xdiff/xutils.c - jrn/git - Git at Google

 /*
  *  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"


 long xdl_bogosqrt(long n) {
 	long i;

 	/*
 	 * Classical integer square root approximation using shifts.
 	 */
 	for (i = 1; n > 0; n >>= 2)
 		i <<= 1;

 	return i;
 }


 int xdl_emit_diffrec(char const *rec, long size, char const *pre, long psize,
 		     xdemitcb_t *ecb) {
 	int i = 2;
 	mmbuffer_t mb[3];

 	mb[0].ptr = (char *) pre;
 	mb[0].size = psize;
 	mb[1].ptr = (char *) rec;
 	mb[1].size = size;
 	if (size > 0 && rec[size - 1] != '\n') {
 		mb[2].ptr = (char *) "\n\\ No newline at end of file\n";
 		mb[2].size = strlen(mb[2].ptr);
 		i++;
 	}
 	if (ecb->out_line(ecb->priv, mb, i) < 0) {

 		return -1;
 	}

 	return 0;
 }

 void *xdl_mmfile_first(mmfile_t *mmf, long *size)
 {
 	*size = mmf->size;
 	return mmf->ptr;
 }


 long xdl_mmfile_size(mmfile_t *mmf)
 {
 	return mmf->size;
 }


 int xdl_cha_init(chastore_t *cha, long isize, long icount) {

 	cha->head = cha->tail = NULL;
 	cha->isize = isize;
 	cha->nsize = icount * isize;
 	cha->ancur = cha->sncur = NULL;
 	cha->scurr = 0;

 	return 0;
 }


 void xdl_cha_free(chastore_t *cha) {
 	chanode_t *cur, *tmp;

 	for (cur = cha->head; (tmp = cur) != NULL;) {
 		cur = cur->next;
 		xdl_free(tmp);
 	}
 }


 void *xdl_cha_alloc(chastore_t *cha) {
 	chanode_t *ancur;
 	void *data;

 	if (!(ancur = cha->ancur) || ancur->icurr == cha->nsize) {
 		if (!(ancur = (chanode_t *) xdl_malloc(sizeof(chanode_t) + cha->nsize))) {

 			return NULL;
 		}
 		ancur->icurr = 0;
 		ancur->next = NULL;
 		if (cha->tail)
 			cha->tail->next = ancur;
 		if (!cha->head)
 			cha->head = ancur;
 		cha->tail = ancur;
 		cha->ancur = ancur;
 	}

 	data = (char *) ancur + sizeof(chanode_t) + ancur->icurr;
 	ancur->icurr += cha->isize;

 	return data;
 }

 long xdl_guess_lines(mmfile_t *mf, long sample) {
 	long nl = 0, size, tsize = 0;
 	char const *data, *cur, *top;

 	if ((cur = data = xdl_mmfile_first(mf, &size))) {
 		for (top = data + size; nl < sample && cur < top; ) {
 			nl++;
 			if (!(cur = memchr(cur, '\n', top - cur)))
 				cur = top;
 			else
 				cur++;
 		}
 		tsize += (long) (cur - data);
 	}

 	if (nl && tsize)
 		nl = xdl_mmfile_size(mf) / (tsize / nl);

 	return nl + 1;
 }

 int xdl_blankline(const char *line, long size, long flags)
 {
 	long i;

 	if (!(flags & XDF_WHITESPACE_FLAGS))
 		return (size <= 1);

 	for (i = 0; i < size && XDL_ISSPACE(line[i]); i++)
 		;

 	return (i == size);
 }

 /*
  * Have we eaten everything on the line, except for an optional
  * CR at the very end?
  */
 static int ends_with_optional_cr(const char *l, long s, long i)
 {
 	int complete = s && l[s-1] == '\n';

 	if (complete)
 		s--;
 	if (s == i)
 		return 1;
 	/* do not ignore CR at the end of an incomplete line */
 	if (complete && s == i + 1 && l[i] == '\r')
 		return 1;
 	return 0;
 }

 int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags)
 {
 	int i1, i2;

 	if (s1 == s2 && !memcmp(l1, l2, s1))
 		return 1;
 	if (!(flags & XDF_WHITESPACE_FLAGS))
 		return 0;

 	i1 = 0;
 	i2 = 0;

