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Diffstat (limited to 'lib/jdiff/src/util/Diff.java')
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diff --git a/lib/jdiff/src/util/Diff.java b/lib/jdiff/src/util/Diff.java new file mode 100644 index 000000000..a7d3ff84b --- /dev/null +++ b/lib/jdiff/src/util/Diff.java @@ -0,0 +1,848 @@ +package jdiff.util; + +import java.util.Hashtable; + +/** 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 Diff +{ + + /** 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 Diff(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 final int inserted; + /** # lines of file 0 changed here. */ + public final 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; + + } +} |