line-counter.js•1.45 kB
'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;