mozilla-central/testing/web-platform/tests/streams/readable-streams/floating-point-total-queue-size.any.js (file symbol)

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// META: global=window,worker,shadowrealm
'use strict';
// 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 };
}