272 lines
7.7 KiB
JavaScript
272 lines
7.7 KiB
JavaScript
// Copyright (c) 2006, 2008 Tony Garnock-Jones <[email protected]>
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// Copyright (c) 2006, 2008 LShift Ltd. <[email protected]>
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//
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// Permission is hereby granted, free of charge, to any person
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// obtaining a copy of this software and associated documentation files
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// (the "Software"), to deal in the Software without restriction,
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// including without limitation the rights to use, copy, modify, merge,
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// publish, distribute, sublicense, and/or sell copies of the Software,
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// and to permit persons to whom the Software is furnished to do so,
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// subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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var onp = require('./onp');
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function longestCommonSubsequence(file1, file2) {
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var diff = new onp(file1, file2);
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diff.compose();
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var ses = diff.getses();
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var root;
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var prev;
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var file1RevIdx = file1.length - 1,
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file2RevIdx = file2.length - 1;
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for (var i = ses.length - 1; i >= 0; --i) {
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if (ses[i].t === diff.SES_COMMON) {
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if (prev) {
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prev.chain = {
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file1index: file1RevIdx,
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file2index: file2RevIdx,
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chain: null
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};
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prev = prev.chain;
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} else {
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root = {
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file1index: file1RevIdx,
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file2index: file2RevIdx,
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chain: null
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};
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prev = root;
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}
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file1RevIdx--;
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file2RevIdx--;
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} else if (ses[i].t === diff.SES_DELETE) {
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file1RevIdx--;
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} else if (ses[i].t === diff.SES_ADD) {
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file2RevIdx--;
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}
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}
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var tail = {
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file1index: -1,
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file2index: -1,
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chain: null
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};
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if (!prev) {
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return tail;
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}
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prev.chain = tail;
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return root;
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}
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function diffIndices(file1, file2) {
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// We apply the LCS to give a simple representation of the
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// offsets and lengths of mismatched chunks in the input
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// files. This is used by diff3_merge_indices below.
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var result = [];
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var tail1 = file1.length;
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var tail2 = file2.length;
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for (var candidate = longestCommonSubsequence(file1, file2); candidate !== null; candidate = candidate.chain) {
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var mismatchLength1 = tail1 - candidate.file1index - 1;
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var mismatchLength2 = tail2 - candidate.file2index - 1;
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tail1 = candidate.file1index;
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tail2 = candidate.file2index;
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if (mismatchLength1 || mismatchLength2) {
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result.push({
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file1: [tail1 + 1, mismatchLength1],
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file2: [tail2 + 1, mismatchLength2]
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});
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}
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}
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result.reverse();
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return result;
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}
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function diff3MergeIndices(a, o, b) {
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// Given three files, A, O, and B, where both A and B are
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// independently derived from O, returns a fairly complicated
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// internal representation of merge decisions it's taken. The
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// interested reader may wish to consult
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//
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// Sanjeev Khanna, Keshav Kunal, and Benjamin C. Pierce. "A
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// Formal Investigation of Diff3." In Arvind and Prasad,
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// editors, Foundations of Software Technology and Theoretical
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// Computer Science (FSTTCS), December 2007.
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//
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// (http://www.cis.upenn.edu/~bcpierce/papers/diff3-short.pdf)
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var i;
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var m1 = diffIndices(o, a);
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var m2 = diffIndices(o, b);
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var hunks = [];
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function addHunk(h, side) {
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hunks.push([h.file1[0], side, h.file1[1], h.file2[0], h.file2[1]]);
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}
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for (i = 0; i < m1.length; i++) {
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addHunk(m1[i], 0);
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}
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for (i = 0; i < m2.length; i++) {
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addHunk(m2[i], 2);
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}
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hunks.sort(function(x, y) {
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return x[0] - y[0]
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});
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var result = [];
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var commonOffset = 0;
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function copyCommon(targetOffset) {
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if (targetOffset > commonOffset) {
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result.push([1, commonOffset, targetOffset - commonOffset]);
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commonOffset = targetOffset;
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}
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}
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for (var hunkIndex = 0; hunkIndex < hunks.length; hunkIndex++) {
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var firstHunkIndex = hunkIndex;
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var hunk = hunks[hunkIndex];
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var regionLhs = hunk[0];
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var regionRhs = regionLhs + hunk[2];
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while (hunkIndex < hunks.length - 1) {
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var maybeOverlapping = hunks[hunkIndex + 1];
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var maybeLhs = maybeOverlapping[0];
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if (maybeLhs > regionRhs) break;
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regionRhs = Math.max(regionRhs, maybeLhs + maybeOverlapping[2]);
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hunkIndex++;
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}
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copyCommon(regionLhs);
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if (firstHunkIndex == hunkIndex) {
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// The "overlap" was only one hunk long, meaning that
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// there's no conflict here. Either a and o were the
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// same, or b and o were the same.
