PHP's xdiff_string_patch in JavaScript

How to use

You you can install via yarn add locutus and require this function via const xdiff_string_patch = require('locutus/php/xdiff/xdiff_string_patch').

It is important to use a bundler that supports tree-shaking so that you only ship the functions that you actually use to your browser, instead of all of Locutus, which is massive. Examples are: Parcel, webpack, or rollup.js. For server-side use this is typically less of a concern.

Examples

Please note that these examples are distilled from test cases that automatically verify our functions still work correctly. This could explain some quirky ones.

#	code	expected result
1	xdiff_string_patch('', '@@ -0,0 +1,1 @@\n+Hello world!')	'Hello world!'

Notes

• The XDIFF_PATCH_IGNORESPACE flag and the error argument are not currently supported.

• This has not been tested exhaustively yet.

• The errorObj parameter (optional) if used must be passed in as a object. The errors will then be written by reference into it’s value property

Here’s what our current JavaScript equivalent to PHP's xdiff_string_patch looks like.

module.exports = function xdiff_string_patch(originalStr, patch, flags, errorObj) {
  //  discuss at: https://locutus.io/php/xdiff_string_patch/
  // original by: Brett Zamir (https://brett-zamir.me)
  // improved by: Steven Levithan (stevenlevithan.com)
  //      note 1: The XDIFF_PATCH_IGNORESPACE flag and the error argument are not
  //      note 1: currently supported.
  //      note 2: This has not been tested exhaustively yet.
  //      note 3: The errorObj parameter (optional) if used must be passed in as a
  //      note 3: object. The errors will then be written by reference into it's `value` property
  //   example 1: xdiff_string_patch('', '@@ -0,0 +1,1 @@\n+Hello world!')
  //   returns 1: 'Hello world!'

  // First two functions were adapted from Steven Levithan, also under an MIT license
  // Adapted from XRegExp 1.5.0
  // (c) 2007-2010 Steven Levithan
  // MIT License
  // <https://xregexp.com>

  const _getNativeFlags = function (regex) {
    // Proposed for ES4; included in AS3
    return [
      regex.global ? 'g' : '',
      regex.ignoreCase ? 'i' : '',
      regex.multiline ? 'm' : '',
      regex.extended ? 'x' : '',
      regex.sticky ? 'y' : '',
    ].join('')
  }

  const _cbSplit = function (string, sep) {
    // If separator `s` is not a regex, use the native `split`
    if (!(sep instanceof RegExp)) {
      // Had problems to get it to work here using prototype test
      return String.prototype.split.apply(string, arguments)
    }
    const str = String(string)
    const output = []
    let lastLastIndex = 0
    let match
    let lastLength
    const limit = Infinity
    const x = sep._xregexp
    // This is required if not `s.global`, and it avoids needing to set `s.lastIndex` to zero
    // and restore it to its original value when we're done using the regex
    // Brett paring down
    const s = new RegExp(sep.source, _getNativeFlags(sep) + 'g')
    if (x) {
      s._xregexp = {
        source: x.source,
        captureNames: x.captureNames ? x.captureNames.slice(0) : null,
      }
    }

    while ((match = s.exec(str))) {
      // Run the altered `exec` (required for `lastIndex` fix, etc.)
      if (s.lastIndex > lastLastIndex) {
        output.push(str.slice(lastLastIndex, match.index))

        if (match.length > 1 && match.index < str.length) {
          Array.prototype.push.apply(output, match.slice(1))
        }

        lastLength = match[0].length
        lastLastIndex = s.lastIndex

        if (output.length >= limit) {
          break
        }
      }

      if (s.lastIndex === match.index) {
        s.lastIndex++
      }
    }

    if (lastLastIndex === str.length) {
      if (!s.test('') || lastLength) {
        output.push('')
      }
    } else {
      output.push(str.slice(lastLastIndex))
    }

