thodg/got/lib/diff3.c

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• Hash : d7b5a0e8
  Author :
  Date : 2022-04-20T14:00:12
  

  inline struct got_object_id in struct got_object_qid Saves us from doing a malloc/free call for every item on the list. ok op@

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• lib/diff3.c

• /*	$OpenBSD: diff3.c,v 1.41 2016/10/18 21:06:52 millert Exp $	*/
  
  /*
   * Copyright (C) Caldera International Inc.  2001-2002.
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code and documentation must retain the above
   *    copyright notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *	This product includes software developed or owned by Caldera
   *	International, Inc.
   * 4. Neither the name of Caldera International, Inc. nor the names of other
   *    contributors may be used to endorse or promote products derived from
   *    this software without specific prior written permission.
   *
   * USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
   * INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
   * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   * IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE FOR ANY DIRECT,
   * INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
   * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   */
  /*-
   * Copyright (c) 1991, 1993
   *	The Regents of the University of California.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   *	@(#)diff3.c	8.1 (Berkeley) 6/6/93
   */
  
  #include <sys/stat.h>
  #include <sys/queue.h>
  
  #include <ctype.h>
  #include <limits.h>
  #include <sha1.h>
  #include <stdio.h>
  #include <stdarg.h>
  #include <stdlib.h>
  #include <string.h>
  #include <time.h>
  #include <unistd.h>
  
  #include "got_error.h"
  #include "got_opentemp.h"
  #include "got_object.h"
  
  #include "buf.h"
  #include "rcsutil.h"
  #include "got_lib_diff.h"
  
  #ifndef nitems
  #define nitems(_a) (sizeof(_a) / sizeof((_a)[0]))
  #endif
  
  /* diff3 - 3-way differential file comparison */
  
  /* diff3 [-ex3EX] d13 d23 f1 f2 f3 [m1 m3]
   *
   * d13 = diff report on f1 vs f3
   * d23 = diff report on f2 vs f3
   * f1, f2, f3 the 3 files
   * if changes in f1 overlap with changes in f3, m1 and m3 are used
   * to mark the overlaps; otherwise, the file names f1 and f3 are used
   * (only for options E and X).
   */
  
  /*
   * "from" is first in range of changed lines; "to" is last+1
   * from=to=line after point of insertion for added lines.
   */
  struct line_range {
  	int from;
  	int to;
  };
  
  struct off_range {
  	off_t from;
  	off_t to;
  };
  
  struct diff {
  	struct line_range old;
  	struct line_range new;
  	struct off_range oldo;
  	struct off_range newo;
  };
  
  struct diff3_state {
  	size_t szchanges;
  
  	struct diff *d13;
  	struct diff *d23;
  
  	/*
  	 * "de" is used to gather editing scripts.  These are later spewed out
  	 * in reverse order.  Its first element must be all zero, the "new"
  	 * component of "de" contains line positions, and "oldo" and "newo"
  	 * components contain byte positions.
  	 * Array overlap indicates which sections in "de" correspond to lines
  	 * that are different in all three files.
  	 */
  	struct diff *de;
  	char *overlap;
  	int overlapcnt;
  	FILE *fp[3];
  	int cline[3];		/* # of the last-read line in each file (0-2) */
  
  	/*
  	 * the latest known correspondence between line numbers of the 3 files
  	 * is stored in last[1-3];
  	 */
  	int last[4];
  	char f1mark[PATH_MAX];
  	char f2mark[PATH_MAX];
  	char f3mark[PATH_MAX];
  
  	char *buf;
  
  	BUF *diffbuf;
  };
  
  
  static const struct got_error *duplicate(int *, int, struct line_range *,
      struct line_range *, struct diff3_state *);
  static const struct got_error *edit(struct diff *, int, int *,
      struct diff3_state *);
  static const struct got_error *getchange(char **, FILE *, struct diff3_state *);
  static const struct got_error *get_line(char **, FILE *, size_t *,
      struct diff3_state *);
  static int number(char **);
  static const struct got_error *readin(size_t *, char *, struct diff **,
      struct diff3_state *);
  static int ed_patch_lines(struct rcs_lines *, struct rcs_lines *);
  static const struct got_error *skip(size_t *, int, int, struct diff3_state *);
  static const struct got_error *edscript(int, struct diff3_state *);
  static const struct got_error *merge(size_t, size_t, struct diff3_state *);
  static const struct got_error *prange(struct line_range *,
      struct diff3_state *);
  static const struct got_error *repos(int, struct diff3_state *);
  static const struct got_error *increase(struct diff3_state *);
  static const struct got_error *diff3_internal(char *, char *, char *,
      char *, char *, const char *, const char *, struct diff3_state *,
      const char *, const char *, const char *);
  
