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operators.js
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operators.js
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'use strict';
const { AbortController } = require('internal/abort_controller');
const {
codes: {
ERR_INVALID_ARG_TYPE,
},
AbortError,
} = require('internal/errors');
const { validateInteger } = require('internal/validators');
const { kWeakHandler } = require('internal/event_target');
const {
ArrayPrototypePush,
MathFloor,
Promise,
PromiseReject,
PromisePrototypeCatch,
Symbol,
} = primordials;
const kEmpty = Symbol('kEmpty');
const kEof = Symbol('kEof');
async function * map(fn, options) {
if (typeof fn !== 'function') {
throw new ERR_INVALID_ARG_TYPE(
'fn', ['Function', 'AsyncFunction'], fn);
}
if (options != null && typeof options !== 'object') {
throw new ERR_INVALID_ARG_TYPE('options', ['Object']);
}
let concurrency = 1;
if (options?.concurrency != null) {
concurrency = MathFloor(options.concurrency);
}
validateInteger(concurrency, 'concurrency', 1);
const ac = new AbortController();
const stream = this;
const queue = [];
const signal = ac.signal;
const signalOpt = { signal };
const abort = () => ac.abort();
if (options?.signal?.aborted) {
abort();
}
options?.signal?.addEventListener('abort', abort);
let next;
let resume;
let done = false;
function onDone() {
done = true;
}
async function pump() {
try {
for await (let val of stream) {
if (done) {
return;
}
if (signal.aborted) {
throw new AbortError();
}
try {
val = fn(val, signalOpt);
} catch (err) {
val = PromiseReject(err);
}
if (val === kEmpty) {
continue;
}
if (typeof val?.catch === 'function') {
val.catch(onDone);
}
queue.push(val);
if (next) {
next();
next = null;
}
if (!done && queue.length && queue.length >= concurrency) {
await new Promise((resolve) => {
resume = resolve;
});
}
}
queue.push(kEof);
} catch (err) {
const val = PromiseReject(err);
PromisePrototypeCatch(val, onDone);
queue.push(val);
} finally {
done = true;
if (next) {
next();
next = null;
}
options?.signal?.removeEventListener('abort', abort);
}
}
pump();
try {
while (true) {
while (queue.length > 0) {
const val = await queue[0];
if (val === kEof) {
return;
}
if (signal.aborted) {
throw new AbortError();
}
if (val !== kEmpty) {
yield val;
}
queue.shift();
if (resume) {
resume();
resume = null;
}
}
await new Promise((resolve) => {
next = resolve;
});
}
} finally {
ac.abort();
done = true;
if (resume) {
resume();
resume = null;
}
}
}
async function some(fn, options) {
// https://tc39.es/proposal-iterator-helpers/#sec-iteratorprototype.some
// Note that some does short circuit but also closes the iterator if it does
const ac = new AbortController();
if (options?.signal) {
if (options.signal.aborted) {
ac.abort();
}
options.signal.addEventListener('abort', () => ac.abort(), {
[kWeakHandler]: this,
once: true,
});
}
const mapped = this.map(fn, { ...options, signal: ac.signal });
for await (const result of mapped) {
if (result) {
ac.abort();
return true;
}
}
return false;
}
async function every(fn, options) {
if (typeof fn !== 'function') {
throw new ERR_INVALID_ARG_TYPE(
'fn', ['Function', 'AsyncFunction'], fn);
}
// https://en.wikipedia.org/wiki/De_Morgan%27s_laws
return !(await some.call(this, async (x) => {
return !(await fn(x));
}, options));
}
async function forEach(fn, options) {
if (typeof fn !== 'function') {
throw new ERR_INVALID_ARG_TYPE(
'fn', ['Function', 'AsyncFunction'], fn);
}
async function forEachFn(value, options) {
await fn(value, options);
return kEmpty;
}
// eslint-disable-next-line no-unused-vars
for await (const unused of this.map(forEachFn, options));
}
async function * filter(fn, options) {
if (typeof fn !== 'function') {
throw new ERR_INVALID_ARG_TYPE(
'fn', ['Function', 'AsyncFunction'], fn);
}
async function filterFn(value, options) {
if (await fn(value, options)) {
return value;
}
return kEmpty;
}
yield* this.map(filterFn, options);
}
async function toArray(options) {
const result = [];
for await (const val of this) {
if (options?.signal?.aborted) {
throw new AbortError({ cause: options.signal.reason });
}
ArrayPrototypePush(result, val);
}
return result;
}
async function* flatMap(fn, options) {
for await (const val of this.map(fn, options)) {
yield* val;
}
}
module.exports.streamReturningOperators = {
filter,
flatMap,
map,
};
module.exports.promiseReturningOperators = {
every,
forEach,
toArray,
some,
};