 	/*
 	 * -w matches everything that matches with -b, and -b in turn
 	 * matches everything that matches with --ignore-space-at-eol,
 	 * which in turn matches everything that matches with --ignore-cr-at-eol.
 	 *
 	 * Each flavor of ignoring needs different logic to skip whitespaces
 	 * while we have both sides to compare.
 	 */
 	if (flags & XDF_IGNORE_WHITESPACE) {
 		goto skip_ws;
 		while (i1 < s1 && i2 < s2) {
 			if (l1[i1++] != l2[i2++])
 				return 0;
 		skip_ws:
 			while (i1 < s1 && XDL_ISSPACE(l1[i1]))
 				i1++;
 			while (i2 < s2 && XDL_ISSPACE(l2[i2]))
 				i2++;
 		}
 	} else if (flags & XDF_IGNORE_WHITESPACE_CHANGE) {
 		while (i1 < s1 && i2 < s2) {
 			if (XDL_ISSPACE(l1[i1]) && XDL_ISSPACE(l2[i2])) {
 				/* Skip matching spaces and try again */
 				while (i1 < s1 && XDL_ISSPACE(l1[i1]))
 					i1++;
 				while (i2 < s2 && XDL_ISSPACE(l2[i2]))
 					i2++;
 				continue;
 			}
 			if (l1[i1++] != l2[i2++])
 				return 0;
 		}
 	} else if (flags & XDF_IGNORE_WHITESPACE_AT_EOL) {
 		while (i1 < s1 && i2 < s2 && l1[i1] == l2[i2]) {
 			i1++;
 			i2++;
 		}
 	} else if (flags & XDF_IGNORE_CR_AT_EOL) {
 		/* Find the first difference and see how the line ends */
 		while (i1 < s1 && i2 < s2 && l1[i1] == l2[i2]) {
 			i1++;
 			i2++;
 		}
 		return (ends_with_optional_cr(l1, s1, i1) &&
 			ends_with_optional_cr(l2, s2, i2));
 	}

 	/*
 	 * After running out of one side, the remaining side must have
 	 * nothing but whitespace for the lines to match.  Note that
 	 * ignore-whitespace-at-eol case may break out of the loop
 	 * while there still are characters remaining on both lines.
 	 */
 	if (i1 < s1) {
 		while (i1 < s1 && XDL_ISSPACE(l1[i1]))
 			i1++;
 		if (s1 != i1)
 			return 0;
 	}
 	if (i2 < s2) {
 		while (i2 < s2 && XDL_ISSPACE(l2[i2]))
 			i2++;
 		return (s2 == i2);
 	}
 	return 1;
 }

 static unsigned long xdl_hash_record_with_whitespace(char const **data,
 		char const *top, long flags) {
 	unsigned long ha = 5381;
 	char const *ptr = *data;
 	int cr_at_eol_only = (flags & XDF_WHITESPACE_FLAGS) == XDF_IGNORE_CR_AT_EOL;

 	for (; ptr < top && *ptr != '\n'; ptr++) {
 		if (cr_at_eol_only) {
 			/* do not ignore CR at the end of an incomplete line */
 			if (*ptr == '\r' &&
 			    (ptr + 1 < top && ptr[1] == '\n'))
 				continue;
 		}
 		else if (XDL_ISSPACE(*ptr)) {
 			const char *ptr2 = ptr;
 			int at_eol;
 			while (ptr + 1 < top && XDL_ISSPACE(ptr[1])
 					&& ptr[1] != '\n')
 				ptr++;
 			at_eol = (top <= ptr + 1 || ptr[1] == '\n');
 			if (flags & XDF_IGNORE_WHITESPACE)
 				; /* already handled */
 			else if (flags & XDF_IGNORE_WHITESPACE_CHANGE
 				 && !at_eol) {
 				ha += (ha << 5);
 				ha ^= (unsigned long) ' ';
 			}
 			else if (flags & XDF_IGNORE_WHITESPACE_AT_EOL
 				 && !at_eol) {
 				while (ptr2 != ptr + 1) {
 					ha += (ha << 5);
 					ha ^= (unsigned long) *ptr2;
 					ptr2++;
 				}
 			}
 			continue;
 		}
 		ha += (ha << 5);
 		ha ^= (unsigned long) *ptr;
 	}
 	*data = ptr < top ? ptr + 1: ptr;

 	return ha;
 }

 unsigned long xdl_hash_record(char const **data, char const *top, long flags) {
 	unsigned long ha = 5381;
 	char const *ptr = *data;

