
+  sound.data = sound.data.map((byte, index) => {
+    if (index % 2 === 0) {
+      var short = composeBytes(byte, sound.data[index + 1]);
+      var range = 1 << sound.bitsPerSample - 1;
+      
+      if (short >= range) {
+        short |= ~(range -1);
+      }
+      return (short / range);
+
+    }
+  }).filter((item) => {
+    return item !== undefined;
+  });
+
+  sound.data.leftChannel = sound.data.map((short, index) => {
+    if (index % 2 === 0)
+      return short;
+  }).filter( (item) => {
+    return item !== undefined;
+  });
+
+  sound.data.rightChannel = sound.data.map((short, index) => {
+    if (index % 2 !== 0)
+      return short;
+  }).filter( (item) => {
+    return item !== undefined;
+  });
+
+  document.querySelector('.play-button').addEventListener('click', play.bind(null, sound));
+};
+
+const composeBytes = (low, high) => {
+  return parseInt(`0x${('00' + high.toString(16)).substr(-2)}${('00' + low.toString(16)).substr(-2)}`);
+};
+
+const toLittleEndian = (array) => {
+  return parseInt(array.slice().reverse().reduce((prev, current) => {
+    // review if
+    if (current)
+      return prev.toString(16) + current.toString(16);
+    
+    return '';
+  }, ''), 16);
+};
+
+document.querySelector('.load-button').addEventListener('click', load);
\ No newline at end of file
diff --git a/src/sampler.js b/src/sampler.js
new file mode 100644
index 0000000..7ac6cb7
--- /dev/null
+++ b/src/sampler.js
@@ -0,0 +1,22 @@
+export const play = (sound) => {
+  var audio = new (window.AudioContext || window.webkitAudioContext)();
+
+  let data = audio.createBuffer(2, sound.dataLength / 2 * 8 / sound.bitsPerSample, sound.sampleRate);
+
+  for (var channel = 0; channel < sound.channelNumber; channel++) {
+    var nowBuffering = data.getChannelData(channel);
+    for (var i = 0; i < data.length; i++) {
+      if (channel === 0)
+        nowBuffering[i] = sound.data.leftChannel[i];
+      else
+        nowBuffering[i] = sound.data.rightChannel[i];
+    }
+  }
+
+  var source = audio.createBufferSource();
+  source.buffer = data;
+
+  source.connect(audio.destination);
+
+  source.start();
+};
\ No newline at end of file