farm out arraybuffers.concat to Buffer

Author: trevj

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() {

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(arrayBuffers: ArrayBuffer[], size?: number): ArrayBuffer {
+  // The Buffer instances share memory with their source ArrayBuffers.
+  return Buffer.concat(arrayBuffers.map(ab => new Buffer(ab)), size).buffer;
 }
 
 // Break an array buffer into multiple array buffers that are at most |size|