 	if (flags & XDF_WHITESPACE_FLAGS)
 		return xdl_hash_record_with_whitespace(data, top, flags);

 	for (; ptr < top && *ptr != '\n'; ptr++) {
 		ha += (ha << 5);
 		ha ^= (unsigned long) *ptr;
 	}
 	*data = ptr < top ? ptr + 1: ptr;

 	return ha;
 }

 unsigned int xdl_hashbits(unsigned int size) {
 	unsigned int val = 1, bits = 0;

 	for (; val < size && bits < CHAR_BIT * sizeof(unsigned int); val <<= 1, bits++);
 	return bits ? bits: 1;
 }


 int xdl_num_out(char *out, long val) {
 	char *ptr, *str = out;
 	char buf[32];

 	ptr = buf + sizeof(buf) - 1;
 	*ptr = '\0';
 	if (val < 0) {
 		*--ptr = '-';
 		val = -val;
 	}
 	for (; val && ptr > buf; val /= 10)
 		*--ptr = "0123456789"[val % 10];
 	if (*ptr)
 		for (; *ptr; ptr++, str++)
 			*str = *ptr;
 	else
 		*str++ = '0';
 	*str = '\0';

 	return str - out;
 }

 static int xdl_format_hunk_hdr(long s1, long c1, long s2, long c2,
 			       const char *func, long funclen,
 			       xdemitcb_t *ecb) {
 	int nb = 0;
 	mmbuffer_t mb;
 	char buf[128];

 	memcpy(buf, "@@ -", 4);
 	nb += 4;

 	nb += xdl_num_out(buf + nb, c1 ? s1: s1 - 1);

 	if (c1 != 1) {
 		memcpy(buf + nb, ",", 1);
 		nb += 1;

 		nb += xdl_num_out(buf + nb, c1);
 	}

 	memcpy(buf + nb, " +", 2);
 	nb += 2;

 	nb += xdl_num_out(buf + nb, c2 ? s2: s2 - 1);

 	if (c2 != 1) {
 		memcpy(buf + nb, ",", 1);
 		nb += 1;

 		nb += xdl_num_out(buf + nb, c2);
 	}

 	memcpy(buf + nb, " @@", 3);
 	nb += 3;
 	if (func && funclen) {
 		buf[nb++] = ' ';
 		if (funclen > sizeof(buf) - nb - 1)
 			funclen = sizeof(buf) - nb - 1;
 		memcpy(buf + nb, func, funclen);
 		nb += funclen;
 	}
 	buf[nb++] = '\n';

 	mb.ptr = buf;
 	mb.size = nb;
 	if (ecb->out_line(ecb->priv, &mb, 1) < 0)
 		return -1;
 	return 0;
 }

 int xdl_emit_hunk_hdr(long s1, long c1, long s2, long c2,
 		      const char *func, long funclen,
 		      xdemitcb_t *ecb) {
 	if (!ecb->out_hunk)
 		return xdl_format_hunk_hdr(s1, c1, s2, c2, func, funclen, ecb);
 	if (ecb->out_hunk(ecb->priv,
 			  c1 ? s1 : s1 - 1, c1,
 			  c2 ? s2 : s2 - 1, c2,
 			  func, funclen) < 0)
 		return -1;
 	return 0;
 }

 int xdl_fall_back_diff(xdfenv_t *diff_env, xpparam_t const *xpp,
 		int line1, int count1, int line2, int count2)
 {
 	/*
 	 * This probably does not work outside Git, since
 	 * we have a very simple mmfile structure.
 	 *
 	 * Note: ideally, we would reuse the prepared environment, but
 	 * the libxdiff interface does not (yet) allow for diffing only
 	 * ranges of lines instead of the whole files.
 	 */
 	mmfile_t subfile1, subfile2;
 	xdfenv_t env;

 	subfile1.ptr = (char *)diff_env->xdf1.recs[line1 - 1]->ptr;
 	subfile1.size = diff_env->xdf1.recs[line1 + count1 - 2]->ptr +
 		diff_env->xdf1.recs[line1 + count1 - 2]->size - subfile1.ptr;
 	subfile2.ptr = (char *)diff_env->xdf2.recs[line2 - 1]->ptr;
 	subfile2.size = diff_env->xdf2.recs[line2 + count2 - 2]->ptr +
 		diff_env->xdf2.recs[line2 + count2 - 2]->size - subfile2.ptr;
 	if (xdl_do_diff(&subfile1, &subfile2, xpp, &env) < 0)
 		return -1;

 	memcpy(diff_env->xdf1.rchg + line1 - 1, env.xdf1.rchg, count1);
 	memcpy(diff_env->xdf2.rchg + line2 - 1, env.xdf2.rchg, count2);

 	xdl_free_env(&env);

 	return 0;
 }
	/*
	* 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"


	long xdl_bogosqrt(long n) {
	long i;

