| package jdiff; |
| |
| import java.io.*; |
| import java.util.*; |
| |
| /** A class to compare vectors of objects. The result of comparison |
| is a list of <code>change</code> objects which form an |
| edit script. The objects compared are traditionally lines |
| of text from two files. Comparison options such as "ignore |
| whitespace" are implemented by modifying the <code>equals</code> |
| and <code>hashcode</code> methods for the objects compared. |
| <p> |
| The basic algorithm is described in: </br> |
| "An O(ND) Difference Algorithm and its Variations", Eugene Myers, |
| Algorithmica Vol. 1 No. 2, 1986, p 251. |
| <p> |
| This class outputs different results from GNU diff 1.15 on some |
| inputs. Our results are actually better (smaller change list, smaller |
| total size of changes), but it would be nice to know why. Perhaps |
| there is a memory overwrite bug in GNU diff 1.15. |
| |
| @author Stuart D. Gathman, translated from GNU diff 1.15 |
| Copyright (C) 2000 Business Management Systems, Inc. |
| <p> |
| This program is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 1, or (at your option) |
| any later version. |
| <p> |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| <p> |
| You should have received a copy of the <a href=COPYING.txt> |
| GNU General Public License</a> |
| along with this program; if not, write to the Free Software |
| Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
| |
| */ |
| |
| public class DiffMyers |
| { |
| |
| /** Prepare to find differences between two arrays. Each element of |
| the arrays is translated to an "equivalence number" based on |
| the result of <code>equals</code>. The original Object arrays |
| are no longer needed for computing the differences. They will |
| be needed again later to print the results of the comparison as |
| an edit script, if desired. |
| */ |
| public DiffMyers(Object[] a,Object[] b) |
| { |
| Hashtable h = new Hashtable(a.length + b.length); |
| filevec[0] = new file_data(a,h); |
| filevec[1] = new file_data(b,h); |
| } |
| |
| /** 1 more than the maximum equivalence value used for this or its |
| sibling file. */ |
| private int equiv_max = 1; |
| |
| /** When set to true, the comparison uses a heuristic to speed it up. |
| With this heuristic, for files with a constant small density |
| of changes, the algorithm is linear in the file size. */ |
| public boolean heuristic = false; |
| |
| /** When set to true, the algorithm returns a guarranteed minimal |
| set of changes. This makes things slower, sometimes much slower. */ |
| public boolean no_discards = false; |
| |
| private int[] xvec, yvec; /* Vectors being compared. */ |
| private int[] fdiag; /* Vector, indexed by diagonal, containing |
| the X coordinate of the point furthest |
| along the given diagonal in the forward |
| search of the edit matrix. */ |
| private int[] bdiag; /* Vector, indexed by diagonal, containing |
| the X coordinate of the point furthest |
| along the given diagonal in the backward |
| search of the edit matrix. */ |
| private int fdiagoff, bdiagoff; |
| private final file_data[] filevec = new file_data[2]; |
| private int cost; |
| |
| /** Find the midpoint of the shortest edit script for a specified |
| portion of the two files. |
| |
| We scan from the beginnings of the files, and simultaneously from the ends, |
| doing a breadth-first search through the space of edit-sequence. |
| When the two searches meet, we have found the midpoint of the shortest |
| edit sequence. |
| |
| The value returned is the number of the diagonal on which the midpoint lies. |
| The diagonal number equals the number of inserted lines minus the number |
| of deleted lines (counting only lines before the midpoint). |
