How to read stdin?

[guest271314]

Question

What I tried

const reader: ReadableStreamDefaultReader = process.stdin.getReader();

reader.read().then((data) => {
  process.stdout.write(data);
});

Error message

node_modules/.bin/asc --config ./node_modules/@assemblyscript/wasi-shim/asconfig.json  module.ts -o module.wasm
ERROR TS2304: Cannot find name 'ReadableStreamDefaultReader'.
    :
 71 │ const reader: ReadableStreamDefaultReader = process.stdin.getReader();
    │               ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    └─ in module.ts(71,15)

FAILURE 1 compile error(s)

[CountBleck]

Since you're using wasi-shim, looks like you're supposed to use process.stdin.read(buffer), where buffer is an ArrayBuffer of the desired size. AS doesn't have any kind of async support.

[guest271314]

Thanks. I figured it out during you writing your answer reading this

@unmanaged
abstract class ReadableStream extends Stream {
  read(buffer: ArrayBuffer, offset: isize = 0): i32 {
    var end = <usize>buffer.byteLength;
    if (offset < 0 || <usize>offset > end) {
      throw new Error(E_INDEXOUTOFRANGE);
    }
    store<usize>(tempbuf, changetype<usize>(buffer) + offset);
    store<usize>(tempbuf, end - offset, sizeof<usize>());
    var err = fd_read(<u32>changetype<usize>(this), tempbuf, 1, tempbuf + 2 * sizeof<usize>());
    if (err) throw new Error(errnoToString(err));
    return <i32>load<isize>(tempbuf, 2 * sizeof<usize>());
  }
}

let input: string = "0";
let lex: string = "0";

if (process.argv.length > 1) {
  input = process.argv.at(-2);
  lex = process.argv.at(-1);
} else {
  let stdin = process.stdin;
  let buffer = new ArrayBuffer(64);
  let n: number = stdin.read(buffer);
  // process.stdout.write(`${n}`);
  if (n > 0) {
    let data = String.UTF8.decode(buffer);
    input = data.slice(0, data.indexOf(" "));
    lex = data.slice(q.indexOf(" "), data.length);
    process.stdout.write(input);
    process.stdout.write(lex);
  }
}

[CountBleck]

Yup, I was reading that exact snippet.

[guest271314]

@CountBleck Any idea why Binaryen's wasm2js throws Fatal: error in validating input?

[CountBleck]

No, I have no idea. Have you tried looking at the output of wasm-opt --validate?

[guest271314]

../binaryen/bin/wasm-opt --validate module.wasm
Unknown option '--validate'

This is at the top of wasm2js output

[wasm-validator error in function 82] unexpected false: all used features should be allowed, on 
(i32.trunc_sat_f64_s
 (local.get $23)
)
[wasm-validator error in function 132] unexpected false: all used features should be allowed, on 
(i32.trunc_sat_f64_s
 (call $118
  (local.get $5)
  (i32.const 0)
 )
)
[wasm-validator error in function 132] unexpected false: all used features should be allowed, on 
(i32.trunc_sat_f64_s
 (call $118
  (local.get $5)
  (i32.const 0)
 )
)
[wasm-validator error in function 132] unexpected false: all used features should be allowed, on 
(i32.trunc_sat_f64_s
 (call $118
  (local.get $5)
  (i32.const 0)
 )
)
[wasm-validator error in function 132] unexpected false: all used features should be allowed, on 
(i32.trunc_sat_f64_s
 (call $118
  (local.get $5)
  (i32.const 0)
 )
)