typed arrays: add slice() support to ArrayBuffer

src/v8_typed_array.cc

@@ -71,6 +71,13 @@ class ArrayBuffer {
     v8::Local<v8::ObjectTemplate> instance = ft_cache->InstanceTemplate();
     instance->SetInternalFieldCount(1);  // Buffer.
 
+    v8::Local<v8::Signature> default_signature = v8::Signature::New(ft_cache);
+
+    instance->Set(v8::String::New("slice"),
+                  v8::FunctionTemplate::New(&ArrayBuffer::slice,
+                                            v8::Handle<v8::Value>(),
+                                            default_signature));
+
     return ft_cache;
   }
 
@@ -139,6 +146,42 @@ class ArrayBuffer {
 
     return args.This();
   }
+
+  static v8::Handle<v8::Value> slice(const v8::Arguments& args) {
+    if (args.Length() < 1)
+       return ThrowError("Wrong number of arguments.");
+
+    unsigned int length =
+        args.This()->Get(v8::String::New("byteLength"))->Uint32Value();
+    int begin = args[0]->Int32Value();
+    int end = length;
+    if (args.Length() > 1)
+      end = args[1]->Int32Value();
+
+    if (begin < 0) begin = length + begin;
+    if (begin < 0) begin = 0;
+    if (static_cast<unsigned>(begin) > length) begin = length;
+
+    if (end < 0) end = length + end;
+    if (end < 0) end = 0;
+    if (static_cast<unsigned>(end) > length) end = length;
+
+    if (begin > end) begin = end;
+
+    unsigned int slice_length = end - begin;
+    v8::Local<v8::Value> argv[] = {
+        v8::Integer::New(slice_length)};
+    v8::Local<v8::Object> buffer = ArrayBuffer::GetTemplate()->
+        GetFunction()->NewInstance(1, argv);
+
+    if (buffer.IsEmpty()) return v8::Undefined();  // constructor failed
+
+    void* src = args.This()->GetPointerFromInternalField(0);
+    void* dest = buffer->GetPointerFromInternalField(0);
+    memcpy(dest, static_cast<char*>(src) + begin, slice_length);
+
+    return buffer;
+  }
 };
 
 static bool checkAlignment(size_t val, unsigned int bytes) {

test/simple/test-arraybuffer-slice.js

@@ -0,0 +1,89 @@
+// Copyright Joyent, Inc. and other Node contributors.
+
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+/*
+ * Tests to verify slice functionality of ArrayBuffer.
+ * (http://www.khronos.org/registry/typedarray/specs/latest/#5)
+ */
+
+var common = require('../common');
+var assert = require('assert');
+
+var buffer = new ArrayBuffer(8);
+var sub;
+var i;
+
+for (var i = 0; i < 8; i++) {
+  buffer[i] = i;
+}
+
+// slice a copy of buffer
+sub = buffer.slice(2, 6);
+
+// make sure it copied correctly
+assert.ok(sub instanceof ArrayBuffer);
+assert.equal(sub.byteLength, 4);
+
+for (i = 0; i < 4; i++) {
+  assert.equal(sub[i], i+2);
+}
+
+// modifications to the new slice shouldn't affect the original
+sub[0] = 999;
+
+for (i = 0; i < 8; i++) {
+  assert.equal(buffer[i], i);
+}
+
+// test optional end param
+sub = buffer.slice(5);
+
+assert.ok(sub instanceof ArrayBuffer);
+assert.equal(sub.byteLength, 3);
+for (i = 0; i < 3; i++) {
+  assert.equal(sub[i], i+5);
+}
+
+// test clamping
+sub = buffer.slice(-3, -1);
+
+assert.ok(sub instanceof ArrayBuffer);
+assert.equal(sub.byteLength, 2);
+for (i = 0; i < 2; i++) {
+  assert.equal(sub[i], i+5);
+}
+
+// test invalid clamping range
+sub = buffer.slice(-1, -3);
+
+assert.ok(sub instanceof ArrayBuffer);
+assert.equal(sub.byteLength, 0);
+
+// test wrong number of arguments
+var gotError = false;
+
+try {
+  sub = buffer.slice();
+} catch (e) {
+  gotError = true;
+}
+
+assert.ok(gotError);