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+ 7C13EDE685F2C92F24A015E44B9609494E4D5DA9BC6A192B62A9CAB92F36C2543F5092FDADD7436FEAC45CA0AB54D19EA0692848C5C94F9819B885BEEC08E179
vtools/src/analyze.c

(0 . 0)(1 . 597)

#include "diff.h"
#include <cmpbuf.h>
#include <error.h>
#include <xalloc.h>
#include <stdlib.h>

/* The core of the Diff algorithm.  */
#define ELEMENT lin
#define EQUAL(x, y) ((x) == (y))
#define OFFSET lin
#define EXTRA_CONTEXT_FIELDS /* none */
#define NOTE_DELETE(c, xoff) (files[0].changed[files[0].realindexes[xoff]] = 1)
#define NOTE_INSERT(c, yoff) (files[1].changed[files[1].realindexes[yoff]] = 1)
#define USE_HEURISTIC 1
#include <limits.h>
#include <diffseq.h>
#include <sys/stat.h>

/* Discard lines from one file that have no matches in the other 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.

   When we discard a line, we also mark it as a deletion or insertion
   so that it will be printed in the output.  */

static void
discard_confusing_lines(struct file_data filevec[]) {
    int f;
    lin i;
    char *discarded[2];
    lin *equiv_count[2];
    lin *p;

    /* Allocate our results.  */
    p = xmalloc((filevec[0].buffered_lines + filevec[1].buffered_lines)
                * (2 * sizeof *p));
    for (f = 0; f < 2; f++) {
        filevec[f].undiscarded = p;
        p += filevec[f].buffered_lines;
        filevec[f].realindexes = p;
        p += filevec[f].buffered_lines;
    }

    /* Set up |equiv_count[f][i]| as the number of lines in file |f|
       that fall in equivalence class |i|.  */

    p = zalloc(filevec[0].equiv_max * (2 * sizeof *p));
    equiv_count[0] = p;
    equiv_count[1] = p + filevec[0].equiv_max;

    for (i = 0; i < filevec[0].buffered_lines; ++i)
        ++equiv_count[0][filevec[0].equivs[i]];
    for (i = 0; i < filevec[1].buffered_lines; ++i)
        ++equiv_count[1][filevec[1].equivs[i]];

    /* Set up tables of which lines are going to be discarded.  */

    discarded[0] = zalloc(filevec[0].buffered_lines
                          + filevec[1].buffered_lines);
    discarded[1] = discarded[0] + filevec[0].buffered_lines;

    /* Mark to be discarded each line that matches no line of the
       other file.  If a line matches many lines, mark it as
       provisionally discardable.  */

    for (f = 0; f < 2; f++) {
        size_t end = filevec[f].buffered_lines;
        char *discards = discarded[f];
        lin *counts = equiv_count[1 - f];
        lin *equivs = filevec[f].equivs;
        size_t many = 5;
        size_t 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 (i = 0; i < end; i++) {
            lin nmatch;
            if (equivs[i] == 0)
                continue;
            nmatch = counts[equivs[i]];
            if (nmatch == 0)
                discards[i] = 1;
            else if (nmatch > many)
                discards[i] = 2;
        }
    }

    /* Don't really discard the provisional lines except when they
       occur in a run of discardables, with nonprovisionals at the
       beginning and end.  */

    for (f = 0; f < 2; f++) {
        lin end = filevec[f].buffered_lines;
        register char *discards = discarded[f];

        for (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.  */
                register lin j;
                lin length;
                lin 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 {
                    register lin consec;
                    lin minimum = 1;
                    lin tem = length >> 2;

                    /* |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 (0 < (tem >>= 2))
                        minimum <<= 1;
                    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. */
    for (f = 0; f < 2; f++) {
        char *discards = discarded[f];
        lin end = filevec[f].buffered_lines;
        lin j = 0;
        for (i = 0; i < end; ++i)
            if (minimal || discards[i] == 0) {
                filevec[f].undiscarded[j] = filevec[f].equivs[i];
                filevec[f].realindexes[j++] = i;
            } else
                filevec[f].changed[i] = 1;
        filevec[f].nondiscarded_lines = j;
    }

    free(discarded[0]);
    free(equiv_count[0]);
}

/* Adjust inserts/deletes of identical lines to join changes as much
   as possible.