  static const struct got_error *
  diff_output(BUF *diffbuf, const char *fmt, ...)
  {
  	const struct got_error *err = NULL;
  	va_list vap;
  	int i;
  	char *str;
  	size_t newsize;
  
  	va_start(vap, fmt);
  	i = vasprintf(&str, fmt, vap);
  	va_end(vap);
  	if (i == -1)
  		return got_error_from_errno("vasprintf");
  	err = buf_append(&newsize, diffbuf, str, strlen(str));
  	free(str);
  	return err;
  }
  
  static const struct got_error*
  diffreg(BUF **d, const char *path1, const char *path2,
      enum got_diff_algorithm diff_algo)
  {
  	const struct got_error *err = NULL;
  	FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
  	char *outpath = NULL;
  	struct got_diffreg_result *diffreg_result = NULL;
  
  	*d = NULL;
  
  	f1 = fopen(path1, "re");
  	if (f1 == NULL) {
  		err = got_error_from_errno2("fopen", path1);
  		goto done;
  	}
  	f2 = fopen(path2, "re");
  	if (f1 == NULL) {
  		err = got_error_from_errno2("fopen", path2);
  		goto done;
  	}
  
  	err = got_opentemp_named(&outpath, &outfile,
  	    GOT_TMPDIR_STR "/got-diffreg");
  	if (err)
  		goto done;
  
  	err = got_diffreg(&diffreg_result, f1, f2, diff_algo, 0, 0);
  	if (err)
  		goto done;
  
  	if (diffreg_result) {
  		struct diff_result *diff_result = diffreg_result->result;
  		int atomizer_flags = (diff_result->left->atomizer_flags |
  		    diff_result->right->atomizer_flags);
  		if ((atomizer_flags & DIFF_ATOMIZER_FOUND_BINARY_DATA)) {
  			err = got_error(GOT_ERR_FILE_BINARY);
  			goto done;
  		}
  	}
  
  	err = got_diffreg_output(NULL, NULL, diffreg_result, 1, 1, "", "",
  	    GOT_DIFF_OUTPUT_EDSCRIPT, 0, outfile);
  	if (err)
  		goto done;
  
  	if (fflush(outfile) != 0) {
  		err = got_error_from_errno2("fflush", outpath);
  		goto done;
  	}
  	if (fseek(outfile, 0L, SEEK_SET) == -1) {
  		err = got_ferror(outfile, GOT_ERR_IO);
  		goto done;
  	}
  
  	err = buf_load(d, outfile);
  done:
  	if (outpath) {
  		if (unlink(outpath) == -1 && err == NULL)
  			err = got_error_from_errno2("unlink", outpath);
  		free(outpath);
  	}
  	if (outfile && fclose(outfile) == EOF && err == NULL)
  		err = got_error_from_errno("fclose");
  	if (f1 && fclose(f1) == EOF && err == NULL)
  		err = got_error_from_errno("fclose");
  	if (f2 && fclose(f2) == EOF && err == NULL)
  		err = got_error_from_errno("fclose");
  	return err;
  }
  
  /*
   * For merge(1).
   */
  const struct got_error *
  got_merge_diff3(int *overlapcnt, int outfd, FILE *f1, FILE *f2,
      FILE *f3, const char *label1, const char *label2, const char *label3,
      enum got_diff_algorithm diff_algo)
  {
  	const struct got_error *err = NULL;
  	char *dp13, *dp23, *path1, *path2, *path3;
  	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
  	u_char *data, *patch;
  	size_t dlen, plen, i;
  	struct diff3_state *d3s;
  
  	*overlapcnt = 0;
  
  	d3s = calloc(1, sizeof(*d3s));
  	if (d3s == NULL)
  		return got_error_from_errno("calloc");
  
