/*
* LibXDiff by Davide Libenzi ( File Differential Library )
* Copyright (C) 2003 Davide Libenzi
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see
* <http://www.gnu.org/licenses/>.
*
* Davide Libenzi <davidel@xmailserver.org>
*
*/
#include "xinclude.h"
#define XDL_MAX_COST_MIN 256
#define XDL_HEUR_MIN_COST 256
#define XDL_LINE_MAX (long)((1UL << (CHAR_BIT * sizeof(long) - 1)) - 1)
#define XDL_SNAKE_CNT 20
#define XDL_K_HEUR 4
/* VC 2008 doesn't know about the inline keyword. */
#if defined(_MSC_VER)
#define inline __forceinline
#endif
typedef struct s_xdpsplit {
int64_t i1, i2;
int min_lo, min_hi;
} xdpsplit_t;
static int64_t xdl_split(uint64_t const *ha1, int64_t off1, int64_t lim1,
uint64_t const *ha2, int64_t off2, int64_t lim2,
int64_t *kvdf, int64_t *kvdb, int need_min, xdpsplit_t *spl,
xdalgoenv_t *xenv);
static xdchange_t *xdl_add_change(xdchange_t *xscr, int64_t i1, int64_t i2, int64_t chg1, int64_t chg2);
/*
* See "An O(ND) Difference Algorithm and its Variations", by Eugene Myers.
* Basically considers a "box" (off1, off2, lim1, lim2) and scan from both
* the forward diagonal starting from (off1, off2) and the backward diagonal
* starting from (lim1, lim2). If the K values on the same diagonal crosses
* returns the furthest point of reach. We might end up having to expensive
* cases using this algorithm is full, so a little bit of heuristic is needed
* to cut the search and to return a suboptimal point.
*/
static int64_t xdl_split(uint64_t const *ha1, int64_t off1, int64_t lim1,
uint64_t const *ha2, int64_t off2, int64_t lim2,
int64_t *kvdf, int64_t *kvdb, int need_min, xdpsplit_t *spl,
xdalgoenv_t *xenv) {
int64_t dmin = off1 - lim2, dmax = lim1 - off2;
int64_t fmid = off1 - off2, bmid = lim1 - lim2;
int64_t odd = (fmid - bmid) & 1;
int64_t fmin = fmid, fmax = fmid;
int64_t bmin = bmid, bmax = bmid;
int64_t ec, d, i1, i2, prev1, best, dd, v, k;
/*
* Set initial diagonal values for both forward and backward path.
*/
kvdf[fmid] = off1;
kvdb[bmid] = lim1;
for (ec = 1;; ec++) {
int got_snake = 0;
/*
* We need to extent the diagonal "domain" by one. If the next
* values exits the box boundaries we need to change it in the
* opposite direction because (max - min) must be a power of two.
* Also we initialize the external K value to -1 so that we can
* avoid extra conditions check inside the core loop.
*/
if (fmin > dmin)
kvdf[--fmin - 1] = -1;
else
++fmin;
if (fmax < dmax)
kvdf[++fmax + 1] = -1;
else
--fmax;
for (d = fmax; d >= fmin; d -= 2) {
if (kvdf[d - 1] >= kvdf[d + 1])
i1 = kvdf[d - 1] + 1;
else
i1 = kvdf[d + 1];
prev1 = i1;
i2 = i1 - d;
for (; i1 < lim1 && i2 < lim2 && ha1[i1] == ha2[i2]; i1++, i2++);
if (i1 - prev1 > xenv->snake_cnt)
got_snake = 1;
kvdf[d] = i1;
if (odd && bmin <= d && d <= bmax && kvdb[d] <= i1) {
spl->i1 = i1;
spl->i2 = i2;
spl->min_lo = spl->min_hi = 1;
return ec;
}
}
/*
* We need to extent the diagonal "domain" by one. If the next
* values exits the box boundaries we need to change it in the
* opposite direction because (max - min) must be a power of two.
* Also we initialize the external K value to -1 so that we can
* avoid extra conditions check inside the core loop.