| The edit cost is stored into COST; this is the total number of |
| lines inserted or deleted (counting only lines before the midpoint). |
| |
| This function assumes that the first lines of the specified portions |
| of the two files do not match, and likewise that the last lines do not |
| match. The caller must trim matching lines from the beginning and end |
| of the portions it is going to specify. |
| |
| Note that if we return the "wrong" diagonal value, or if |
| the value of bdiag at that diagonal is "wrong", |
| the worst this can do is cause suboptimal diff output. |
| It cannot cause incorrect diff output. */ |
| |
| private int diag (int xoff, int xlim, int yoff, int ylim) |
| { |
| final int[] fd = fdiag; // Give the compiler a chance. |
| final int[] bd = bdiag; // Additional help for the compiler. |
| final int[] xv = xvec; // Still more help for the compiler. |
| final int[] yv = yvec; // And more and more . . . |
| final int dmin = xoff - ylim; // Minimum valid diagonal. |
| final int dmax = xlim - yoff; // Maximum valid diagonal. |
| final int fmid = xoff - yoff; // Center diagonal of top-down search. |
| final int bmid = xlim - ylim; // Center diagonal of bottom-up search. |
| int fmin = fmid, fmax = fmid; // Limits of top-down search. |
| int bmin = bmid, bmax = bmid; // Limits of bottom-up search. |
| /* True if southeast corner is on an odd |
| diagonal with respect to the northwest. */ |
| final boolean odd = (fmid - bmid & 1) != 0; |
| |
| fd[fdiagoff + fmid] = xoff; |
| bd[bdiagoff + bmid] = xlim; |
| |
| for (int c = 1;; ++c) |
| { |
| int d; /* Active diagonal. */ |
| boolean big_snake = false; |
| |
| /* Extend the top-down search by an edit step in each diagonal. */ |
| if (fmin > dmin) |
| fd[fdiagoff + --fmin - 1] = -1; |
| else |
| ++fmin; |
| if (fmax < dmax) |
| fd[fdiagoff + ++fmax + 1] = -1; |
| else |
| --fmax; |
| for (d = fmax; d >= fmin; d -= 2) |
| { |
| int x, y, oldx, tlo = fd[fdiagoff + d - 1], thi = fd[fdiagoff + d + 1]; |
| |
| if (tlo >= thi) |
| x = tlo + 1; |
| else |
| x = thi; |
| oldx = x; |
| y = x - d; |
| while (x < xlim && y < ylim && xv[x] == yv[y]) { |
| ++x; ++y; |
| } |
| if (x - oldx > 20) |
| big_snake = true; |
| fd[fdiagoff + d] = x; |
| if (odd && bmin <= d && d <= bmax && bd[bdiagoff + d] <= fd[fdiagoff + d]) |
| { |
| cost = 2 * c - 1; |
| return d; |
| } |
| } |
| |
| /* Similar extend the bottom-up search. */ |
| if (bmin > dmin) |
| bd[bdiagoff + --bmin - 1] = Integer.MAX_VALUE; |
| else |
| ++bmin; |
| if (bmax < dmax) |
| bd[bdiagoff + ++bmax + 1] = Integer.MAX_VALUE; |
| else |
| --bmax; |
| for (d = bmax; d >= bmin; d -= 2) |
| { |
| int x, y, oldx, tlo = bd[bdiagoff + d - 1], thi = bd[bdiagoff + d + 1]; |
| |
| if (tlo < thi) |
| x = tlo; |
| else |
| x = thi - 1; |
| oldx = x; |
| y = x - d; |
| while (x > xoff && y > yoff && xv[x - 1] == yv[y - 1]) { |
| --x; --y; |
| } |
| if (oldx - x > 20) |
| big_snake = true; |
| bd[bdiagoff + d] = x; |
| if (!odd && fmin <= d && d <= fmax && bd[bdiagoff + d] <= fd[fdiagoff + d]) |
| { |
| cost = 2 * c; |
| return d; |
| } |
| } |
| |
| /* Heuristic: check occasionally for a diagonal that has made |
| lots of progress compared with the edit distance. |
| If we have any such, find the one that has made the most |
| progress and return it as if it had succeeded. |
| |
| With this heuristic, for files with a constant small density |
| of changes, the algorithm is linear in the file size. */ |
| |
| if (c > 200 && big_snake && heuristic) |
| { |
| int best = 0; |
| int bestpos = -1; |
| |
| for (d = fmax; d >= fmin; d -= 2) |
| { |
| int dd = d - fmid; |
| if ((fd[fdiagoff + d] - xoff)*2 - dd > 12 * (c + (dd > 0 ? dd : -dd))) |