  	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
  	dp13 = dp23 = path1 = path2 = path3 = NULL;
  	data = patch = NULL;
  
  	err = buf_load(&b1, f1);
  	if (err)
  		goto out;
  	err = buf_load(&b2, f2);
  	if (err)
  		goto out;
  	err = buf_load(&b3, f3);
  	if (err)
  		goto out;
  
  	err = buf_alloc(&diffb, 128);
  	if (err)
  		goto out;
  
  	if (asprintf(&path1, GOT_TMPDIR_STR "/got-diff1.XXXXXXXX") == -1) {
  		err = got_error_from_errno("asprintf");
  		goto out;
  	}
  	if (asprintf(&path2, GOT_TMPDIR_STR "/got-diff2.XXXXXXXX") == -1) {
  		err = got_error_from_errno("asprintf");
  		goto out;
  	}
  	if (asprintf(&path3, GOT_TMPDIR_STR "/got-diff3.XXXXXXXX") == -1) {
  		err = got_error_from_errno("asprintf");
  		goto out;
  	}
  
  	err = buf_write_stmp(b1, path1);
  	if (err)
  		goto out;
  	err = buf_write_stmp(b2, path2);
  	if (err)
  		goto out;
  	err = buf_write_stmp(b3, path3);
  	if (err)
  		goto out;
  
  	buf_free(b2);
  	b2 = NULL;
  
  	err = diffreg(&d1, path1, path3, diff_algo);
  	if (err) {
  		buf_free(diffb);
  		diffb = NULL;
  		goto out;
  
  	}
  	err = diffreg(&d2, path2, path3, diff_algo);
  	if (err) {
  		buf_free(diffb);
  		diffb = NULL;
  		goto out;
  	}
  
  	if (asprintf(&dp13, GOT_TMPDIR_STR "/got-d13.XXXXXXXXXX") == -1) {
  		err = got_error_from_errno("asprintf");
  		goto out;
  	}
  	err = buf_write_stmp(d1, dp13);
  	if (err)
  		goto out;
  
  	buf_free(d1);
  	d1 = NULL;
  
  	if (asprintf(&dp23, GOT_TMPDIR_STR "/got-d23.XXXXXXXXXX") == -1) {
  		err = got_error_from_errno("asprintf");
  		goto out;
  	}
  	err = buf_write_stmp(d2, dp23);
  	if (err)
  		goto out;
  
  	buf_free(d2);
  	d2 = NULL;
  
  	d3s->diffbuf = diffb;
  	err = diff3_internal(dp13, dp23, path1, path2, path3,
  	    label1, label3, d3s, label1, label2, label3);
  	if (err) {
  		buf_free(diffb);
  		diffb = NULL;
  		goto out;
  	}
  
  	plen = buf_len(diffb);
  	patch = buf_release(diffb);
  	dlen = buf_len(b1);
  	data = buf_release(b1);
  
  	diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
  out:
  	buf_free(b2);
  	buf_free(b3);
  	buf_free(d1);
  	buf_free(d2);
  
  	if (unlink(path1) == -1 && err == NULL)
  		err = got_error_from_errno2("unlink", path1);
  	if (unlink(path2) == -1 && err == NULL)
  		err = got_error_from_errno2("unlink", path2);
  	if (unlink(path3) == -1 && err == NULL)
  		err = got_error_from_errno2("unlink", path3);
  	if (unlink(dp13) == -1 && err == NULL)
  		err = got_error_from_errno2("unlink", dp13);
  	if (unlink(dp23) == -1 && err == NULL)
  		err = got_error_from_errno2("unlink", dp23);
  
  	free(path1);
  	free(path2);
  	free(path3);
  	free(dp13);
  	free(dp23);
  	free(data);
  	free(patch);
  
  	for (i = 0; i < nitems(d3s->fp); i++) {
  		if (d3s->fp[i] && fclose(d3s->fp[i]) == EOF && err == NULL)
  			err = got_error_from_errno("fclose");
  	}
  	if (err == NULL && diffb) {
  		if (buf_write_fd(diffb, outfd) < 0)
  			err = got_error_from_errno("buf_write_fd");
  		*overlapcnt = d3s->overlapcnt;
  	}
  	free(d3s);
  	buf_free(diffb);
  	return err;
  }
  
  static const struct got_error *
  diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
      const char *fmark, const char *rmark, struct diff3_state *d3s,
      const char *label1, const char *label2, const char *label3)
  {
  	const struct got_error *err = NULL;
  	ssize_t m, n;
  	int i;
  