*/
if (bmin > dmin)
kvdb[--bmin - 1] = XDL_LINE_MAX;
else
++bmin;
if (bmax < dmax)
kvdb[++bmax + 1] = XDL_LINE_MAX;
else
--bmax;
for (d = bmax; d >= bmin; d -= 2) {
if (kvdb[d - 1] < kvdb[d + 1])
i1 = kvdb[d - 1];
else
i1 = kvdb[d + 1] - 1;
prev1 = i1;
i2 = i1 - d;
for (; i1 > off1 && i2 > off2 && ha1[i1 - 1] == ha2[i2 - 1]; i1--, i2--);
if (prev1 - i1 > xenv->snake_cnt)
got_snake = 1;
kvdb[d] = i1;
if (!odd && fmin <= d && d <= fmax && i1 <= kvdf[d]) {
spl->i1 = i1;
spl->i2 = i2;
spl->min_lo = spl->min_hi = 1;
return ec;
}
}
if (need_min)
continue;
/*
* If the edit cost is above the heuristic trigger and if
* we got a good snake, we sample current diagonals to see
* if some of the, have reached an "interesting" path. Our
* measure is a function of the distance from the diagonal
* corner (i1 + i2) penalized with the distance from the
* mid diagonal itself. If this value is above the current
* edit cost times a magic factor (XDL_K_HEUR) we consider
* it interesting.
*/
if (got_snake && ec > xenv->heur_min) {
for (best = 0, d = fmax; d >= fmin; d -= 2) {
dd = d > fmid ? d - fmid: fmid - d;
i1 = kvdf[d];
i2 = i1 - d;
v = (i1 - off1) + (i2 - off2) - dd;
if (v > XDL_K_HEUR * ec && v > best &&
off1 + xenv->snake_cnt <= i1 && i1 < lim1 &&
off2 + xenv->snake_cnt <= i2 && i2 < lim2) {
for (k = 1; ha1[i1 - k] == ha2[i2 - k]; k++)
if (k == xenv->snake_cnt) {
best = v;
spl->i1 = i1;
spl->i2 = i2;
break;
}
}
}
if (best > 0) {
spl->min_lo = 1;
spl->min_hi = 0;
return ec;
}
for (best = 0, d = bmax; d >= bmin; d -= 2) {
dd = d > bmid ? d - bmid: bmid - d;
i1 = kvdb[d];
i2 = i1 - d;
v = (lim1 - i1) + (lim2 - i2) - dd;
if (v > XDL_K_HEUR * ec && v > best &&
off1 < i1 && i1 <= lim1 - xenv->snake_cnt &&
off2 < i2 && i2 <= lim2 - xenv->snake_cnt) {
for (k = 0; ha1[i1 + k] == ha2[i2 + k]; k++)
if (k == xenv->snake_cnt - 1) {
best = v;
spl->i1 = i1;
spl->i2 = i2;
break;
}
}
}
if (best > 0) {
spl->min_lo = 0;
spl->min_hi = 1;
return ec;
}
}
/*
* Enough is enough. We spent too much time here and now we collect
* the furthest reaching path using the (i1 + i2) measure.
*/
if (ec >= xenv->mxcost) {
int64_t fbest, fbest1, bbest, bbest1;
fbest = fbest1 = -1;
for (d = fmax; d >= fmin; d -= 2) {
i1 = XDL_MIN(kvdf[d], lim1);
i2 = i1 - d;
if (lim2 < i2)
i1 = lim2 + d, i2 = lim2;
if (fbest < i1 + i2) {
fbest = i1 + i2;
fbest1 = i1;
}
}
bbest = bbest1 = XDL_LINE_MAX;
for (d = bmax; d >= bmin; d -= 2) {
i1 = XDL_MAX(off1, kvdb[d]);
i2 = i1 - d;
if (i2 < off2)
i1 = off2 + d, i2 = off2;
if (i1 + i2 < bbest) {
bbest = i1 + i2;
bbest1 = i1;
}
}
if ((lim1 + lim2) - bbest < fbest - (off1 + off2)) {
spl->i1 = fbest1;
spl->i2 = fbest - fbest1;
spl->min_lo = 1;
spl->min_hi = 0;
} else {
spl->i1 = bbest1;
spl->i2 = bbest - bbest1;
spl->min_lo = 0;
spl->min_hi = 1;
}
return ec;
}
}
}
/*
* Rule: "Divide et Impera". Recursively split the box in sub-boxes by calling
* the box splitting function. Note that the real job (marking changed lines)
* is done in the two boundary reaching checks.
