Re: [v8-users] Implement reading STDIN to an ArrayBuffer. Precedent: writeFile("/proc/self/fd/1")

[guest271314]

For anyone who happens to have interest in this domain, what I wound up 
doing is getting the PID of the current d8 process, then reading the STDIN 
to d8 using dd.

nm_d8.js

#!/usr/bin/env -S /home/user/.jsvu/engines/v8/v8 --enable-os-system
// d8 Native Messaging host
// guest271314 7-7-2023, 6-20-2024

function encodeMessage(str) {
  return new Uint8Array([...str].map((s) => s.codePointAt()));
}

function getMessage(pid) {
  try {
    // readline() doesn't read past the Uint32Array equivalent message 
length
    // V8 authors are not interested in reading STDIN to an ArrayBuffer in 
d8
    // https://groups.google.com/g/v8-users/c/NsnStT6bx3Y/m/Yr_Z1FwgAQAJ
    // Use dd to get message length and return message from Bash script
    const stdin = (os.system("./getNativeMessage.sh", [pid])).trim();
    return encodeMessage(stdin);
  } catch (e) {
    writeFile("getMessageError.txt", encodeMessage(e.message));
  }
}

function sendMessage(message) {
  const header = new Uint32Array([message.length]);
  writeFile("/proc/self/fd/1", header);
  writeFile("/proc/self/fd/1", message);
}

function main() {
  // Get PID of current process
  const pid = (os.system("pgrep", ["-n", "-f", os.d8Path])).replace(/\D+/g, 
"");
  while (true) {
    const message = getMessage(pid);
    sendMessage(message);
  }
}

try {
  main();
} catch (e) {
  writeFile("mainError.txt", encodeMessage(e.message));
  quit();
}

getNativeMessage.sh

#!/bin/bash
# Bash Native Messaging host
# Read STDIN for V8's d8 shell, return message to d8
# guest271314 2024

set -x
set -o posix

getNativeMessage() {
  # https://lists.gnu.org/archive/html/help-bash/2023-06/msg00036.html
  length=$(dd iflag=fullblock bs=4 count=1 if=/proc/$@/fd/0 | od -An -td4)
  message=$(dd iflag=fullblock bs=$((length)) count=1 if=/proc/$@/fd/0)
  echo "$message" 
}

getNativeMessage "$1"

in an MV3 browser extension ServiceWorker (background.js); or via 
"web_accessible_resources" and "externally_connectable" from any arbitrary 
Web page; or an offscreen document

globalThis.name = chrome.runtime.getManifest().short_name;

globalThis.port = chrome.runtime.connectNative(globalThis.name);
port.onMessage.addListener((message) => console.log(message));
port.onDisconnect.addListener((p) => console.log(chrome.runtime.lastError));
port.postMessage(new Array(209715));

chrome.runtime.onInstalled.addListener((reason) => {
  console.log(reason);
});



On Thursday, June 20, 2024 at 8:17:48 AM UTC-7 guest271314 wrote:

> Node.js does not serve the needs of what I'm doing in d8. 
>
> I'm talking about d8 specifically. 
>
> I'm developing V8 and pointing out an omission that can be addressed by 
> providing an option to remove UTF-8 checks for readline() or by adjusting 
> read("path", "binary") to not check for file length, thus providingthe 
> capability to read from STDIN to an ArrayBuffer.
>
> As to this mailing list, I've read all kinds of proposals here, from 
> Float16Array to others that wind up in TC-39.
>
> I don't understand the resistance to developer feedback from the field. 
>
> Nothing horrible can happen by providing a means to read STDIN in d8.
>
> I'm not an adversary here. I'm diving in the JavaScript and sharing my 
> feedback.
>
> Anyway, thanks. Have a great day.
>
>
> On Thu, Jun 20, 2024 at 7:30 AM Jakob Kummerow <jkum...@chromium.org> 
> wrote:
>
>> d8's readline() is useless for reading STDIN where standard input is not 
>>> UTF-8
>>
>>
>> That's OK. As I told you before, d8 isn't trying to be a general-purpose 
>> shell; it's a tool for developing V8. If you want a V8-embedding shell that 
>> does more than d8 offers, find one or write your own. In the other thread, 
>> you said that Node.js serves your needs -- great, problem solved.
>>
>> Something like [snip...] should be standardized for JavaScript 
>>>
>>
>> This mailing list isn't the right place to propose or discuss possible JS 
>> language additions.
>>
>> -- 
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>>  
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>

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