buffer-apg-js/src/apg-exp/split.js

JavaScript APG, an ABNF Parser Generator

/*  *************************************************************************************
 *   copyright: Copyright (c) 2021 Lowell D. Thomas, all rights reserved
 *     license: BSD-2-Clause (https://opensource.org/licenses/BSD-2-Clause)
 *   ********************************************************************************* */
// This module implements the `split()` function.
/* called by split() to split the string */
exports.split = function exportsSplit(p, str, limit) {
  'use strict;';

  const exp = p.thisThis;
  let result;
  let beg;
  let end;
  let last;
  const phrases = [];
  const splits = [];
  let count = 0;
  exp.lastIndex = 0;
  const TRUE = true;
  while (TRUE) {
    last = exp.lastIndex;
    result = exp.exec(str);
    if (result === null) {
      break;
    }
    phrases.push({
      phrase: result[0],
      index: result.index,
    });
    /* ignore flags, uses bump-along mode (increment one character on empty string matches) */
    if (result[0].length === 0) {
      exp.lastIndex = last + 1;
    } else {
      exp.lastIndex = result.index + result[0].length;
    }
    count += 1;
    if (count > limit) {
      break;
    }
  }
  if (phrases.length === 0) {
    /* no phrases found, return array with the original string */
    return [str.slice(0)];
  }
  if (phrases.length === 1 || phrases[0].phrase.length === str.length) {
    /* one phrase found and it is the entire string */
    return [''];
  }
  /* first segment, if any */
  if (phrases[0].index > 0) {
    beg = 0;
    end = phrases[0].index;
    splits.push(str.slice(beg, end));
  }
  /* middle segments, if any */
  const endi = phrases.length - 1;
  for (let i = 0; i < endi; i += 1) {
    beg = phrases[i].index + phrases[i].phrase.length;
    end = phrases[i + 1].index;
    splits.push(str.slice(beg, end));
  }
  /* last segment, if any */
  last = phrases[phrases.length - 1];
  beg = last.index + last.phrase.length;
  if (beg < str.length) {
    end = str.length;
    splits.push(str.slice(beg, end));
  }
  return splits;
};