	/*
	* Classical integer square root approximation using shifts.
	*/
	for (i = 1; n > 0; n >>= 2)
	i <<= 1;

	return i;
	}


	int xdl_emit_diffrec(char const rec, long size, char const pre, long psize,
	xdemitcb_t *ecb) {
	int i = 2;
	mmbuffer_t mb[3];

	mb[0].ptr = (char *) pre;
	mb[0].size = psize;
	mb[1].ptr = (char *) rec;
	mb[1].size = size;
	if (size > 0 && rec[size - 1] != '\n') {
	mb[2].ptr = (char *) "\n\\ No newline at end of file\n";
	mb[2].size = strlen(mb[2].ptr);
	i++;
	}
	if (ecb->out_line(ecb->priv, mb, i) < 0) {

	return -1;
	}

	return 0;
	}

	void xdl_mmfile_first(mmfile_t mmf, long *size)
	{
	*size = mmf->size;
	return mmf->ptr;
	}


	long xdl_mmfile_size(mmfile_t *mmf)
	{
	return mmf->size;
	}


	int xdl_cha_init(chastore_t *cha, long isize, long icount) {

	cha->head = cha->tail = NULL;
	cha->isize = isize;
	cha->nsize = icount * isize;
	cha->ancur = cha->sncur = NULL;
	cha->scurr = 0;

	return 0;
	}


	void xdl_cha_free(chastore_t *cha) {
	chanode_t cur, tmp;

	for (cur = cha->head; (tmp = cur) != NULL;) {
	cur = cur->next;
	xdl_free(tmp);
	}
	}


	void xdl_cha_alloc(chastore_t cha) {
	chanode_t *ancur;
	void *data;

	if (!(ancur = cha->ancur) \|\| ancur->icurr == cha->nsize) {
	if (!(ancur = (chanode_t *) xdl_malloc(sizeof(chanode_t) + cha->nsize))) {

	return NULL;
	}
	ancur->icurr = 0;
	ancur->next = NULL;
	if (cha->tail)
	cha->tail->next = ancur;
	if (!cha->head)
	cha->head = ancur;
	cha->tail = ancur;
	cha->ancur = ancur;
	}

	data = (char *) ancur + sizeof(chanode_t) + ancur->icurr;
	ancur->icurr += cha->isize;

	return data;
	}

	long xdl_guess_lines(mmfile_t *mf, long sample) {
	long nl = 0, size, tsize = 0;
	char const data, cur, *top;

	if ((cur = data = xdl_mmfile_first(mf, &size))) {
	for (top = data + size; nl < sample && cur < top; ) {
	nl++;
	if (!(cur = memchr(cur, '\n', top - cur)))
	cur = top;
	else
	cur++;
	}
	tsize += (long) (cur - data);
	}

	if (nl && tsize)
	nl = xdl_mmfile_size(mf) / (tsize / nl);

	return nl + 1;
	}

	int xdl_blankline(const char *line, long size, long flags)
	{
	long i;

	if (!(flags & XDF_WHITESPACE_FLAGS))
	return (size <= 1);

	for (i = 0; i < size && XDL_ISSPACE(line[i]); i++)
	;

	return (i == size);
	}

	/*
	* Have we eaten everything on the line, except for an optional
	* CR at the very end?
	*/
	static int ends_with_optional_cr(const char *l, long s, long i)
	{
	int complete = s && l[s-1] == '\n';

	if (complete)
	s--;
	if (s == i)
	return 1;
	/* do not ignore CR at the end of an incomplete line */
	if (complete && s == i + 1 && l[i] == '\r')
	return 1;
	return 0;
	}

	int xdl_recmatch(const char l1, long s1, const char l2, long s2, long flags)
	{
	int i1, i2;

	if (s1 == s2 && !memcmp(l1, l2, s1))
	return 1;
	if (!(flags & XDF_WHITESPACE_FLAGS))
	return 0;

	i1 = 0;
	i2 = 0;