   We do something when a run of changed lines include a line at one
   end and have an excluded, identical line at the other.  We are free
   to choose which identical line is included.  |compareseq| usually
   chooses the one at the beginning, but usually it is cleaner to
   consider the following identical line to be the "change".  */

static void
shift_boundaries(struct file_data filevec[]) {
    int f;

    for (f = 0; f < 2; f++) {
        char *changed = filevec[f].changed;
        char *other_changed = filevec[1 - f].changed;
        lin const *equivs = filevec[f].equivs;
        lin i = 0;
        lin j = 0;
        lin i_end = filevec[f].buffered_lines;

        while (1) {
            lin runlength, start, corresponding;

            /* 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[i]) {
                while (other_changed[j++])
                    continue;
                i++;
            }

            if (i == i_end)
                break;

            start = i;

            /* Find the end of this run of changes.  */

            while (changed[++i])
                continue;
            while (other_changed[j])
                j++;

            do {
                /* Record the length of this run of changes, so that
               we can later determine whether the run has grown.  */
                runlength = i - start;

                /* Move the changed region back, so long as the
               previous unchanged line matches the last changed one.
               This merges with previous changed regions.  */

                while (start && equivs[start - 1] == equivs[i - 1]) {
                    changed[--start] = 1;
                    changed[--i] = 0;
                    while (changed[start - 1])
                        start--;
                    while (other_changed[--j])
                        continue;
                }

                /* Set |corresponding| to the end of the changed run,
               at the last point where it corresponds to a changed run
               in the other file.  |corresponding == i_end| means no
               such point has been found.  */
                corresponding = other_changed[j - 1] ? i : i_end;

                /* Move the changed region forward, so long as the
               first changed line matches the following unchanged one.
               This merges with following changed regions.  Do this
               second, so that if there are no merges, the changed
               region is moved forward as far as possible.  */

                while (i != i_end && equivs[start] == equivs[i]) {
                    changed[start++] = 0;
                    changed[i++] = 1;
                    while (changed[i])
                        i++;
                    while (other_changed[++j])
                        corresponding = i;
                }
            } while (runlength != i - start);

            /* If possible, move the fully-merged run of changes back
               to a corresponding run in the other file.  */

            while (corresponding < i) {
                changed[--start] = 1;
                changed[--i] = 0;
                while (other_changed[--j])
                    continue;
            }
        }
    }
}

/* 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|.  */

static struct change *
add_change(lin line0, lin line1, lin deleted, lin inserted,
           struct change *old) {
    struct change *new = xmalloc(sizeof *new);

    new->line0 = line0;
    new->line1 = line1;
    new->inserted = inserted;
    new->deleted = deleted;
    new->link = old;
    return new;
}

/* Scan the tables of which lines are inserted and deleted, producing
   an edit script in reverse order.  */

static struct change *
build_reverse_script(struct file_data const filevec[]) {
    struct change *script = 0;
    char *changed0 = filevec[0].changed;
    char *changed1 = filevec[1].changed;
    lin len0 = filevec[0].buffered_lines;
    lin len1 = filevec[1].buffered_lines;

    /* Note that |changedN[lenN]| does exist, and is 0.  */

    lin i0 = 0, i1 = 0;

    while (i0 < len0 || i1 < len1) {
        if (changed0[i0] | changed1[i1]) {
            lin line0 = i0, line1 = i1;

            /* Find \# lines changed here in each file.  */
            while (changed0[i0]) ++i0;
            while (changed1[i1]) ++i1;

            /* Record this change.  */
            script = add_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.  */

static struct change *
build_script(struct file_data const filevec[]) {
    struct change *script = 0;
    char *changed0 = filevec[0].changed;
    char *changed1 = filevec[1].changed;
    lin i0 = filevec[0].buffered_lines, i1 = filevec[1].buffered_lines;

    /* Note that |changedN[-1]| does exist, and is 0.  */

    while (i0 >= 0 || i1 >= 0) {
        if (changed0[i0 - 1] | changed1[i1 - 1]) {
            lin line0 = i0, line1 = i1;

            /* Find \# lines changed here in each file.  */
            while (changed0[i0 - 1]) --i0;
            while (changed1[i1 - 1]) --i1;

            /* Record this change.  */
            script = add_change(i0, i1, line0 - i0, line1 - i1, script);
        }

        /* We have reached lines in the two files that match each
           other.  */
        i0--, i1--;
    }

    return script;
}

/* If |changes|, briefly report that two files differed.  */
static void
briefly_report(int changes, struct file_data const filevec[]) {
    if (changes)
        message((brief
                 ? "Files %s and %s differ\n"
                 : "Binary files %s and %s differ\n"),
                file_label[0] ? file_label[0] : filevec[0].name,
                file_label[1] ? file_label[1] : filevec[1].name);
}

/* Report the differences of two files.  */
int
diff_2_files(struct comparison *cmp) {
    int f;
    struct change *e, *p;
    struct change *script;
    int changes;


    /* If we have detected that either file is binary, compare the two
       files as binary.  This can happen only when the first chunk is
       read. */

    if (read_files(cmp->file, files_can_be_treated_as_binary)) {
        /* Files with different lengths must be different.  */
        if (cmp->file[0].stat.st_size != cmp->file[1].stat.st_size
            && 0 < cmp->file[0].stat.st_size
            && 0 < cmp->file[1].stat.st_size
            && (cmp->file[0].desc < 0 || S_ISREG (cmp->file[0].stat.st_mode))
            && (cmp->file[1].desc < 0 || S_ISREG (cmp->file[1].stat.st_mode)))
            changes = 1;

