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/* undo.c: This file contains the undo routines for the ed line editor */
/*-
* Copyright (c) 1993 Andrew Moore, Talke Studio.
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
*
* @(#)undo.c,v 1.1 1994/02/01 00:34:44 alm Exp
* $FreeBSD: src/bin/ed/undo.c,v 1.12 2002/06/30 05:13:53 obrien Exp $
* $DragonFly: src/bin/ed/undo.c,v 1.4 2007/04/06 23:36:54 pavalos Exp $
*/

#include "ed.h"


#define USIZE 100 /* undo stack size */
undo_t *ustack = NULL; /* undo stack */
long usize = 0; /* stack size variable */
long u_p = 0; /* undo stack pointer */

/* push_undo_stack: return pointer to initialized undo node */
undo_t *
push_undo_stack(int type, long from, long to)
{
undo_t *t;

#if defined(sun) || defined(NO_REALLOC_NULL)
if (ustack == NULL &&
(ustack = (undo_t *) malloc((usize = USIZE) * sizeof(undo_t))) == NULL) {
fprintf(stderr, "%s\n", strerror(errno));
errmsg = "out of memory";
return NULL;
}
#endif
t = ustack;
if (u_p < usize ||
(t = (undo_t *) realloc(ustack, (usize += USIZE) * sizeof(undo_t))) != NULL) {
ustack = t;
ustack[u_p].type = type;
ustack[u_p].t = get_addressed_line_node(to);
ustack[u_p].h = get_addressed_line_node(from);
return ustack + u_p++;
}
/* out of memory - release undo stack */
fprintf(stderr, "%s\n", strerror(errno));
errmsg = "out of memory";
clear_undo_stack();
free(ustack);
ustack = NULL;
usize = 0;
return NULL;
}


/* USWAP: swap undo nodes */
#define USWAP(x,y) { \
undo_t utmp; \
utmp = x, x = y, y = utmp; \
}


long u_current_addr = -1; /* if >= 0, undo enabled */
long u_addr_last = -1; /* if >= 0, undo enabled */

/* pop_undo_stack: undo last change to the editor buffer */
int
pop_undo_stack(void)
{
long n;
long o_current_addr = current_addr;
long o_addr_last = addr_last;

if (u_current_addr == -1 || u_addr_last == -1) {
errmsg = "nothing to undo";
return ERR;
} else if (u_p)
modified = 1;
get_addressed_line_node(0); /* this get_addressed_line_node last! */
SPL1();
for (n = u_p; n-- > 0;) {
switch(ustack[n].type) {
case UADD:
REQUE(ustack[n].h->q_back, ustack[n].t->q_forw);
break;
case UDEL:
REQUE(ustack[n].h->q_back, ustack[n].h);
REQUE(ustack[n].t, ustack[n].t->q_forw);
break;
case UMOV:
case VMOV:
REQUE(ustack[n - 1].h, ustack[n].h->q_forw);
REQUE(ustack[n].t->q_back, ustack[n - 1].t);
REQUE(ustack[n].h, ustack[n].t);
n--;
break;
default:
/*NOTREACHED*/
;
}
ustack[n].type ^= 1;
}
/* reverse undo stack order */
for (n = u_p; n-- > (u_p + 1)/ 2;)
USWAP(ustack[n], ustack[u_p - 1 - n]);
if (isglobal)
clear_active_list();
current_addr = u_current_addr, u_current_addr = o_current_addr;
addr_last = u_addr_last, u_addr_last = o_addr_last;
SPL0();
return 0;
}


/* clear_undo_stack: clear the undo stack */
void
clear_undo_stack(void)
{
line_t *lp, *ep, *tl;

while (u_p--)
if (ustack[u_p].type == UDEL) {
ep = ustack[u_p].t->q_forw;
for (lp = ustack[u_p].h; lp != ep; lp = tl) {
unmark_line_node(lp);
tl = lp->q_forw;
free(lp);
}
}
u_p = 0;
u_current_addr = current_addr;
u_addr_last = addr_last;
}
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