    return output.length > limit ? output.slice(0, limit) : output
  }

  let i = 0
  let ll = 0
  let ranges = []
  let lastLinePos = 0
  let firstChar = ''
  const rangeExp = /^@@\s+-(\d+),(\d+)\s+\+(\d+),(\d+)\s+@@$/
  const lineBreaks = /\r?\n/
  const lines = _cbSplit(patch.replace(/(\r?\n)+$/, ''), lineBreaks)
  const origLines = _cbSplit(originalStr, lineBreaks)
  const newStrArr = []
  let linePos = 0
  const errors = ''
  let optTemp = 0 // Both string & integer (constant) input is allowed
  const OPTS = {
    // Unsure of actual PHP values, so better to rely on string
    XDIFF_PATCH_NORMAL: 1,
    XDIFF_PATCH_REVERSE: 2,
    XDIFF_PATCH_IGNORESPACE: 4,
  }

  // Input defaulting & sanitation
  if (typeof originalStr !== 'string' || !patch) {
    return false
  }
  if (!flags) {
    flags = 'XDIFF_PATCH_NORMAL'
  }

  if (typeof flags !== 'number') {
    // Allow for a single string or an array of string flags
    flags = [].concat(flags)
    for (i = 0; i < flags.length; i++) {
      // Resolve string input to bitwise e.g. 'XDIFF_PATCH_NORMAL' becomes 1
      if (OPTS[flags[i]]) {
        optTemp = optTemp | OPTS[flags[i]]
      }
    }
    flags = optTemp
  }

  if (flags & OPTS.XDIFF_PATCH_NORMAL) {
    for (i = 0, ll = lines.length; i < ll; i++) {
      ranges = lines[i].match(rangeExp)
      if (ranges) {
        lastLinePos = linePos
        linePos = ranges[1] - 1
        while (lastLinePos < linePos) {
          newStrArr[newStrArr.length] = origLines[lastLinePos++]
        }
        while (lines[++i] && rangeExp.exec(lines[i]) === null) {
          firstChar = lines[i].charAt(0)
          switch (firstChar) {
            case '-':
              // Skip including that line
              ++linePos
              break
            case '+':
              newStrArr[newStrArr.length] = lines[i].slice(1)
              break
            case ' ':
              newStrArr[newStrArr.length] = origLines[linePos++]
              break
            default:
              // Reconcile with returning errrors arg?
              throw new Error('Unrecognized initial character in unidiff line')
          }
        }
        if (lines[i]) {
          i--
        }
      }
    }
    while (linePos > 0 && linePos < origLines.length) {
      newStrArr[newStrArr.length] = origLines[linePos++]
    }
  } else if (flags & OPTS.XDIFF_PATCH_REVERSE) {
    // Only differs from above by a few lines
    for (i = 0, ll = lines.length; i < ll; i++) {
      ranges = lines[i].match(rangeExp)
      if (ranges) {
        lastLinePos = linePos
        linePos = ranges[3] - 1
        while (lastLinePos < linePos) {
          newStrArr[newStrArr.length] = origLines[lastLinePos++]
        }
        while (lines[++i] && rangeExp.exec(lines[i]) === null) {
          firstChar = lines[i].charAt(0)
          switch (firstChar) {
            case '-':
              newStrArr[newStrArr.length] = lines[i].slice(1)
              break
            case '+':
              // Skip including that line
              ++linePos
              break
            case ' ':
              newStrArr[newStrArr.length] = origLines[linePos++]
              break
            default:
              // Reconcile with returning errrors arg?
              throw new Error('Unrecognized initial character in unidiff line')
          }
        }
        if (lines[i]) {
          i--
        }
      }
    }
    while (linePos > 0 && linePos < origLines.length) {
      newStrArr[newStrArr.length] = origLines[linePos++]
    }
  }

  if (errorObj) {
    errorObj.value = errors
  }

  return newStrArr.join('\n')
}

A community effort

Not unlike Wikipedia, Locutus is an ongoing community effort. Our philosophy follows The McDonald’s Theory. This means that we assimilate first iterations with imperfections, hoping for others to take issue with-and improve them. This unorthodox approach has worked very well to foster fun and fruitful collaboration, but please be reminded to use our creations at your own risk. THE SOFTWARE IS PROVIDED "AS IS" has never been more true than for Locutus.

Now go and: [ View on GitHub | Edit on GitHub | View Raw ]

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