xref: /openbsd/usr.bin/less/cmdbuf.c (revision 771fbea0)

/*
 * Copyright (C) 1984-2012  Mark Nudelman
 * Modified for use with illumos by Garrett D'Amore.
 * Copyright 2014 Garrett D'Amore <garrett@damore.org>
 *
 * You may distribute under the terms of either the GNU General Public
 * License or the Less License, as specified in the README file.
 *
 * For more information, see the README file.
 */

/*
 * Functions which manipulate the command buffer.
 * Used only by command() and related functions.
 */

#include <sys/stat.h>

#include "charset.h"
#include "cmd.h"
#include "less.h"

extern int sc_width;
extern int utf_mode;

static char cmdbuf[CMDBUF_SIZE]; /* Buffer for holding a multi-char command */
static int cmd_col;		/* Current column of the cursor */
static int prompt_col;		/* Column of cursor just after prompt */
static char *cp;		/* Pointer into cmdbuf */
static int cmd_offset;		/* Index into cmdbuf of first displayed char */
static int literal;		/* Next input char should not be interpreted */
static int updown_match = -1;	/* Prefix length in up/down movement */

static int cmd_complete(int);
/*
 * These variables are statics used by cmd_complete.
 */
static int in_completion = 0;
static char *tk_text;
static char *tk_original;
static char *tk_ipoint;
static char *tk_trial;
static struct textlist tk_tlist;

static int cmd_left(void);
static int cmd_right(void);

char openquote = '"';
char closequote = '"';

/* History file */
#define	HISTFILE_FIRST_LINE	".less-history-file:"
#define	HISTFILE_SEARCH_SECTION	".search"
#define	HISTFILE_SHELL_SECTION	".shell"

/*
 * A mlist structure represents a command history.
 */
struct mlist {
	struct mlist *next;
	struct mlist *prev;
	struct mlist *curr_mp;
	char *string;
	int modified;
};

/*
 * These are the various command histories that exist.
 */
struct mlist mlist_search =
	{ &mlist_search,  &mlist_search,  &mlist_search,  NULL, 0 };
void * const ml_search = (void *) &mlist_search;

struct mlist mlist_examine =
	{ &mlist_examine, &mlist_examine, &mlist_examine, NULL, 0 };
void * const ml_examine = (void *) &mlist_examine;

struct mlist mlist_shell =
	{ &mlist_shell,   &mlist_shell,   &mlist_shell,   NULL, 0 };
void * const ml_shell = (void *) &mlist_shell;

/*
 * History for the current command.
 */
static struct mlist *curr_mlist = NULL;
static int curr_cmdflags;

static char cmd_mbc_buf[MAX_UTF_CHAR_LEN];
static int cmd_mbc_buf_len;
static int cmd_mbc_buf_index;


/*
 * Reset command buffer (to empty).
 */
void
cmd_reset(void)
{
	cp = cmdbuf;
	*cp = '\0';
	cmd_col = 0;
	cmd_offset = 0;
	literal = 0;
	cmd_mbc_buf_len = 0;
	updown_match = -1;
}

/*
 * Clear command line.
 */
void
clear_cmd(void)
{
	cmd_col = prompt_col = 0;
	cmd_mbc_buf_len = 0;
	updown_match = -1;
}

/*
 * Display an ASCII string, usually as a prompt for input,
 * into the command buffer.
 */
void
cmd_putstr(char *s)
{
	while (*s != '\0') {
		putchr(*s++);
		cmd_col++;
		prompt_col++;
	}
}

