bc518174
 王天杨
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import type { SourceMapSegment, ReverseSegment } from './sourcemap-segment';
import { COLUMN } from './sourcemap-segment';
export type MemoState = {
lastKey: number;
lastNeedle: number;
lastIndex: number;
};
export let found = false;
/**
* A binary search implementation that returns the index if a match is found.
* If no match is found, then the left-index (the index associated with the item that comes just
* before the desired index) is returned. To maintain proper sort order, a splice would happen at
* the next index:
*
* ```js
* const array = [1, 3];
* const needle = 2;
* const index = binarySearch(array, needle, (item, needle) => item - needle);
*
* assert.equal(index, 0);
* array.splice(index + 1, 0, needle);
* assert.deepEqual(array, [1, 2, 3]);
* ```
*/
export function binarySearch(
haystack: SourceMapSegment[] | ReverseSegment[],
needle: number,
low: number,
high: number,
): number {
while (low <= high) {
const mid = low + ((high - low) >> 1);
const cmp = haystack[mid][COLUMN] - needle;
if (cmp === 0) {
found = true;
return mid;
}
if (cmp < 0) {
low = mid + 1;
} else {
high = mid - 1;
}
}
found = false;
return low - 1;
}
export function upperBound(
haystack: SourceMapSegment[] | ReverseSegment[],
needle: number,
index: number,
): number {
for (let i = index + 1; i < haystack.length; index = i++) {
if (haystack[i][COLUMN] !== needle) break;
}
return index;
}
export function lowerBound(
haystack: SourceMapSegment[] | ReverseSegment[],
needle: number,
index: number,
): number {
for (let i = index - 1; i >= 0; index = i--) {
if (haystack[i][COLUMN] !== needle) break;
}
return index;
}
export function memoizedState(): MemoState {
return {
lastKey: -1,
lastNeedle: -1,
lastIndex: -1,
};
}
/**
* This overly complicated beast is just to record the last tested line/column and the resulting
* index, allowing us to skip a few tests if mappings are monotonically increasing.
*/
export function memoizedBinarySearch(
haystack: SourceMapSegment[] | ReverseSegment[],
needle: number,
state: MemoState,
key: number,
): number {
const { lastKey, lastNeedle, lastIndex } = state;
let low = 0;
let high = haystack.length - 1;
if (key === lastKey) {
if (needle === lastNeedle) {
found = lastIndex !== -1 && haystack[lastIndex][COLUMN] === needle;
return lastIndex;
}
if (needle >= lastNeedle) {
// lastIndex may be -1 if the previous needle was not found.
low = lastIndex === -1 ? 0 : lastIndex;
} else {
high = lastIndex;
}
}
state.lastKey = key;
state.lastNeedle = needle;
return (state.lastIndex = binarySearch(haystack, needle, low, high));
}
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