	/*
	* -w matches everything that matches with -b, and -b in turn
	* matches everything that matches with --ignore-space-at-eol,
	* which in turn matches everything that matches with --ignore-cr-at-eol.
	*
	* Each flavor of ignoring needs different logic to skip whitespaces
	* while we have both sides to compare.
	*/
	if (flags & XDF_IGNORE_WHITESPACE) {
	goto skip_ws;
	while (i1 < s1 && i2 < s2) {
	if (l1[i1++] != l2[i2++])
	return 0;
	skip_ws:
	while (i1 < s1 && XDL_ISSPACE(l1[i1]))
	i1++;
	while (i2 < s2 && XDL_ISSPACE(l2[i2]))
	i2++;
	}
	} else if (flags & XDF_IGNORE_WHITESPACE_CHANGE) {
	while (i1 < s1 && i2 < s2) {
	if (XDL_ISSPACE(l1[i1]) && XDL_ISSPACE(l2[i2])) {
	/* Skip matching spaces and try again */
	while (i1 < s1 && XDL_ISSPACE(l1[i1]))
	i1++;
	while (i2 < s2 && XDL_ISSPACE(l2[i2]))
	i2++;
	continue;
	}
	if (l1[i1++] != l2[i2++])
	return 0;
	}
	} else if (flags & XDF_IGNORE_WHITESPACE_AT_EOL) {
	while (i1 < s1 && i2 < s2 && l1[i1] == l2[i2]) {
	i1++;
	i2++;
	}
	} else if (flags & XDF_IGNORE_CR_AT_EOL) {
	/* Find the first difference and see how the line ends */
	while (i1 < s1 && i2 < s2 && l1[i1] == l2[i2]) {
	i1++;
	i2++;
	}
	return (ends_with_optional_cr(l1, s1, i1) &&
	ends_with_optional_cr(l2, s2, i2));
	}

	/*
	* After running out of one side, the remaining side must have
	* nothing but whitespace for the lines to match. Note that
	* ignore-whitespace-at-eol case may break out of the loop
	* while there still are characters remaining on both lines.
	*/
	if (i1 < s1) {
	while (i1 < s1 && XDL_ISSPACE(l1[i1]))
	i1++;
	if (s1 != i1)
	return 0;
	}
	if (i2 < s2) {
	while (i2 < s2 && XDL_ISSPACE(l2[i2]))
	i2++;
	return (s2 == i2);
	}
	return 1;
	}

	static unsigned long xdl_hash_record_with_whitespace(char const **data,
	char const *top, long flags) {
	unsigned long ha = 5381;
	char const ptr = data;
	int cr_at_eol_only = (flags & XDF_WHITESPACE_FLAGS) == XDF_IGNORE_CR_AT_EOL;

	for (; ptr < top && *ptr != '\n'; ptr++) {
	if (cr_at_eol_only) {
	/* do not ignore CR at the end of an incomplete line */
	if (*ptr == '\r' &&
	(ptr + 1 < top && ptr[1] == '\n'))
	continue;
	}
	else if (XDL_ISSPACE(*ptr)) {
	const char *ptr2 = ptr;
	int at_eol;
	while (ptr + 1 < top && XDL_ISSPACE(ptr[1])
	&& ptr[1] != '\n')
	ptr++;
	at_eol = (top <= ptr + 1 \|\| ptr[1] == '\n');
	if (flags & XDF_IGNORE_WHITESPACE)
	; /* already handled */
	else if (flags & XDF_IGNORE_WHITESPACE_CHANGE
	&& !at_eol) {
	ha += (ha << 5);
	ha ^= (unsigned long) ' ';
	}
	else if (flags & XDF_IGNORE_WHITESPACE_AT_EOL
	&& !at_eol) {
	while (ptr2 != ptr + 1) {
	ha += (ha << 5);
	ha ^= (unsigned long) *ptr2;
	ptr2++;
	}
	}
	continue;
	}
	ha += (ha << 5);
	ha ^= (unsigned long) *ptr;
	}
	*data = ptr < top ? ptr + 1: ptr;

	return ha;
	}

	unsigned long xdl_hash_record(char const *data, char const top, long flags) {
	unsigned long ha = 5381;
	char const ptr = data;

	if (flags & XDF_WHITESPACE_FLAGS)
	return xdl_hash_record_with_whitespace(data, top, flags);

