buffer: return offset for end of last write

Author: trevnorris

lib/buffer.js

@@ -574,6 +574,7 @@ Buffer.prototype.writeUInt8 = function(value, offset, noAssert) {
   if (!noAssert)
     checkInt(this, value, offset, 1, 0xff, 0);
   this[offset] = value;
+  return offset + 1;
 };
 
 
@@ -594,6 +595,7 @@ Buffer.prototype.writeUInt16LE = function(value, offset, noAssert) {
   if (!noAssert)
     checkInt(this, value, offset, 2, 0xffff, 0);
   writeUInt16(this, value, offset, false);
+  return offset + 2;
 };
 
 
@@ -603,6 +605,7 @@ Buffer.prototype.writeUInt16BE = function(value, offset, noAssert) {
   if (!noAssert)
     checkInt(this, value, offset, 2, 0xffff, 0);
   writeUInt16(this, value, offset, true);
+  return offset + 2;
 };
 
 
@@ -627,6 +630,7 @@ Buffer.prototype.writeUInt32LE = function(value, offset, noAssert) {
   if (!noAssert)
     checkInt(this, value, offset, 4, 0xffffffff, 0);
   writeUInt32(this, value, offset, false);
+  return offset + 4;
 };
 
 
@@ -636,6 +640,7 @@ Buffer.prototype.writeUInt32BE = function(value, offset, noAssert) {
   if (!noAssert)
     checkInt(this, value, offset, 4, 0xffffffff, 0);
   writeUInt32(this, value, offset, true);
+  return offset + 4;
 };
 
 
@@ -683,6 +688,7 @@ Buffer.prototype.writeInt8 = function(value, offset, noAssert) {
     checkInt(this, value, offset, 1, 0x7f, -0x80);
   if (value < 0) value = 0xff + value + 1;
   this[offset] = value;
+  return offset + 1;
 };
 
 
@@ -693,6 +699,7 @@ Buffer.prototype.writeInt16LE = function(value, offset, noAssert) {
     checkInt(this, value, offset, 2, 0x7fff, -0x8000);
   if (value < 0) value = 0xffff + value + 1;
   writeUInt16(this, value, offset, false);
+  return offset + 2;
 };
 
 
@@ -703,6 +710,7 @@ Buffer.prototype.writeInt16BE = function(value, offset, noAssert) {
     checkInt(this, value, offset, 2, 0x7fff, -0x8000);
   if (value < 0) value = 0xffff + value + 1;
   writeUInt16(this, value, offset, true);
+  return offset + 2;
 };
 
 
@@ -713,6 +721,7 @@ Buffer.prototype.writeInt32LE = function(value, offset, noAssert) {
     checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000);
   if (value < 0) value = 0xffffffff + value + 1;
   writeUInt32(this, value, offset, false);
+  return offset + 4;
 };
 
 
@@ -723,4 +732,5 @@ Buffer.prototype.writeInt32BE = function(value, offset, noAssert) {
     checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000);
   if (value < 0) value = 0xffffffff + value + 1;
   writeUInt32(this, value, offset, true);
+  return offset + 4;
 };

src/node_buffer.cc

@@ -485,18 +485,23 @@ void ReadDoubleBE(const FunctionCallbackInfo<Value>& args) {
 
 
 template <typename T, enum Endianness endianness>
-void WriteFloatGeneric(const FunctionCallbackInfo<Value>& args) {
+uint32_t WriteFloatGeneric(const FunctionCallbackInfo<Value>& args) {
   bool doAssert = !args[2]->BooleanValue();
 
   T val = static_cast<T>(args[0]->NumberValue());
   size_t offset;
 
-  CHECK_NOT_OOB(ParseArrayIndex(args[1], 0, &offset));
+  if (!ParseArrayIndex(args[1], 0, &offset)) {
+    ThrowRangeError("out of range index");
+    return 0;
+  }
 
   if (doAssert) {
     size_t len = Length(args.This());
-    if (offset + sizeof(T) > len || offset + sizeof(T) < offset)
-      return ThrowRangeError("Trying to write beyond buffer length");
+    if (offset + sizeof(T) > len || offset + sizeof(T) < offset) {
+      ThrowRangeError("Trying to write beyond buffer length");
+      return 0;
+    }
   }
 
   union NoAlias {
@@ -509,26 +514,27 @@ void WriteFloatGeneric(const FunctionCallbackInfo<Value>& args) {
   char* ptr = static_cast<char*>(data) + offset;
   if (endianness != GetEndianness()) Swizzle(na.bytes, sizeof(na.bytes));
   memcpy(ptr, na.bytes, sizeof(na.bytes));
+  return offset + sizeof(na.bytes);
 }
 
 
 void WriteFloatLE(const FunctionCallbackInfo<Value>& args) {
-  WriteFloatGeneric<float, kLittleEndian>(args);
+  args.GetReturnValue().Set(WriteFloatGeneric<float, kLittleEndian>(args));
 }
 
 
 void WriteFloatBE(const FunctionCallbackInfo<Value>& args) {
-  WriteFloatGeneric<float, kBigEndian>(args);
+  args.GetReturnValue().Set(WriteFloatGeneric<float, kBigEndian>(args));
 }
 
 
 void WriteDoubleLE(const FunctionCallbackInfo<Value>& args) {
-  WriteFloatGeneric<double, kLittleEndian>(args);
+  args.GetReturnValue().Set(WriteFloatGeneric<double, kLittleEndian>(args));
 }
 
 
 void WriteDoubleBE(const FunctionCallbackInfo<Value>& args) {
-  WriteFloatGeneric<double, kBigEndian>(args);
+  args.GetReturnValue().Set(WriteFloatGeneric<double, kBigEndian>(args));
 }
 
 

test/simple/test-buffer.js

@@ -778,6 +778,14 @@ assert.equal(buf[3], 0xFF);
   assert.equal(buf[3], 0xFF);
 });
 
+// test offset returns are correct
+var b = new Buffer(16);
+assert.equal(4, b.writeUInt32LE(0, 0));
+assert.equal(6, b.writeUInt16LE(0, 4));
+assert.equal(7, b.writeUInt8(0, 6));
+assert.equal(8, b.writeInt8(0, 7));
+assert.equal(16, b.writeDoubleLE(0, 8));
+
 // test for buffer overrun
 buf = new Buffer([0, 0, 0, 0, 0]); // length: 5
 var sub = buf.slice(0, 4);         // length: 4