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#ifndef NODE_BUFFER_H_
#define NODE_BUFFER_H_
#include <node.h>
#include <node_object_wrap.h>
#include <v8.h>
#include <assert.h>
namespace node {
/* A buffer is a chunk of memory stored outside the V8 heap, mirrored by an
* object in javascript. The object is not totally opaque, one can access
* individual bytes with [] and slice it into substrings or sub-buffers
* without copying memory.
* // return an ascii encoded string - no memory is copied
* buffer.asciiSlice(0, 3)
The C++ API for Buffer changed radically between v0.2 and v0.3, in fact
it was the reason for bumping the version. In v0.2 JavaScript Buffers and
C++ Buffers were in one-to-one correspondence via ObjectWrap. We found
that it was faster to expose the C++ Buffers to JavaScript as a
"SlowBuffer" which is used as a private backend to pure JavaScript
"Buffer" objects - a 'Buffer' in v0.3 might look like this:
{ _parent: s,
_offset: 520,
length: 5 }
Migrating code C++ Buffer code from v0.2 to v0.3 is difficult. Here are
some tips:
- buffer->data() calls should become Buffer::Data(buffer) calls.
- buffer->length() calls should become Buffer::Length(buffer) calls.
- There should not be any ObjectWrap::Unwrap<Buffer>() calls. You should
not be storing pointers to Buffer objects at all - as they are
now considered internal structures. Instead consider making a
JavaScript reference to the buffer.
See the source code node-png as an example of a module which successfully
compiles on both v0.2 and v0.3 while making heavy use of the C++ Buffer
class Buffer : public ObjectWrap {
static bool HasInstance(v8::Handle<v8::Value> val);
static inline char* Data(v8::Handle<v8::Object> obj) {
return (char*)obj->GetIndexedPropertiesExternalArrayData();
static inline char* Data(Buffer *b) {
return Buffer::Data(b->handle_);
static inline size_t Length(v8::Handle<v8::Object> obj) {
return (size_t)obj->GetIndexedPropertiesExternalArrayDataLength();
static inline size_t Length(Buffer *b) {
return Buffer::Length(b);
typedef void (*free_callback)(char *data, void *hint);
// C++ API for constructing fast buffer
static v8::Handle<v8::Object> New(v8::Handle<v8::String> string);
static void Initialize(v8::Handle<v8::Object> target);
static Buffer* New(size_t length); // public constructor
static Buffer* New(char *data, size_t len); // public constructor
static Buffer* New(char *data, size_t length,
free_callback callback, void *hint); // public constructor
static v8::Persistent<v8::FunctionTemplate> constructor_template;
static v8::Handle<v8::Value> New(const v8::Arguments &args);
static v8::Handle<v8::Value> BinarySlice(const v8::Arguments &args);
static v8::Handle<v8::Value> AsciiSlice(const v8::Arguments &args);
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> 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);
static v8::Handle<v8::Value> Utf8Write(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> Copy(const v8::Arguments &args);
Buffer(v8::Handle<v8::Object> wrapper, size_t length);
void Replace(char *data, size_t length, free_callback callback, void *hint);
size_t length_;
char* data_;
free_callback callback_;
void* callback_hint_;
} // namespace node buffer
#endif // NODE_BUFFER_H_
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