react-native/Libraries/Blob/Blob.js

157 lines
4.3 KiB
JavaScript

/**
* Copyright (c) 2013-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*
* @providesModule Blob
* @flow
*/
'use strict';
const invariant = require('fbjs/lib/invariant');
/* $FlowFixMe(>=0.54.0 site=react_native_oss) This comment suppresses an error
* found when Flow v0.54 was deployed. To see the error delete this comment and
* run Flow. */
const uuid = require('uuid');
const { BlobModule } = require('NativeModules');
import type { BlobProps } from 'BlobTypes';
/**
* Opaque JS representation of some binary data in native.
*
* The API is modeled after the W3C Blob API, with one caveat
* regarding explicit deallocation. Refer to the `close()`
* method for further details.
*
* Example usage in a React component:
*
* class WebSocketImage extends React.Component {
* state = {blob: null};
* componentDidMount() {
* let ws = this.ws = new WebSocket(...);
* ws.binaryType = 'blob';
* ws.onmessage = (event) => {
* if (this.state.blob) {
* this.state.blob.close();
* }
* this.setState({blob: event.data});
* };
* }
* componentUnmount() {
* if (this.state.blob) {
* this.state.blob.close();
* }
* this.ws.close();
* }
* render() {
* if (!this.state.blob) {
* return <View />;
* }
* return <Image source={{uri: URL.createObjectURL(this.state.blob)}} />;
* }
* }
*
* Reference: https://developer.mozilla.org/en-US/docs/Web/API/Blob
*/
class Blob {
/**
* Size of the data contained in the Blob object, in bytes.
*/
size: number;
/*
* String indicating the MIME type of the data contained in the Blob.
* If the type is unknown, this string is empty.
*/
type: string;
/*
* Unique id to identify the blob on native side (non-standard)
*/
blobId: string;
/*
* Offset to indicate part of blob, used when sliced (non-standard)
*/
offset: number;
/**
* Construct blob instance from blob data from native.
* Used internally by modules like XHR, WebSocket, etc.
*/
static create(props: BlobProps): Blob {
return Object.assign(Object.create(Blob.prototype), props);
}
/**
* Constructor for JS consumers.
* Currently we only support creating Blobs from other Blobs.
* Reference: https://developer.mozilla.org/en-US/docs/Web/API/Blob/Blob
*/
constructor(parts: Array<Blob>, options: any) {
const blobId = uuid();
let size = 0;
parts.forEach((part) => {
invariant(part instanceof Blob, 'Can currently only create a Blob from other Blobs');
size += part.size;
});
BlobModule.createFromParts(parts, blobId);
return Blob.create({
blobId,
offset: 0,
size,
});
}
/*
* This method is used to create a new Blob object containing
* the data in the specified range of bytes of the source Blob.
* Reference: https://developer.mozilla.org/en-US/docs/Web/API/Blob/slice
*/
slice(start?: number, end?: number): Blob {
let offset = this.offset;
let size = this.size;
if (typeof start === 'number') {
if (start > size) {
start = size;
}
offset += start;
size -= start;
if (typeof end === 'number') {
if (end < 0) {
end = this.size + end;
}
size = end - start;
}
}
return Blob.create({
blobId: this.blobId,
offset,
size,
});
}
/**
* This method is in the standard, but not actually implemented by
* any browsers at this point. It's important for how Blobs work in
* React Native, however, since we cannot de-allocate resources automatically,
* so consumers need to explicitly de-allocate them.
*
* Note that the semantics around Blobs created via `blob.slice()`
* and `new Blob([blob])` are different. `blob.slice()` creates a
* new *view* onto the same binary data, so calling `close()` on any
* of those views is enough to deallocate the data, whereas
* `new Blob([blob, ...])` actually copies the data in memory.
*/
close() {
BlobModule.release(this.blobId);
}
}
module.exports = Blob;