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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,34 @@ | ||
| const END_OF_BUFFER_ERROR_MESSAGE = 'Reached end of buffer unexpectedly'; | ||
|
|
||
| /** | ||
| * Delegates to `Array#shift`, but throws if the array is zero-length. | ||
| */ | ||
| export function guardedShift<T>(byteArray: T[]): T { | ||
| if (byteArray.length === 0) { | ||
| throw new Error(END_OF_BUFFER_ERROR_MESSAGE); | ||
| } | ||
| return byteArray.shift() as T; | ||
| } | ||
|
|
||
| /** | ||
| * Delegates to `Array#splice`, but throws if the section being spliced out extends past the end of | ||
| * the array. | ||
| */ | ||
| export function guardedSplice<T>( | ||
| byteArray: T[], | ||
| ...args: | ||
| | [start: number, deleteCount?: number] | ||
| | [start: number, deleteCount: number, ...items: T[]] | ||
| ): T[] { | ||
| const [start] = args; | ||
| if ( | ||
| args.length === 2 // Implies that `deleteCount` was supplied | ||
| ? start + (args[1] ?? 0) > byteArray.length | ||
| : start >= byteArray.length | ||
| ) { | ||
| throw new Error(END_OF_BUFFER_ERROR_MESSAGE); | ||
| } | ||
| return byteArray.splice( | ||
| ...(args as Parameters<typeof Array.prototype.splice>), | ||
| ); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,52 @@ | ||
| import {expect} from 'chai'; | ||
| import {spy} from 'sinon'; | ||
|
|
||
| import {guardedShift, guardedSplice} from '../src/utils/guarded-array-utils'; | ||
|
|
||
| describe('guardedShift', () => { | ||
| it('delegates to Array#shift', () => { | ||
| const arr = [1, 2, 3]; | ||
| const shiftSpy = spy(arr, 'shift'); | ||
| const result = guardedShift(arr); | ||
| expect(shiftSpy).is.calledWithExactly(); | ||
| expect(result).to.eq(shiftSpy.returnValues[0]); | ||
| }); | ||
| it('throws when the array is zero-length', () => { | ||
| const arr: number[] = []; | ||
| expect(() => guardedShift(arr)).to.throw(); | ||
| }); | ||
| }); | ||
|
|
||
| describe('guardedSplice', () => { | ||
| it('delegates to Array#splice', () => { | ||
| const arr = [1, 2, 3]; | ||
| const spliceSpy = spy(arr, 'splice'); | ||
| const result = guardedSplice( | ||
| arr, | ||
| /* start */ 0, | ||
| /* deleteCount */ 3, | ||
| /* ...items */ | ||
| 100, | ||
| 101, | ||
| 102, | ||
| ); | ||
| expect(spliceSpy).is.calledWithExactly(0, 3, 100, 101, 102); | ||
| expect(result).to.eq(spliceSpy.returnValues[0]); | ||
| }); | ||
| it('allows zero-length splices', () => { | ||
| const arr: number[] = [1, 2, 3]; | ||
| expect(guardedSplice(arr, 0, 0)).to.be.an.empty('array'); | ||
| }); | ||
| it('allows zero-length splices via the `deleteCount` argument being the explicit value `undefined`', () => { | ||
| const arr: number[] = [1, 2, 3]; | ||
| expect(guardedSplice(arr, 0, undefined)).to.be.an.empty('array'); | ||
| }); | ||
| it('throws when the `start` would take you past the end of the array', () => { | ||
| const arr: number[] = [1, 2, 3]; | ||
| expect(() => guardedSplice(arr, 3)).to.throw(); | ||
| }); | ||
| it('throws when the `deleteCount` and `start` would take you past the end of the array', () => { | ||
| const arr: number[] = [1, 2, 3]; | ||
| expect(() => guardedSplice(arr, 1, 3)).to.throw(); | ||
| }); | ||
| }); |