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-/****************************************************************************
- * Copyright (c) 1998 Free Software Foundation, Inc. *
- * *
- * Permission is hereby granted, free of charge, to any person obtaining a *
- * copy of this software and associated documentation files (the *
- * "Software"), to deal in the Software without restriction, including *
- * without limitation the rights to use, copy, modify, merge, publish, *
- * distribute, distribute with modifications, sublicense, and/or sell *
- * copies of the Software, and to permit persons to whom the Software is *
- * furnished to do so, subject to the following conditions: *
- * *
- * The above copyright notice and this permission notice shall be included *
- * in all copies or substantial portions of the Software. *
- * *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
- * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
- * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
- * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
- * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
- * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
- * THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
- * *
- * Except as contained in this notice, the name(s) of the above copyright *
- * holders shall not be used in advertising or otherwise to promote the *
- * sale, use or other dealings in this Software without prior written *
- * authorization. *
- ****************************************************************************/
-
-/****************************************************************************
- * Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995 *
- * and: Eric S. Raymond <esr@snark.thyrsus.com> *
- ****************************************************************************/
-
-
-/******************************************************************************
-
-NAME
- hardscroll.c -- hardware-scrolling optimization for ncurses
-
-SYNOPSIS
- void _nc_scroll_optimize(void)
-
-DESCRIPTION
- OVERVIEW
-
-This algorithm for computes optimum hardware scrolling to transform an
-old screen (curscr) into a new screen (newscr) via vertical line moves.
-
-Because the screen has a `grain' (there are insert/delete/scroll line
-operations but no insert/delete/scroll column operations), it is efficient
-break the update algorithm into two pieces: a first stage that does only line
-moves, optimizing the end product of user-invoked insertions, deletions, and
-scrolls; and a second phase (corresponding to the present doupdate code in
-ncurses) that does only line transformations.
-
-The common case we want hardware scrolling for is to handle line insertions
-and deletions in screen-oriented text-editors. This two-stage approach will
-accomplish that at a low computation and code-size cost.
-
- LINE-MOVE COMPUTATION
-
-Now, to a discussion of the line-move computation.
-
-For expository purposes, consider the screen lines to be represented by
-integers 0..23 (with the understanding that the value of 23 may vary).
-Let a new line introduced by insertion, scrolling, or at the bottom of
-the screen following a line delete be given the index -1.
-
-Assume that the real screen starts with lines 0..23. Now, we have
-the following possible line-oriented operations on the screen:
-
-Insertion: inserts a line at a given screen row, forcing all lines below
-to scroll forward. The last screen line is lost. For example, an insertion
-at line 5 would produce: 0..4 -1 5..23.
-
-Deletion: deletes a line at a given screen row, forcing all lines below
-to scroll forward. The last screen line is made new. For example, a deletion
-at line 7 would produce: 0..6 8..23 -1.
-
-Scroll up: move a range of lines up 1. The bottom line of the range
-becomes new. For example, scrolling up the region from 9 to 14 will
-produce 0..8 10..14 -1 15..23.
-
-Scroll down: move a range of lines down 1. The top line of the range
-becomes new. For example, scrolling down the region from 12 to 16 will produce
-0..11 -1 12..15 17..23.
-
-Now, an obvious property of all these operations is that they preserve the
-order of old lines, though not their position in the sequence.
-
-The key trick of this algorithm is that the original line indices described
-above are actually maintained as _line[].oldindex fields in the window
-structure, and stick to each line through scroll and insert/delete operations.
-
-Thus, it is possible at update time to look at the oldnum fields and compute
-an optimal set of il/dl/scroll operations that will take the real screen
-lines to the virtual screen lines. Once these vertical moves have been done,
-we can hand off to the second stage of the update algorithm, which does line
-transformations.
-
-Note that the move computation does not need to have the full generality
-of a diff algorithm (which it superficially resembles) because lines cannot
-be moved out of order.
-
- THE ALGORITHM
-
-The scrolling is done in two passes. The first pass is from top to bottom
-scroling hunks UP. The second one is from bottom to top scrolling hunks DOWN.
-Obviously enough, no lines to be scrolled will be destroyed. (lav)
-
-HOW TO TEST THIS:
-
-Use the following production:
-
-hardscroll: hardscroll.c
- $(CC) -g -DSCROLLDEBUG hardscroll.c -o hardscroll
-
-Then just type scramble vectors and watch. The following test loads are
-a representative sample of cases:
-
------------------------------ CUT HERE ------------------------------------
-# No lines moved
- 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
-#
-# A scroll up
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 -1
-#
-# A scroll down
--1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
-#
-# An insertion (after line 12)
- 0 1 2 3 4 5 6 7 8 9 10 11 12 -1 13 14 15 16 17 18 19 20 21 22
-#
-# A simple deletion (line 10)
- 0 1 2 3 4 5 6 7 8 9 11 12 13 14 15 16 17 18 19 20 21 22 23 -1
-#
-# A more complex case
--1 -1 -1 -1 -1 3 4 5 6 7 -1 -1 8 9 10 11 12 13 14 15 16 17 -1 -1
------------------------------ CUT HERE ------------------------------------
-
-AUTHOR
- Eric S. Raymond <esr@snark.thyrsus.com>, November 1994
- New algorithm by Alexander V. Lukyanov <lav@yars.free.net>, Aug 1997
-
-*****************************************************************************/
-
-#include <curses.priv.h>
-
-MODULE_ID("$Id$")
-
-#if defined(SCROLLDEBUG) || defined(HASHDEBUG)
-
-# undef screen_lines
-# define screen_lines MAXLINES
-int oldnums[MAXLINES];
-# define OLDNUM(n) oldnums[n]
-# define _tracef printf
-# undef TR
-# define TR(n, a) if (_nc_tracing & (n)) { _tracef a ; putchar('\n'); }
-
-#else /* no debug */
-
-/* OLDNUM(n) indicates which line will be shifted to the position n.
