emnapi

简体中文

English

简体中文

English

Appearance

函数绑定 ​

参数处理 ​

假设需要编写一个 C 函数来连接两个 JavaScript 字符串：

ts
export declare function concatString (str1: string, str2: string): string
export declare function concatString (str1: string, str2: string): string
js
Module.onRuntimeInitialized = function () {  const result = Module.emnapiExports.concatString('Hello ', '世界')  console.log(result) // 'Hello 世界' }
Module.onRuntimeInitialized = function () {  const result = Module.emnapiExports.concatString('Hello ', '世界')  console.log(result) // 'Hello 世界' }

Node-API 实现 ​

c
#include <node_api.h> #include <string.h> #include <stdlib.h>  #define NAPI_CALL(env, the_call) /* ... */  static napi_value js_concat_string(napi_env env, napi_callback_info info) {  size_t argc = 2;  napi_value args[2];  NAPI_CALL(env, napi_get_cb_info(env, info, &argc, args, NULL, NULL));   if (argc < 2) {  napi_throw_type_error(env, NULL, "Wrong number of arguments");  return NULL;  }   napi_valuetype valuetype0, valuetype1;  NAPI_CALL(env, napi_typeof(env, args[0], &valuetype0));  NAPI_CALL(env, napi_typeof(env, args[1], &valuetype1));   if (valuetype0 != napi_string || valuetype1 != napi_string) {  napi_throw_type_error(env, NULL, "Wrong arguments");  return NULL;  }   size_t len1 = 0;  size_t len2 = 0;  NAPI_CALL(env, napi_get_value_string_utf8(env, args[0], NULL, 0, &len1));  NAPI_CALL(env, napi_get_value_string_utf8(env, args[1], NULL, 0, &len2));   size_t total_buffer_size = len1 + len2 + 1;  char* str = (char*) malloc(total_buffer_size);  if (str == NULL) {  napi_throw_error(env, NULL, "malloc failed");  return NULL;  }  napi_status status = napi_get_value_string_utf8(env, args[0],  str, total_buffer_size, &len1);  if (status != napi_ok) {  free(str);  NAPI_CALL(env, status);  }  status = napi_get_value_string_utf8(env, args[1],  str + len1, total_buffer_size - len1, &len2);  if (status != napi_ok) {  free(str);  NAPI_CALL(env, status);  }  *(str + len1 + len2) = '\0';   napi_value ret;  status = napi_create_string_utf8(env, str, len1 + len2, &ret);  free(str);  NAPI_CALL(env, status);  return ret; }  NAPI_MODULE_INIT() {  napi_value concat_string_fn;  NAPI_CALL(env, napi_create_function(env, "concatString", NAPI_AUTO_LENGTH,  js_concat_string, NULL, &concat_string_fn));  NAPI_CALL(env, napi_set_named_property(env, exports,  "concatString", concat_string_fn));  return exports; }
#include <node_api.h> #include <string.h> #include <stdlib.h>  #define NAPI_CALL(env, the_call) /* ... */  static napi_value js_concat_string(napi_env env, napi_callback_info info) {  size_t argc = 2;  napi_value args[2];  NAPI_CALL(env, napi_get_cb_info(env, info, &argc, args, NULL, NULL));   if (argc < 2) {  napi_throw_type_error(env, NULL, "Wrong number of arguments");  return NULL;  }   napi_valuetype valuetype0, valuetype1;  NAPI_CALL(env, napi_typeof(env, args[0], &valuetype0));  NAPI_CALL(env, napi_typeof(env, args[1], &valuetype1));   if (valuetype0 != napi_string || valuetype1 != napi_string) {  napi_throw_type_error(env, NULL, "Wrong arguments");  return NULL;  }   size_t len1 = 0;  size_t len2 = 0;  NAPI_CALL(env, napi_get_value_string_utf8(env, args[0], NULL, 0, &len1));  NAPI_CALL(env, napi_get_value_string_utf8(env, args[1], NULL, 0, &len2));   size_t total_buffer_size = len1 + len2 + 1;  char* str = (char*) malloc(total_buffer_size);  if (str == NULL) {  napi_throw_error(env, NULL, "malloc failed");  return NULL;  }  napi_status status = napi_get_value_string_utf8(env, args[0],  str, total_buffer_size, &len1);  if (status != napi_ok) {  free(str);  NAPI_CALL(env, status);  }  status = napi_get_value_string_utf8(env, args[1],  str + len1, total_buffer_size - len1, &len2);  if (status != napi_ok) {  free(str);  NAPI_CALL(env, status);  }  *(str + len1 + len2) = '\0';   napi_value ret;  status = napi_create_string_utf8(env, str, len1 + len2, &ret);  free(str);  NAPI_CALL(env, status);  return ret; }  NAPI_MODULE_INIT() {  napi_value concat_string_fn;  NAPI_CALL(env, napi_create_function(env, "concatString", NAPI_AUTO_LENGTH,  js_concat_string, NULL, &concat_string_fn));  NAPI_CALL(env, napi_set_named_property(env, exports,  "concatString", concat_string_fn));  return exports; }

