Add Buffer::fill method to do memset

Fixes #477.

lib/buffer.js

@@ -373,6 +373,39 @@ Buffer.prototype.toString = function(encoding, start, end) {
 Buffer.byteLength = SlowBuffer.byteLength;
 
 
+// fill(value, start=0, end=buffer.length)
+Buffer.prototype.fill = function fill (value, start, end) {
+  value || (value = 0);
+  start || (start = 0);
+  end   || (end   = this.length);
+
+  if (typeof value === "string") {
+    value = value.charCodeAt(0);
+  }
+  if (!(typeof value === "number") || isNaN(value)) {
+    throw new Error("value is not a number");
+  }
+
+  if (end < start) throw new Error("end < start");
+
+  // Fill 0 bytes; we're done
+  if (end === start) return 0;
+  if (this.length == 0) return 0;
+
+  if (start < 0 || start >= this.length) {
+    throw new Error("start out of bounds");
+  }
+
+  if (end < 0 || end > this.length) {
+    throw new Error("end out of bounds");
+  }
+
+  return this.parent.fill(value,
+                          start + this.offset,
+                          end + this.offset);
+};
+
+
 // copy(targetBuffer, targetStart=0, sourceStart=0, sourceEnd=buffer.length)
 Buffer.prototype.copy = function(target, target_start, start, end) {
   var source = this;

src/node_buffer.cc

@@ -376,6 +376,27 @@ Handle<Value> Buffer::Base64Slice(const Arguments &args) {
 }
 
 
+// buffer.fill(value, start, end);
+Handle<Value> Buffer::Fill(const Arguments &args) {
+  HandleScope scope;
+
+  if (!args[0]->IsInt32()) {
+    return ThrowException(Exception::Error(String::New(
+            "value is not a number")));
+  }
+  int value = (char)args[0]->Int32Value();
+
+  Buffer *parent = ObjectWrap::Unwrap<Buffer>(args.This());
+  SLICE_ARGS(args[1], args[2])
+
+  memset( (void*)(parent->data_ + start),
+          value,
+          end - start);
+
+  return Undefined();
+}
+
+
 // var bytesCopied = buffer.copy(target, targetStart, sourceStart, sourceEnd);
 Handle<Value> Buffer::Copy(const Arguments &args) {
   HandleScope scope;
@@ -734,6 +755,7 @@ void Buffer::Initialize(Handle<Object> target) {
   NODE_SET_PROTOTYPE_METHOD(constructor_template, "binaryWrite", Buffer::BinaryWrite);
   NODE_SET_PROTOTYPE_METHOD(constructor_template, "base64Write", Buffer::Base64Write);
   NODE_SET_PROTOTYPE_METHOD(constructor_template, "ucs2Write", Buffer::Ucs2Write);
+  NODE_SET_PROTOTYPE_METHOD(constructor_template, "fill", Buffer::Fill);
   NODE_SET_PROTOTYPE_METHOD(constructor_template, "copy", Buffer::Copy);
 
   NODE_SET_METHOD(constructor_template->GetFunction(),

src/node_buffer.h

@@ -117,6 +117,7 @@ class Buffer : public ObjectWrap {
   static v8::Handle<v8::Value> Ucs2Write(const v8::Arguments &args);
   static v8::Handle<v8::Value> ByteLength(const v8::Arguments &args);
   static v8::Handle<v8::Value> MakeFastBuffer(const v8::Arguments &args);
+  static v8::Handle<v8::Value> Fill(const v8::Arguments &args);
   static v8::Handle<v8::Value> Copy(const v8::Arguments &args);
 
   Buffer(v8::Handle<v8::Object> wrapper, size_t length);

test/simple/test-buffer.js

@@ -540,3 +540,20 @@ console.log(z.length)
 assert.equal(2, z.length);
 assert.equal(0x66, z[0]);
 assert.equal(0x6f, z[1]);
+assert.equal(0, Buffer('hello').slice(0, 0).length)
+
+b = new Buffer(50);
+b.fill("h");
+for (var i = 0; i < b.length; i++) {
+  assert.equal("h".charCodeAt(0), b[i]);
+}
+
+b.fill(0);
+for (var i = 0; i < b.length; i++) {
+  assert.equal(0, b[i]);
+}
+
+b.fill(1, 16, 32);
+for (var i = 0; i < 16; i++) assert.equal(0, b[i]);
+for (; i < 32; i++) assert.equal(1, b[i]);
+for (; i < b.length; i++) assert.equal(0, b[i]);