  	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark),
  	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_BEGIN,
  	    label1 ? " " : "", label1 ? label1 : "");
  	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
  		return got_error(GOT_ERR_NO_SPACE);
  
  	i = snprintf(d3s->f2mark, sizeof(d3s->f2mark),
  	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_ORIG,
  	    label2 ? " " : "", label2 ? label2 : "");
  	if (i < 0 || i >= (int)sizeof(d3s->f2mark))
  		return got_error(GOT_ERR_NO_SPACE);
  
  	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark),
  	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_END,
  	    label3 ? " " : "", label3 ? label3 : "");
  	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
  		return got_error(GOT_ERR_NO_SPACE);
  
  	err = increase(d3s);
  	if (err)
  		return err;
  
  	err = readin(&m, dp13, &d3s->d13, d3s);
  	if (err)
  		return err;
  	err = readin(&n, dp23, &d3s->d23, d3s);
  	if (err)
  		return err;
  
  	if ((d3s->fp[0] = fopen(path1, "re")) == NULL)
  		return got_error_from_errno2("fopen", path1);
  	if ((d3s->fp[1] = fopen(path2, "re")) == NULL)
  		return got_error_from_errno2("fopen", path2);
  	if ((d3s->fp[2] = fopen(path3, "re")) == NULL)
  		return got_error_from_errno2("fopen", path3);
  
  	return merge(m, n, d3s);
  }
  
  static int
  ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
  {
  	char op, *ep;
  	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
  	int start, end, i, lineno;
  	u_char tmp;
  
  	dlp = TAILQ_FIRST(&(dlines->l_lines));
  	lp = TAILQ_FIRST(&(plines->l_lines));
  
  	end = 0;
  	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
  	    lp = TAILQ_NEXT(lp, l_list)) {
  		/* Skip blank lines */
  		if (lp->l_len < 2)
  			continue;
  
  		/* NUL-terminate line buffer for strtol() safety. */
  		tmp = lp->l_line[lp->l_len - 1];
  		lp->l_line[lp->l_len - 1] = '\0';
  
  		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
  		op = lp->l_line[lp->l_len - 2];
  		start = (int)strtol(lp->l_line, &ep, 10);
  
  		/* Restore the last byte of the buffer */
  		lp->l_line[lp->l_len - 1] = tmp;
  
  		if (op == 'a') {
  			if (start > dlines->l_nblines ||
  			    start < 0 || *ep != 'a')
  				return -1;
  		} else if (op == 'c') {
  			if (start > dlines->l_nblines ||
  			    start < 0 || (*ep != ',' && *ep != 'c'))
  				return -1;
  
  			if (*ep == ',') {
  				ep++;
  				end = (int)strtol(ep, &ep, 10);
  				if (end < 0 || *ep != 'c')
  					return -1;
  			} else {
  				end = start;
  			}
  		}
  
  
  		for (;;) {
  			if (dlp == NULL)
  				break;
  			if (dlp->l_lineno == start)
  				break;
  			if (dlp->l_lineno > start) {
  				dlp = TAILQ_PREV(dlp, tqh, l_list);
  			} else if (dlp->l_lineno < start) {
  				ndlp = TAILQ_NEXT(dlp, l_list);
  				if (ndlp->l_lineno > start)
  					break;
  				dlp = ndlp;
  			}
  		}
  
  		if (dlp == NULL)
  			return -1;
  
  
  		if (op == 'c') {
  			insert_after = TAILQ_PREV(dlp, tqh, l_list);
  			for (i = 0; i <= (end - start); i++) {
  				ndlp = TAILQ_NEXT(dlp, l_list);
  				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
  				dlp = ndlp;
  			}
  			dlp = insert_after;
  		}
  
  		if (op == 'a' || op == 'c') {
  			for (;;) {
  				ndlp = lp;
  				lp = TAILQ_NEXT(lp, l_list);
  				if (lp == NULL)
  					return -1;
  
