node. js C + + extension implementation

Because of the node.js,javascript can be used for server-side programming. With various extensions, node. js can become very powerful. Share today how to create a node. js extension in C + +.

Reference Original: Making dynamsoft Barcode SDK an Addon for node. js

Build NODEJS development environment

To build the extension, you need to install Node-gyp:

NPM install-g Node-gyp

This library contains the header files and dependent libraries required by the JavaScript V8 engine.

Create a C + + file dbr.cc and configuration file Binding.gyp. Open the configuration file and include the extension and source code files:

{"Targets": [{"Target_name": "DBR", "Sources": ["dbr.cc"]}]}

can now be used to build Dbr.node, the dynamic link library for node. js, equivalent to a DLL. On the command line, enter:

Node-gyp Configure Install

This line of command did two things, first generating a project file for Visual Studio. Then the compiler that calls vs builds the dynamic-link library. You can look at the resulting file structure:

Build/binding.sln/dbr.vcxproj/dbr.vcxproj.filters/config.gypi/release/dbr.node/ Dbr.pdb/obj

For more information, refer to the official document, node. js Addons.

Encapsulating the Dynamsoft Barcode SDK as a node. js extension

Next we just need to use Visual Studio to write code and build the project. Because Node-gyp has added the header file path and the dependent library path to the project file at the time of configuration, we only need to make minor changes. Now double-click the binding.sln Import Project. Add Dynamsoft Barcode SDK-related header file path and library path. Finally add the post-build event to copy the DLL to the build directory:

Copy "{Installation Directory}\dynamsoft\barcode Reader 2.0 Trial\redist\c_c++\*.dll" "$ (OutDir)"

Now start writing C + + code. Similar to Java,python, when writing native code, you need to register the native function first. Initialize the barcode decoding interface:

void Init (Handle<object> exports) {Node_set_method (exports, "DecodeFile", DecodeFile);} Node_module (DBR, Init)

The

Next we convert the obtained data into the V8 data type. Use local<object> to store a barcode result, using local<array> to store all local<object> . Finally, the result is returned to the JavaScript layer through a callback function.

Void decodefile (Const functioncallbackinfo<value>& args)  {      isolate* isolate = isolate::getcurrent ();    handlescope  scope (isolate);      // convert v8 string to char *     string::utf8value utfstr (Args[0]->tostring ());     char  *pfilename = *utfstr;     int option_imaxbarcodesnumperpage  = -1;    int option_llBarcodeFormat = -1;      pBarcodeResultArray pResults = NULL;    ReaderOptions  Option;    setoptions (&option, option_imaxbarcodesnumperpage, option_ Llbarcodeformat);     // decode barcode image file     int ret = dbr_decodefIle (        pFileName,         &option,        &pResults         );     if  (RET&NBSP;==&NBSP;DBR_OK) {         int count = pResults->iBarcodeCount;         pBarcodeResult* ppBarcodes = pResults->ppBarcodes;         pBarcodeResult tmp = NULL;          // javascript callback function        Local< Function> cb = local<function>::cast (args[1]);         const unsigned argc = 1;           array for storing barcode results        local<array>  Barcoderesults = array::new (Isolate);         for  (int i = 0; i < count; i++)          {            tmp = ppBarcodes[i];              local<object> result  = object::new (Isolate);             Result->set (String::newfromutf8 (isolate,  "format"),  number::new (Isolate, tmp->llformat));             result->set (String::NewFromUtf8 ( isolate,  "value"),  string::newfromutf8 (isolate, tmp->pbarcodedata));        &nbsP;     barcoderesults->set (Number::new (isolate, i),  result);         }         // release  memory        dbr_freebarcoderesults (&pResults);          local<value> argv[argc] = { barcoderesults  };        cb->call (Isolate->getcurrentcontext ()->Global (),  argc, argv);     }}

Documents can refer to V8.h and chrome V8

Now create a JavaScript script file to test it:

Var dbr = require ('./build/release/dbr '); Var readline = require (' ReadLine ');  var rl = readline.createinterface ({  input: process.stdin,   Output: process.stdout});  rl.question ("Please input a barcode image path:   ",  function (answer)  {  // e.g. f:\git\dynamsoft-barcode-reader\images\ Allsupportedbarcodetypes.tif  dbr.decodefile (    answer,     function (msg) {      var result = null;       for  (index in msg)  {        result  = msg[index]        console.log (result[' format ');         console.log (result[' value ');         console.log ("################## ");      }    }  );    Rl.close ();});

Finally, run through the command line to view the results:

Source

Https://github.com/Dynamsoft/Dynamsoft-Barcode-Reader/tree/master/samples/Node.js

node. js C + + extension implementation