tor-browser

helper_diff.js (9359B)

---

/**
* This diff utility is taken from:
* https://github.com/Slava/diff.js
*
* The MIT License (MIT)
*
* Copyright (c) 2014 Slava
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/

/**
* USAGE:
*   diff(text1, text2);
*/

/**
* Longest Common Subsequence
*
* @param A - sequence of atoms - Array
* @param B - sequence of atoms - Array
* @param equals - optional comparator of atoms - returns true or false,
*                 if not specified, triple equals operator is used
* @returns Array - sequence of atoms, one of LCSs, edit script from A to B
*/
var LCS = function (A, B, /* optional */ equals) {
 // We just compare atoms with default equals operator by default
 if (equals === undefined)
   equals = function (a, b) { return a === b; };

 // NOTE: all intervals from now on are both sides inclusive
 // Get the points in Edit Graph, one of the LCS paths goes through.
 // The points are located on the same diagonal and represent the middle
 // snake ([D/2] out of D+1) in the optimal edit path in edit graph.
 // @param startA, endA - substring of A we are working on
 // @param startB, endB - substring of B we are working on
 // @returns Array - [
 //                   [x, y], - beginning of the middle snake
 //                   [u, v], - end of the middle snake
 //                    D,     - optimal edit distance
 //                    LCS ]  - length of LCS
 var findMidSnake = function (startA, endA, startB, endB) {
   var N = endA - startA + 1;
   var M = endB - startB + 1;
   var Max = N + M;
   var Delta = N - M;
   var halfMaxCeil = (Max + 1) / 2 | 0;

   var foundOverlap = false;
   var overlap = null;

   // Maps -Max .. 0 .. +Max, diagonal index to endpoints for furthest reaching
   // D-path on current iteration.
   var V = {};
   // Same but for reversed paths.
   var U = {};

   // Special case for the base case, D = 0, k = 0, x = y = 0
   V[1] = 0;
   // Special case for the base case reversed, D = 0, k = 0, x = N, y = M
   U[Delta - 1] = N;

   // Iterate over each possible length of edit script
   for (var D = 0; D <= halfMaxCeil; D++) {
     // Iterate over each diagonal
     for (var k = -D; k <= D && !overlap; k += 2) {
       // Positions in sequences A and B of furthest going D-path on diagonal k.
       var x, y;

       // Choose from each diagonal we extend
       if (k === -D || (k !== D && V[k - 1] < V[k + 1]))
         // Extending path one point down, that's why x doesn't change, y
         // increases implicitly
         x = V[k + 1];
       else
         // Extending path one point to the right, x increases
         x = V[k - 1] + 1;

       // We can calculate the y out of x and diagonal index.
       y = x - k;

       if (isNaN(y) || x > N || y > M)
         continue;

       var xx = x;
       // Try to extend the D-path with diagonal paths. Possible only if atoms
       // A_x match B_y
       while (x < N && y < M // if there are atoms to compare
              && equals(A[startA + x], B[startB + y])) {
         x++; y++;
       }

       // We can safely update diagonal k, since on every iteration we consider
       // only even or only odd diagonals and the result of one depends only on
       // diagonals of different iteration.
       V[k] = x;

       // Check feasibility, Delta is checked for being odd.
       if ((Delta & 1) === 1 && inRange(k, Delta - (D - 1), Delta + (D - 1)))
         // Forward D-path can overlap with reversed D-1-path
         if (V[k] >= U[k])
           // Found an overlap, the middle snake, convert X-components to dots
           overlap = [xx, x].map(toPoint, k); // XXX ES5
     }

     if (overlap)
       var SES = D * 2 - 1;

     // Iterate over each diagonal for reversed case
     for (var k = -D; k <= D && !overlap; k += 2) {
       // The real diagonal we are looking for is k + Delta
       var K = k + Delta;
       var x, y;
       if (k === D || (k !== -D && U[K - 1] < U[K + 1]))
         x = U[K - 1];
       else
         x = U[K + 1] - 1;

       y = x - K;
       if (isNaN(y) || x < 0 || y < 0)
         continue;
       var xx = x;
       while (x > 0 && y > 0 && equals(A[startA + x - 1], B[startB + y - 1])) {
         x--; y--;
       }
       U[K] = x;

       if (Delta % 2 === 0 && inRange(K, -D, D))
         if (U[K] <= V[K])
           overlap = [x, xx].map(toPoint, K); // XXX ES5
     }