*/
int xdl_recs_cmp(diffdata_t *dd1, int64_t off1, int64_t lim1,
diffdata_t *dd2, int64_t off2, int64_t lim2,
int64_t *kvdf, int64_t *kvdb, int need_min, xdalgoenv_t *xenv) {
uint64_t const *ha1 = dd1->ha, *ha2 = dd2->ha;
/*
* Shrink the box by walking through each diagonal snake (SW and NE).
*/
for (; off1 < lim1 && off2 < lim2 && ha1[off1] == ha2[off2]; off1++, off2++);
for (; off1 < lim1 && off2 < lim2 && ha1[lim1 - 1] == ha2[lim2 - 1]; lim1--, lim2--);
/*
* If one dimension is empty, then all records on the other one must
* be obviously changed.
*/
if (off1 == lim1) {
char *rchg2 = dd2->rchg;
int64_t *rindex2 = dd2->rindex;
for (; off2 < lim2; off2++)
rchg2[rindex2[off2]] = 1;
} else if (off2 == lim2) {
char *rchg1 = dd1->rchg;
int64_t *rindex1 = dd1->rindex;
for (; off1 < lim1; off1++)
rchg1[rindex1[off1]] = 1;
} else {
xdpsplit_t spl;
spl.i1 = spl.i2 = 0;
/*
* Divide ...
*/
if (xdl_split(ha1, off1, lim1, ha2, off2, lim2, kvdf, kvdb,
need_min, &spl, xenv) < 0) {
return -1;
}
/*
* ... et Impera.
*/
if (xdl_recs_cmp(dd1, off1, spl.i1, dd2, off2, spl.i2,
kvdf, kvdb, spl.min_lo, xenv) < 0 ||
xdl_recs_cmp(dd1, spl.i1, lim1, dd2, spl.i2, lim2,
kvdf, kvdb, spl.min_hi, xenv) < 0) {
return -1;
}
}
return 0;
}
int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
xdfenv_t *xe) {
int64_t ndiags;
int64_t *kvd, *kvdf, *kvdb;
xdalgoenv_t xenv;
diffdata_t dd1, dd2;
if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
return -1;
}
/*
* Allocate and setup K vectors to be used by the differential algorithm.
* One is to store the forward path and one to store the backward path.
*/
ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
if (!(kvd = (int64_t *) xdl_malloc((2 * ndiags + 2) * sizeof(int64_t)))) {
xdl_free_env(xe);
return -1;
}
kvdf = kvd;
kvdb = kvdf + ndiags;
kvdf += xe->xdf2.nreff + 1;
kvdb += xe->xdf2.nreff + 1;
xenv.mxcost = xdl_bogosqrt(ndiags);
if (xenv.mxcost < XDL_MAX_COST_MIN)
xenv.mxcost = XDL_MAX_COST_MIN;
xenv.snake_cnt = XDL_SNAKE_CNT;
xenv.heur_min = XDL_HEUR_MIN_COST;
dd1.nrec = xe->xdf1.nreff;
dd1.ha = xe->xdf1.ha;
dd1.rchg = xe->xdf1.rchg;
dd1.rindex = xe->xdf1.rindex;
dd2.nrec = xe->xdf2.nreff;
dd2.ha = xe->xdf2.ha;
dd2.rchg = xe->xdf2.rchg;
dd2.rindex = xe->xdf2.rindex;
if (xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,
kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0, &xenv) < 0) {
xdl_free(kvd);
xdl_free_env(xe);
return -1;
}
xdl_free(kvd);
return 0;
}
static xdchange_t *xdl_add_change(xdchange_t *xscr, int64_t i1, int64_t i2, int64_t chg1, int64_t chg2) {
xdchange_t *xch;
if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t))))
return NULL;
xch->next = xscr;
xch->i1 = i1;
xch->i2 = i2;
xch->chg1 = chg1;
xch->chg2 = chg2;
xch->ignore = 0;
return xch;
}
static int recs_match(xrecord_t *rec1, xrecord_t *rec2)
{
return (rec1->ha == rec2->ha &&
xdl_recmatch(rec1->ptr, rec1->size,
rec2->ptr, rec2->size));
}
/*
* If a line is indented more than this, get_indent() just returns this value.