  				if (lp->l_len == 2 &&
  				    lp->l_line[0] == '.' &&
  				    lp->l_line[1] == '\n')
  					break;
  
  				if (lp->l_line[0] == ':') {
  					lp->l_line++;
  					lp->l_len--;
  				}
  				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
  				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
  				    lp, l_list);
  				dlp = lp;
  
  				lp->l_lineno = start;
  				lp = ndlp;
  			}
  		}
  
  		/*
  		 * always resort lines as the markers might be put at the
  		 * same line as we first started editing.
  		 */
  		lineno = 0;
  		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
  			sort->l_lineno = lineno++;
  		dlines->l_nblines = lineno - 1;
  	}
  
  	return (0);
  }
  
  /*
   * Pick up the line numbers of all changes from one change file.
   * (This puts the numbers in a vector, which is not strictly necessary,
   * since the vector is processed in one sequential pass.
   * The vector could be optimized out of existence)
   */
  static const struct got_error *
  readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
  {
  	const struct got_error *err = NULL;
  	FILE *f;
  	int a, b, c, d;
  	char kind, *p;
  	size_t i = 0;
  
  	*n = 0;
  
  	f = fopen(name, "re");
  	if (f == NULL)
  		return got_error_from_errno2("fopen", name);
  	err = getchange(&p, f, d3s);
  	if (err)
  		goto done;
  	for (i = 0; p; i++) {
  		if (i >= d3s->szchanges - 1) {
  			err = increase(d3s);
  			if (err)
  				goto done;
  		}
  		a = b = number(&p);
  		if (*p == ',') {
  			p++;
  			b = number(&p);
  		}
  		kind = *p++;
  		c = d = number(&p);
  		if (*p == ',') {
  			p++;
  			d = number(&p);
  		}
  		if (kind == 'a')
  			a++;
  		if (kind == 'd')
  			c++;
  		b++;
  		d++;
  		(*dd)[i].old.from = a;
  		(*dd)[i].old.to = b;
  		(*dd)[i].new.from = c;
  		(*dd)[i].new.to = d;
  
  		err = getchange(&p, f, d3s);
  		if (err)
  			goto done;
  	}
  
  	if (i) {
  		(*dd)[i].old.from = (*dd)[i - 1].old.to;
  		(*dd)[i].new.from = (*dd)[i - 1].new.to;
  	}
  done:
  	if (fclose(f) == EOF && err == NULL)
  		err = got_error_from_errno("fclose");
  	if (err == NULL)
  		*n = i;
  	return err;
  }
  
  static int
  number(char **lc)
  {
  	int nn;
  
  	nn = 0;
  	while (isdigit((unsigned char)(**lc)))
  		nn = nn*10 + *(*lc)++ - '0';
  
  	return (nn);
  }
  
  static const struct got_error *
  getchange(char **line, FILE *b, struct diff3_state *d3s)
  {
  	const struct got_error *err = NULL;
  
  	*line = NULL;
  	do {
  		if (*line && isdigit((unsigned char)(*line)[0]))
  			return NULL;
  		err = get_line(line, b, NULL, d3s);
  		if (err)
  			return err;
  	} while (*line);
  
  	return NULL;
  }
  
  static const struct got_error *
  get_line(char **ret, FILE *b, size_t *n, struct diff3_state *d3s)
  {
  	const struct got_error *err = NULL;
  	char *cp = NULL;
  	size_t size;
  	ssize_t len;
  	char *new;
  
  	*ret = NULL;
  	if (n != NULL)
  		*n = 0;
  
  	len = getline(&cp, &size, b);
  	if (len == -1) {
  		if (ferror(b))
  			err = got_error_from_errno("getline");
  		goto done;
  	}
  
  	if (cp[len - 1] != '\n') {
  		len++;
  		if (len + 1 > size) {
  			new = realloc(cp, len + 1);
  			if (new == NULL) {
  				err = got_error_from_errno("realloc");
  				goto done;
  			}
  			cp = new;
  		}
  		cp[len - 1] = '\n';
  		cp[len] = '\0';
  	}
  
  	free(d3s->buf);
  	*ret = d3s->buf = cp;
  	cp = NULL;
  	if (n != NULL)
  		*n = len;
  done:
  	free(cp);
  	return err;
  }
  
  static const struct got_error *
  merge(size_t m1, size_t m2, struct diff3_state *d3s)
  {
  	const struct got_error *err = NULL;
  	struct diff *d1, *d2;
  	int dpl, j, t1, t2;
  
  	d1 = d3s->d13;
  	d2 = d3s->d23;
  	j = 0;
  	for (;;) {
  		t1 = (d1 < d3s->d13 + m1);
  		t2 = (d2 < d3s->d23 + m2);
  		if (!t1 && !t2)
  			break;
  
