Header-only library to expose C++ classes and functions into V8 to use them in JavaScript code. v8pp uses heavy template metaprogramming and variadic template parameters which requires modern compiler with C++11 support. The library has been tested on:
- Microsoft Visual C++ 2015/2017 (Windows 10)
- GCC 5.4.0 (Ubuntu 16.04)
- Clang 5.0.0 (Ubuntu 16.04)
v8pp supports V8 versions after 6.3 with v8::Isolate usage in API. There are 2 targets for binding:
v8pp::module, a wrapper class aroundv8::ObjectTemplatev8pp::class_, a template class wrapper aroundv8::FunctionTemplate
Both of them require a pointer to v8::Isolate instance. They allows to bind from C++ code such items as variables, functions, constants with a function set(name, item):
v8::Isolate* isolate;
int var;
int get_var() { return var + 1; }
void set_var(int x) { var = x + 1; }
struct X
{
X(int v, bool u) : var(v) {}
int var;
int get() const { return var; }
void set(int x) { var = x; }
};
// bind free variables and functions
v8pp::module mylib(isolate);
mylib
// set read-only attribute
.set_const("PI", 3.1415)
// set variable available in JavaScript with name `var`
.set("var", var)
// set function get_var as `fun`
.set("fun", &get_var)
// set property `prop` with getter get_var() and setter set_var()
.set("prop", property(get_var, set_var));
// bind class
v8pp::class_<X> X_class(isolate);
X_class
// specify X constructor signature
.ctor<int, bool>()
// bind variable
.set("var", &X::var)
// bind function
.set("fun", &X::set)
// bind read-only property
.set("prop", property(&X::get));
// set class into the module template
mylib.set("X", X_class);
// set bindings in global object as `mylib`
isolate->GetCurrentContext()->Global()->Set(
v8::String::NewFromUtf8(isolate, "mylib"), mylib.new_instance());After that bindings will be available in JavaScript:
mylib.var = mylib.PI + mylib.fun();
var x = new mylib.X(1, true);
mylib.prop = x.prop + x.fun();The library is suitable to make Node.js and io.js addons. See addons document.
void RegisterModule(v8::Local<v8::Object> exports)
{
v8pp::module addon(v8::Isolate::GetCurrent());
// set bindings...
addon
.set("fun", &function)
.set("cls", my_class)
;
// set bindings as exports object prototype
exports->SetPrototype(addon.new_instance());
}v8pp- a static library to add several global functions (load/require to the v8 JavaScript context.require()is a system for loading plugins from shared libraries.test- A binary for running JavaScript files in a context which has v8pp module loading functions provided.
#include <iostream>
#include <v8pp/module.hpp>
namespace console {
void log(v8::FunctionCallbackInfo<v8::Value> const& args)
{
v8::HandleScope handle_scope(args.GetIsolate());
for (int i = 0; i < args.Length(); ++i)
{
if (i > 0) std::cout << ' ';
v8::String::Utf8Value str(args[i]);
std::cout << *str;
}
std::cout << std::endl;
}
v8::Local<v8::Value> init(v8::Isolate* isolate)
{
v8pp::module m(isolate);
m.set("log", &log);
return m.new_instance();
}
} // namespace consoleV8PP_PLUGIN_INIT(v8::Isolate* isolate)
{
return console::init(isolate);
}#include <v8pp/module.hpp>
#include <v8pp/class.hpp>
#include <fstream>
namespace file {
bool rename(char const* src, char const* dest)
{
return std::rename(src, dest) == 0;
}
class file_base
{
public:
bool is_open() const { return stream_.is_open(); }
bool good() const { return stream_.good(); }
bool eof() const { return stream_.eof(); }
void close() { stream_.close(); }
protected:
std::fstream stream_;
};
class file_writer : public file_base
{
public:
explicit file_writer(v8::FunctionCallbackInfo<v8::Value> const& args)
{
if (args.Length() == 1)
{
v8::String::Utf8Value str(args[0]);
open(*str);
}
}
bool open(char const* path)
{
stream_.open(path, std::ios_base::out);
return stream_.good();
}
void print(v8::FunctionCallbackInfo<v8::Value> const& args)
