1# NAPI<a name="EN-US_TOPIC_0000001149901711"></a> 2 3- [Introduction](#section11660541593) 4- [Directory Structure](#section161941989596) 5- [When to Use](#section11759141594811) 6- [Available APIs](#section1611515555510) 7- [How to Develop](#section937267212) 8- [Repositories Involved](#section3970193518214) 9 10## Introduction<a name="section11660541593"></a> 11 12The **foundation/arkui/napi** repository contains a development framework for extending the JS Native Module and provides APIs developed based on Node.js N-API for external use. 13 14**Figure 1** Architecture<a name="fig1049423884819"></a> 15 16 17 18 19- **NativeEngine** 20 21 NativeEngine is the JS engine abstraction layer. It unifies API behavior of the JS engines at the NAPI layer. 22 23- **ModuleManager** 24 25 ModuleManager is used to load modules and cache module information. 26 27- **ScopeManager** 28 29 ScopeManager manages the NativeValue lifecycle. 30 31- **ReferenceManager** 32 33 ReferenceManager manages the NativeReference lifecycle. 34 35 36## Directory Structure<a name="section161941989596"></a> 37 38The source code directory structure of this repository is as follows: 39 40``` 41foundation/arkui/napi 42 ├── interfaces 43 │ └── kits 44 │ └── napi # NAPI header files 45 ├── module_manager # Module manager 46 ├── native_engine # NativeEngine abstraction layer 47 │ └── impl 48 │ └── ark # Ark-based NativeEngine implementation 49 ├── scope_manager # Scope manager 50 └── test # Test code 51``` 52 53## When to Use<a name="section11759141594811"></a> 54 55NAPI is suitable for processing I/O- and CPU-intensive tasks and system tasks. It encapsulates the capabilities and provides them to apps as JS APIs. NAPI can be used to implement mutual access between JS and C/C++ code. You can use NAPI to develop modules such as network communications, serial port access, multimedia decoding, and sensor data collection. 56 57## Available APIs<a name="section1611515555510"></a> 58 59For details about the API implementation, see the **foundation/arkui/napi** repository. 60 61**Table 1** Available NAPIs 62 63<a name="table10789351555"></a> 64<table><thead align="left"><tr id="row1878635175515"><th class="cellrowborder" valign="top" width="19.439999999999998%" id="mcps1.2.3.1.1"><p id="p27816352556"><a name="p27816352556"></a><a name="p27816352556"></a>Category</p> 65</th> 66<th class="cellrowborder" valign="top" width="80.56%" id="mcps1.2.3.1.2"><p id="p078835105514"><a name="p078835105514"></a><a name="p078835105514"></a>Description</p> 67</th> 68</tr> 69</thead> 70<tbody><tr id="row17863535520"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p678143512552"><a name="p678143512552"></a><a name="p678143512552"></a>Module registration</p> 71</td> 72<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p4781035185515"><a name="p4781035185515"></a><a name="p4781035185515"></a>Registers module information with a manager.</p> 73</td> 74</tr> 75<tr id="row67951538205618"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p127961438195616"><a name="p127961438195616"></a><a name="p127961438195616"></a>Exception & Error handling</p> 76</td> 77<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p47961338195617"><a name="p47961338195617"></a><a name="p47961338195617"></a>Throws exceptions.</p> 78</td> 79</tr> 80<tr id="row778417510579"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p1878575185715"><a name="p1878575185715"></a><a name="p1878575185715"></a>Object lifecycle</p> 81</td> 82<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p1178565175711"><a name="p1178565175711"></a><a name="p1178565175711"></a>Manages NAPI object lifecycle within limited scopes.</p> 83</td> 84</tr> 85<tr id="row83179619572"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p1531786125717"><a name="p1531786125717"></a><a name="p1531786125717"></a>JS object</p> 86</td> 87<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p12317663572"><a name="p12317663572"></a><a name="p12317663572"></a>Creates standard object types.