Index: third_party/WebKit/LayoutTests/external/wpt/streams/readable-streams/floating-point-total-queue-size.js |
diff --git a/third_party/WebKit/LayoutTests/external/wpt/streams/readable-streams/floating-point-total-queue-size.js b/third_party/WebKit/LayoutTests/external/wpt/streams/readable-streams/floating-point-total-queue-size.js |
new file mode 100644 |
index 0000000000000000000000000000000000000000..3bb3b6a90d052611df2e7622a6e602ec26aff693 |
--- /dev/null |
+++ b/third_party/WebKit/LayoutTests/external/wpt/streams/readable-streams/floating-point-total-queue-size.js |
@@ -0,0 +1,119 @@ |
+'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 }; |
+} |