/*
 * How many characters are in the command buffer?
 */
int
len_cmdbuf(void)
{
	char *s = cmdbuf;
	char *endline = s + strlen(s);
	int len = 0;

	while (*s != '\0') {
		step_char(&s, +1, endline);
		len++;
	}
	return (len);
}

/*
 * Common part of cmd_step_right() and cmd_step_left().
 */
static char *
cmd_step_common(char *p, LWCHAR ch, int len, int *pwidth, int *bswidth)
{
	char *pr;

	if (len == 1) {
		pr = prchar((int)ch);
		if (pwidth != NULL || bswidth != NULL) {
			int prlen = strlen(pr);
			if (pwidth != NULL)
				*pwidth = prlen;
			if (bswidth != NULL)
				*bswidth = prlen;
		}
	} else {
		pr = prutfchar(ch);
		if (pwidth != NULL || bswidth != NULL) {
			if (is_composing_char(ch)) {
				if (pwidth != NULL)
					*pwidth = 0;
				if (bswidth != NULL)
					*bswidth = 0;
			} else if (is_ubin_char(ch)) {
				int prlen = strlen(pr);
				if (pwidth != NULL)
					*pwidth = prlen;
				if (bswidth != NULL)
					*bswidth = prlen;
			} else {
				if (pwidth != NULL)
					*pwidth	= is_wide_char(ch) ? 2 : 1;
				if (bswidth != NULL)
					*bswidth = 1;
			}
		}
	}

	return (pr);
}

/*
 * Step a pointer one character right in the command buffer.
 */
static char *
cmd_step_right(char **pp, int *pwidth, int *bswidth)
{
	char *p = *pp;
	LWCHAR ch = step_char(pp, +1, p + strlen(p));

	return (cmd_step_common(p, ch, *pp - p, pwidth, bswidth));
}

/*
 * Step a pointer one character left in the command buffer.
 */
static char *
cmd_step_left(char **pp, int *pwidth, int *bswidth)
{
	char *p = *pp;
	LWCHAR ch = step_char(pp, -1, cmdbuf);

	return (cmd_step_common(*pp, ch, p - *pp, pwidth, bswidth));
}

/*
 * Repaint the line from cp onwards.
 * Then position the cursor just after the char old_cp (a pointer into cmdbuf).
 */
static void
cmd_repaint(char *old_cp)
{
	/*
	 * Repaint the line from the current position.
	 */
	clear_eol();
	while (*cp != '\0') {
		char *np = cp;
		int width;
		char *pr = cmd_step_right(&np, &width, NULL);
		if (cmd_col + width >= sc_width)
			break;
		cp = np;
		putstr(pr);
		cmd_col += width;
	}
	while (*cp != '\0') {
		char *np = cp;
		int width;
		char *pr = cmd_step_right(&np, &width, NULL);
		if (width > 0)
			break;
		cp = np;
		putstr(pr);
	}

	/*
	 * Back up the cursor to the correct position.
	 */
	while (cp > old_cp)
		cmd_left();
}

/*
 * Put the cursor at "home" (just after the prompt),
 * and set cp to the corresponding char in cmdbuf.
 */
static void
cmd_home(void)
{
	while (cmd_col > prompt_col) {
		int width, bswidth;

		cmd_step_left(&cp, &width, &bswidth);
		while (bswidth-- > 0)
			putbs();
		cmd_col -= width;
	}

	cp = &cmdbuf[cmd_offset];
}

/*
 * Shift the cmdbuf display left a half-screen.
 */
static void
cmd_lshift(void)
{
	char *s;
	char *save_cp;
	int cols;

	/*
	 * Start at the first displayed char, count how far to the
	 * right we'd have to move to reach the center of the screen.
	 */
	s = cmdbuf + cmd_offset;
	cols = 0;
	while (cols < (sc_width - prompt_col) / 2 && *s != '\0') {
		int width;
		cmd_step_right(&s, &width, NULL);
		cols += width;
	}
	while (*s != '\0') {
		int width;
		char *ns = s;
		cmd_step_right(&ns, &width, NULL);
		if (width > 0)
			break;
		s = ns;
	}

	cmd_offset = s - cmdbuf;
	save_cp = cp;
	cmd_home();
	cmd_repaint(save_cp);
}

/*
 * Shift the cmdbuf display right a half-screen.
 */
static void
cmd_rshift(void)
{
	char *s;
	char *save_cp;
	int cols;

