Making Dynamsoft Barcode SDK an Addon for Node.js

December 22, 2017 by  Filed under: Computer 
 

Do you know which programming language is currently ranking first on GitHub? It is JavaScript! JavaScript is not only used for HTML5 Web application development, but also for server-side programming…

Do you know which programming language is currently ranking first on GitHub? It is JavaScript! JavaScript is not only used for HTML5 Web application development, but also for server-side programming with runtime environment Node.js. With npm, the package manager for Node.js, it is so easy to install any Web frameworks or utilities. Although Node.js has provided many powerful JavaScript APIs, sometimes we have to create add-ons to empower Node.js with extra functionalities. In this tutorial, I’d like to share how to implement a JavaScript Barcode application with the custom addon, wrapped with C/C++ APIs of Dynamsoft Barcode SDK, for Node.js.

 

Setting Up Environment for Node.js Addon Development

To build add-ons for Node.js, we need to install the tool node-gyp:

1npm install -g node-gyp

Create an empty C/C++ file dbr.cc and a configuration file binding.gyp. Specify add-on name and C/C++ source files:

12345678{  “targets”: [    {      “target_name”: “dbr”,      “sources”: [ “dbr.cc” ]    }  ]}

Build dbr.node with the following command:

1node-gyp configure install

Under folder build, you will see Visual Studio files and dbr.node:

123456789build    / binding.sln    / dbr.vcxproj    / dbr.vcxproj.filters    / config.gypi    / Release        / dbr.node        / dbr.pdb        / obj

For more information, please read the basic tutorial of Node.js addons.

Wrapping Dynamsoft Barcode SDK as the Addon for Node.js

Let’s double-click binding.sln to import the project to Visual Studio. Since node-gyp has added Node.js-relevant configurations, you just need to insert the directories of Dynamsoft Barcode SDK header files and libraries. Besides, add the post-build event:

1copy “{installation directory}DynamsoftBarcode Reader 2.0 TrialRedistC_C++*.dll” “$(OutDir)”

Register a native method, and export the initialization function:

12345void Init(Handle exports) {    NODE_SET_METHOD(exports, “decodeFile”, DecodeFile);} NODE_MODULE(dbr, Init)

Convert barcode results to readable data for V8 JavaScript engine:

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253void DecodeFile(const FunctionCallbackInfo& 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 == DBR_OK){        int count = pResults->iBarcodeCount;        pBarcodeResult* ppBarcodes = pResults->ppBarcodes;        pBarcodeResult tmp = NULL;         // javascript callback function        Local cb = Local::Cast(args[1]);        const unsigned argc = 1;         // array for storing barcode results        Local barcodeResults = Array::New(isolate);         for (int i = 0; i Set(String::NewFromUtf8(isolate, “format”), Number::New(isolate, tmp->llFormat));            result->Set(String::NewFromUtf8(isolate, “value”), String::NewFromUtf8(isolate, tmp->pBarcodeData));             barcodeResults->Set(Number::New(isolate, i), result);        }         // release memory        DBR_FreeBarcodeResults(&pResults);         Local argv[argc] = { barcodeResults };        cb->Call(isolate->GetCurrentContext()->Global(), argc, argv);    }}

For more information, please refer to v8.h and Chrome V8.

Create a JavaScript file for test:

12345678910111213141516171819202122232425var 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:gitDynamsoft-Barcode-ReaderImagesAllSupportedBarcodeTypes.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 your simple JavaScript Barcode application with command line tool:

Source Code

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

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