1 | // Copyright (c) Jupyter Development Team.
|
2 | // Distributed under the terms of the Modified BSD License.
|
3 | /*-----------------------------------------------------------------------------
|
4 | | Copyright (c) 2014-2017, PhosphorJS Contributors
|
5 | |
|
6 | | Distributed under the terms of the BSD 3-Clause License.
|
7 | |
|
8 | | The full license is in the file LICENSE, distributed with this software.
|
9 | |----------------------------------------------------------------------------*/
|
10 | import { IIterator, iter, IterableOrArrayLike } from './iter';
|
11 |
|
12 | /**
|
13 | * Chain together several iterables.
|
14 | *
|
15 | * @param objects - The iterable or array-like objects of interest.
|
16 | *
|
17 | * @returns An iterator which yields the values of the iterables
|
18 | * in the order in which they are supplied.
|
19 | *
|
20 | * #### Example
|
21 | * ```typescript
|
22 | * import { chain, toArray } from '@lumino/algorithm';
|
23 | *
|
24 | * let data1 = [1, 2, 3];
|
25 | * let data2 = [4, 5, 6];
|
26 | *
|
27 | * let stream = chain(data1, data2);
|
28 | *
|
29 | * toArray(stream); // [1, 2, 3, 4, 5, 6]
|
30 | * ```
|
31 | */
|
32 | export function chain<T>(...objects: IterableOrArrayLike<T>[]): IIterator<T> {
|
33 | return new ChainIterator<T>(iter(objects.map(iter)));
|
34 | }
|
35 |
|
36 | /**
|
37 | * An iterator which chains together several iterators.
|
38 | */
|
39 | export class ChainIterator<T> implements IIterator<T> {
|
40 | /**
|
41 | * Construct a new chain iterator.
|
42 | *
|
43 | * @param source - The iterator of iterators of interest.
|
44 | */
|
45 | constructor(source: IIterator<IIterator<T>>) {
|
46 | this._source = source;
|
47 | this._active = undefined;
|
48 | }
|
49 |
|
50 | /**
|
51 | * Get an iterator over the object's values.
|
52 | *
|
53 | * @returns An iterator which yields the object's values.
|
54 | */
|
55 | iter(): IIterator<T> {
|
56 | return this;
|
57 | }
|
58 |
|
59 | /**
|
60 | * Create an independent clone of the iterator.
|
61 | *
|
62 | * @returns A new independent clone of the iterator.
|
63 | */
|
64 | clone(): IIterator<T> {
|
65 | let result = new ChainIterator<T>(this._source.clone());
|
66 | result._active = this._active && this._active.clone();
|
67 | result._cloned = true;
|
68 | this._cloned = true;
|
69 | return result;
|
70 | }
|
71 |
|
72 | /**
|
73 | * Get the next value from the iterator.
|
74 | *
|
75 | * @returns The next value from the iterator, or `undefined`.
|
76 | */
|
77 | next(): T | undefined {
|
78 | if (this._active === undefined) {
|
79 | let active = this._source.next();
|
80 | if (active === undefined) {
|
81 | return undefined;
|
82 | }
|
83 | this._active = this._cloned ? active.clone() : active;
|
84 | }
|
85 | let value = this._active.next();
|
86 | if (value !== undefined) {
|
87 | return value;
|
88 | }
|
89 | this._active = undefined;
|
90 | return this.next();
|
91 | }
|
92 |
|
93 | private _source: IIterator<IIterator<T>>;
|
94 | private _active: IIterator<T> | undefined;
|
95 | private _cloned = false;
|
96 | }
|