	/*
	 * Start at the first displayed char, count how far to the
	 * left we'd have to move to traverse a half-screen width
	 * of displayed characters.
	 */
	s = cmdbuf + cmd_offset;
	cols = 0;
	while (cols < (sc_width - prompt_col) / 2 && s > cmdbuf) {
		int width;
		cmd_step_left(&s, &width, NULL);
		cols += width;
	}

	cmd_offset = s - cmdbuf;
	save_cp = cp;
	cmd_home();
	cmd_repaint(save_cp);
}

/*
 * Move cursor right one character.
 */
static int
cmd_right(void)
{
	char *pr;
	char *ncp;
	int width;

	if (*cp == '\0') {
		/* Already at the end of the line. */
		return (CC_OK);
	}
	ncp = cp;
	pr = cmd_step_right(&ncp, &width, NULL);
	if (cmd_col + width >= sc_width)
		cmd_lshift();
	else if (cmd_col + width == sc_width - 1 && cp[1] != '\0')
		cmd_lshift();
	cp = ncp;
	cmd_col += width;
	putstr(pr);
	while (*cp != '\0') {
		pr = cmd_step_right(&ncp, &width, NULL);
		if (width > 0)
			break;
		putstr(pr);
		cp = ncp;
	}
	return (CC_OK);
}

/*
 * Move cursor left one character.
 */
static int
cmd_left(void)
{
	char *ncp;
	int width, bswidth;

	if (cp <= cmdbuf) {
		/* Already at the beginning of the line */
		return (CC_OK);
	}
	ncp = cp;
	while (ncp > cmdbuf) {
		cmd_step_left(&ncp, &width, &bswidth);
		if (width > 0)
			break;
	}
	if (cmd_col < prompt_col + width)
		cmd_rshift();
	cp = ncp;
	cmd_col -= width;
	while (bswidth-- > 0)
		putbs();
	return (CC_OK);
}

/*
 * Insert a char into the command buffer, at the current position.
 */
static int
cmd_ichar(char *cs, int clen)
{
	char *s;

	if (strlen(cmdbuf) + clen >= sizeof (cmdbuf)-1) {
		/* No room in the command buffer for another char. */
		ring_bell();
		return (CC_ERROR);
	}

	/*
	 * Make room for the new character (shift the tail of the buffer right).
	 */
	for (s = &cmdbuf[strlen(cmdbuf)]; s >= cp; s--)
		s[clen] = s[0];
	/*
	 * Insert the character into the buffer.
	 */
	for (s = cp; s < cp + clen; s++)
		*s = *cs++;
	/*
	 * Reprint the tail of the line from the inserted char.
	 */
	updown_match = -1;
	cmd_repaint(cp);
	cmd_right();
	return (CC_OK);
}

/*
 * Backspace in the command buffer.
 * Delete the char to the left of the cursor.
 */
static int
cmd_erase(void)
{
	char *s;
	int clen;

	if (cp == cmdbuf) {
		/*
		 * Backspace past beginning of the buffer:
		 * this usually means abort the command.
		 */
		return (CC_QUIT);
	}
	/*
	 * Move cursor left (to the char being erased).
	 */
	s = cp;
	cmd_left();
	clen = s - cp;

	/*
	 * Remove the char from the buffer (shift the buffer left).
	 */
	for (s = cp; ; s++) {
		s[0] = s[clen];
		if (s[0] == '\0')
			break;
	}

	/*
	 * Repaint the buffer after the erased char.
	 */
	updown_match = -1;
	cmd_repaint(cp);

	/*
	 * We say that erasing the entire command string causes us
	 * to abort the current command, if CF_QUIT_ON_ERASE is set.
	 */
	if ((curr_cmdflags & CF_QUIT_ON_ERASE) && cp == cmdbuf && *cp == '\0')
		return (CC_QUIT);
	return (CC_OK);
}