* This avoids having to do absurd amounts of work for data that are not
* human-readable text, and also ensures that the output of get_indent fits within
* an int.
*/
#define MAX_INDENT 200
/*
* Return the amount of indentation of the specified line, treating TAB as 8
* columns. Return -1 if line is empty or contains only whitespace. Clamp the
* output value at MAX_INDENT.
*/
static int get_indent(xrecord_t *rec)
{
int64_t i;
int ret = 0;
for (i = 0; i < rec->size; i++) {
char c = rec->ptr[i];
if (!XDL_ISSPACE(c))
return ret;
else if (c == ' ')
ret += 1;
else if (c == '\t')
ret += 8 - ret % 8;
/* ignore other whitespace characters */
if (ret >= MAX_INDENT)
return MAX_INDENT;
}
/* The line contains only whitespace. */
return -1;
}
/*
* If more than this number of consecutive blank rows are found, just return this
* value. This avoids requiring O(N^2) work for pathological cases, and also
* ensures that the output of score_split fits in an int.
*/
#define MAX_BLANKS 20
/* Characteristics measured about a hypothetical split position. */
struct split_measurement {
/*
* Is the split at the end of the file (aside from any blank lines)?
*/
int end_of_file;
/*
* How much is the line immediately following the split indented (or -1 if
* the line is blank):
*/
int indent;
/*
* How many consecutive lines above the split are blank?
*/
int pre_blank;
/*
* How much is the nearest non-blank line above the split indented (or -1
* if there is no such line)?
*/
int pre_indent;
/*
* How many lines after the line following the split are blank?
*/
int post_blank;
/*
* How much is the nearest non-blank line after the line following the
* split indented (or -1 if there is no such line)?
*/
int post_indent;
};
struct split_score {
/* The effective indent of this split (smaller is preferred). */
int effective_indent;
/* Penalty for this split (smaller is preferred). */
int penalty;
};
/*
* Fill m with information about a hypothetical split of xdf above line split.
*/
static void measure_split(const xdfile_t *xdf, int64_t split,
struct split_measurement *m)
{
int64_t i;
if (split >= xdf->nrec) {
m->end_of_file = 1;
m->indent = -1;
} else {
m->end_of_file = 0;
m->indent = get_indent(xdf->recs[split]);
}
m->pre_blank = 0;
m->pre_indent = -1;
for (i = split - 1; i >= 0; i--) {
m->pre_indent = get_indent(xdf->recs[i]);
if (m->pre_indent != -1)
break;
m->pre_blank += 1;
if (m->pre_blank == MAX_BLANKS) {
m->pre_indent = 0;
break;
}
}
m->post_blank = 0;
m->post_indent = -1;
for (i = split + 1; i < xdf->nrec; i++) {
m->post_indent = get_indent(xdf->recs[i]);
if (m->post_indent != -1)
break;
m->post_blank += 1;
if (m->post_blank == MAX_BLANKS) {
m->post_indent = 0;
break;
}
}
}
/*
* The empirically-determined weight factors used by score_split() below.
* Larger values means that the position is a less favorable place to split.
*
* Note that scores are only ever compared against each other, so multiplying
* all of these weight/penalty values by the same factor wouldn't change the
* heuristic's behavior. Still, we need to set that arbitrary scale *somehow*.
* In practice, these numbers are chosen to be large enough that they can be
* adjusted relative to each other with sufficient precision despite using
* integer math.
