fox-send/app/streams.js

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/* global TransformStream */
export function transformStream(readable, transformer, oncancel) {
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try {
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return readable.pipeThrough(new TransformStream(transformer));
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} catch (e) {
const reader = readable.getReader();
return new ReadableStream({
start(controller) {
if (transformer.start) {
return transformer.start(controller);
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}
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},
async pull(controller) {
let enqueued = false;
const wrappedController = {
enqueue(d) {
enqueued = true;
controller.enqueue(d);
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}
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};
while (!enqueued) {
const data = await reader.read();
if (data.done) {
if (transformer.flush) {
await transformer.flush(controller);
}
return controller.close();
}
await transformer.transform(data.value, wrappedController);
}
},
cancel(reason) {
readable.cancel(reason);
if (oncancel) {
oncancel(reason);
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}
}
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});
}
}
class BlobStreamController {
constructor(blob, size) {
this.blob = blob;
this.index = 0;
this.chunkSize = size || 1024 * 64;
}
pull(controller) {
return new Promise((resolve, reject) => {
const bytesLeft = this.blob.size - this.index;
if (bytesLeft <= 0) {
controller.close();
return resolve();
}
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const size = Math.min(this.chunkSize, bytesLeft);
const slice = this.blob.slice(this.index, this.index + size);
const reader = new FileReader();
reader.onload = () => {
controller.enqueue(new Uint8Array(reader.result));
resolve();
};
reader.onerror = reject;
reader.readAsArrayBuffer(slice);
this.index += size;
});
}
}
export function blobStream(blob, size) {
return new ReadableStream(new BlobStreamController(blob, size));
}
class ConcatStreamController {
constructor(streams) {
this.streams = streams;
this.index = 0;
this.reader = null;
this.nextReader();
}
nextReader() {
const next = this.streams[this.index++];
this.reader = next && next.getReader();
}
async pull(controller) {
if (!this.reader) {
return controller.close();
}
const data = await this.reader.read();
if (data.done) {
this.nextReader();
return this.pull(controller);
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}
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controller.enqueue(data.value);
}
}
export function concatStream(streams) {
return new ReadableStream(new ConcatStreamController(streams));
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}