/*
 * Delete the char under the cursor.
 */
static int
cmd_delete(void)
{
	if (*cp == '\0') {
		/* At end of string; there is no char under the cursor. */
		return (CC_OK);
	}
	/*
	 * Move right, then use cmd_erase.
	 */
	cmd_right();
	cmd_erase();
	return (CC_OK);
}

/*
 * Delete the "word" to the left of the cursor.
 */
static int
cmd_werase(void)
{
	if (cp > cmdbuf && cp[-1] == ' ') {
		/*
		 * If the char left of cursor is a space,
		 * erase all the spaces left of cursor (to the first non-space).
		 */
		while (cp > cmdbuf && cp[-1] == ' ')
			(void) cmd_erase();
	} else {
		/*
		 * If the char left of cursor is not a space,
		 * erase all the nonspaces left of cursor (the whole "word").
		 */
		while (cp > cmdbuf && cp[-1] != ' ')
			(void) cmd_erase();
	}
	return (CC_OK);
}

/*
 * Delete the "word" under the cursor.
 */
static int
cmd_wdelete(void)
{
	if (*cp == ' ') {
		/*
		 * If the char under the cursor is a space,
		 * delete it and all the spaces right of cursor.
		 */
		while (*cp == ' ')
			(void) cmd_delete();
	} else {
		/*
		 * If the char under the cursor is not a space,
		 * delete it and all nonspaces right of cursor (the whole word).
		 */
		while (*cp != ' ' && *cp != '\0')
			(void) cmd_delete();
	}
	return (CC_OK);
}

/*
 * Delete all chars in the command buffer.
 */
static int
cmd_kill(void)
{
	if (cmdbuf[0] == '\0') {
		/* Buffer is already empty; abort the current command. */
		return (CC_QUIT);
	}
	cmd_offset = 0;
	cmd_home();
	*cp = '\0';
	updown_match = -1;
	cmd_repaint(cp);

	/*
	 * We say that erasing the entire command string causes us
	 * to abort the current command, if CF_QUIT_ON_ERASE is set.
	 */
	if (curr_cmdflags & CF_QUIT_ON_ERASE)
		return (CC_QUIT);
	return (CC_OK);
}

/*
 * Select an mlist structure to be the current command history.
 */
void
set_mlist(void *mlist, int cmdflags)
{
	curr_mlist = (struct mlist *)mlist;
	curr_cmdflags = cmdflags;

	/* Make sure the next up-arrow moves to the last string in the mlist. */
	if (curr_mlist != NULL)
		curr_mlist->curr_mp = curr_mlist;
}

/*
 * Move up or down in the currently selected command history list.
 * Only consider entries whose first updown_match chars are equal to
 * cmdbuf's corresponding chars.
 */
static int
cmd_updown(int action)
{
	char *s;
	struct mlist *ml;

	if (curr_mlist == NULL) {
		/*
		 * The current command has no history list.
		 */
		ring_bell();
		return (CC_OK);
	}

	if (updown_match < 0) {
		updown_match = cp - cmdbuf;
	}

	/*
	 * Find the next history entry which matches.
	 */
	for (ml = curr_mlist->curr_mp; ; ) {
		ml = (action == EC_UP) ? ml->prev : ml->next;
		if (ml == curr_mlist) {
			/*
			 * We reached the end (or beginning) of the list.
			 */
			break;
		}
		if (strncmp(cmdbuf, ml->string, updown_match) == 0) {
			/*
			 * This entry matches; stop here.
			 * Copy the entry into cmdbuf and echo it on the screen.
			 */
			curr_mlist->curr_mp = ml;
			s = ml->string;
			if (s == NULL)
				s = "";
			cmd_home();
			clear_eol();
			strlcpy(cmdbuf, s, sizeof (cmdbuf));
			for (cp = cmdbuf; *cp != '\0'; )
				cmd_right();
			return (CC_OK);
		}
	}
	/*
	 * We didn't find a history entry that matches.
	 */
	ring_bell();
	return (CC_OK);
}

/*
 * Add a string to a history list.
 */
void
cmd_addhist(struct mlist *mlist, const char *cmd)
{
	struct mlist *ml;