*/
/* Penalty if there are no non-blank lines before the split */
#define START_OF_FILE_PENALTY 1
/* Penalty if there are no non-blank lines after the split */
#define END_OF_FILE_PENALTY 21
/* Multiplier for the number of blank lines around the split */
#define TOTAL_BLANK_WEIGHT (-30)
/* Multiplier for the number of blank lines after the split */
#define POST_BLANK_WEIGHT 6
/*
* Penalties applied if the line is indented more than its predecessor
*/
#define RELATIVE_INDENT_PENALTY (-4)
#define RELATIVE_INDENT_WITH_BLANK_PENALTY 10
/*
* Penalties applied if the line is indented less than both its predecessor and
* its successor
*/
#define RELATIVE_OUTDENT_PENALTY 24
#define RELATIVE_OUTDENT_WITH_BLANK_PENALTY 17
/*
* Penalties applied if the line is indented less than its predecessor but not
* less than its successor
*/
#define RELATIVE_DEDENT_PENALTY 23
#define RELATIVE_DEDENT_WITH_BLANK_PENALTY 17
/*
* We only consider whether the sum of the effective indents for splits are
* less than (-1), equal to (0), or greater than (+1) each other. The resulting
* value is multiplied by the following weight and combined with the penalty to
* determine the better of two scores.
*/
#define INDENT_WEIGHT 60
/*
* Compute a badness score for the hypothetical split whose measurements are
* stored in m. The weight factors were determined empirically using the tools and
* corpus described in
*
* https://github.com/mhagger/diff-slider-tools
*
* Also see that project if you want to improve the weights based on, for example,
* a larger or more diverse corpus.
*/
static void score_add_split(const struct split_measurement *m, struct split_score *s)
{
/*
* A place to accumulate penalty factors (positive makes this index more
* favored):
*/
int post_blank, total_blank, indent, any_blanks;
if (m->pre_indent == -1 && m->pre_blank == 0)
s->penalty += START_OF_FILE_PENALTY;
if (m->end_of_file)
s->penalty += END_OF_FILE_PENALTY;
/*
* Set post_blank to the number of blank lines following the split,
* including the line immediately after the split:
*/
post_blank = (m->indent == -1) ? 1 + m->post_blank : 0;
total_blank = m->pre_blank + post_blank;
/* Penalties based on nearby blank lines: */
s->penalty += TOTAL_BLANK_WEIGHT * total_blank;
s->penalty += POST_BLANK_WEIGHT * post_blank;
if (m->indent != -1)
indent = m->indent;
else
indent = m->post_indent;
any_blanks = (total_blank != 0);
/* Note that the effective indent is -1 at the end of the file: */
s->effective_indent += indent;
if (indent == -1) {
/* No additional adjustments needed. */
} else if (m->pre_indent == -1) {
/* No additional adjustments needed. */
} else if (indent > m->pre_indent) {
/*
* The line is indented more than its predecessor.
*/
s->penalty += any_blanks ?
RELATIVE_INDENT_WITH_BLANK_PENALTY :
RELATIVE_INDENT_PENALTY;
} else if (indent == m->pre_indent) {
/*
* The line has the same indentation level as its predecessor.
* No additional adjustments needed.
*/
} else {
/*
* The line is indented less than its predecessor. It could be
* the block terminator of the previous block, but it could
* also be the start of a new block (e.g., an "else" block, or
* maybe the previous block didn't have a block terminator).
* Try to distinguish those cases based on what comes next:
*/
if (m->post_indent != -1 && m->post_indent > indent) {
/*
* The following line is indented more. So it is likely
* that this line is the start of a block.
*/
s->penalty += any_blanks ?
RELATIVE_OUTDENT_WITH_BLANK_PENALTY :
RELATIVE_OUTDENT_PENALTY;
} else {
/*
* That was probably the end of a block.
*/
s->penalty += any_blanks ?
