EM_JS：如何将 int argc、char **argv 转换为 JS 字符串数组？

Question

I'm trying to call JS function from C/C++ with an array of strings as an argument.我正在尝试从 C/C++ 调用 JS function，并使用字符串数组作为参数。

Here's my example code:这是我的示例代码：

main.c: main.c：

#include <stdio.h>
#include <emscripten.h>

EM_JS(void, call_myFunc, (int argc, char **argv), {
     
    var arr = [];
    for (let i = 0; i < argc; i++) {
      arr.push(UTF8ToString(argv[i]));
    }
    myFunc(arr);
});

int main()
{
    int argc = 4;
    char *argv[5] = { "ab", "cd", "ef", "gh" };
    call_myFunc(argc, argv);
}

index.html:索引.html：

<!DOCTYPE html>
<html>

<head>
</head>

<body>
  <script>
  function myFunc(args) {
    console.log(args);
  }
  </script>
  <script async src="main.js"></script>
</body>

</html>

build:建造：

emcc main.c -o main.html

result I get:结果我得到：

["", "", "", ""]

result I want:我想要的结果：

["ab", "cd", "ef", "gh"]

How can I properly convert char **argv to a JS array of strings?如何正确地将char **argv转换为 JS 字符串数组？

Answer 1

How can I properly convert char **argv to a JS array of strings?如何正确地将char **argv转换为 JS 字符串数组？

From the documentation of emscripten.h :从emscripten.h的文档中：

Null-terminated C strings can also be passed into EM_JS functions, but to operate on them, they need to be copied out from the heap to convert to high-level JavaScript strings.以空结尾的 C 字符串也可以传递给EM_JS函数，但要对其进行操作，需要将它们从堆中复制出来以转换为高级 JavaScript 字符串。

EM_JS(void, say_hello, (const char* str), {
  console.log('hello ' + UTF8ToString(str));
}

In the same manner, pointers to any type (including void * ) can be passed inside EM_JS code, where they appear as integers like char * pointers above did.以同样的方式，指向任何类型的指针（包括void * ）都可以在EM_JS代码中传递，它们像上面的char *指针一样显示为整数。 Accessing the data can be managed by reading the heap directly.可以通过直接读取堆来管理访问数据。

EM_JS(void, read_data, (int* data), {
  console.log('Data: ' + HEAP32[data>>2] + ', ' + HEAP32[(data+4)>>2]);
});

int main() {
  int arr[2] = { 30, 45 };
  read_data(arr);
  return 0;
}

So, you can use HEAP32 along with UTF8ToString like this:因此，您可以像这样使用HEAP32和UTF8ToString ：

main.c main.c

#include <stdio.h>
#include <emscripten.h>

EM_JS(void, call_myFunc, (const int argc, const char** argv), {
    var arr = [];
    for (let i = 0; i < argc; i++) {
        const mem = HEAP32[(argv + (i * 4)) >> 2];
        const str = UTF8ToString(mem);
        arr.push(str);
    }
    console.log(arr);
});

int main() {
    const int argc = 4;
    const char* argv[] = { "ab", "cd", "ef", "gh" };
    call_myFunc(argc, argv);
    return 0;
}

Compile:编译：

emcc main.c -o main.html

Run with node :使用node运行：

node main.js

Output: Output：

[ 'ab', 'cd', 'ef', 'gh' ]

EM_JS：如何将 int argc、char **argv 转换为 JS 字符串数组？

问题描述

1 个解决方案

解决方案1
2 已采纳 2020-08-09 05:53:06

EM_JS：如何将 int argc、char **argv 转换为 JS 字符串数组？

问题描述

1 个解决方案

解决方案1 2 已采纳 2020-08-09 05:53:06

解决方案1
2 已采纳 2020-08-09 05:53:06