| { |
| if (fd[fdiagoff + d] * 2 - dd > best |
| && fd[fdiagoff + d] - xoff > 20 |
| && fd[fdiagoff + d] - d - yoff > 20) |
| { |
| int k; |
| int x = fd[fdiagoff + d]; |
| |
| /* We have a good enough best diagonal; |
| now insist that it end with a significant snake. */ |
| for (k = 1; k <= 20; k++) |
| if (xvec[x - k] != yvec[x - d - k]) |
| break; |
| |
| if (k == 21) |
| { |
| best = fd[fdiagoff + d] * 2 - dd; |
| bestpos = d; |
| } |
| } |
| } |
| } |
| if (best > 0) |
| { |
| cost = 2 * c - 1; |
| return bestpos; |
| } |
| |
| best = 0; |
| for (d = bmax; d >= bmin; d -= 2) |
| { |
| int dd = d - bmid; |
| if ((xlim - bd[bdiagoff + d])*2 + dd > 12 * (c + (dd > 0 ? dd : -dd))) |
| { |
| if ((xlim - bd[bdiagoff + d]) * 2 + dd > best |
| && xlim - bd[bdiagoff + d] > 20 |
| && ylim - (bd[bdiagoff + d] - d) > 20) |
| { |
| /* We have a good enough best diagonal; |
| now insist that it end with a significant snake. */ |
| int k; |
| int x = bd[bdiagoff + d]; |
| |
| for (k = 0; k < 20; k++) |
| if (xvec[x + k] != yvec[x - d + k]) |
| break; |
| if (k == 20) |
| { |
| best = (xlim - bd[bdiagoff + d]) * 2 + dd; |
| bestpos = d; |
| } |
| } |
| } |
| } |
| if (best > 0) |
| { |
| cost = 2 * c - 1; |
| return bestpos; |
| } |
| } |
| } |
| } |
| |
| /** Compare in detail contiguous subsequences of the two files |
| which are known, as a whole, to match each other. |
| |
| The results are recorded in the vectors filevec[N].changed_flag, by |
| storing a 1 in the element for each line that is an insertion or deletion. |
| |
| The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1. |
| |
| Note that XLIM, YLIM are exclusive bounds. |
| All line numbers are origin-0 and discarded lines are not counted. */ |
| |
| private void compareseq (int xoff, int xlim, int yoff, int ylim) { |
| /* Slide down the bottom initial diagonal. */ |
| while (xoff < xlim && yoff < ylim && xvec[xoff] == yvec[yoff]) { |
| ++xoff; ++yoff; |
| } |
| /* Slide up the top initial diagonal. */ |
| while (xlim > xoff && ylim > yoff && xvec[xlim - 1] == yvec[ylim - 1]) { |
| --xlim; --ylim; |
| } |
| |
| /* Handle simple cases. */ |
| if (xoff == xlim) |
| while (yoff < ylim) |
| filevec[1].changed_flag[1+filevec[1].realindexes[yoff++]] = true; |
| else if (yoff == ylim) |
| while (xoff < xlim) |
| filevec[0].changed_flag[1+filevec[0].realindexes[xoff++]] = true; |
| else |
| { |
| /* Find a point of correspondence in the middle of the files. */ |
| |
| int d = diag (xoff, xlim, yoff, ylim); |
| int c = cost; |
| int f = fdiag[fdiagoff + d]; |
| int b = bdiag[bdiagoff + d]; |
| |
| if (c == 1) |
| { |
| /* This should be impossible, because it implies that |
| one of the two subsequences is empty, |
| and that case was handled above without calling `diag'. |
| Let's verify that this is true. */ |
| throw new IllegalArgumentException("Empty subsequence"); |
| } |
| else |
| { |
| /* Use that point to split this problem into two subproblems. */ |
| compareseq (xoff, b, yoff, b - d); |
| /* This used to use f instead of b, |
| but that is incorrect! |
| It is not necessarily the case that diagonal d |
| has a snake from b to f. */ |
| compareseq (b, xlim, b - d, ylim); |
| } |
| } |
| } |
| |
| /** Discard lines from one file that have no matches in the other file. |
| */ |
| |
| private void discard_confusing_lines() { |
| filevec[0].discard_confusing_lines(filevec[1]); |
| filevec[1].discard_confusing_lines(filevec[0]); |
| } |
| |
| private boolean inhibit = false; |
| |
| /** Adjust inserts/deletes of blank lines to join changes |
| as much as possible. |
| */ |
| |
| private void shift_boundaries() { |
| if (inhibit) |
| return; |
