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47 lines
1.3 KiB
JavaScript
47 lines
1.3 KiB
JavaScript
"use strict";
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const pipe = require("@promistream/pipe");
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const propagatePeek = require("@promistream/propagate-peek");
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const propagateAbort = require("@promistream/propagate-abort");
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const EndOfStream = require("@promistream/end-of-stream");
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const unreachable = require("@joepie91/unreachable")("@promistream/dynamic");
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module.exports = function singleValueProcessor(processingStream) {
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// NOTE: This is *not* compliant with the Promistream spec! It can only be used with code that is specifically written to handle it.
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let streamEnded = true;
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let gateStream = {
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_promistreamVersion: 0,
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description: `single-value processor gate stream`,
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peek: propagatePeek, // FIXME: Is this correct? Should this not be dependent on whether a peek and/or read has already been done for this iteration?
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abort: propagateAbort,
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read: function produceValue_singleValueGateStream(source) {
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if (streamEnded === false) {
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streamEnded = true;
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return source.read();
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} else {
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throw new EndOfStream;
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}
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},
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};
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let wrappedPipeline = pipe([
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gateStream,
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processingStream
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]);
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return {
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read: function (source) {
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return wrappedPipeline.read(source);
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},
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reset: function () {
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if (streamEnded === true) {
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streamEnded = false;
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} else {
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throw unreachable("Tried to reset a non-ended stream");
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}
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}
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};
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};
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