  		/* first file is different from others */
  		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
  			/* stuff peculiar to 1st file */
  			d1++;
  			continue;
  		}
  
  		/* second file is different from others */
  		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
  			d2++;
  			continue;
  		}
  
  		/*
  		 * Merge overlapping changes in first file
  		 * this happens after extension (see below).
  		 */
  		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
  			d1[1].old.from = d1->old.from;
  			d1[1].new.from = d1->new.from;
  			d1++;
  			continue;
  		}
  
  		/* merge overlapping changes in second */
  		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
  			d2[1].old.from = d2->old.from;
  			d2[1].new.from = d2->new.from;
  			d2++;
  			continue;
  		}
  		/* stuff peculiar to third file or different in all */
  		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
  			err = duplicate(&dpl, j, &d1->old, &d2->old, d3s);
  			if (err)
  				return err;
  
  			/*
  			 * dpl = 0 means all files differ
  			 * dpl = 1 means files 1 and 2 identical
  			 */
  			err = edit(d1, dpl, &j, d3s);
  			if (err)
  				return err;
  			d1++;
  			d2++;
  			continue;
  		}
  
  		/*
  		 * Overlapping changes from file 1 and 2; extend changes
  		 * appropriately to make them coincide.
  		 */
  		if (d1->new.from < d2->new.from) {
  			d2->old.from -= d2->new.from - d1->new.from;
  			d2->new.from = d1->new.from;
  		} else if (d2->new.from < d1->new.from) {
  			d1->old.from -= d1->new.from - d2->new.from;
  			d1->new.from = d2->new.from;
  		}
  		if (d1->new.to > d2->new.to) {
  			d2->old.to += d1->new.to - d2->new.to;
  			d2->new.to = d1->new.to;
  		} else if (d2->new.to > d1->new.to) {
  			d1->old.to += d2->new.to - d1->new.to;
  			d1->new.to = d2->new.to;
  		}
  	}
  
  	return (edscript(j, d3s));
  }
  
  /*
   * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
   */
  static const struct got_error *
  prange(struct line_range *rold, struct diff3_state *d3s)
  {
  	const struct got_error *err = NULL;
  
  	if (rold->to <= rold->from) {
  		err = diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
  		if (err)
  			return err;
  	} else {
  		err = diff_output(d3s->diffbuf, "%d", rold->from);
  		if (err)
  			return err;
  		if (rold->to > rold->from + 1) {
  			err = diff_output(d3s->diffbuf, ",%d", rold->to - 1);
  			if (err)
  				return err;
  		}
  		err = diff_output(d3s->diffbuf, "c\n");
  		if (err)
  			return err;
  	}
  
  	return NULL;
  }
  
  /*
   * Skip to just before line number from in file "i".
   * Return the number of bytes skipped in *nskipped.
   */
  static const struct got_error *
  skip(size_t *nskipped, int i, int from, struct diff3_state *d3s)
  {
  	const struct got_error *err = NULL;
  	size_t len, n;
  	char *line;
  
  	*nskipped = 0;
  	for (n = 0; d3s->cline[i] < from - 1; n += len) {
  		err = get_line(&line, d3s->fp[i], &len, d3s);
  		if (err)
  			return err;
  		d3s->cline[i]++;
  	}
  	*nskipped = n;
  	return NULL;
  }
  
  /*
   * Set *dpl to 1 or 0 according as the old range (in file 1) contains exactly
   * the same data as the new range (in file 2).
   *
   * If this change could overlap, remember start/end offsets in file 2 so we
   * can write out the original lines of text if a merge conflict occurs.
   */
  static const struct got_error *
  duplicate(int *dpl, int j, struct line_range *r1, struct line_range *r2,
      struct diff3_state *d3s)
  {
  	const struct got_error *err = NULL;
  	int c,d;
  	int nchar;
  	int nline;
  	size_t nskipped;
  	off_t off;
  