| filevec[0].shift_boundaries(filevec[1]); |
| filevec[1].shift_boundaries(filevec[0]); |
| } |
| |
| /** Scan the tables of which lines are inserted and deleted, |
| producing an edit script in reverse order. */ |
| |
| private change build_reverse_script() { |
| change script = null; |
| final boolean[] changed0 = filevec[0].changed_flag; |
| final boolean[] changed1 = filevec[1].changed_flag; |
| final int len0 = filevec[0].buffered_lines; |
| final int len1 = filevec[1].buffered_lines; |
| |
| /* Note that changedN[len0] does exist, and contains 0. */ |
| |
| int i0 = 0, i1 = 0; |
| |
| while (i0 < len0 || i1 < len1) |
| { |
| if (changed0[1+i0] || changed1[1+i1]) |
| { |
| int line0 = i0, line1 = i1; |
| |
| /* Find # lines changed here in each file. */ |
| while (changed0[1+i0]) ++i0; |
| while (changed1[1+i1]) ++i1; |
| |
| /* Record this change. */ |
| script = new change(line0, line1, i0 - line0, i1 - line1, script); |
| } |
| |
| /* We have reached lines in the two files that match each other. */ |
| i0++; i1++; |
| } |
| |
| return script; |
| } |
| |
| /** Scan the tables of which lines are inserted and deleted, |
| producing an edit script in forward order. */ |
| |
| private change build_script() { |
| change script = null; |
| final boolean[] changed0 = filevec[0].changed_flag; |
| final boolean[] changed1 = filevec[1].changed_flag; |
| final int len0 = filevec[0].buffered_lines; |
| final int len1 = filevec[1].buffered_lines; |
| int i0 = len0, i1 = len1; |
| |
| /* Note that changedN[-1] does exist, and contains 0. */ |
| |
| while (i0 >= 0 || i1 >= 0) |
| { |
| if (changed0[i0] || changed1[i1]) |
| { |
| int line0 = i0, line1 = i1; |
| |
| /* Find # lines changed here in each file. */ |
| while (changed0[i0]) --i0; |
| while (changed1[i1]) --i1; |
| |
| /* Record this change. */ |
| script = new change(i0, i1, line0 - i0, line1 - i1, script); |
| } |
| |
| /* We have reached lines in the two files that match each other. */ |
| i0--; i1--; |
| } |
| |
| return script; |
| } |
| |
| /* Report the differences of two files. DEPTH is the current directory |
| depth. */ |
| public change diff_2(final boolean reverse) { |
| |
| /* Some lines are obviously insertions or deletions |
| because they don't match anything. Detect them now, |
| and avoid even thinking about them in the main comparison algorithm. */ |
| |
| discard_confusing_lines (); |
| |
| /* Now do the main comparison algorithm, considering just the |
| undiscarded lines. */ |
| |
| xvec = filevec[0].undiscarded; |
| yvec = filevec[1].undiscarded; |
| |
| int diags = |
| filevec[0].nondiscarded_lines + filevec[1].nondiscarded_lines + 3; |
| fdiag = new int[diags]; |
| fdiagoff = filevec[1].nondiscarded_lines + 1; |
| bdiag = new int[diags]; |
| bdiagoff = filevec[1].nondiscarded_lines + 1; |
| |
| compareseq (0, filevec[0].nondiscarded_lines, |
| 0, filevec[1].nondiscarded_lines); |
| fdiag = null; |
| bdiag = null; |
| |
| /* Modify the results slightly to make them prettier |
| in cases where that can validly be done. */ |
| |
| shift_boundaries (); |
| |
| /* Get the results of comparison in the form of a chain |
| of `struct change's -- an edit script. */ |
| |
| if (reverse) |
| return build_reverse_script(); |
| else |
| return build_script(); |
| } |
| |
| /** The result of comparison is an "edit script": a chain of change objects. |
| Each change represents one place where some lines are deleted |
| and some are inserted. |
| |
| LINE0 and LINE1 are the first affected lines in the two files (origin 0). |
| DELETED is the number of lines deleted here from file 0. |
| INSERTED is the number of lines inserted here in file 1. |
| |
| If DELETED is 0 then LINE0 is the number of the line before |
