| // Copyright (C) 2018 Rick Waldron. All rights reserved. |
| // This code is governed by the BSD license found in the LICENSE file. |
| |
| /*--- |
| esid: sec-atomics.compareExchange |
| description: > |
| Atomics.compareExchange returns the value that existed at the |
| index prior to the operation. |
| info: | |
| Atomics.compareExchange( typedArray, index, expectedValue, replacementValue ) |
| |
| ... |
| 12. Let compareExchange denote a semantic function of two List of |
| byte values arguments that returns the second argument if the |
| first argument is element-wise equal to expectedBytes. |
| 13. Return GetModifySetValueInBuffer(buffer, indexedPosition, |
| elementType, replacement, compareExchange). |
| |
| |
| GetModifySetValueInBuffer( arrayBuffer, |
| byteIndex, type, value, op [ , isLittleEndian ] ) |
| |
| ... |
| 16. Return RawBytesToNumber(type, rawBytesRead, isLittleEndian). |
| |
| features: [Atomics, SharedArrayBuffer, TypedArray] |
| ---*/ |
| |
| const buffer = new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 4); |
| const i32a = new Int32Array(buffer); |
| const update = 0b00000001000000001000000010000001; |
| |
| i32a[0] = update; |
| |
| assert.sameValue( |
| Atomics.compareExchange(i32a, 0, update, 0), |
| update, |
| 'Atomics.compareExchange(i32a, 0, update, 0) returns the value of `update` (0b00000001000000001000000010000001)' |
| ); |
| assert.sameValue(i32a[0], 0, 'The value of i32a[0] is 0'); |
