本機擴展 - C++本機庫

Question

對於C庫鏈接，samples_extension工作正常，但C++庫如何？

我有++庫我想作爲一個原生擴展使用基於類的C，所以我們有，例如： -

class Connect { 
     open(...); 
    .... 
} 

在C++中，我想在DART相似的類。

看着dart_api.h和dart_native_api.h，我不清楚我是如何將類指針從C++傳遞到Dart的，以及如何在它們上調用方法並將其綁定到Dart類實例。 ResolveName如何與connection-> open（）類型的調用一起工作，或者我們完全不同的做法。

Answer 1

OK，挖掘一下的，我現在已經sussed這一點，我這樣做是在飛鏢： -

bool open() native 'Connection::open'; 

，在我的解析器尋找字符串「連接::開」然後調用本地功能。 所以，這意味着我的本地函數被命名爲'connectionOpen'和'messageOpen'等，所以我可以解決這些問題。

Answer 2

基本項目，可以得到問題的答案：

cpp_extension.cc

#include <string.h> 
#include <stdlib.h> 
#include <stdio.h> 

#ifdef _WIN32 
#include "windows.h" 
#else 
#include <stdbool.h> 
#include <dlfcn.h> 
#include <unistd.h> 
#include <sys/mman.h> 
#endif 

#include "dart_api.h" 

Dart_NativeFunction ResolveName(Dart_Handle name, int argc, bool* auto_setup_scope); 

DART_EXPORT Dart_Handle cpp_extension_Init(Dart_Handle parent_library) { 
    if (Dart_IsError(parent_library)) { return parent_library; } 

    Dart_Handle result_code = Dart_SetNativeResolver(parent_library, ResolveName); 
    if (Dart_IsError(result_code)) return result_code; 

    return Dart_Null(); 
} 

Dart_Handle HandleError(Dart_Handle handle) { 
    if (Dart_IsError(handle)) Dart_PropagateError(handle); 
    return handle; 
} 

class Connection { 
    int* buffer; 
    bool opened; 

    public: 
    Connection() { 
     opened = false; 
     buffer = new int[1000000]; 
     memset(buffer, 1, 1000000); 
    } 

    void close() { 
     opened = false; 
    } 

    void open(const char* connectionString) { 
     opened = true; 
    } 

    ~Connection() { 
     delete buffer; 
    } 
}; 

void ConnectionClose(Dart_NativeArguments arguments) { 
    Connection* connection; 
    Dart_Handle dh_handle; 

    Dart_EnterScope(); 
    dh_handle = Dart_GetNativeArgument(arguments, 0); 
    connection = (Connection*)dh_handle; 
    connection->close(); 
    Dart_Handle result = Dart_Null(); 
    Dart_SetReturnValue(arguments, result); 
    Dart_ExitScope(); 
} 

void ConnectionCreate(Dart_NativeArguments arguments) { 
    Connection* connection; 
    Dart_Handle result; 

    Dart_EnterScope(); 
    connection = new Connection(); 
    result = Dart_NewInteger((int64_t)connection); 
    Dart_SetReturnValue(arguments, result); 
    Dart_ExitScope(); 
} 

void ConnectionPeerFinalizer(Dart_WeakPersistentHandle handle, void *peer) { 
    delete (Connection*) peer; 
} 

void ConnectionPeerRegister(Dart_NativeArguments arguments) { 
    int64_t peer; 
    Dart_Handle dh_object; 
    Dart_Handle dh_peer; 

    Dart_EnterScope(); 
    dh_object = Dart_GetNativeArgument(arguments, 0); 
    dh_peer = Dart_GetNativeArgument(arguments, 1); 
    Dart_IntegerToInt64(dh_peer, &peer); 
    Dart_NewWeakPersistentHandle(dh_object, (void*)peer, ConnectionPeerFinalizer); 
    Dart_SetReturnValue(arguments, Dart_Null()); 
    Dart_ExitScope(); 
} 

void ConnectionOpen(Dart_NativeArguments arguments) { 
    Connection* connection; 
    const char* connectionString; 
    Dart_Handle dh_connectionString; 
    Dart_Handle dh_handle; 

    Dart_EnterScope(); 
    dh_handle = Dart_GetNativeArgument(arguments, 0); 
    dh_connectionString = Dart_GetNativeArgument(arguments, 1); 
    Dart_StringToCString(dh_connectionString, &connectionString); 
    connection = (Connection*)dh_handle; 
    connection->open(connectionString); 
    Dart_Handle result = Dart_Null(); 
    Dart_SetReturnValue(arguments, result); 
    Dart_ExitScope(); 
} 

struct FunctionLookup { 
    const char* name; 
    Dart_NativeFunction function; 
}; 

FunctionLookup function_list[] = { 
    {"ConnectionClose", ConnectionClose}, 
    {"ConnectionCreate", ConnectionCreate}, 
    {"ConnectionOpen", ConnectionOpen}, 
    {"ConnectionPeerRegister", ConnectionPeerRegister}, 
    {NULL, NULL}}; 

Dart_NativeFunction ResolveName(Dart_Handle name, int argc, bool* auto_setup_scope) { 
    if (!Dart_IsString(name)) return NULL; 
    Dart_NativeFunction result = NULL; 
    Dart_EnterScope(); 
    const char* cname; 
    HandleError(Dart_StringToCString(name, &cname)); 

    for (int i=0; function_list[i].name != NULL; ++i) { 
    if (strcmp(function_list[i].name, cname) == 0) { 
     result = function_list[i].function; 
     break; 
    } 
    } 
    Dart_ExitScope(); 
    return result; 
} 

cpp_extension.dart

library dart_and_cpp_classes.ext_cpp_extension; 

import "dart-ext:cpp_extension"; 

class Connection { 
    final String connectionString; 

    int _handle; 

    bool _opened = false; 

    Connection(this.connectionString) { 
    _handle = _create(); 
    _peerRegister(this, _handle); 
    } 

    bool get opened => _opened; 

    void close() { 
    _close(_handle); 
    _opened = false; 
    } 

    void open() { 
    _open(_handle, connectionString); 
    _opened = true; 
    } 

    int _create() native "ConnectionCreate"; 

    void _close(int handle) native "ConnectionClose"; 

    void _open(int handle, String connectionString) native "ConnectionOpen"; 

    void _peerRegister(Object object, int handle) native "ConnectionPeerRegister"; 
} 

use_cpp_extension.dart

import 'package:dart_and_cpp_classes/cpp_extension.dart'; 

void main() { 
    var count = 500; 
    var connections = []; 
    for(var i = 0; i < count; i++) { 
    var connection = new Connection("MYSQL"); 
    connection.open(); 
    connection.close(); 
    connections.add(connection); 
    } 

    connections = null; 
    print("Done"); 
} 

這是基本的（即用型）封裝在GitHub上：https://github.com/mezoni/dart_and_cpp_classes

其他在這個包所需的文件。

運行：

• 斌/ build_cpp_extension.dart
• 斌/ use_cpp_extension.dart

附：

我不是C++程序員。

請原諒我對這種語言的任何錯誤。