[thirdparty/git.git] / xdiff / xdiffi.c

/*
 *  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, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  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 << (8 * sizeof(long) - 1)) - 1)
#define XDL_SNAKE_CNT 20
#define XDL_K_HEUR 4


typedef struct s_xdpsplit {
	long i1, i2;
	int min_lo, min_hi;
} xdpsplit_t;


static long xdl_split(unsigned long const *ha1, long off1, long lim1,
		      unsigned long const *ha2, long off2, long lim2,
		      long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
		      xdalgoenv_t *xenv);
static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long 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 long xdl_split(unsigned long const *ha1, long off1, long lim1,
		      unsigned long const *ha2, long off2, long lim2,
		      long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
		      xdalgoenv_t *xenv) {
	long dmin = off1 - lim2, dmax = lim1 - off2;
	long fmid = off1 - off2, bmid = lim1 - lim2;
	long odd = (fmid - bmid) & 1;
	long fmin = fmid, fmax = fmid;
	long bmin = bmid, bmax = bmid;
	long 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 extenal 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 extenal 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) {
			long fbest, fbest1, bbest, bbest1;

			fbest = -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 = 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;
		}
	}

	return -1;
}


/*
 * 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, long off1, long lim1,
		 diffdata_t *dd2, long off2, long lim2,
		 long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv) {
	unsigned long 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;
		long *rindex2 = dd2->rindex;

		for (; off2 < lim2; off2++)
			rchg2[rindex2[off2]] = 1;
	} else if (off2 == lim2) {
		char *rchg1 = dd1->rchg;
		long *rindex1 = dd1->rindex;

		for (; off1 < lim1; off1++)
			rchg1[rindex1[off1]] = 1;
	} else {
		long ec;
		xdpsplit_t spl;

		/*
		 * Divide ...
		 */
		if ((ec = 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) {
	long ndiags;
	long *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 = (long *) xdl_malloc((2 * ndiags + 2) * sizeof(long)))) {

		xdl_free_env(xe);
		return -1;
	}
	kvdf = kvd;
	kvdb = kvdf + ndiags;
	kvdf += xe->xdf2.nreff + 1;
	kvdb += xe->xdf2.nreff + 1;

	/*
	 * Classical integer square root approximation using shifts.
	 */
	xenv.mxcost = 1;
	for (; ndiags; ndiags >>= 2)
		xenv.mxcost <<= 1;
	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, long i1, long i2, long chg1, long 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;

	return xch;
}


int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
	xdchange_t *cscr = NULL, *xch;
	char *rchg1 = xe->xdf1.rchg, *rchg2 = xe->xdf2.rchg;
	long 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);
	}
}


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_build_script(&xe, &xscr) < 0) {