- if OLDNUM(n) == _NEWINDEX, then the line n in new, not shifted from
- somewhere. */
-# if USE_HASHMAP
-int *_nc_oldnums = 0;
-static int oldnums_allocated = 0;
-# define oldnums _nc_oldnums
-# define OLDNUM(n) oldnums[n]
-# else /* !USE_HASHMAP */
-# define OLDNUM(n) newscr->_line[n].oldindex
-# endif /* !USE_HASHMAP */
-
-#endif /* defined(SCROLLDEBUG) || defined(HASHDEBUG) */
-
-
-void _nc_scroll_optimize(void)
-/* scroll optimization to transform curscr to newscr */
-{
- int i;
- int start, end, shift;
-
- TR(TRACE_ICALLS, ("_nc_scroll_optimize() begins"));
-
-#if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
-#if USE_HASHMAP
- /* get enough storage */
- if (oldnums_allocated < screen_lines)
- {
- int *new_oldnums = typeRealloc(int, screen_lines, oldnums);
- if (!new_oldnums)
- return;
- oldnums = new_oldnums;
- oldnums_allocated = screen_lines;
- }
- /* calculate the indices */
- _nc_hash_map();
-#endif
-#endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
-
-#ifdef TRACE
- if (_nc_tracing & (TRACE_UPDATE | TRACE_MOVE))
- _nc_linedump();
-#endif /* TRACE */
-
- /* pass 1 - from top to bottom scrolling up */
- for (i = 0; i < screen_lines; )
- {
- while (i < screen_lines && (OLDNUM(i) == _NEWINDEX || OLDNUM(i) <= i))
- i++;
- if (i >= screen_lines)
- break;
-
- shift = OLDNUM(i) - i; /* shift > 0 */
- start = i;
-
- i++;
- while (i < screen_lines && OLDNUM(i) != _NEWINDEX && OLDNUM(i) - i == shift)
- i++;
- end = i-1 + shift;
-
- TR(TRACE_UPDATE | TRACE_MOVE, ("scroll [%d, %d] by %d", start, end, shift));
-#if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
- if (_nc_scrolln(shift, start, end, screen_lines - 1) == ERR)
- {
- TR(TRACE_UPDATE | TRACE_MOVE, ("unable to scroll"));
- continue;
- }
-#endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
- }
-
- /* pass 2 - from bottom to top scrolling down */
- for (i = screen_lines-1; i >= 0; )
- {
- while (i >= 0 && (OLDNUM(i) == _NEWINDEX || OLDNUM(i) >= i))
- i--;
- if (i < 0)
- break;
-
- shift = OLDNUM(i) - i; /* shift < 0 */
- end = i;
-
- i--;
- while (i >= 0 && OLDNUM(i) != _NEWINDEX && OLDNUM(i) - i == shift)
- i--;
- start = i+1 - (-shift);
-
- TR(TRACE_UPDATE | TRACE_MOVE, ("scroll [%d, %d] by %d", start, end, shift));
-#if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
- if (_nc_scrolln(shift, start, end, screen_lines - 1) == ERR)
- {
- TR(TRACE_UPDATE | TRACE_MOVE, ("unable to scroll"));
- continue;
- }
-#endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
- }
-}
-
-#if defined(TRACE) || defined(SCROLLDEBUG) || defined(HASHDEBUG)
-void _nc_linedump(void)
-/* dump the state of the real and virtual oldnum fields */
-{
- static size_t have;
- static char *buf;
-
- int n;
- size_t want = (screen_lines + 1) * 4;
-
- if (have < want)
- buf = typeMalloc(char, have = want);
-
- (void) strcpy(buf, "virt");
- for (n = 0; n < screen_lines; n++)
- (void) sprintf(buf + strlen(buf), " %02d", OLDNUM(n));
- TR(TRACE_UPDATE | TRACE_MOVE, (buf));
-#if NO_LEAKS
- free(buf);
- have = 0;
-#endif
-}
-#endif /* defined(TRACE) || defined(SCROLLDEBUG) */
-
-#ifdef SCROLLDEBUG
-
-int
-main(int argc GCC_UNUSED, char *argv[] GCC_UNUSED)
-{
- char line[BUFSIZ], *st;
-
-#ifdef TRACE
- _nc_tracing = TRACE_MOVE;
-#endif
- for (;;)
- {
- int n;
-
- for (n = 0; n < screen_lines; n++)
- oldnums[n] = _NEWINDEX;
-
- /* grab the test vector */
- if (fgets(line, sizeof(line), stdin) == (char *)NULL)
- exit(EXIT_SUCCESS);
-
- /* parse it */
- n = 0;
- if (line[0] == '#')
- {
- (void) fputs(line, stderr);
- continue;
- }
- st = strtok(line, " ");
- do {
- oldnums[n++] = atoi(st);
- } while
- ((st = strtok((char *)NULL, " ")) != 0);
-
- /* display it */
- (void) fputs("Initial input:\n", stderr);
- _nc_linedump();
-
- _nc_scroll_optimize();
- }
-}
-
-#endif /* SCROLLDEBUG */
-
-/* hardscroll.c ends here */
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