buffer: optimize Buffer.prototype.toString('hex')

Move the implementation to C++ land. The old JS implementation used
string concatenation, was dog slow and consumed copious amounts of
memory for large buffers. Example:

  var buf = Buffer(0x1000000);  // 16 MB
  buf.toString('hex')           // Used 3+ GB of memory.

The new implementation operates in O(n) time and space.

Fixes #4700.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/node_buffer.h b/src/node_buffer.h
index 48d0dd2727..27991fcfc0 100644
--- a/src/node_buffer.h
+++ b/src/node_buffer.h
@@ -118,6 +118,7 @@ class NODE_EXTERN Buffer: public ObjectWrap {
   static v8::Handle<v8::Value> Base64Slice(const v8::Arguments &args);
   static v8::Handle<v8::Value> Utf8Slice(const v8::Arguments &args);
   static v8::Handle<v8::Value> Ucs2Slice(const v8::Arguments &args);
+  static v8::Handle<v8::Value> HexSlice(const v8::Arguments &args);
   static v8::Handle<v8::Value> BinaryWrite(const v8::Arguments &args);
   static v8::Handle<v8::Value> Base64Write(const v8::Arguments &args);
   static v8::Handle<v8::Value> AsciiWrite(const v8::Arguments &args);