{
v8::HandleScope scope(args.GetIsolate());
for (int i = 0; i < args.Length(); ++i)
{
if (i > 0) stream_ << ' ';
v8::String::Utf8Value str(args[i]);
stream_ << *str;
}
}
void println(v8::FunctionCallbackInfo<v8::Value> const& args)
{
print(args);
stream_ << std::endl;
}
};
class file_reader : public file_base
{
public:
explicit file_reader(char const* path)
{
open(path);
}
bool open(const char* path)
{
stream_.open(path, std::ios_base::in);
return stream_.good();
}
v8::Local<v8::Value> getline(v8::Isolate* isolate)
{
if ( stream_.good() && ! stream_.eof())
{
std::string line;
std::getline(stream_, line);
return v8pp::to_v8(isolate, line);
}
else
{
return v8::Undefined(isolate);
}
}
};
v8::Local<v8::Value> init(v8::Isolate* isolate)
{
v8::EscapableHandleScope scope(isolate);
// file_base binding, no .ctor() specified, object creation disallowed in JavaScript
v8pp::class_<file_base> file_base_class(isolate);
file_base_class
.set("close", &file_base::close)
.set("good", &file_base::good)
.set("is_open", &file_base::is_open)
.set("eof", &file_base::eof)
;
// .ctor<> template arguments declares types of file_writer constructor
// file_writer inherits from file_base_class
v8pp::class_<file_writer> file_writer_class(isolate);
file_writer_class
.ctor<v8::FunctionCallbackInfo<v8::Value> const&>()
.inherit<file_base>()
.set("open", &file_writer::open)
.set("print", &file_writer::print)
.set("println", &file_writer::println)
;
// .ctor<> template arguments declares types of file_reader constructor.
// file_base inherits from file_base_class
v8pp::class_<file_reader> file_reader_class(isolate);
file_reader_class
.ctor<char const*>()
.inherit<file_base>()
.set("open", &file_reader::open)
.set("getln", &file_reader::getline)
;
// Create a module to add classes and functions to and return a
// new instance of the module to be embedded into the v8 context
v8pp::module m(isolate);
m.set("rename", &rename)
.set("writer", file_writer_class)
.set("reader", file_reader_class)
;
return scope.Escape(m.new_instance());
}
} // namespace file
V8PP_PLUGIN_INIT(v8::Isolate* isolate)
{
return file::init(isolate);
}#include <v8pp/context.hpp>
v8pp::context context;
context.set_lib_path("path/to/plugins/lib");
// script can now use require() function. An application
// that uses v8pp::context must link against v8pp library.
v8::HandleScope scope(context.isolate());
context.run_file("some_file.js");// Load the file module from the class binding example and the
// console module.
var file = require('file'),
console = require('console')
var writer = new file.writer("file")
if (writer.is_open()) {
writer.println("some text")
writer.close()
if (! file.rename("file", "newfile"))
console.log("could not rename file")
}
else console.log("could not open `file'")
console.log("exit")// Memory for C++ class will remain when JavaScript object is deleted.
// Useful for classes you only wish to inject.
typedef v8pp::class_<my_class> my_class_wrapper;
v8::Local<v8::Value> val = my_class_wrapper::reference_external(isolate, &my_class::instance());
// Assuming my_class::instance() returns reference to class// Memory for c++ object will be reclaimed by JavaScript using "delete" when
// JavaScript class is deleted.
typedef v8pp::class_<my_class> my_class_wrapper;
v8::Local<v8::Value> val = my_class_wrapper::import_external(isolate, new my_class);The library uses several preprocessor macros, defined in v8pp/config.hpp file:
V8PP_ISOLATE_DATA_SLOT- A v8::Isolate data slot number, used to store v8pp internal dataV8PP_PLUGIN_INIT_PROC_NAME- Plugin initialization procedure name that should be exported from a v8pp plugin.V8PP_PLUGIN_SUFFIX- Plugin filename suffix that would be added if the plugin name used inrequire()doesn't end with it.V8PP_HEADER_ONLY- Use header-only implemenation, enabled by default.