forked from Fediversity/fediversity.eu
42 lines
1.4 KiB
JavaScript
42 lines
1.4 KiB
JavaScript
'use strict';
|
|
|
|
/**
|
|
* Tracks newlines during parsing in order to provide an efficient API for
|
|
* determining the one-indexed `{ line, col }` position for any offset
|
|
* within the input.
|
|
*/
|
|
class LineCounter {
|
|
constructor() {
|
|
this.lineStarts = [];
|
|
/**
|
|
* Should be called in ascending order. Otherwise, call
|
|
* `lineCounter.lineStarts.sort()` before calling `linePos()`.
|
|
*/
|
|
this.addNewLine = (offset) => this.lineStarts.push(offset);
|
|
/**
|
|
* Performs a binary search and returns the 1-indexed { line, col }
|
|
* position of `offset`. If `line === 0`, `addNewLine` has never been
|
|
* called or `offset` is before the first known newline.
|
|
*/
|
|
this.linePos = (offset) => {
|
|
let low = 0;
|
|
let high = this.lineStarts.length;
|
|
while (low < high) {
|
|
const mid = (low + high) >> 1; // Math.floor((low + high) / 2)
|
|
if (this.lineStarts[mid] < offset)
|
|
low = mid + 1;
|
|
else
|
|
high = mid;
|
|
}
|
|
if (this.lineStarts[low] === offset)
|
|
return { line: low + 1, col: 1 };
|
|
if (low === 0)
|
|
return { line: 0, col: offset };
|
|
const start = this.lineStarts[low - 1];
|
|
return { line: low, col: offset - start + 1 };
|
|
};
|
|
}
|
|
}
|
|
|
|
exports.LineCounter = LineCounter;
|