     if (overlap) {
       SES = SES || D * 2;
       // Remember we had offset of each sequence?
       for (var i = 0; i < 2; i++) for (var j = 0; j < 2; j++)
         overlap[i][j] += [startA, startB][j] - i;
       return overlap.concat([ SES, (Max - SES) / 2 ]);
     }
   }
 };

 var lcsAtoms = [];
 var lcs = function (startA, endA, startB, endB) {
   var N = endA - startA + 1;
   var M = endB - startB + 1;

   if (N > 0 && M > 0) {
     var middleSnake = findMidSnake(startA, endA, startB, endB);
     // A[x;u] == B[y,v] and is part of LCS
     var x = middleSnake[0][0], y = middleSnake[0][1];
     var u = middleSnake[1][0], v = middleSnake[1][1];
     var D = middleSnake[2];

     if (D > 1) {
       lcs(startA, x - 1, startB, y - 1);
       if (x <= u) {
         [].push.apply(lcsAtoms, A.slice(x, u + 1));
       }
       lcs(u + 1, endA, v + 1, endB);
     } else if (M > N)
       [].push.apply(lcsAtoms, A.slice(startA, endA + 1));
     else
       [].push.apply(lcsAtoms, B.slice(startB, endB + 1));
   }
 };

 lcs(0, A.length - 1, 0, B.length - 1);
 return lcsAtoms;
};

// Helpers
var inRange = function (x, l, r) {
 return (l <= x && x <= r) || (r <= x && x <= l);
};

// Takes X-component as argument, diagonal as context,
// returns array-pair of form x, y
var toPoint = function (x) {
 return [x, x - this];  // XXX context is not the best way to pass diagonal
};

// Wrappers
LCS.StringLCS = function (A, B) {
 return LCS(A.split(''), B.split('')).join('');
};

/**
* Diff sequence
*
* @param A - sequence of atoms - Array
* @param B - sequence of atoms - Array
* @param equals - optional comparator of atoms - returns true or false,
*                 if not specified, triple equals operator is used
* @returns Array - sequence of objects in a form of:
*   - operation: one of "none", "add", "delete"
*   - atom: the atom found in either A or B
* Applying operations from diff sequence you should be able to transform A to B
*/
function diff(A, B, equals) {
 // We just compare atoms with default equals operator by default
 if (equals === undefined)
   equals = function (a, b) { return a === b; };

 var diff = [];
 var i = 0, j = 0;
 var N = A.length, M = B.length, K = 0;

 while (i < N && j < M && equals(A[i], B[j]))
   i++, j++;

 while (i < N && j < M && equals(A[N-1], B[M-1]))
   N--, M--, K++;

 [].push.apply(diff, A.slice(0, i).map(function (atom) {
   return { operation: "none", atom: atom }; }));

 var lcs = LCS(A.slice(i, N), B.slice(j, M), equals);

 for (var k = 0; k < lcs.length; k++) {
   var atom = lcs[k];
   var ni = customIndexOf.call(A, atom, i, equals);
   var nj = customIndexOf.call(B, atom, j, equals);

   // XXX ES5 map
   // Delete unmatched atoms from A
   [].push.apply(diff, A.slice(i, ni).map(function (atom) {
     return { operation: "delete", atom: atom };
   }));

   // Add unmatched atoms from B
   [].push.apply(diff, B.slice(j, nj).map(function (atom) {
     return { operation: "add", atom: atom };
   }));

   // Add the atom found in both sequences
   diff.push({ operation: "none", atom: atom });

   i = ni + 1;
   j = nj + 1;
 }

 // Don't forget about the rest

 [].push.apply(diff, A.slice(i, N).map(function (atom) {
   return { operation: "delete", atom: atom };
 }));

 [].push.apply(diff, B.slice(j, M).map(function (atom) {
   return { operation: "add", atom: atom };
 }));

 [].push.apply(diff, A.slice(N, N + K).map(function (atom) {
   return { operation: "none", atom: atom }; }));

 return diff;
};

// Accepts custom comparator
var customIndexOf = function(item, start, equals){
 var arr = this;
 for (var i = start; i < arr.length; i++)
   if (equals(item, arr[i]))
     return i;
 return -1;
};

function textDiff(text1, text2) {
 return diff(text1.split("\n"), text2.split("\n"));
}