		xdl_free_env(&xe);
		return -1;
	}

	if (xscr) {
		if (xdl_emit_diff(&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;
}
Commit	Line	Data
3443546f LT	1	/*
	2	* LibXDiff by Davide Libenzi ( File Differential Library )
	3	* Copyright (C) 2003 Davide Libenzi
	4	*
	5	* This library is free software; you can redistribute it and/or
	6	* modify it under the terms of the GNU Lesser General Public
	7	* License as published by the Free Software Foundation; either
	8	* version 2.1 of the License, or (at your option) any later version.
	9	*
	10	* This library is distributed in the hope that it will be useful,
	11	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	13	* Lesser General Public License for more details.
	14	*
	15	* You should have received a copy of the GNU Lesser General Public
	16	* License along with this library; if not, write to the Free Software
	17	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	18	*
	19	* Davide Libenzi <davidel@xmailserver.org>
	20	*
	21	*/
	22
	23	#include "xinclude.h"
	24
	25
	26
	27	#define XDL_MAX_COST_MIN 256
	28	#define XDL_HEUR_MIN_COST 256
	29	#define XDL_LINE_MAX (long)((1UL << (8 * sizeof(long) - 1)) - 1)
	30	#define XDL_SNAKE_CNT 20
	31	#define XDL_K_HEUR 4
	32
	33
	34
	35	typedef struct s_xdpsplit {
	36	long i1, i2;
	37	int min_lo, min_hi;
	38	} xdpsplit_t;
	39
	40
	41
	42
	43	static long xdl_split(unsigned long const *ha1, long off1, long lim1,
	44	unsigned long const *ha2, long off2, long lim2,
	45	long kvdf, long kvdb, int need_min, xdpsplit_t *spl,
	46	xdalgoenv_t *xenv);
	47	static xdchange_t xdl_add_change(xdchange_t xscr, long i1, long i2, long chg1, long chg2);
	48
	49
	50
	51
	52	/*
	53	* See "An O(ND) Difference Algorithm and its Variations", by Eugene Myers.
	54	* Basically considers a "box" (off1, off2, lim1, lim2) and scan from both
	55	* the forward diagonal starting from (off1, off2) and the backward diagonal
	56	* starting from (lim1, lim2). If the K values on the same diagonal crosses
	57	* returns the furthest point of reach. We might end up having to expensive
	58	* cases using this algorithm is full, so a little bit of heuristic is needed
	59	* to cut the search and to return a suboptimal point.
	60	*/
	61	static long xdl_split(unsigned long const *ha1, long off1, long lim1,
	62	unsigned long const *ha2, long off2, long lim2,
	63	long kvdf, long kvdb, int need_min, xdpsplit_t *spl,
	64	xdalgoenv_t *xenv) {
65	long dmin = off1 - lim2, dmax = lim1 - off2;
66	long fmid = off1 - off2, bmid = lim1 - lim2;
67	long odd = (fmid - bmid) & 1;
68	long fmin = fmid, fmax = fmid;
69	long bmin = bmid, bmax = bmid;
70	long ec, d, i1, i2, prev1, best, dd, v, k;
71
72	/*
73	* Set initial diagonal values for both forward and backward path.
74	*/
75	kvdf[fmid] = off1;
76	kvdb[bmid] = lim1;
77
78	for (ec = 1;; ec++) {
79	int got_snake = 0;
80
81	/*
82	* We need to extent the diagonal "domain" by one. If the next
83	* values exits the box boundaries we need to change it in the
84	* opposite direction because (max - min) must be a power of two.
85	* Also we initialize the extenal K value to -1 so that we can