	for (; ptr < top && *ptr != '\n'; ptr++) {
	ha += (ha << 5);
	ha ^= (unsigned long) *ptr;
	}
	*data = ptr < top ? ptr + 1: ptr;

	return ha;
	}

	unsigned int xdl_hashbits(unsigned int size) {
	unsigned int val = 1, bits = 0;

	for (; val < size && bits < CHAR_BIT * sizeof(unsigned int); val <<= 1, bits++);
	return bits ? bits: 1;
	}


	int xdl_num_out(char *out, long val) {
	char ptr, str = out;
	char buf[32];

	ptr = buf + sizeof(buf) - 1;
	*ptr = '\0';
	if (val < 0) {
	*--ptr = '-';
	val = -val;
	}
	for (; val && ptr > buf; val /= 10)
	*--ptr = "0123456789"[val % 10];
	if (*ptr)
	for (; *ptr; ptr++, str++)
	str = ptr;
	else
	*str++ = '0';
	*str = '\0';

	return str - out;
	}

	static int xdl_format_hunk_hdr(long s1, long c1, long s2, long c2,
	const char *func, long funclen,
	xdemitcb_t *ecb) {
	int nb = 0;
	mmbuffer_t mb;
	char buf[128];

	memcpy(buf, "@@ -", 4);
	nb += 4;

	nb += xdl_num_out(buf + nb, c1 ? s1: s1 - 1);

	if (c1 != 1) {
	memcpy(buf + nb, ",", 1);
	nb += 1;

	nb += xdl_num_out(buf + nb, c1);
	}

	memcpy(buf + nb, " +", 2);
	nb += 2;

	nb += xdl_num_out(buf + nb, c2 ? s2: s2 - 1);

	if (c2 != 1) {
	memcpy(buf + nb, ",", 1);
	nb += 1;

	nb += xdl_num_out(buf + nb, c2);
	}

	memcpy(buf + nb, " @@", 3);
	nb += 3;
	if (func && funclen) {
	buf[nb++] = ' ';
	if (funclen > sizeof(buf) - nb - 1)
	funclen = sizeof(buf) - nb - 1;
	memcpy(buf + nb, func, funclen);
	nb += funclen;
	}
	buf[nb++] = '\n';

	mb.ptr = buf;
	mb.size = nb;
	if (ecb->out_line(ecb->priv, &mb, 1) < 0)
	return -1;
	return 0;
	}

	int xdl_emit_hunk_hdr(long s1, long c1, long s2, long c2,
	const char *func, long funclen,
	xdemitcb_t *ecb) {
	if (!ecb->out_hunk)
	return xdl_format_hunk_hdr(s1, c1, s2, c2, func, funclen, ecb);
	if (ecb->out_hunk(ecb->priv,
	c1 ? s1 : s1 - 1, c1,
	c2 ? s2 : s2 - 1, c2,
	func, funclen) < 0)
	return -1;
	return 0;
	}

	int xdl_fall_back_diff(xdfenv_t diff_env, xpparam_t const xpp,
	int line1, int count1, int line2, int count2)
	{
	/*
	* This probably does not work outside Git, since
	* we have a very simple mmfile structure.
	*
	* Note: ideally, we would reuse the prepared environment, but
	* the libxdiff interface does not (yet) allow for diffing only
	* ranges of lines instead of the whole files.
	*/
	mmfile_t subfile1, subfile2;
	xdfenv_t env;

	subfile1.ptr = (char *)diff_env->xdf1.recs[line1 - 1]->ptr;
	subfile1.size = diff_env->xdf1.recs[line1 + count1 - 2]->ptr +
	diff_env->xdf1.recs[line1 + count1 - 2]->size - subfile1.ptr;
	subfile2.ptr = (char *)diff_env->xdf2.recs[line2 - 1]->ptr;
	subfile2.size = diff_env->xdf2.recs[line2 + count2 - 2]->ptr +
	diff_env->xdf2.recs[line2 + count2 - 2]->size - subfile2.ptr;
	if (xdl_do_diff(&subfile1, &subfile2, xpp, &env) < 0)
	return -1;

	memcpy(diff_env->xdf1.rchg + line1 - 1, env.xdf1.rchg, count1);
	memcpy(diff_env->xdf2.rchg + line2 - 1, env.xdf2.rchg, count2);

	xdl_free_env(&env);

	return 0;
	}