| '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 { reader, controller } = setupTestStream(); |
| |
| controller.enqueue(2); |
| assert_equals(controller.desiredSize, 0 - 2, 'desiredSize must be -2 after enqueueing such a chunk'); |
| |
| controller.enqueue(Number.MAX_SAFE_INTEGER); |
| assert_equals(controller.desiredSize, 0 - Number.MAX_SAFE_INTEGER - 2, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (adding a second chunk)'); |
| |
| return reader.read().then(() => { |
| assert_equals(controller.desiredSize, 0 - Number.MAX_SAFE_INTEGER - 2 + 2, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (subtracting a chunk)'); |
| |
| return reader.read(); |
| }).then(() => { |
| assert_equals(controller.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 { reader, controller } = setupTestStream(); |
| |
| controller.enqueue(1e-16); |
| assert_equals(controller.desiredSize, 0 - 1e-16, 'desiredSize must be -1e16 after enqueueing such a chunk'); |
| |
| controller.enqueue(1); |
| assert_equals(controller.desiredSize, 0 - 1e-16 - 1, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (adding a second chunk)'); |
| |
| return reader.read().then(() => { |
| assert_equals(controller.desiredSize, 0 - 1e-16 - 1 + 1e-16, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (subtracting a chunk)'); |
| |
| return reader.read(); |
| }).then(() => { |
| assert_equals(controller.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 { reader, controller } = setupTestStream(); |
| |
| controller.enqueue(1e-16); |
| assert_equals(controller.desiredSize, 0 - 1e-16, 'desiredSize must be -2e16 after enqueueing such a chunk'); |
| |
| controller.enqueue(1); |
| assert_equals(controller.desiredSize, 0 - 1e-16 - 1, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (adding a second chunk)'); |
| |
| controller.enqueue(2e-16); |
| assert_equals(controller.desiredSize, 0 - 1e-16 - 1 - 2e-16, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (adding a third chunk)'); |
| |
| return reader.read().then(() => { |
| assert_equals(controller.desiredSize, 0 - 1e-16 - 1 - 2e-16 + 1e-16, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (subtracting a chunk)'); |
| |
| return reader.read(); |
| }).then(() => { |
| assert_equals(controller.desiredSize, 0 - 1e-16 - 1 - 2e-16 + 1e-16 + 1, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (subtracting a second chunk)'); |
| |
| return reader.read(); |
| }).then(() => { |
| assert_equals(controller.desiredSize, 0 - 1e-16 - 1 - 2e-16 + 1e-16 + 1 + 2e-16, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (subtracting a third chunk)'); |
| }); |
| }, 'Floating point arithmetic must manifest near 0 (total ends up positive, and not clamped)'); |
| |
| promise_test(() => { |
| const { reader, controller } = setupTestStream(); |
| |
| controller.enqueue(2e-16); |
| assert_equals(controller.desiredSize, 0 - 2e-16, 'desiredSize must be -2e16 after enqueueing such a chunk'); |
| |
| controller.enqueue(1); |
| assert_equals(controller.desiredSize, 0 - 2e-16 - 1, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (adding a second chunk)'); |
| |
| return reader.read().then(() => { |
| assert_equals(controller.desiredSize, 0 - 2e-16 - 1 + 2e-16, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (subtracting a chunk)'); |
| |
| return reader.read(); |
| }).then(() => { |
| assert_equals(controller.desiredSize, 0, |
| 'desiredSize must be calculated using double-precision floating-point arithmetic (subtracting a second chunk)'); |
| }); |
| }, 'Floating point arithmetic must manifest near 0 (total ends up zero)'); |
| |
| function setupTestStream() { |
| const strategy = { |
| size(x) { |
| return x; |
| }, |
| highWaterMark: 0 |
| }; |
| |
| let controller; |
| const rs = new ReadableStream({ |
| start(c) { |
| controller = c; |
| } |
| }, strategy); |
| |
| return { reader: rs.getReader(), controller }; |
| } |
| |
| done(); |