            /* Standard input equals itself.  */
        else if (cmp->file[0].desc == cmp->file[1].desc)
            changes = 0;

        else
            /* Scan both files, a buffer at a time, looking for a
               difference.  */
        {
            /* Allocate same-sized buffers for both files.  */
            size_t lcm_max = PTRDIFF_MAX - 1;
            size_t buffer_size =
                    buffer_lcm(sizeof(word),
                               buffer_lcm(STAT_BLOCKSIZE (cmp->file[0].stat),
                                          STAT_BLOCKSIZE (cmp->file[1].stat),
                                          lcm_max),
                               lcm_max);
            for (f = 0; f < 2; f++)
                cmp->file[f].buffer = xrealloc(cmp->file[f].buffer, buffer_size);

            for (;; cmp->file[0].buffered = cmp->file[1].buffered = 0) {
                /* Read a buffer's worth from both files.  */
                for (f = 0; f < 2; f++)
                    if (0 <= cmp->file[f].desc)
                        file_block_read(&cmp->file[f],
                                        buffer_size - cmp->file[f].buffered);

                /* If the buffers differ, the files differ.  */
                if (cmp->file[0].buffered != cmp->file[1].buffered
                    || memcmp(cmp->file[0].buffer,
                              cmp->file[1].buffer,
                              cmp->file[0].buffered)) {
                    changes = 1;
                    break;
                }

                /* If we reach end of file, the files are the
                   same.  */
                if (cmp->file[0].buffered != buffer_size) {
                    changes = 0;
                    break;
                }
            }
        }

        briefly_report(changes, cmp->file);
    } else {
        struct context ctxt;
        lin diags;
        lin too_expensive;

        /* Allocate vectors for the results of comparison: a flag for
       each line of each file, saying whether that line is an
       insertion or deletion.  Allocate an extra element, always 0, at
       each end of each vector.  */

        size_t s = cmp->file[0].buffered_lines + cmp->file[1].buffered_lines + 4;
        char *flag_space = zalloc(s);
        cmp->file[0].changed = flag_space + 1;
        cmp->file[1].changed = flag_space + cmp->file[0].buffered_lines + 3;

        /* 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(cmp->file);

        /* Now do the main comparison algorithm, considering just the
       undiscarded lines.  */

        ctxt.xvec = cmp->file[0].undiscarded;
        ctxt.yvec = cmp->file[1].undiscarded;
        diags = (cmp->file[0].nondiscarded_lines
                 + cmp->file[1].nondiscarded_lines + 3);
        ctxt.fdiag = xmalloc(diags * (2 * sizeof *ctxt.fdiag));
        ctxt.bdiag = ctxt.fdiag + diags;
        ctxt.fdiag += cmp->file[1].nondiscarded_lines + 1;
        ctxt.bdiag += cmp->file[1].nondiscarded_lines + 1;

        ctxt.heuristic = speed_large_files;

        /* Set |too_expensive| to be the approximate square root of
       the input size, bounded below by 4096.  4096 seems to be good
       for circa-2016 CPUs; see |Bug#16848| and |Bug#24715|.  */
        too_expensive = 1;
        for (; diags != 0; diags >>= 2)
            too_expensive <<= 1;
        ctxt.too_expensive = MAX (4096, too_expensive);

        files[0] = cmp->file[0];
        files[1] = cmp->file[1];

        compareseq(0, cmp->file[0].nondiscarded_lines,
                   0, cmp->file[1].nondiscarded_lines, minimal, &ctxt);

        free(ctxt.fdiag - (cmp->file[1].nondiscarded_lines + 1));

        /* Modify the results slightly to make them prettier in cases
       where that can validly be done.  */

        shift_boundaries(cmp->file);

        /* Get the results of comparison in the form of a chain of
       |struct change|s -- an edit script.  */

        script = build_script(cmp->file);

        /* Set |changes| if we had any diffs.  If some changes are
       ignored, we must scan the script to decide.  */
        changes = (script != 0);

        if (brief)
            briefly_report(changes, cmp->file);
        else {
            if (changes) {
                /* Record info for starting up output, to be used if
               and when we have some output to print.  */
                setup_output(file_label[0] ? file_label[0] : cmp->file[0].name,
                             file_label[1] ? file_label[1] : cmp->file[1].name,
                             cmp->parent != 0);
                print_context_script(script);
                finish_output();
            }
        }

        free(cmp->file[0].undiscarded);

        free(flag_space);

        for (f = 0; f < 2; f++) {
            free(cmp->file[f].equivs);
            free(cmp->file[f].linbuf + cmp->file[f].linbuf_base);
        }

        for (e = script; e; e = p) {
            p = e->link;
            free(e);
        }

        for (f = 0; f < 2; ++f)
            if (cmp->file[f].missing_newline) {
                error(0, 0, "%s: %s\n",
                      file_label[f] ? file_label[f] : cmp->file[f].name,
                      "No newline at end of file");
                changes = 2;
            }
    }

    if (cmp->file[0].buffer != cmp->file[1].buffer)
        free(cmp->file[0].buffer);
    free(cmp->file[1].buffer);

    return changes;
}