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assert: improve deepEqual perf for large input

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Use a Map instead of an array for checking previously found
cyclic references.

This reduces complexity for an array-of-objects case from
O(n²) to O(n·log n).

Fixes: https://github.com/nodejs/node/issues/12842
PR-URL: https://github.com/nodejs/node/pull/12849
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
This commit is contained in:
Anna Henningsen 2017-05-05 11:04:20 +02:00
parent 3fd890a06e
commit 7e5f500c98
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GPG Key ID: D8B9F5AEAE84E4CF
1 changed files with 15 additions and 6 deletions
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21
lib/assert.js
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@ -285,15 +285,24 @@ function _deepEqual(actual, expected, strict, memos) {
// Note: this accounts for both named and indexed properties on Arrays.
// Use memos to handle cycles.
memos = memos || { actual: [], expected: [] };
const actualIndex = memos.actual.indexOf(actual);
if (actualIndex !== -1) {
if (actualIndex === memos.expected.indexOf(expected)) {
if (!memos) {
memos = {
actual: { map: new Map(), position: 0 },
expected: { map: new Map(), position: 0 }
};
}
const actualPosition = memos.actual.map.get(actual);
if (actualPosition !== undefined) {
if (actualPosition === memos.expected.map.get(expected)) {
return true;
}
} else {
memos.actual.map.set(actual, memos.actual.position++);
}
if (!memos.expected.map.has(expected)) {
memos.expected.map.set(expected, memos.expected.position++);
}
memos.actual.push(actual);
memos.expected.push(expected);
return objEquiv(actual, expected, strict, memos);
}