How to implement fgets using FFI?

[guest271314]

Static Hermes has these FFI examples https://github.com/facebook/hermes/blob/static_h/examples/ffi/.

I modified fopen.js to read stdin with fopen

let f = fopen("/dev/stdin", "r");

That works for the most part. However, fails when using wasmtime. wasmer evidently does something different when "/dev/stdin" is encountered. bytecodealliance/wasmtime#9922 (comment)

WASI doesn't have /dev nor /dev/stdin. Looks like Wasmer adds /dev/stdin as non-standard extension: https://github.com/wasmerio/wasmer/blob/1d03406174b204ac403f61e2deb0a41601c8e41b/lib/virtual-fs/src/builder.rs#L106-L110 Instead of using fopen("/dev/stdin") you can use the stdin global variable instead. This is of type FILE * just like the return value of fopen. You just have to make sure not to fclose it.

So now I'm trying to implement defining stdin in the JavaScript context so fgets can be used.

This is what I've tried so far, from code I found in the field (https://github.com/thejustinwalsh/sh-raylib/blob/main/src/bunny-mark/resources.js, https://github.com/thejustinwalsh/sh-raylib/blob/main/src/bunny-mark/resources.h), havn;t gotten to fgets yet.

  const get_resource_path = $SHBuiltin.extern_c(
    {include: "resources.h"}, 
    function _get_resource_path(): c_ptr { throw 0; }
  );

  function grp(): string {
    "use unsafe";

   // let pathz: c_ptr = c_null;
    try {
    //  pathz = stringToAsciiz(path);
      //let filePtr = get_resource_path();
      //print(String(filePtr));
      //let result = asciizToString_unsafe(filePtr, 10);
     // return String(result);
     const buffer = new ArrayBuffer(10);
     const r = _read(0, buffer, 10);
     print(r);
     return "z";
    } finally {
   //   _free(pathz);
    }
  } 

  let g = grp();

  print(g);

[guest271314]

This is what I came up with using getchar()

  const _getchar = $SHBuiltin.extern_c(
    { include: "stdio.h" },
    function getchar(): c_int {
      throw 0;
    },
  );

  function getchars(): string {
    "use unsafe";
    try {
      let n: number = 50;
      let c: string = String();
      while (--n) {
        let int: number = _getchar();
        if (int === -1) {
          break;
        }
        c += String.fromCodePoint(int);
        // print("int:", int);
        // print("string:", c);
      }
      return String(c).trim();
    } catch (e) {
      return String(e.message);
    }
  }

  let stdin = getchars();

  print(stdin);