  	*dpl = 0;
  
  	if (r1->to - r1->from != r2->to - r2->from)
  		return NULL;
  
  	err = skip(&nskipped, 0, r1->from, d3s);
  	if (err)
  		return err;
  	err = skip(&nskipped, 1, r2->from, d3s);
  	if (err)
  		return err;
  
  	off = ftello(d3s->fp[1]);
  	if (off == -1)
  		return got_error_from_errno("ftello");
  	d3s->de[j + 1].oldo.from = off; /* original lines start here */
  
  	nchar = 0;
  	for (nline = 0; nline < r1->to - r1->from; nline++) {
  		do {
  			c = getc(d3s->fp[0]);
  			d = getc(d3s->fp[1]);
  			if (c == EOF && d == EOF)
  				break;
  			else if (c == EOF)
  				return got_ferror(d3s->fp[0], GOT_ERR_EOF);
  			else if (d == EOF)
  				return got_ferror(d3s->fp[1], GOT_ERR_EOF);
  			nchar++;
  			if (c != d) {
  				long orig_line_len = nchar;
  				while (d != '\n') {
  					d = getc(d3s->fp[1]);
  					if (d == EOF)
  						break;
  					orig_line_len++;
  				}
  				if (orig_line_len > nchar &&
  				    fseek(d3s->fp[1], -(orig_line_len - nchar),
  				    SEEK_CUR) == -1)
  					return got_ferror(d3s->fp[1],
  						GOT_ERR_IO);
  				/* original lines end here */
  				d3s->de[j + 1].oldo.to = off + orig_line_len;
  				err = repos(nchar, d3s);
  				if (err)
  					return err;
  				return NULL;
  			}
  		} while (c != '\n');
  	}
  
  	/* original lines end here */
  	d3s->de[j + 1].oldo.to = off + nchar;
  
  	err = repos(nchar, d3s);
  	if (err)
  		return err;
  	*dpl = 1;
  	return NULL;
  }
  
  static const struct got_error *
  repos(int nchar, struct diff3_state *d3s)
  {
  	int i;
  
  	for (i = 0; i < 2; i++) {
  		if (fseek(d3s->fp[i], (long)-nchar, SEEK_CUR) == -1)
  			return got_ferror(d3s->fp[i], GOT_ERR_IO);
  	}
  
  	return NULL;
  }
  
  /*
   * collect an editing script for later regurgitation
   */
  static const struct got_error *
  edit(struct diff *diff, int fdup, int *j, struct diff3_state *d3s)
  {
  	const struct got_error *err = NULL;
  	size_t nskipped;
  
  	if (((fdup + 1) & 3) == 0)
  		return NULL;
  	(*j)++;
  	d3s->overlap[*j] = !fdup;
  	if (!fdup)
  		d3s->overlapcnt++;
  	d3s->de[*j].old.from = diff->old.from;
  	d3s->de[*j].old.to = diff->old.to;
  
  	err = skip(&nskipped, 2, diff->new.from, d3s);
  	if (err)
  		return err;
  	d3s->de[*j].newo.from = d3s->de[*j - 1].newo.to + nskipped;
  
  	err = skip(&nskipped, 2, diff->new.to, d3s);
  	if (err)
  		return err;
  	d3s->de[*j].newo.to = d3s->de[*j].newo.from + nskipped;
  	return NULL;
  }
  
  /* regurgitate */
  static const struct got_error *
  edscript(int n, struct diff3_state *d3s)
  {
  	const struct got_error *err = NULL;
  	off_t len;
  	char *line = NULL;
  	size_t linesize = 0;
  	ssize_t linelen = 0, k;
  