RELATIVE_DEDENT_WITH_BLANK_PENALTY :
RELATIVE_DEDENT_PENALTY;
}
}
}
static int score_cmp(struct split_score *s1, struct split_score *s2)
{
/* -1 if s1.effective_indent < s2->effective_indent, etc. */
int cmp_indents = ((s1->effective_indent > s2->effective_indent) -
(s1->effective_indent < s2->effective_indent));
return INDENT_WEIGHT * cmp_indents + (s1->penalty - s2->penalty);
}
/*
* Represent a group of changed lines in an xdfile_t (i.e., a contiguous group
* of lines that was inserted or deleted from the corresponding version of the
* file). We consider there to be such a group at the beginning of the file, at
* the end of the file, and between any two unchanged lines, though most such
* groups will usually be empty.
*
* If the first line in a group is equal to the line following the group, then
* the group can be slid down. Similarly, if the last line in a group is equal
* to the line preceding the group, then the group can be slid up. See
* group_slide_down() and group_slide_up().
*
* Note that loops that are testing for changed lines in xdf->rchg do not need
* index bounding since the array is prepared with a zero at position -1 and N.
*/
struct xdlgroup {
/*
* The index of the first changed line in the group, or the index of
* the unchanged line above which the (empty) group is located.
*/
int64_t start;
/*
* The index of the first unchanged line after the group. For an empty
* group, end is equal to start.
*/
int64_t end;
};
/*
* Initialize g to point at the first group in xdf.
*/
static void group_init(xdfile_t *xdf, struct xdlgroup *g)
{
g->start = g->end = 0;
while (xdf->rchg[g->end])
g->end++;
}
/*
* Move g to describe the next (possibly empty) group in xdf and return 0. If g
* is already at the end of the file, do nothing and return -1.
*/
static inline int group_next(xdfile_t *xdf, struct xdlgroup *g)
{
if (g->end == xdf->nrec)
return -1;
g->start = g->end + 1;
for (g->end = g->start; xdf->rchg[g->end]; g->end++)
;
return 0;
}
/*
* Move g to describe the previous (possibly empty) group in xdf and return 0.
* If g is already at the beginning of the file, do nothing and return -1.
*/
static inline int group_previous(xdfile_t *xdf, struct xdlgroup *g)
{
if (g->start == 0)
return -1;
g->end = g->start - 1;
for (g->start = g->end; xdf->rchg[g->start - 1]; g->start--)
;
return 0;
}
/*
* If g can be slid toward the end of the file, do so, and if it bumps into a
* following group, expand this group to include it. Return 0 on success or -1
* if g cannot be slid down.
*/
static int group_slide_down(xdfile_t *xdf, struct xdlgroup *g)
{
if (g->end < xdf->nrec &&
recs_match(xdf->recs[g->start], xdf->recs[g->end])) {
xdf->rchg[g->start++] = 0;
xdf->rchg[g->end++] = 1;
while (xdf->rchg[g->end])
g->end++;
return 0;
} else {
return -1;
}
}
/*
* If g can be slid toward the beginning of the file, do so, and if it bumps
* into a previous group, expand this group to include it. Return 0 on success
* or -1 if g cannot be slid up.
*/
static int group_slide_up(xdfile_t *xdf, struct xdlgroup *g)
{
if (g->start > 0 &&
recs_match(xdf->recs[g->start - 1], xdf->recs[g->end - 1])) {
xdf->rchg[--g->start] = 1;
xdf->rchg[--g->end] = 0;
while (xdf->rchg[g->start - 1])
g->start--;
return 0;
} else {
return -1;
}
}
static void xdl_bug(const char *msg)
{
fprintf(stderr, "BUG: %s\n", msg);
exit(1);
}
/*
* For indentation heuristic, skip searching for better slide position after
* checking MAX_BORING lines without finding an improvement. This defends the
* indentation heuristic logic against pathological cases. The value is not
* picked scientifically but should be good enough.
*/
#define MAX_BORING 100
/*
* Move back and forward change groups for a consistent and pretty diff output.
* This also helps in finding joinable change groups and reducing the diff
* size.
*/
int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, int64_t flags) {
struct xdlgroup g, go;
int64_t earliest_end, end_matching_other;
int64_t groupsize;
group_init(xdf, &g);
group_init(xdfo, &go);
while (1) {
/* If the group is empty in the to-be-compacted file, skip it: */
if (g.end == g.start)
goto next;
/*
* Now shift the change up and then down as far as possible in
* each direction. If it bumps into any other changes, merge them.