</p> 88</td> 89</tr> 90<tr id="row63859616579"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p438696165720"><a name="p438696165720"></a><a name="p438696165720"></a>C-to-NAPI</p> 91</td> 92<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p14386462570"><a name="p14386462570"></a><a name="p14386462570"></a>Converts data types from C to NAPI.</p> 93</td> 94</tr> 95<tr id="row1145119612578"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p13451116115716"><a name="p13451116115716"></a><a name="p13451116115716"></a>NAPI-to-C</p> 96</td> 97<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p12451464574"><a name="p12451464574"></a><a name="p12451464574"></a>Converts data types from NAPI to C.</p> 98</td> 99</tr> 100<tr id="row1451436155720"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p155147625713"><a name="p155147625713"></a><a name="p155147625713"></a>Global instance</p> 101</td> 102<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p551466195713"><a name="p551466195713"></a><a name="p551466195713"></a>Obtains global instances.</p> 103</td> 104</tr> 105<tr id="row65815617579"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p458119617577"><a name="p458119617577"></a><a name="p458119617577"></a>JS value</p> 106</td> 107<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p125818625711"><a name="p125818625711"></a><a name="p125818625711"></a>Provides APIs executing <strong id="b18893622126"><a name="b18893622126"></a><a name="b18893622126"></a>===</strong>, <strong id="b5190121451212"><a name="b5190121451212"></a><a name="b5190121451212"></a>typeof</strong>, <strong id="b01299162121"><a name="b01299162121"></a><a name="b01299162121"></a>instanceof</strong>, and other operations alike.</p> 108</td> 109</tr> 110<tr id="row10649166145711"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p18649196195716"><a name="p18649196195716"></a><a name="p18649196195716"></a>JS object property</p> 111</td> 112<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p164919615574"><a name="p164919615574"></a><a name="p164919615574"></a>Provides functions for performing operations on object properties.</p> 113</td> 114</tr> 115<tr id="row0714260574"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p37143675714"><a name="p37143675714"></a><a name="p37143675714"></a>JS function</p> 116</td> 117<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p771466115711"><a name="p771466115711"></a><a name="p771466115711"></a>Invokes functions and creates instances.</p> 118</td> 119</tr> 120<tr id="row1578176155717"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p1782126155711"><a name="p1782126155711"></a><a name="p1782126155711"></a>Object encapsulation</p> 121</td> 122<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p87821967572"><a name="p87821967572"></a><a name="p87821967572"></a>Binds the external context of JS objects.</p> 123</td> 124</tr> 125<tr id="row8854116105717"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p1685414619578"><a name="p1685414619578"></a><a name="p1685414619578"></a>Simple asynchronization</p> 126</td> 127<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p1685411612574"><a name="p1685411612574"></a><a name="p1685411612574"></a>Creates asynchronous tasks.</p> 128</td> 129</tr> 130<tr id="row109154635718"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p391556195720"><a name="p391556195720"></a><a name="p391556195720"></a>Promise</p> 131</td> 132<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p1091566135717"><a name="p1091566135717"></a><a name="p1091566135717"></a>Creates a function set for a promise.</p> 133</td> 134</tr> 135<tr id="row1671493313016"><td class="cellrowborder" valign="top" width="19.439999999999998%" headers="mcps1.2.3.1.1 "><p id="p1971512331709"><a name="p1971512331709"></a><a name="p1971512331709"></a>Script</p> 136</td> 137<td class="cellrowborder" valign="top" width="80.56%" headers="mcps1.2.3.1.2 "><p id="p371517332013"><a name="p371517332013"></a><a name="p371517332013"></a>Runs JS code.