| which the insertion was done; vice versa for INSERTED and LINE1. */ |
| |
| public static class change { |
| /** Previous or next edit command. */ |
| public change link; |
| /** # lines of file 1 changed here. */ |
| public int inserted; |
| /** # lines of file 0 changed here. */ |
| public int deleted; |
| /** Line number of 1st deleted line. */ |
| public final int line0; |
| /** Line number of 1st inserted line. */ |
| public final int line1; |
| |
| /** Cons an additional entry onto the front of an edit script OLD. |
| LINE0 and LINE1 are the first affected lines in the two files (origin 0). |
| DELETED is the number of lines deleted here from file 0. |
| INSERTED is the number of lines inserted here in file 1. |
| |
| If DELETED is 0 then LINE0 is the number of the line before |
| which the insertion was done; vice versa for INSERTED and LINE1. */ |
| change(int line0, int line1, int deleted, int inserted, change old) { |
| this.line0 = line0; |
| this.line1 = line1; |
| this.inserted = inserted; |
| this.deleted = deleted; |
| this.link = old; |
| //System.err.println(line0+","+line1+","+inserted+","+deleted); |
| } |
| } |
| |
| /** Data on one input file being compared. |
| */ |
| |
| class file_data { |
| |
| /** Allocate changed array for the results of comparison. */ |
| void clear() { |
| /* Allocate a flag for each line of each file, saying whether that line |
| is an insertion or deletion. |
| Allocate an extra element, always zero, at each end of each vector. |
| */ |
| changed_flag = new boolean[buffered_lines + 2]; |
| } |
| |
| /** Return equiv_count[I] as the number of lines in this file |
| that fall in equivalence class I. |
| @return the array of equivalence class counts. |
| */ |
| int[] equivCount() { |
| int[] equiv_count = new int[equiv_max]; |
| for (int i = 0; i < buffered_lines; ++i) |
| ++equiv_count[equivs[i]]; |
| return equiv_count; |
| } |
| |
| /** Discard lines that have no matches in another file. |
| |
| A line which is discarded will not be considered by the actual |
| comparison algorithm; it will be as if that line were not in the file. |
| The file's `realindexes' table maps virtual line numbers |
| (which don't count the discarded lines) into real line numbers; |
| this is how the actual comparison algorithm produces results |
| that are comprehensible when the discarded lines are counted. |
| <p> |
| When we discard a line, we also mark it as a deletion or insertion |
| so that it will be printed in the output. |
| @param f the other file |
| */ |
| void discard_confusing_lines(file_data f) { |
| clear(); |
| /* Set up table of which lines are going to be discarded. */ |
| final byte[] discarded = discardable(f.equivCount()); |
| |
| /* Don't really discard the provisional lines except when they occur |
| in a run of discardables, with nonprovisionals at the beginning |
| and end. */ |
| filterDiscards(discarded); |
| |
| /* Actually discard the lines. */ |
| discard(discarded); |
| } |
| |
| /** Mark to be discarded each line that matches no line of another file. |
| If a line matches many lines, mark it as provisionally discardable. |
| @see equivCount() |
| @param counts The count of each equivalence number for the other file. |
| @return 0=nondiscardable, 1=discardable or 2=provisionally discardable |
| for each line |
| */ |
| |
| private byte[] discardable(final int[] counts) { |
| final int end = buffered_lines; |
| final byte[] discards = new byte[end]; |
| final int[] equivs = this.equivs; |
| int many = 5; |
| int tem = end / 64; |
| |
| /* Multiply MANY by approximate square root of number of lines. |
| That is the threshold for provisionally discardable lines. */ |
