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Use BitSet for bundler intersections (#8862)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,126 @@ | ||
| // @flow strict-local | ||
| import nullthrows from 'nullthrows'; | ||
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| // As our current version of flow doesn't support BigInt's, these values/types | ||
| // have been hoisted to keep the flow errors to a minimum. This can be removed | ||
| // if we upgrade to a flow version that supports BigInt's | ||
| // $FlowFixMe | ||
| type TmpBigInt = bigint; | ||
| // $FlowFixMe | ||
| const BIGINT_ZERO = 0n; | ||
| // $FlowFixMe | ||
| const BIGINT_ONE = 1n; | ||
| // $FlowFixMe | ||
| let numberToBigInt = (v: number): TmpBigInt => BigInt(v); | ||
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| let bitUnion = (a: TmpBigInt, b: TmpBigInt): TmpBigInt => a | b; | ||
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| export class BitSet<Item> { | ||
| _value: TmpBigInt; | ||
| _lookup: Map<Item, TmpBigInt>; | ||
| _items: Array<Item>; | ||
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| constructor({ | ||
| initial, | ||
| items, | ||
| lookup, | ||
| }: {| | ||
| items: Array<Item>, | ||
| lookup: Map<Item, number>, | ||
| initial?: BitSet<Item> | TmpBigInt, | ||
| |}) { | ||
| if (initial instanceof BitSet) { | ||
| this._value = initial?._value; | ||
| } else if (initial) { | ||
| this._value = initial; | ||
| } else { | ||
| this._value = BIGINT_ZERO; | ||
| } | ||
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| this._items = items; | ||
| this._lookup = lookup; | ||
| } | ||
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| static from(items: Array<Item>): BitSet<Item> { | ||
| let lookup: Map<Item, TmpBigInt> = new Map(); | ||
| for (let i = 0; i < items.length; i++) { | ||
| lookup.set(items[i], numberToBigInt(i)); | ||
| } | ||
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| return new BitSet({items, lookup}); | ||
| } | ||
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| static union(a: BitSet<Item>, b: BitSet<Item>): BitSet<Item> { | ||
| return new BitSet({ | ||
| initial: bitUnion(a._value, b._value), | ||
| lookup: a._lookup, | ||
| items: a._items, | ||
| }); | ||
| } | ||
|
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| #getIndex(item: Item) { | ||
| return nullthrows(this._lookup.get(item), 'Item is missing from BitSet'); | ||
| } | ||
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| add(item: Item) { | ||
| this._value |= BIGINT_ONE << this.#getIndex(item); | ||
| } | ||
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| delete(item: Item) { | ||
| this._value &= ~(BIGINT_ONE << this.#getIndex(item)); | ||
| } | ||
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| has(item: Item): boolean { | ||
| return Boolean(this._value & (BIGINT_ONE << this.#getIndex(item))); | ||
| } | ||
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| intersect(v: BitSet<Item>) { | ||
| this._value = this._value & v._value; | ||
| } | ||
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| union(v: BitSet<Item>) { | ||
| this._value = bitUnion(this._value, v._value); | ||
| } | ||
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| clear() { | ||
| this._value = BIGINT_ZERO; | ||
| } | ||
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| cloneEmpty(): BitSet<Item> { | ||
| return new BitSet({ | ||
| lookup: this._lookup, | ||
| items: this._items, | ||
| }); | ||
| } | ||
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| clone(): BitSet<Item> { | ||
| return new BitSet({ | ||
| lookup: this._lookup, | ||
| items: this._items, | ||
| initial: this._value, | ||
| }); | ||
| } | ||
|
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| values(): Array<Item> { | ||
| let values = []; | ||
| let tmpValue = this._value; | ||
| let i; | ||
|
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| // This implementation is optimized for BitSets that contain a very small percentage | ||
| // of items compared to the total number of potential items. This makes sense for | ||
| // our bundler use-cases where Sets often contain <1% coverage of the total item count. | ||
| // In cases where Sets contain a larger percentage of the total items, a regular looping | ||
| // strategy would be more performant. | ||
| while (tmpValue > BIGINT_ZERO) { | ||
| // Get last set bit | ||
| i = tmpValue.toString(2).length - 1; | ||
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| values.push(this._items[i]); | ||
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| // Unset last set bit | ||
| tmpValue &= ~(BIGINT_ONE << numberToBigInt(i)); | ||
| } | ||
|
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| return values; | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
|
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@@ -73,3 +73,4 @@ export { | |
| loadSourceMap, | ||
| remapSourceLocation, | ||
| } from './sourcemap'; | ||
| export {BitSet} from './BitSet'; | ||
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