</p> 138</td> 139</tr> 140</tbody> 141</table> 142 143## How to Develop<a name="section937267212"></a> 144 145The following example describes how to use NAPI to develop a JS API for obtaining the application bundle name. 146 147The prototype of the JS API is as follows: 148 149``` 150function getAppName(): string; 151``` 152 153The implementation code of the JS API is as follows: 154 155``` 156// app.cpp 157#include <stdio.h> 158#include <string.h> 159#include "napi/native_api.h" 160#include "napi/native_node_api.h" 161 162struct AsyncCallbackInfo { 163 napi_env env; 164 napi_async_work asyncWork; 165 napi_deferred deferred; 166}; 167 168// C/C++ function corresponding to getAppName() 169napi_value JSGetAppName(napi_env env, napi_callback_info info) { 170 napi_deferred deferred; 171 napi_value promise; 172 // Create a promise. 173 NAPI_CALL(env, napi_create_promise(env, &deferred, &promise)); 174 175 AsyncCallbackInfo* asyncCallbackInfo = new AsyncCallbackInfo { 176 .env = env, 177 .asyncWork = nullptr, 178 .deferred = deferred, 179 }; 180 181 napi_value resourceName; 182 napi_create_string_latin1(env, "GetAppName", NAPI_AUTO_LENGTH, &resourceName); 183 // Create a queue of asynchronous tasks. 184 napi_create_async_work( 185 env, nullptr, resourceName, 186 // Callback for an asynchronous task 187 [](napi_env env, void* data) {}, 188 // Callback after the asynchronous task is complete 189 [](napi_env env, napi_status status, void* data) { 190 AsyncCallbackInfo* asyncCallbackInfo = (AsyncCallbackInfo*)data; 191 napi_value appName; 192 const char* str = "com.example.helloworld"; 193 napi_create_string_utf8(env, str, strlen(str), &appName); 194 // Trigger the callback. 195 napi_resolve_deferred(asyncCallbackInfo->env, asyncCallbackInfo->deferred, appName); 196 napi_delete_async_work(env, asyncCallbackInfo->asyncWork); 197 delete asyncCallbackInfo; 198 }, 199 (void*)asyncCallbackInfo, &asyncCallbackInfo->asyncWork); 200 napi_queue_async_work(env, asyncCallbackInfo->asyncWork); 201 return promise; 202} 203 204// Export the module. 205static napi_value AppExport(napi_env env, napi_value exports) 206{ 207 static napi_property_descriptor desc[] = { 208 DECLARE_NAPI_FUNCTION("getAppName", JSGetAppName), 209 }; 210 NAPI_CALL(env, napi_define_properties(env, exports, sizeof(desc) / sizeof(desc[0]), desc)); 211 return exports; 212} 213 214// App module description 215static napi_module appModule = { 216 .nm_version = 1, 217 .nm_flags = 0, 218 .nm_filename = nullptr, 219 .nm_register_func = AppExport, 220 .nm_modname = "app", 221 .nm_priv = ((void*)0), 222 .reserved = {0} 223}; 224 225// Register the module. 226extern "C" __attribute__((constructor)) void AppRegister() 227{ 228 napi_module_register(&appModule); 229} 230``` 231 232The build script is as follows: 233 234``` 235// BUILD.gn 236import("//build/ohos.gni") 237ohos_shared_library("app") { 238 # Specify the source file to build. 239 sources = [ 240 "app.cpp", 241 ] 242 # Specify build dependencies. 243 deps = [ "//foundation/arkui/napi:ace_napi" ] 244 # Specify the directory where the library is generated. 245 relative_install_dir = "module" 246 subsystem_name = "arkui" 247 part_name = "napi" 248} 249``` 250 251Test code to run in your app is as follows: 252 253``` 254import app from '@ohos.app' 255export default { 256 testGetAppName() { 257 app.getAppName().then(function (data) { 258 console.info('app name: ' + data); 259 }); 260 } 261} 262``` 263 264## Repositories Involved<a name="section3970193518214"></a> 265[ArkUI framework](https://gitee.com/openharmony/docs/blob/master/en/readme/arkui.md) 266 267[arkui\_ace\_engine](https://gitee.com/openharmony/arkui_ace_engine/blob/master/README.md) 268 269[arkui\_ace\_engine\_lite](https://gitee.com/openharmony/arkui_ace_engine_lite/blob/master/README.md) 270 271**arkui\_napi** 272 273