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if (hunk[4] > 0) {
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result.push([hunk[1], hunk[3], hunk[4]]);
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}
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} else {
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// A proper conflict. Determine the extents of the
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// regions involved from a, o and b. Effectively merge
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// all the hunks on the left into one giant hunk, and
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// do the same for the right; then, correct for skew
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// in the regions of o that each side changed, and
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// report appropriate spans for the three sides.
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var regions = {
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0: [a.length, -1, o.length, -1],
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2: [b.length, -1, o.length, -1]
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};
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for (i = firstHunkIndex; i <= hunkIndex; i++) {
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hunk = hunks[i];
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var side = hunk[1];
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var r = regions[side];
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var oLhs = hunk[0];
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var oRhs = oLhs + hunk[2];
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var abLhs = hunk[3];
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var abRhs = abLhs + hunk[4];
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r[0] = Math.min(abLhs, r[0]);
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r[1] = Math.max(abRhs, r[1]);
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r[2] = Math.min(oLhs, r[2]);
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r[3] = Math.max(oRhs, r[3]);
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}
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var aLhs = regions[0][0] + (regionLhs - regions[0][2]);
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var aRhs = regions[0][1] + (regionRhs - regions[0][3]);
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var bLhs = regions[2][0] + (regionLhs - regions[2][2]);
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var bRhs = regions[2][1] + (regionRhs - regions[2][3]);
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result.push([-1,
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aLhs, aRhs - aLhs,
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regionLhs, regionRhs - regionLhs,
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bLhs, bRhs - bLhs
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]);
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}
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commonOffset = regionRhs;
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}
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copyCommon(o.length);
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return result;
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}
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function diff3Merge(a, o, b) {
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// Applies the output of Diff.diff3_merge_indices to actually
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// construct the merged file; the returned result alternates
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// between "ok" and "conflict" blocks.
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var result = [];
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var files = [a, o, b];
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var indices = diff3MergeIndices(a, o, b);
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var okLines = [];
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function flushOk() {
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if (okLines.length) {
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result.push({
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ok: okLines
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});
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}
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okLines = [];
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}
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function pushOk(xs) {
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for (var j = 0; j < xs.length; j++) {
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okLines.push(xs[j]);
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}
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}
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function isTrueConflict(rec) {
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if (rec[2] != rec[6]) return true;
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var aoff = rec[1];
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var boff = rec[5];
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for (var j = 0; j < rec[2]; j++) {
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if (a[j + aoff] != b[j + boff]) return true;
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}
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return false;
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}
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for (var i = 0; i < indices.length; i++) {
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var x = indices[i];
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var side = x[0];
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if (side == -1) {
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if (!isTrueConflict(x)) {
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pushOk(files[0].slice(x[1], x[1] + x[2]));
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} else {
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flushOk();
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result.push({
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conflict: {
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a: a.slice(x[1], x[1] + x[2]),
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aIndex: x[1],
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o: o.slice(x[3], x[3] + x[4]),
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oIndex: x[3],
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b: b.slice(x[5], x[5] + x[6]),
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bIndex: x[5]
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}
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});
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}
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} else {
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pushOk(files[side].slice(x[1], x[1] + x[2]));
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}
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}
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flushOk();
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return result;
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}
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module.exports = diff3Merge;
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