mozilla-central/testing/web-platform/tests/streams/writable-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 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();
}