node-addon-api 实现 ​

WARNING

如果运行时不支持 FinalizationRegistry 和 WeakRef则不能使用 node-addon-api。

cpp
#include <napi.h>  Napi::Value JsConcatString(const Napi::CallbackInfo& info) {  Napi::Env env = info.Env();    if (info.Length() < 2) {  Napi::TypeError e = Napi::TypeError::New(env, "Wrong number of arguments");  NAPI_THROW(e, Napi::Value());  }   if (!info[0].IsString() || !info[1].IsString()) {  Napi::TypeError e = Napi::TypeError::New(env, "Wrong arguments");  NAPI_THROW(e, Napi::Value());  }   std::string str1 = info[0].As<Napi::String>().Utf8Value();  std::string str2 = info[1].As<Napi::String>().Utf8Value();  std::string result = str1 + str2;   return Napi::String::New(env, result); }  Napi::Object Init(Napi::Env env, Napi::Object exports) {  exports.Set(Napi::String::New(env, "concatString"),  Napi::Function::New(env, JsConcatString, "concatString"));  return exports; }  NODE_API_MODULE(NODE_GYP_MODULE_NAME, Init)
#include <napi.h>  Napi::Value JsConcatString(const Napi::CallbackInfo& info) {  Napi::Env env = info.Env();    if (info.Length() < 2) {  Napi::TypeError e = Napi::TypeError::New(env, "Wrong number of arguments");  NAPI_THROW(e, Napi::Value());  }   if (!info[0].IsString() || !info[1].IsString()) {  Napi::TypeError e = Napi::TypeError::New(env, "Wrong arguments");  NAPI_THROW(e, Napi::Value());  }   std::string str1 = info[0].As<Napi::String>().Utf8Value();  std::string str2 = info[1].As<Napi::String>().Utf8Value();  std::string result = str1 + str2;   return Napi::String::New(env, result); }  Napi::Object Init(Napi::Env env, Napi::Object exports) {  exports.Set(Napi::String::New(env, "concatString"),  Napi::Function::New(env, JsConcatString, "concatString"));  return exports; }  NODE_API_MODULE(NODE_GYP_MODULE_NAME, Init)

传递回调函数 ​

让我们改一下上面的例子，传递一个 JavaScript 回调函数来接收字符串连接的结果。

ts
export declare function concatString (  str1: string,  str2: string,  callback: (result: string) => void ): void
export declare function concatString (  str1: string,  str2: string,  callback: (result: string) => void ): void
js
Module.onRuntimeInitialized = function () {  Module.emnapiExports.concatString('Hello ', '世界', (result) => {  console.log(result) // 'Hello 世界'  }) }
Module.onRuntimeInitialized = function () {  Module.emnapiExports.concatString('Hello ', '世界', (result) => {  console.log(result) // 'Hello 世界'  }) }

