N-Api&C++ array buffer数据传递预处理_napi_get_arraybuffer_info

C++侧：

基于N-API的实现示例：

#include <assert.h>
#include "addon_api.h"
#include "stdio.h"
 
napi_value CArrayBuffSum(napi_env env, napi_callback_info info)
{
    napi_status status;
    const size_t MaxArgExpected = 1;
    napi_value args[MaxArgExpected];
    size_t argc = sizeof(args) / sizeof(napi_value);
 
    status = napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);
    assert(status == napi_ok);
    if (argc < 1)
        napi_throw_error(env, "EINVAL", "Too few arguments");
 
    napi_value buff = args[0];
    napi_valuetype valuetype;
    status = napi_typeof(env, buff, &valuetype);
    assert(status == napi_ok);
 
    if (valuetype == napi_object)
    {
        bool isArrayBuff = 0;
        status = napi_is_arraybuffer(env, buff, &isArrayBuff);
        assert(status == napi_ok);
 
        if (isArrayBuff != true)
            napi_throw_error(env, "EINVAL", "Expected an ArrayBuffer");
    }
 
    int32_t *buff_data = NULL;
    size_t byte_length = 0;
    int32_t sum = 0;
 
    napi_get_arraybuffer_info(env, buff, (void **)&buff_data, &byte_length);
    assert(status == napi_ok);
 
    printf("\nC:  Int32Array size = %d,  (ie: bytes=%d)",
           (int)(byte_length / sizeof(int32_t)), (int)byte_length);
    for (int i = 0; i < byte_length / sizeof(int32_t); ++i)
    {
        sum += *(buff_data + i);
        printf("\nC:  Int32ArrayBuff[%d] = %d", i, *(buff_data + i));
    }
 
    napi_value rcValue;
    napi_create_int32(env, sum, &rcValue);
 
    return (rcValue);
}

JS侧：

'use strict'
const myaddon = require('bindings')('mync1');
 
function test1() {
    const array = new Int32Array(10);
 
    for (let i = 0; i < 10; ++i)
        array[i] = i * 5;
 
    const sum = myaddon.ArrayBuffSum(array.buffer);
    console.log();
    console.log(`js: Sum of the array  = ${sum}`);
}
 
test1();

运行输出：

C:  Int32Array size = 10,  (ie: bytes=40)
C:  Int32ArrayBuff[0] = 0
C:  Int32ArrayBuff[1] = 5
C:  Int32ArrayBuff[2] = 10
C:  Int32ArrayBuff[3] = 15
C:  Int32ArrayBuff[4] = 20
C:  Int32ArrayBuff[5] = 25
C:  Int32ArrayBuff[6] = 30
C:  Int32ArrayBuff[7] = 35
C:  Int32ArrayBuff[8] = 40
C:  Int32ArrayBuff[9] = 45
js: Sum of the array  = 225