Closes GH-609 Support array-ish args to Buffer ctor

Any array-ish thing (whether a Buffer, an Array, or just an object with
a numeric "length") is interpreted as a list of bytes.

lib/buffer.js

@@ -147,8 +147,8 @@ function Buffer(subject, encoding, offset) {
       pool.used += this.length;
     }
 
-    // Assume object is an array
-    if (Array.isArray(subject)) {
+    // Treat array-ish objects as a byte array.
+    if (isArrayIsh(subject)) {
       for (var i = 0; i < this.length; i++) {
         this.parent[i + this.offset] = subject[i];
       }
@@ -161,6 +161,12 @@ function Buffer(subject, encoding, offset) {
   SlowBuffer.makeFastBuffer(this.parent, this, this.offset, this.length);
 }
 
+function isArrayIsh(subject) {
+  return Array.isArray(subject) || Buffer.isBuffer(subject) ||
+         subject && typeof subject === 'object' &&
+         typeof subject.length === 'number';
+}
+
 exports.SlowBuffer = SlowBuffer;
 exports.Buffer = Buffer;
 

test/simple/test-buffer.js

@@ -216,6 +216,7 @@ assert.equal(d.length, 3);
 assert.equal(d[0], 23);
 assert.equal(d[1], 42);
 assert.equal(d[2], 255);
+assert.deepEqual(d, new Buffer(d));
 
 var e = new Buffer('über');
 console.error('uber: \'%s\'', e.toString());
@@ -234,6 +235,15 @@ console.error('f.length: %d     (should be 12)', f.length);
 assert.deepEqual(f, new Buffer([63, 4, 64, 4, 56, 4, 50, 4, 53, 4, 66, 4]));
 assert.equal(f.toString('ucs2'), 'привет');
 
+
+var arrayIsh = {0: 0, 1: 1, 2: 2, 3: 3, length: 4};
+var g = new Buffer(arrayIsh);
+assert.deepEqual(g, new Buffer([0, 1, 2, 3]));
+var strArrayIsh = {0: '0', 1: '1', 2: '2', 3: '3', length: 4};
+g = new Buffer(strArrayIsh);
+assert.deepEqual(g, new Buffer([0, 1, 2, 3]));
+
+
 //
 // Test toString('base64')
 //