| 'use strict'; |
| |
| if (self.importScripts) { |
| self.importScripts('/resources/testharness.js'); |
| } |
| |
| // Due to the limitations of floating-point precision, the calculation of desiredSize sometimes gives different answers |
| // than adding up the items in the queue would. It is important that implementations give the same result in these edge |
| // cases so that developers do not come to depend on non-standard behaviour. See |
| // https://github.com/whatwg/streams/issues/582 and linked issues for further discussion. |
| |
| promise_test(() => { |
| const writer = setupTestStream(); |
| |
| const writePromises = [ |
| writer.write(2), |
| writer.write(Number.MAX_SAFE_INTEGER) |
| ]; |
| |
| assert_equals(writer.desiredSize, 0 - 2 - Number.MAX_SAFE_INTEGER, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (after writing two chunks)'); |
| |
| return Promise.all(writePromises).then(() => { |
| assert_equals(writer.desiredSize, 0, '[[queueTotalSize]] must clamp to 0 if it becomes negative'); |
| }); |
| }, 'Floating point arithmetic must manifest near NUMBER.MAX_SAFE_INTEGER (total ends up positive)'); |
| |
| promise_test(() => { |
| const writer = setupTestStream(); |
| |
| const writePromises = [ |
| writer.write(1e-16), |
| writer.write(1) |
| ]; |
| |
| assert_equals(writer.desiredSize, 0 - 1e-16 - 1, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (after writing two chunks)'); |
| |
| return Promise.all(writePromises).then(() => { |
| assert_equals(writer.desiredSize, 0, '[[queueTotalSize]] must clamp to 0 if it becomes negative'); |
| }); |
| }, 'Floating point arithmetic must manifest near 0 (total ends up positive, but clamped)'); |
| |
| promise_test(() => { |
| const writer = setupTestStream(); |
| |
| const writePromises = [ |
| writer.write(1e-16), |
| writer.write(1), |
| writer.write(2e-16) |
| ]; |
| |
| assert_equals(writer.desiredSize, 0 - 1e-16 - 1 - 2e-16, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (after writing three chunks)'); |
| |
| return Promise.all(writePromises).then(() => { |
| assert_equals(writer.desiredSize, 0 - 1e-16 - 1 - 2e-16 + 1e-16 + 1 + 2e-16, |
| 'desiredSize must be calculated using floating-point arithmetic (after the three chunks have finished writing)'); |
| }); |
| }, 'Floating point arithmetic must manifest near 0 (total ends up positive, and not clamped)'); |
| |
| promise_test(() => { |
| const writer = setupTestStream(); |
| |
| const writePromises = [ |
| writer.write(2e-16), |
| writer.write(1) |
| ]; |
| |
| assert_equals(writer.desiredSize, 0 - 2e-16 - 1, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (after writing two chunks)'); |
| |
| return Promise.all(writePromises).then(() => { |
| assert_equals(writer.desiredSize, 0 - 2e-16 - 1 + 2e-16 + 1, |
| 'desiredSize must be calculated using floating-point arithmetic (after the two chunks have finished writing)'); |
| }); |
| }, 'Floating point arithmetic must manifest near 0 (total ends up zero)'); |
| |
| function setupTestStream() { |
| const strategy = { |
| size(x) { |
| return x; |
| }, |
| highWaterMark: 0 |
| }; |
| |
| const ws = new WritableStream({}, strategy); |
| |
| return ws.getWriter(); |
| } |
| |
| done(); |