*/
do {
groupsize = g.end - g.start;
/*
* Keep track of the last "end" index that causes this
* group to align with a group of changed lines in the
* other file. -1 indicates that we haven't found such
* a match yet:
*/
end_matching_other = -1;
/* Shift the group backward as much as possible: */
while (!group_slide_up(xdf, &g))
if (group_previous(xdfo, &go))
xdl_bug("group sync broken sliding up");
/*
* This is this highest that this group can be shifted.
* Record its end index:
*/
earliest_end = g.end;
if (go.end > go.start)
end_matching_other = g.end;
/* Now shift the group forward as far as possible: */
while (1) {
if (group_slide_down(xdf, &g))
break;
if (group_next(xdfo, &go))
xdl_bug("group sync broken sliding down");
if (go.end > go.start)
end_matching_other = g.end;
}
} while (groupsize != g.end - g.start);
/*
* If the group can be shifted, then we can possibly use this
* freedom to produce a more intuitive diff.
*
* The group is currently shifted as far down as possible, so the
* heuristics below only have to handle upwards shifts.
*/
if (g.end == earliest_end) {
/* no shifting was possible */
} else if (end_matching_other != -1) {
/*
* Move the possibly merged group of changes back to line
* up with the last group of changes from the other file
* that it can align with.
*/
while (go.end == go.start) {
if (group_slide_up(xdf, &g))
xdl_bug("match disappeared");
if (group_previous(xdfo, &go))
xdl_bug("group sync broken sliding to match");
}
} else if (flags & XDF_INDENT_HEURISTIC) {
/*
* Indent heuristic: a group of pure add/delete lines
* implies two splits, one between the end of the "before"
* context and the start of the group, and another between
* the end of the group and the beginning of the "after"
* context. Some splits are aesthetically better and some
* are worse. We compute a badness "score" for each split,
* and add the scores for the two splits to define a
* "score" for each position that the group can be shifted
* to. Then we pick the shift with the lowest score.
*/
int64_t shift, best_shift = -1;
struct split_score best_score;
/*
* This is O(N * MAX_BLANKS) (N = shift-able lines).
* Even with MAX_BLANKS bounded to a small value, a
* large N could still make this loop take several
* times longer than the main diff algorithm. The
* "boring" value is to help cut down N to something
* like (MAX_BORING + groupsize).
*
* Scan from bottom to top. So we can exit the loop
* without compromising the assumption "for a same best
* score, pick the bottommost shift".
*/
int boring = 0;
for (shift = g.end; shift >= earliest_end; shift--) {
struct split_measurement m;
struct split_score score = {0, 0};
int cmp;
measure_split(xdf, shift, &m);
score_add_split(&m, &score);
measure_split(xdf, shift - groupsize, &m);
score_add_split(&m, &score);
if (best_shift == -1) {
cmp = -1;
} else {
cmp = score_cmp(&score, &best_score);
}
if (cmp < 0) {
boring = 0;
best_score.effective_indent = score.effective_indent;
best_score.penalty = score.penalty;
best_shift = shift;
} else {
boring += 1;
if (boring >= MAX_BORING)
break;
}
}
while (g.end > best_shift) {
if (group_slide_up(xdf, &g))
xdl_bug("best shift unreached");
if (group_previous(xdfo, &go))
xdl_bug("group sync broken sliding to blank line");
}
}
next:
/* Move past the just-processed group: */
if (group_next(xdf, &g))
break;
if (group_next(xdfo, &go))
xdl_bug("group sync broken moving to next group");
}
if (!group_next(xdfo, &go))
xdl_bug("group sync broken at end of file");
return 0;
}
int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
xdchange_t *cscr = NULL, *xch;
char *rchg1 = xe->xdf1.rchg, *rchg2 = xe->xdf2.rchg;
int64_t i1, i2, l1, l2;
/*
* Trivial. Collects "groups" of changes and creates an edit script.