86	* avoid extra conditions check inside the core loop.
87	*/
88	if (fmin > dmin)
89	kvdf[--fmin - 1] = -1;
90	else
91	++fmin;
92	if (fmax < dmax)
93	kvdf[++fmax + 1] = -1;
94	else
95	--fmax;
96
97	for (d = fmax; d >= fmin; d -= 2) {
98	if (kvdf[d - 1] >= kvdf[d + 1])
99	i1 = kvdf[d - 1] + 1;
100	else
101	i1 = kvdf[d + 1];
102	prev1 = i1;
103	i2 = i1 - d;
104	for (; i1 < lim1 && i2 < lim2 && ha1[i1] == ha2[i2]; i1++, i2++);
105	if (i1 - prev1 > xenv->snake_cnt)
106	got_snake = 1;
107	kvdf[d] = i1;
108	if (odd && bmin <= d && d <= bmax && kvdb[d] <= i1) {
109	spl->i1 = i1;
110	spl->i2 = i2;
111	spl->min_lo = spl->min_hi = 1;
112	return ec;
113	}
114	}
115
116	/*
117	* We need to extent the diagonal "domain" by one. If the next
118	* values exits the box boundaries we need to change it in the
119	* opposite direction because (max - min) must be a power of two.
120	* Also we initialize the extenal K value to -1 so that we can
121	* avoid extra conditions check inside the core loop.
122	*/
123	if (bmin > dmin)
124	kvdb[--bmin - 1] = XDL_LINE_MAX;
125	else
126	++bmin;
127	if (bmax < dmax)
128	kvdb[++bmax + 1] = XDL_LINE_MAX;
129	else
130	--bmax;
131
132	for (d = bmax; d >= bmin; d -= 2) {
133	if (kvdb[d - 1] < kvdb[d + 1])
134	i1 = kvdb[d - 1];
135	else
136	i1 = kvdb[d + 1] - 1;
137	prev1 = i1;
138	i2 = i1 - d;
139	for (; i1 > off1 && i2 > off2 && ha1[i1 - 1] == ha2[i2 - 1]; i1--, i2--);
140	if (prev1 - i1 > xenv->snake_cnt)
141	got_snake = 1;
142	kvdb[d] = i1;
143	if (!odd && fmin <= d && d <= fmax && i1 <= kvdf[d]) {
144	spl->i1 = i1;
145	spl->i2 = i2;
146	spl->min_lo = spl->min_hi = 1;
147	return ec;
148	}
149	}
150
151	if (need_min)
152	continue;
153
154	/*
155	* If the edit cost is above the heuristic trigger and if
156	* we got a good snake, we sample current diagonals to see
157	* if some of the, have reached an "interesting" path. Our
158	* measure is a function of the distance from the diagonal
159	* corner (i1 + i2) penalized with the distance from the
160	* mid diagonal itself. If this value is above the current
161	* edit cost times a magic factor (XDL_K_HEUR) we consider
162	* it interesting.
163	*/
164	if (got_snake && ec > xenv->heur_min) {
165	for (best = 0, d = fmax; d >= fmin; d -= 2) {
166	dd = d > fmid ? d - fmid: fmid - d;
167	i1 = kvdf[d];
168	i2 = i1 - d;
169	v = (i1 - off1) + (i2 - off2) - dd;
170
171	if (v > XDL_K_HEUR * ec && v > best &&
172	off1 + xenv->snake_cnt <= i1 && i1 < lim1 &&
173	off2 + xenv->snake_cnt <= i2 && i2 < lim2) {
174	for (k = 1; ha1[i1 - k] == ha2[i2 - k]; k++)
175	if (k == xenv->snake_cnt) {
176	best = v;
177	spl->i1 = i1;
178	spl->i2 = i2;
179	break;
180	}
181	}
182	}
183	if (best > 0) {
184	spl->min_lo = 1;
185	spl->min_hi = 0;
186	return ec;
187	}
188
189	for (best = 0, d = bmax; d >= bmin; d -= 2) {
190	dd = d > bmid ? d - bmid: bmid - d;
191	i1 = kvdb[d];
192	i2 = i1 - d;
193	v = (lim1 - i1) + (lim2 - i2) - dd;
194
195	if (v > XDL_K_HEUR * ec && v > best &&
196	off1 < i1 && i1 <= lim1 - xenv->snake_cnt &&
197	off2 < i2 && i2 <= lim2 - xenv->snake_cnt) {