	/*
	 * Don't save a trivial command.
	 */
	if (strlen(cmd) == 0)
		return;

	/*
	 * Save the command unless it's a duplicate of the
	 * last command in the history.
	 */
	ml = mlist->prev;
	if (ml == mlist || strcmp(ml->string, cmd) != 0) {
		/*
		 * Did not find command in history.
		 * Save the command and put it at the end of the history list.
		 */
		ml = ecalloc(1, sizeof (struct mlist));
		ml->string = estrdup(cmd);
		ml->next = mlist;
		ml->prev = mlist->prev;
		mlist->prev->next = ml;
		mlist->prev = ml;
	}
	/*
	 * Point to the cmd just after the just-accepted command.
	 * Thus, an UPARROW will always retrieve the previous command.
	 */
	mlist->curr_mp = ml->next;
}

/*
 * Accept the command in the command buffer.
 * Add it to the currently selected history list.
 */
void
cmd_accept(void)
{
	/*
	 * Nothing to do if there is no currently selected history list.
	 */
	if (curr_mlist == NULL)
		return;
	cmd_addhist(curr_mlist, cmdbuf);
	curr_mlist->modified = 1;
}

/*
 * Try to perform a line-edit function on the command buffer,
 * using a specified char as a line-editing command.
 * Returns:
 *	CC_PASS	The char does not invoke a line edit function.
 *	CC_OK	Line edit function done.
 *	CC_QUIT	The char requests the current command to be aborted.
 */
static int
cmd_edit(int c)
{
	int action;
	int flags;

#define	not_in_completion()	in_completion = 0

	/*
	 * See if the char is indeed a line-editing command.
	 */
	flags = 0;
	if (curr_mlist == NULL)
		/*
		 * No current history; don't accept history manipulation cmds.
		 */
		flags |= EC_NOHISTORY;
	if (curr_mlist == ml_search)
		/*
		 * In a search command; don't accept file-completion cmds.
		 */
		flags |= EC_NOCOMPLETE;

	action = editchar(c, flags);

	switch (action) {
	case EC_RIGHT:
		not_in_completion();
		return (cmd_right());
	case EC_LEFT:
		not_in_completion();
		return (cmd_left());
	case EC_W_RIGHT:
		not_in_completion();
		while (*cp != '\0' && *cp != ' ')
			cmd_right();
		while (*cp == ' ')
			cmd_right();
		return (CC_OK);
	case EC_W_LEFT:
		not_in_completion();
		while (cp > cmdbuf && cp[-1] == ' ')
			cmd_left();
		while (cp > cmdbuf && cp[-1] != ' ')
			cmd_left();
		return (CC_OK);
	case EC_HOME:
		not_in_completion();
		cmd_offset = 0;
		cmd_home();
		cmd_repaint(cp);
		return (CC_OK);
	case EC_END:
		not_in_completion();
		while (*cp != '\0')
			cmd_right();
		return (CC_OK);
	case EC_INSERT:
		not_in_completion();
		return (CC_OK);
	case EC_BACKSPACE:
		not_in_completion();
		return (cmd_erase());
	case EC_LINEKILL:
		not_in_completion();
		return (cmd_kill());
	case EC_ABORT:
		not_in_completion();
		(void) cmd_kill();
		return (CC_QUIT);
	case EC_W_BACKSPACE:
		not_in_completion();
		return (cmd_werase());
	case EC_DELETE:
		not_in_completion();
		return (cmd_delete());
	case EC_W_DELETE:
		not_in_completion();
		return (cmd_wdelete());
	case EC_LITERAL:
		literal = 1;
		return (CC_OK);
	case EC_UP:
	case EC_DOWN:
		not_in_completion();
		return (cmd_updown(action));
	case EC_F_COMPLETE:
	case EC_B_COMPLETE:
	case EC_EXPAND:
		return (cmd_complete(action));
	case EC_NOACTION:
		return (CC_OK);
	default:
		not_in_completion();
		return (CC_PASS);
	}
}

