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denoland-deno/cli/rt/21_filereader.js

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2020-08-11 08:00:53 -04:00
// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
((window) => {
const base64 = window.__bootstrap.base64;
const setTimeout = window.__bootstrap.timers.setTimeout;
// ProgressEvent could also be used in other DOM progress event emits.
// Current use is for FileReader.
class ProgressEvent extends Event {
constructor(type, eventInitDict = {}) {
super(type, eventInitDict);
this.lengthComputable = eventInitDict?.lengthComputable ?? false;
this.loaded = eventInitDict?.loaded ?? 0;
this.total = eventInitDict?.total ?? 0;
}
}
window.__bootstrap.progressEvent = {
ProgressEvent,
};
async function readOperation(fr, blob, readtype) {
// Implementation from https://w3c.github.io/FileAPI/ notes
// And body of deno blob.ts readBytes
fr.aborting = false;
// 1. If frs state is "loading", throw an InvalidStateError DOMException.
if (fr.readyState === FileReader.LOADING) {
throw new DOMException(
"Invalid FileReader state.",
"InvalidStateError",
);
}
// 2. Set frs state to "loading".
fr.readyState = FileReader.LOADING;
// 3. Set frs result to null.
fr.result = null;
// 4. Set frs error to null.
fr.error = null;
// 5. Let stream be the result of calling get stream on blob.
const stream /*: ReadableStream<ArrayBufferView>*/ = blob.stream();
// 6. Let reader be the result of getting a reader from stream.
const reader = stream.getReader();
// 7. Let bytes be an empty byte sequence.
//let bytes = new Uint8Array();
const chunks /*: Uint8Array[]*/ = [];
// 8. Let chunkPromise be the result of reading a chunk from stream with reader.
let chunkPromise = reader.read();
// 9. Let isFirstChunk be true.
let isFirstChunk = true;
// 10 in parallel while true
while (!fr.aborting) {
// 1. Wait for chunkPromise to be fulfilled or rejected.
try {
const chunk = await chunkPromise;
// 2. If chunkPromise is fulfilled, and isFirstChunk is true, queue a task to fire a progress event called loadstart at fr.
if (isFirstChunk) {
setTimeout(() => {
// fire a progress event for loadstart
const ev = new ProgressEvent("loadstart", {});
fr.dispatchEvent(ev);
if (fr.onloadstart !== null) {
fr.onloadstart(ev);
}
}, 0);
}
// 3. Set isFirstChunk to false.
isFirstChunk = false;
// 4. If chunkPromise is fulfilled with an object whose done property is false
// and whose value property is a Uint8Array object, run these steps:
if (!chunk.done && chunk.value instanceof Uint8Array) {
chunks.push(chunk.value);
// TODO: (only) If roughly 50ms have passed since last progress
{
const size = chunks.reduce((p, i) => p + i.byteLength, 0);
const ev = new ProgressEvent("progress", {
loaded: size,
});
fr.dispatchEvent(ev);
if (fr.onprogress !== null) {
fr.onprogress(ev);
}
}
chunkPromise = reader.read();
} // 5 Otherwise, if chunkPromise is fulfilled with an object whose done property is true, queue a task to run the following steps and abort this algorithm:
else if (chunk.done === true) {
setTimeout(() => {
if (fr.aborting) {
return;
}
// 1. Set frs state to "done".
fr.readyState = FileReader.DONE;
// 2. Let result be the result of package data given bytes, type, blobs type, and encodingName.
const size = chunks.reduce((p, i) => p + i.byteLength, 0);
const bytes = new Uint8Array(size);
let offs = 0;
for (const chunk of chunks) {
bytes.set(chunk, offs);
offs += chunk.byteLength;
}
switch (readtype.kind) {
case "ArrayBuffer": {
fr.result = bytes.buffer;
break;
}
case "Text": {
const decoder = new TextDecoder(readtype.encoding);
fr.result = decoder.decode(bytes.buffer);
break;
}
case "DataUrl": {
fr.result = "data:application/octet-stream;base64," +
base64.fromByteArray(bytes);
break;
}
}
// 4.2 Fire a progress event called load at the fr.
{
const ev = new ProgressEvent("load", {
lengthComputable: true,
loaded: size,
total: size,
});
fr.dispatchEvent(ev);
if (fr.onload !== null) {
fr.onload(ev);
}
}
// 5. If frs state is not "loading", fire a progress event called loadend at the fr.
//Note: Event handler for the load or error events could have started another load, if that happens the loadend event for this load is not fired.
if (fr.readyState !== FileReader.LOADING) {
const ev = new ProgressEvent("loadend", {
lengthComputable: true,
loaded: size,
total: size,
});
fr.dispatchEvent(ev);
if (fr.onloadend !== null) {
fr.onloadend(ev);
}
}
}, 0);
break;
}
} catch (err) {
if (fr.aborting) {
break;
}
// chunkPromise rejected
fr.readyState = FileReader.DONE;
fr.error = err;
{
const ev = new ProgressEvent("error", {});
fr.dispatchEvent(ev);
if (fr.onerror !== null) {
fr.onerror(ev);
}
}
//If frs state is not "loading", fire a progress event called loadend at fr.
//Note: Event handler for the error event could have started another load, if that happens the loadend event for this load is not fired.
if (fr.readyState !== FileReader.LOADING) {
const ev = new ProgressEvent("loadend", {});
fr.dispatchEvent(ev);
if (fr.onloadend !== null) {
fr.onloadend(ev);
}
}
break;
}
}
}
class FileReader extends EventTarget {
error = null;
onabort = null;
onerror = null;
onload = null;
onloadend = null;
onloadstart = null;
onprogress = null;
readyState = FileReader.EMPTY;
result = null;
aborting = false;
constructor() {
super();
}
abort() {
// If context object's state is "empty" or if context object's state is "done" set context object's result to null and terminate this algorithm.
if (
this.readyState === FileReader.EMPTY ||
this.readyState === FileReader.DONE
) {
this.result = null;
return;
}
// If context object's state is "loading" set context object's state to "done" and set context object's result to null.
if (this.readyState === FileReader.LOADING) {
this.readyState = FileReader.DONE;
this.result = null;
}
// If there are any tasks from the context object on the file reading task source in an affiliated task queue, then remove those tasks from that task queue.
// Terminate the algorithm for the read method being processed.
this.aborting = true;
// Fire a progress event called abort at the context object.
const ev = new ProgressEvent("abort", {});
this.dispatchEvent(ev);
if (this.onabort !== null) {
this.onabort(ev);
}
// If context object's state is not "loading", fire a progress event called loadend at the context object.
if (this.readyState !== FileReader.LOADING) {
const ev = new ProgressEvent("loadend", {});
this.dispatchEvent(ev);
if (this.onloadend !== null) {
this.onloadend(ev);
}
}
}
readAsArrayBuffer(blob) {
readOperation(this, blob, { kind: "ArrayBuffer" });
}
readAsBinaryString(blob) {
// alias for readAsArrayBuffer
readOperation(this, blob, { kind: "ArrayBuffer" });
}
readAsDataURL(blob) {
readOperation(this, blob, { kind: "DataUrl" });
}
readAsText(blob, encoding) {
readOperation(this, blob, { kind: "Text", encoding });
}
}
FileReader.EMPTY = 0;
FileReader.LOADING = 1;
FileReader.DONE = 2;
window.__bootstrap.fileReader = {
FileReader,
};
})(this);