198	for (k = 0; ha1[i1 + k] == ha2[i2 + k]; k++)
199	if (k == xenv->snake_cnt - 1) {
200	best = v;
201	spl->i1 = i1;
202	spl->i2 = i2;
203	break;
204	}
205	}
206	}
207	if (best > 0) {
208	spl->min_lo = 0;
209	spl->min_hi = 1;
210	return ec;
211	}
212	}
213
214	/*
215	* Enough is enough. We spent too much time here and now we collect
216	* the furthest reaching path using the (i1 + i2) measure.
217	*/
218	if (ec >= xenv->mxcost) {
219	long fbest, fbest1, bbest, bbest1;
220
221	fbest = -1;
222	for (d = fmax; d >= fmin; d -= 2) {
223	i1 = XDL_MIN(kvdf[d], lim1);
224	i2 = i1 - d;
225	if (lim2 < i2)
226	i1 = lim2 + d, i2 = lim2;
227	if (fbest < i1 + i2) {
228	fbest = i1 + i2;
229	fbest1 = i1;
230	}
231	}
232
233	bbest = XDL_LINE_MAX;
234	for (d = bmax; d >= bmin; d -= 2) {
235	i1 = XDL_MAX(off1, kvdb[d]);
236	i2 = i1 - d;
237	if (i2 < off2)
238	i1 = off2 + d, i2 = off2;
239	if (i1 + i2 < bbest) {
240	bbest = i1 + i2;
241	bbest1 = i1;
242	}
243	}
244
245	if ((lim1 + lim2) - bbest < fbest - (off1 + off2)) {
246	spl->i1 = fbest1;
247	spl->i2 = fbest - fbest1;
248	spl->min_lo = 1;
249	spl->min_hi = 0;
250	} else {
251	spl->i1 = bbest1;
252	spl->i2 = bbest - bbest1;
253	spl->min_lo = 0;
254	spl->min_hi = 1;
255	}
256	return ec;
257	}
258	}
259
260	return -1;
261	}
262
263
264	/*
265	* Rule: "Divide et Impera". Recursively split the box in sub-boxes by calling
266	* the box splitting function. Note that the real job (marking changed lines)
267	* is done in the two boundary reaching checks.
268	*/
269	int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
270	diffdata_t *dd2, long off2, long lim2,
271	long kvdf, long kvdb, int need_min, xdalgoenv_t *xenv) {
272	unsigned long const ha1 = dd1->ha, ha2 = dd2->ha;
273
274	/*
275	* Shrink the box by walking through each diagonal snake (SW and NE).
276	*/
277	for (; off1 < lim1 && off2 < lim2 && ha1[off1] == ha2[off2]; off1++, off2++);
278	for (; off1 < lim1 && off2 < lim2 && ha1[lim1 - 1] == ha2[lim2 - 1]; lim1--, lim2--);
279
280	/*
281	* If one dimension is empty, then all records on the other one must
282	* be obviously changed.
283	*/
284	if (off1 == lim1) {
285	char *rchg2 = dd2->rchg;
286	long *rindex2 = dd2->rindex;
287
288	for (; off2 < lim2; off2++)
289	rchg2[rindex2[off2]] = 1;
290	} else if (off2 == lim2) {
291	char *rchg1 = dd1->rchg;
292	long *rindex1 = dd1->rindex;
293
294	for (; off1 < lim1; off1++)
295	rchg1[rindex1[off1]] = 1;
296	} else {
297	long ec;
298	xdpsplit_t spl;
299
300	/*
301	* Divide ...
302	*/
303	if ((ec = xdl_split(ha1, off1, lim1, ha2, off2, lim2, kvdf, kvdb,
304	need_min, &spl, xenv)) < 0) {
305
306	return -1;
307	}
308
309	/*
310	* ... et Impera.
311	*/
312	if (xdl_recs_cmp(dd1, off1, spl.i1, dd2, off2, spl.i2,
313	kvdf, kvdb, spl.min_lo, xenv) < 0 \|\|
314	xdl_recs_cmp(dd1, spl.i1, lim1, dd2, spl.i2, lim2,
315	kvdf, kvdb, spl.min_hi, xenv) < 0) {
316
317	return -1;
318	}
319	}
320
321	return 0;
322	}
323
324
325	int xdl_do_diff(mmfile_t mf1, mmfile_t mf2, xpparam_t const *xpp,
326	xdfenv_t *xe) {
327	long ndiags;
328	long kvd, kvdf, *kvdb;
329	xdalgoenv_t xenv;
330	diffdata_t dd1, dd2;