Node-API 实现 ​

c
static napi_value js_concat_string(napi_env env, napi_callback_info info) {  size_t argc = 3;  napi_value args[3];  NAPI_CALL(env, napi_get_cb_info(env, info, &argc, args, NULL, NULL));   if (argc < 3) {  napi_throw_type_error(env, NULL, "Wrong number of arguments");  return NULL;  }   napi_valuetype valuetype0, valuetype1, valuetype2;  NAPI_CALL(env, napi_typeof(env, args[0], &valuetype0));  NAPI_CALL(env, napi_typeof(env, args[1], &valuetype1));  NAPI_CALL(env, napi_typeof(env, args[2], &valuetype2));   if (valuetype0 != napi_string ||  valuetype1 != napi_string ||  valuetype2 != napi_function) {  napi_throw_type_error(env, NULL, "Wrong arguments");  return NULL;  }   size_t len1 = 0;  size_t len2 = 0;  NAPI_CALL(env, napi_get_value_string_utf8(env, args[0], NULL, 0, &len1));  NAPI_CALL(env, napi_get_value_string_utf8(env, args[1], NULL, 0, &len2));   size_t total_buffer_size = len1 + len2 + 1;   char* str = (char*) malloc(total_buffer_size);  if (str == NULL) {  napi_throw_error(env, NULL, "malloc failed");  return NULL;  }  napi_status status = napi_get_value_string_utf8(env, args[0],  str, total_buffer_size, &len1);  if (status != napi_ok) {  free(str);  NAPI_CALL(env, status);  }  status = napi_get_value_string_utf8(env, args[1],  str + len1, total_buffer_size - len1, &len2);  if (status != napi_ok) {  free(str);  NAPI_CALL(env, status);  }  *(str + len1 + len2) = '\0';   napi_value ret;  status = napi_create_string_utf8(env, str, len1 + len2, &ret);  free(str);  NAPI_CALL(env, status);   napi_value undefined;  NAPI_CALL(env, napi_get_undefined(env, &undefined));   napi_value ignored;  NAPI_CALL(env, napi_call_function(env, undefined, args[2], 1, &ret, &ignored));   return undefined; }
static napi_value js_concat_string(napi_env env, napi_callback_info info) {  size_t argc = 3;  napi_value args[3];  NAPI_CALL(env, napi_get_cb_info(env, info, &argc, args, NULL, NULL));   if (argc < 3) {  napi_throw_type_error(env, NULL, "Wrong number of arguments");  return NULL;  }   napi_valuetype valuetype0, valuetype1, valuetype2;  NAPI_CALL(env, napi_typeof(env, args[0], &valuetype0));  NAPI_CALL(env, napi_typeof(env, args[1], &valuetype1));  NAPI_CALL(env, napi_typeof(env, args[2], &valuetype2));   if (valuetype0 != napi_string ||  valuetype1 != napi_string ||  valuetype2 != napi_function) {  napi_throw_type_error(env, NULL, "Wrong arguments");  return NULL;  }   size_t len1 = 0;  size_t len2 = 0;  NAPI_CALL(env, napi_get_value_string_utf8(env, args[0], NULL, 0, &len1));  NAPI_CALL(env, napi_get_value_string_utf8(env, args[1], NULL, 0, &len2));   size_t total_buffer_size = len1 + len2 + 1;   char* str = (char*) malloc(total_buffer_size);  if (str == NULL) {  napi_throw_error(env, NULL, "malloc failed");  return NULL;  }  napi_status status = napi_get_value_string_utf8(env, args[0],  str, total_buffer_size, &len1);  if (status != napi_ok) {  free(str);  NAPI_CALL(env, status);  }  status = napi_get_value_string_utf8(env, args[1],  str + len1, total_buffer_size - len1, &len2);  if (status != napi_ok) {  free(str);  NAPI_CALL(env, status);  }  *(str + len1 + len2) = '\0';   napi_value ret;  status = napi_create_string_utf8(env, str, len1 + len2, &ret);  free(str);  NAPI_CALL(env, status);   napi_value undefined;  NAPI_CALL(env, napi_get_undefined(env, &undefined));   napi_value ignored;  NAPI_CALL(env, napi_call_function(env, undefined, args[2], 1, &ret, &ignored));   return undefined; }

node-addon-api 实现 ​

WARNING

如果运行时不支持 FinalizationRegistry 和 WeakRef则不能使用 node-addon-api。

cpp
Napi::Value JsConcatString(const Napi::CallbackInfo& info) {  Napi::Env env = info.Env();    if (info.Length() < 3) {  Napi::TypeError e = Napi::TypeError::New(env, "Wrong number of arguments");  NAPI_THROW(e, Napi::Value());  }   if (!info[0].IsString() || !info[1].IsString() || !info[2].IsFunction()) {  Napi::TypeError e = Napi::TypeError::New(env, "Wrong arguments");  NAPI_THROW(e, Napi::Value());  }   Napi::Value undefined = env.Undefined();   std::string str1 = info[0].As<Napi::String>().Utf8Value();  std::string str2 = info[1].As<Napi::String>().Utf8Value();  std::string result = str1 + str2;   info[2].As<Napi::Function>().Call(undefined, { Napi::String::New(env, result) })   return undefined; }
Napi::Value JsConcatString(const Napi::CallbackInfo& info) {  Napi::Env env = info.Env();    if (info.Length() < 3) {  Napi::TypeError e = Napi::TypeError::New(env, "Wrong number of arguments");  NAPI_THROW(e, Napi::Value());  }   if (!info[0].IsString() || !info[1].IsString() || !info[2].IsFunction()) {  Napi::TypeError e = Napi::TypeError::New(env, "Wrong arguments");  NAPI_THROW(e, Napi::Value());  }   Napi::Value undefined = env.Undefined();   std::string str1 = info[0].As<Napi::String>().Utf8Value();  std::string str2 = info[1].As<Napi::String>().Utf8Value();  std::string result = str1 + str2;   info[2].As<Napi::Function>().Call(undefined, { Napi::String::New(env, result) })   return undefined; }