| while ((tem = tem >> 2) > 0) |
| many *= 2; |
| |
| for (int i = 0; i < end; i++) |
| { |
| int nmatch; |
| if (equivs[i] == 0) |
| continue; |
| nmatch = counts[equivs[i]]; |
| if (nmatch == 0) |
| discards[i] = 1; |
| else if (nmatch > many) |
| discards[i] = 2; |
| } |
| return discards; |
| } |
| |
| /** Don't really discard the provisional lines except when they occur |
| in a run of discardables, with nonprovisionals at the beginning |
| and end. */ |
| |
| private void filterDiscards(final byte[] discards) { |
| final int end = buffered_lines; |
| |
| for (int i = 0; i < end; i++) |
| { |
| /* Cancel provisional discards not in middle of run of discards. */ |
| if (discards[i] == 2) |
| discards[i] = 0; |
| else if (discards[i] != 0) |
| { |
| /* We have found a nonprovisional discard. */ |
| int j; |
| int length; |
| int provisional = 0; |
| |
| /* Find end of this run of discardable lines. |
| Count how many are provisionally discardable. */ |
| for (j = i; j < end; j++) |
| { |
| if (discards[j] == 0) |
| break; |
| if (discards[j] == 2) |
| ++provisional; |
| } |
| |
| /* Cancel provisional discards at end, and shrink the run. */ |
| while (j > i && discards[j - 1] == 2) { |
| discards[--j] = 0; --provisional; |
| } |
| |
| /* Now we have the length of a run of discardable lines |
| whose first and last are not provisional. */ |
| length = j - i; |
| |
| /* If 1/4 of the lines in the run are provisional, |
| cancel discarding of all provisional lines in the run. */ |
| if (provisional * 4 > length) |
| { |
| while (j > i) |
| if (discards[--j] == 2) |
| discards[j] = 0; |
| } |
| else |
| { |
| int consec; |
| int minimum = 1; |
| int tem = length / 4; |
| |
| /* MINIMUM is approximate square root of LENGTH/4. |
| A subrun of two or more provisionals can stand |
| when LENGTH is at least 16. |
| A subrun of 4 or more can stand when LENGTH >= 64. */ |
| while ((tem = tem >> 2) > 0) |
| minimum *= 2; |
| minimum++; |
| |
| /* Cancel any subrun of MINIMUM or more provisionals |
| within the larger run. */ |
| for (j = 0, consec = 0; j < length; j++) |
| if (discards[i + j] != 2) |
| consec = 0; |
| else if (minimum == ++consec) |
| /* Back up to start of subrun, to cancel it all. */ |
| j -= consec; |
| else if (minimum < consec) |
| discards[i + j] = 0; |
| |
| /* Scan from beginning of run |
| until we find 3 or more nonprovisionals in a row |
| or until the first nonprovisional at least 8 lines in. |
| Until that point, cancel any provisionals. */ |
| for (j = 0, consec = 0; j < length; j++) |
| { |
| if (j >= 8 && discards[i + j] == 1) |
| break; |
| if (discards[i + j] == 2) { |
| consec = 0; discards[i + j] = 0; |
| } |
| else if (discards[i + j] == 0) |
| consec = 0; |
| else |
| consec++; |
| if (consec == 3) |
| break; |
| } |
| |
| /* I advances to the last line of the run. */ |
| i += length - 1; |
| |
| /* Same thing, from end. */ |
| for (j = 0, consec = 0; j < length; j++) |
| { |
| if (j >= 8 && discards[i - j] == 1) |
| break; |
| if (discards[i - j] == 2) { |
| consec = 0; discards[i - j] = 0; |
| } |
| else if (discards[i - j] == 0) |
| consec = 0; |
| else |
| consec++; |
| if (consec == 3) |
| break; |
| } |
| } |
| } |
| } |
| } |
| |
| /** Actually discard the lines. |
| @param discards flags lines to be discarded |
| */ |
| private void discard(final byte[] discards) { |
| final int end = buffered_lines; |
| int j = 0; |
| for (int i = 0; i < end; ++i) |
| if (no_discards || discards[i] == 0) |
| { |
| undiscarded[j] = equivs[i]; |
| realindexes[j++] = i; |
| } |
| else |
| changed_flag[1+i] = true; |
| nondiscarded_lines = j; |
| } |
| |
| file_data(Object[] data,Hashtable h) { |
| buffered_lines = data.length; |
| |