331
332	if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
333
334	return -1;
335	}
336
337	/*
338	* Allocate and setup K vectors to be used by the differential algorithm.
339	* One is to store the forward path and one to store the backward path.
340	*/
341	ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
342	if (!(kvd = (long ) xdl_malloc((2 ndiags + 2) * sizeof(long)))) {
343
344	xdl_free_env(xe);
345	return -1;
346	}
347	kvdf = kvd;
348	kvdb = kvdf + ndiags;
349	kvdf += xe->xdf2.nreff + 1;
350	kvdb += xe->xdf2.nreff + 1;
351
352	/*
353	* Classical integer square root approximation using shifts.
354	*/
355	xenv.mxcost = 1;
356	for (; ndiags; ndiags >>= 2)
357	xenv.mxcost <<= 1;
358	if (xenv.mxcost < XDL_MAX_COST_MIN)
359	xenv.mxcost = XDL_MAX_COST_MIN;
360	xenv.snake_cnt = XDL_SNAKE_CNT;
361	xenv.heur_min = XDL_HEUR_MIN_COST;
362
363	dd1.nrec = xe->xdf1.nreff;
364	dd1.ha = xe->xdf1.ha;
365	dd1.rchg = xe->xdf1.rchg;
366	dd1.rindex = xe->xdf1.rindex;
367	dd2.nrec = xe->xdf2.nreff;
368	dd2.ha = xe->xdf2.ha;
369	dd2.rchg = xe->xdf2.rchg;
370	dd2.rindex = xe->xdf2.rindex;
371
372	if (xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,
373	kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0, &xenv) < 0) {
374
375	xdl_free(kvd);
376	xdl_free_env(xe);
377	return -1;
378	}
379
380	xdl_free(kvd);
381
382	return 0;
383	}
384
385
386	static xdchange_t xdl_add_change(xdchange_t xscr, long i1, long i2, long chg1, long chg2) {
387	xdchange_t *xch;
388
389	if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t))))
390	return NULL;
391
392	xch->next = xscr;
393	xch->i1 = i1;
394	xch->i2 = i2;
395	xch->chg1 = chg1;
396	xch->chg2 = chg2;
397
398	return xch;
399	}
400
401
402	int xdl_build_script(xdfenv_t xe, xdchange_t *xscr) {
403	xdchange_t cscr = NULL, xch;
404	char rchg1 = xe->xdf1.rchg, rchg2 = xe->xdf2.rchg;
405	long i1, i2, l1, l2;
406
407	/*
408	* Trivial. Collects "groups" of changes and creates an edit script.
409	*/
410	for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 \|\| i2 >= 0; i1--, i2--)
411	if (rchg1[i1 - 1] \|\| rchg2[i2 - 1]) {
412	for (l1 = i1; rchg1[i1 - 1]; i1--);
413	for (l2 = i2; rchg2[i2 - 1]; i2--);
414
415	if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) {
416	xdl_free_script(cscr);
417	return -1;
418	}
419	cscr = xch;
420	}
421
422	*xscr = cscr;
423
424	return 0;
425	}
426
427
428	void xdl_free_script(xdchange_t *xscr) {
429	xdchange_t *xch;
430
431	while ((xch = xscr) != NULL) {
432	xscr = xscr->next;
433	xdl_free(xch);
434	}
435	}
436
437
438	int xdl_diff(mmfile_t mf1, mmfile_t mf2, xpparam_t const *xpp,
439	xdemitconf_t const xecfg, xdemitcb_t ecb) {
440	xdchange_t *xscr;
441	xdfenv_t xe;
442
443	if (xdl_do_diff(mf1, mf2, xpp, &xe) < 0) {
444
445	return -1;
446	}
447
448	if (xdl_build_script(&xe, &xscr) < 0) {
449
450	xdl_free_env(&xe);
451	return -1;
452	}
453
454	if (xscr) {
455	if (xdl_emit_diff(&xe, xscr, ecb, xecfg) < 0) {
456
457	xdl_free_script(xscr);
458	xdl_free_env(&xe);
459	return -1;
460	}
461
462	xdl_free_script(xscr);
463	}
464
465	xdl_free_env(&xe);
466
467	return 0;
468	}
469