node/src/node_buffer.h at master · samrose/node · GitHub

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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

API.

class Buffer : public ObjectWrap {

public:

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);

}

~Buffer();

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

private:

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> Ucs2Slice(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> 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> 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_

node/src/node_buffer.h at master · samrose/node · GitHub

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