| equivs = new int[buffered_lines]; |
| undiscarded = new int[buffered_lines]; |
| realindexes = new int[buffered_lines]; |
| |
| for (int i = 0; i < data.length; ++i) { |
| Integer ir = (Integer)h.get(data[i]); |
| if (ir == null) |
| h.put(data[i],new Integer(equivs[i] = equiv_max++)); |
| else |
| equivs[i] = ir.intValue(); |
| } |
| } |
| |
| /** Adjust inserts/deletes of blank lines to join changes |
| as much as possible. |
| |
| We do something when a run of changed lines include a blank |
| line at one end and have an excluded blank line at the other. |
| We are free to choose which blank line is included. |
| `compareseq' always chooses the one at the beginning, |
| but usually it is cleaner to consider the following blank line |
| to be the "change". The only exception is if the preceding blank line |
| would join this change to other changes. |
| @param f the file being compared against |
| */ |
| |
| void shift_boundaries(file_data f) { |
| final boolean[] changed = changed_flag; |
| final boolean[] other_changed = f.changed_flag; |
| int i = 0; |
| int j = 0; |
| int i_end = buffered_lines; |
| int preceding = -1; |
| int other_preceding = -1; |
| |
| for (;;) |
| { |
| int start, end, other_start; |
| |
| /* Scan forwards to find beginning of another run of changes. |
| Also keep track of the corresponding point in the other file. */ |
| |
| while (i < i_end && !changed[1+i]) |
| { |
| while (other_changed[1+j++]) |
| /* Non-corresponding lines in the other file |
| will count as the preceding batch of changes. */ |
| other_preceding = j; |
| i++; |
| } |
| |
| if (i == i_end) |
| break; |
| |
| start = i; |
| other_start = j; |
| |
| for (;;) |
| { |
| /* Now find the end of this run of changes. */ |
| |
| while (i < i_end && changed[1+i]) i++; |
| end = i; |
| |
| /* If the first changed line matches the following unchanged one, |
| and this run does not follow right after a previous run, |
| and there are no lines deleted from the other file here, |
| then classify the first changed line as unchanged |
| and the following line as changed in its place. */ |
| |
| /* You might ask, how could this run follow right after another? |
| Only because the previous run was shifted here. */ |
| |
| if (end != i_end |
| && equivs[start] == equivs[end] |
| && !other_changed[1+j] |
| && end != i_end |
| && !((preceding >= 0 && start == preceding) |
| || (other_preceding >= 0 |
| && other_start == other_preceding))) |
| { |
| changed[1+end++] = true; |
| changed[1+start++] = false; |
| ++i; |
| /* Since one line-that-matches is now before this run |
| instead of after, we must advance in the other file |
| to keep in synch. */ |
| ++j; |
| } |
| else |
| break; |
| } |
| |
| preceding = i; |
| other_preceding = j; |
| } |
| } |
| |
| /** Number of elements (lines) in this file. */ |
| final int buffered_lines; |
| |
| /** Vector, indexed by line number, containing an equivalence code for |
| each line. It is this vector that is actually compared with that |
| of another file to generate differences. */ |
| private final int[] equivs; |
| |
| /** Vector, like the previous one except that |
| the elements for discarded lines have been squeezed out. */ |
| final int[] undiscarded; |
| |
| /** Vector mapping virtual line numbers (not counting discarded lines) |
| to real ones (counting those lines). Both are origin-0. */ |
| final int[] realindexes; |
| |
| /** Total number of nondiscarded lines. */ |
| int nondiscarded_lines; |
| |
| /** Array, indexed by real origin-1 line number, |
| containing true for a line that is an insertion or a deletion. |
| The results of comparison are stored here. */ |
| boolean[] changed_flag; |
| |
| } |
| |
| } |