*/
for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 || i2 >= 0; i1--, i2--)
if (rchg1[i1 - 1] || rchg2[i2 - 1]) {
for (l1 = i1; rchg1[i1 - 1]; i1--);
for (l2 = i2; rchg2[i2 - 1]; i2--);
if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) {
xdl_free_script(cscr);
return -1;
}
cscr = xch;
}
*xscr = cscr;
return 0;
}
void xdl_free_script(xdchange_t *xscr) {
xdchange_t *xch;
while ((xch = xscr) != NULL) {
xscr = xscr->next;
xdl_free(xch);
}
}
/*
* Starting at the passed change atom, find the latest change atom to be included
* inside the differential hunk according to the specified configuration.
* Also advance xscr if the first changes must be discarded.
*/
xdchange_t *xdl_get_hunk(xdchange_t **xscr)
{
xdchange_t *xch, *xchp, *lxch;
uint64_t ignored = 0; /* number of ignored blank lines */
/* remove ignorable changes that are too far before other changes */
for (xchp = *xscr; xchp && xchp->ignore; xchp = xchp->next) {
xch = xchp->next;
if (xch == NULL ||
xch->i1 - (xchp->i1 + xchp->chg1) >= 0)
*xscr = xch;
}
if (*xscr == NULL)
return NULL;
lxch = *xscr;
for (xchp = *xscr, xch = xchp->next; xch; xchp = xch, xch = xch->next) {
int64_t distance = xch->i1 - (xchp->i1 + xchp->chg1);
if (distance > 0)
break;
if (distance < 0 && (!xch->ignore || lxch == xchp)) {
lxch = xch;
ignored = 0;
} else if (distance < 0 && xch->ignore) {
ignored += xch->chg2;
} else if (lxch != xchp &&
xch->i1 + ignored - (lxch->i1 + lxch->chg1) > 0) {
break;
} else if (!xch->ignore) {
lxch = xch;
ignored = 0;
} else {
ignored += xch->chg2;
}
}
return lxch;
}
static int xdl_call_hunk_func(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
xdemitconf_t const *xecfg)
{
int64_t p = xe->nprefix, s = xe->nsuffix;
xdchange_t *xch, *xche;
if (!xecfg->hunk_func)
return -1;
if ((xecfg->flags & XDL_EMIT_BDIFFHUNK) != 0) {
int64_t i1 = 0, i2 = 0, n1 = xe->xdf1.nrec, n2 = xe->xdf2.nrec;
for (xch = xscr; xch; xch = xche->next) {
xche = xdl_get_hunk(&xch);
if (!xch)
break;
if (xch != xche)
xdl_bug("xch != xche");
xch->i1 += p;
xch->i2 += p;
if (xch->i1 > i1 || xch->i2 > i2) {
if (xecfg->hunk_func(i1, xch->i1, i2, xch->i2, ecb->priv) < 0)
return -1;
}
i1 = xche->i1 + xche->chg1;
i2 = xche->i2 + xche->chg2;
}
if (xecfg->hunk_func(i1, n1 + p + s, i2, n2 + p + s,
ecb->priv) < 0)
return -1;
} else {
for (xch = xscr; xch; xch = xche->next) {
xche = xdl_get_hunk(&xch);
if (!xch)
break;
if (xecfg->hunk_func(xch->i1 + p,
xche->i1 + xche->chg1 - xch->i1,
xch->i2 + p,
xche->i2 + xche->chg2 - xch->i2,
ecb->priv) < 0)
return -1;
}
}
return 0;
}
int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
xdemitconf_t const *xecfg, xdemitcb_t *ecb) {
xdchange_t *xscr;
xdfenv_t xe;
if (xdl_do_diff(mf1, mf2, xpp, &xe) < 0) {
return -1;
}
if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||
xdl_change_compact(&xe.xdf2, &xe.xdf1, xpp->flags) < 0 ||
xdl_build_script(&xe, &xscr) < 0) {
xdl_free_env(&xe);
return -1;
}
if (xdl_call_hunk_func(&xe, xscr, ecb, xecfg) < 0) {
xdl_free_script(xscr);
xdl_free_env(&xe);
return -1;
}
xdl_free_script(xscr);
xdl_free_env(&xe);
return 0;
}