  	for (; n > 0; n--) {
  		if (!d3s->overlap[n]) {
  			err = prange(&d3s->de[n].old, d3s);
  			if (err)
  				return err;
  		} else if (d3s->de[n].oldo.from < d3s->de[n].oldo.to) {
  			/* Output a block of 3-way diff base file content. */
  			err = diff_output(d3s->diffbuf, "%da\n:%s\n",
  			    d3s->de[n].old.to - 1, d3s->f2mark);
  			if (err)
  				return err;
  			if (fseeko(d3s->fp[1], d3s->de[n].oldo.from, SEEK_SET)
  			    == -1)
  				return got_error_from_errno("fseeko");
  			len = (d3s->de[n].oldo.to - d3s->de[n].oldo.from);
  			for (k = 0; k < (ssize_t)len; k += linelen) {
  				linelen = getline(&line, &linesize, d3s->fp[1]);
  				if (linelen == -1) {
  					if (feof(d3s->fp[1]))
  						break;
  					err = got_ferror(d3s->fp[1],
  					    GOT_ERR_IO);
  					goto done;
  				}
  				err = diff_output(d3s->diffbuf, ":%s", line);
  				if (err)
  					goto done;
  			}
  			err = diff_output(d3s->diffbuf, "%s%s\n",
  			    linelen > 0 && line[linelen] == '\n' ? ":" : "",
  			    GOT_DIFF_CONFLICT_MARKER_SEP);
  			if (err)
  				goto done;
  		} else {
  			err = diff_output(d3s->diffbuf, "%da\n:%s\n",
  			    d3s->de[n].old.to -1, GOT_DIFF_CONFLICT_MARKER_SEP);
  			if (err)
  				goto done;
  		}
  		if (fseeko(d3s->fp[2], d3s->de[n].newo.from, SEEK_SET)
  		    == -1) {
  			err = got_error_from_errno("fseek");
  			goto done;
  		}
  		len = (d3s->de[n].newo.to - d3s->de[n].newo.from);
  		for (k = 0; k < (ssize_t)len; k += linelen) {
  			linelen = getline(&line, &linesize, d3s->fp[2]);
  			if (linelen == -1) {
  				if (feof(d3s->fp[2]))
  					break;
  				err = got_ferror(d3s->fp[2], GOT_ERR_IO);
  				goto done;
  			}
  			err = diff_output(d3s->diffbuf, ":%s", line);
  			if (err)
  				goto done;
  		}
  
  		if (!d3s->overlap[n]) {
  			err = diff_output(d3s->diffbuf, ".\n");
  			if (err)
  				goto done;
  		} else {
  			err = diff_output(d3s->diffbuf, "%s%s\n.\n",
  			    linelen > 0 && line[linelen] == '\n' ? ":" : "",
  			    d3s->f3mark);
  			if (err)
  				goto done;
  			err = diff_output(d3s->diffbuf, "%da\n:%s\n.\n",
  			    d3s->de[n].old.from - 1, d3s->f1mark);
  			if (err)
  				goto done;
  		}
  	}
  done:
  	free(line);
  	return err;
  }
  
  static const struct got_error *
  increase(struct diff3_state *d3s)
  {
  	size_t newsz, incr;
  	struct diff *d;
  	char *s;
  
  	/* are the memset(3) calls needed? */
  	newsz = d3s->szchanges == 0 ? 64 : 2 * d3s->szchanges;
  	incr = newsz - d3s->szchanges;
  
  	d = reallocarray(d3s->d13, newsz, sizeof(*d3s->d13));
  	if (d == NULL)
  		return got_error_from_errno("reallocarray");
  	d3s->d13 = d;
  	memset(d3s->d13 + d3s->szchanges, 0, incr * sizeof(*d3s->d13));
  
  	d = reallocarray(d3s->d23, newsz, sizeof(*d3s->d23));
  	if (d == NULL)
  		return got_error_from_errno("reallocarray");
  	d3s->d23 = d;
  	memset(d3s->d23 + d3s->szchanges, 0, incr * sizeof(*d3s->d23));
  
  	d = reallocarray(d3s->de, newsz, sizeof(*d3s->de));
  	if (d == NULL)
  		return got_error_from_errno("reallocarray");
  	d3s->de = d;
  	memset(d3s->de + d3s->szchanges, 0, incr * sizeof(*d3s->de));
  
  	s = reallocarray(d3s->overlap, newsz, sizeof(*d3s->overlap));
  	if (s == NULL)
  		return got_error_from_errno("reallocarray");
  	d3s->overlap = s;
  	memset(d3s->overlap + d3s->szchanges, 0, incr * sizeof(*d3s->overlap));
  	d3s->szchanges = newsz;
  
  	return NULL;
  }
  

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