42 lines
1.8 KiB
JavaScript
42 lines
1.8 KiB
JavaScript
import {TRANSFORM_TYPES} from '../stdio/type.js';
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/*
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Retrieve the `objectMode`s of a single transform.
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`objectMode` determines the return value's type, i.e. the `readableObjectMode`.
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The chunk argument's type is based on the previous generator's return value, i.e. the `writableObjectMode` is based on the previous `readableObjectMode`.
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The last input's generator is read by `subprocess.stdin` which:
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- should not be in `objectMode` for performance reasons.
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- can only be strings, Buffers and Uint8Arrays.
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Therefore its `readableObjectMode` must be `false`.
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The same applies to the first output's generator's `writableObjectMode`.
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*/
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export const getTransformObjectModes = (objectMode, index, newTransforms, direction) => direction === 'output'
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? getOutputObjectModes(objectMode, index, newTransforms)
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: getInputObjectModes(objectMode, index, newTransforms);
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const getOutputObjectModes = (objectMode, index, newTransforms) => {
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const writableObjectMode = index !== 0 && newTransforms[index - 1].value.readableObjectMode;
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const readableObjectMode = objectMode ?? writableObjectMode;
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return {writableObjectMode, readableObjectMode};
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};
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const getInputObjectModes = (objectMode, index, newTransforms) => {
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const writableObjectMode = index === 0
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? objectMode === true
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: newTransforms[index - 1].value.readableObjectMode;
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const readableObjectMode = index !== newTransforms.length - 1 && (objectMode ?? writableObjectMode);
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return {writableObjectMode, readableObjectMode};
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};
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// Retrieve the `objectMode` of a file descriptor, e.g. `stdout` or `stderr`
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export const getFdObjectMode = (stdioItems, direction) => {
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const lastTransform = stdioItems.findLast(({type}) => TRANSFORM_TYPES.has(type));
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if (lastTransform === undefined) {
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return false;
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}
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return direction === 'input'
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? lastTransform.value.writableObjectMode
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: lastTransform.value.readableObjectMode;
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};
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