From 5bb0cb908280bf6d48909897c1a93541609a226b Mon Sep 17 00:00:00 2001
From: Trevor Johnston <trevj@google.com>
Date: Thu, 14 Apr 2016 19:48:33 -0400
Subject: [PATCH] farm out arraybuffers.concat to Buffer

---
 src/arraybuffers/arraybuffers.spec.ts | 38 +--------------------------
 src/arraybuffers/arraybuffers.ts      | 22 +++++-----------
 2 files changed, 7 insertions(+), 53 deletions(-)

diff --git a/src/arraybuffers/arraybuffers.spec.ts b/src/arraybuffers/arraybuffers.spec.ts
index f4bf557..8e8e1eb 100644
--- a/src/arraybuffers/arraybuffers.spec.ts
+++ b/src/arraybuffers/arraybuffers.spec.ts
@@ -68,49 +68,13 @@ describe('ArrayBuffers <-> Hex Strings', function() {
   });
 });
 
-describe('ArrayBuffers concat & chunk', function() {
+describe('ArrayBuffers chunk', function() {
   it('chunk(array12, 6).length == 3', function() {
     expect(arraybuffers.chunk(array12,6).length).toBe(3);
   });
   it('chunk(array12, 1).length == 15', function() {
     expect(arraybuffers.chunk(array12,1).length).toBe(15);
   });
-  it('concat(array1,array2) == array12', function() {
-    expect(arraybuffers.byteEquality(
-        arraybuffers.concat([array1, array2]),
-        array12))
-      .toBe(true);
-  });
-  it('concat(chunk(array12, 1)) == array12', function() {
-    expect(arraybuffers.byteEquality(
-        arraybuffers.concat(arraybuffers.chunk(array12,1)),
-        array12))
-      .toBe(true);
-  });
-  it('concat(chunk(array12, 4)) == array12', function() {
-    expect(arraybuffers.byteEquality(
-        arraybuffers.concat(arraybuffers.chunk(array12,4)),
-        array12))
-      .toBe(true);
-  });
-  it('concat(chunk(array12, 5)) == array12', function() {
-    expect(arraybuffers.byteEquality(
-        arraybuffers.concat(arraybuffers.chunk(array12,5)),
-        array12))
-      .toBe(true);
-  });
-  it('concat(chunk(array12, array12.byteLength)) == array12', function() {
-    expect(arraybuffers.byteEquality(
-        arraybuffers.concat(arraybuffers.chunk(array12,array12.byteLength)),
-        array12))
-      .toBe(true);
-  });
-  it('concat(chunk(array12, 20)) == array12', function() {
-    expect(arraybuffers.byteEquality(
-        arraybuffers.concat(arraybuffers.chunk(array12,20)),
-        array12))
-      .toBe(true);
-  });
 });
 
 describe('ArrayBuffers <-> strings', function() {
diff --git a/src/arraybuffers/arraybuffers.ts b/src/arraybuffers/arraybuffers.ts
index d3010d4..41fd72b 100644
--- a/src/arraybuffers/arraybuffers.ts
+++ b/src/arraybuffers/arraybuffers.ts
@@ -6,22 +6,12 @@ export function byteEquality(b1: ArrayBuffer, b2: ArrayBuffer): boolean {
   return new Buffer(b1).equals(new Buffer(b2));
 }
 
-// Concat |ArrayBuffer|s into a single ArrayBuffer. If size is given, then
-// the destination array buffer is of the given size. If size is not given or
-// zero, the  size of all buffers is summed to make the new array buffer.
-export function concat(buffers:ArrayBuffer[], size?:number)
-    :ArrayBuffer {
-  if(!size) {
-    size = 0;
-    buffers.forEach(a => { size += a.byteLength });
-  }
-  var accumulatorBuffer = new Uint8Array(size);
-  var location = 0;
-  buffers.forEach(a => {
-    accumulatorBuffer.set(new Uint8Array(a), location);
-    location += a.byteLength;
-  });
-  return accumulatorBuffer.buffer;
+// Returns a new ArrayBuffer which is the result of concatenating all the
+// supplied ArrayBuffers together. If size is supplied, the resulting
+// ArrayBuffer will be of the given size.
+export function concat(buffers: ArrayBuffer[], size?: number): ArrayBuffer {
+  // The Buffer instances share memory with their source ArrayBuffers.
+  return Buffer.concat(buffers.map(buffer => new Buffer(buffer)), size).buffer;
 }
 
 // Break an array buffer into multiple array buffers that are at most |size|