/*
 * Insert a string into the command buffer, at the current position.
 */
static int
cmd_istr(char *str)
{
	char *s;
	int action;
	char *endline = str + strlen(str);

	for (s = str; *s != '\0'; ) {
		char *os = s;
		step_char(&s, +1, endline);
		action = cmd_ichar(os, s - os);
		if (action != CC_OK) {
			ring_bell();
			return (action);
		}
	}
	return (CC_OK);
}

/*
 * Find the beginning and end of the "current" word.
 * This is the word which the cursor (cp) is inside or at the end of.
 * Return pointer to the beginning of the word and put the
 * cursor at the end of the word.
 */
static char *
delimit_word(void)
{
	char *word;
	char *p;
	int delim_quoted = 0;
	int meta_quoted = 0;
	char *esc = get_meta_escape();
	int esclen = strlen(esc);

	/*
	 * Move cursor to end of word.
	 */
	if (*cp != ' ' && *cp != '\0') {
		/*
		 * Cursor is on a nonspace.
		 * Move cursor right to the next space.
		 */
		while (*cp != ' ' && *cp != '\0')
			cmd_right();
	}

	/*
	 * Find the beginning of the word which the cursor is in.
	 */
	if (cp == cmdbuf)
		return (NULL);
	/*
	 * If we have an unbalanced quote (that is, an open quote
	 * without a corresponding close quote), we return everything
	 * from the open quote, including spaces.
	 */
	for (word = cmdbuf; word < cp; word++)
		if (*word != ' ')
			break;
	if (word >= cp)
		return (cp);
	for (p = cmdbuf; p < cp; p++) {
		if (meta_quoted) {
			meta_quoted = 0;
		} else if (esclen > 0 && p + esclen < cp &&
		    strncmp(p, esc, esclen) == 0) {
			meta_quoted = 1;
			p += esclen - 1;
		} else if (delim_quoted) {
			if (*p == closequote)
				delim_quoted = 0;
		} else { /* (!delim_quoted) */
			if (*p == openquote)
				delim_quoted = 1;
			else if (*p == ' ')
				word = p+1;
		}
	}
	return (word);
}

/*
 * Set things up to enter completion mode.
 * Expand the word under the cursor into a list of filenames
 * which start with that word, and set tk_text to that list.
 */
static void
init_compl(void)
{
	char *word;
	char c;

	free(tk_text);
	tk_text = NULL;
	/*
	 * Find the original (uncompleted) word in the command buffer.
	 */
	word = delimit_word();
	if (word == NULL)
		return;
	/*
	 * Set the insertion point to the point in the command buffer
	 * where the original (uncompleted) word now sits.
	 */
	tk_ipoint = word;
	/*
	 * Save the original (uncompleted) word
	 */
	free(tk_original);
	tk_original = ecalloc(cp-word+1, sizeof (char));
	(void) strncpy(tk_original, word, cp-word);
	/*
	 * Get the expanded filename.
	 * This may result in a single filename, or
	 * a blank-separated list of filenames.
	 */
	c = *cp;
	*cp = '\0';
	if (*word != openquote) {
		tk_text = fcomplete(word);
	} else {
		char *qword = shell_quote(word+1);
		if (qword == NULL)
			tk_text = fcomplete(word+1);
		else
			tk_text = fcomplete(qword);
		free(qword);
	}
	*cp = c;
}

/*
 * Return the next word in the current completion list.
 */
static char *
next_compl(int action, char *prev)
{
	switch (action) {
	case EC_F_COMPLETE:
		return (forw_textlist(&tk_tlist, prev));
	case EC_B_COMPLETE:
		return (back_textlist(&tk_tlist, prev));
	}
	/* Cannot happen */
	return ("?");
}

/*
 * Complete the filename before (or under) the cursor.
 * cmd_complete may be called multiple times.  The global in_completion
 * remembers whether this call is the first time (create the list),
 * or a subsequent time (step thru the list).
 */
static int
cmd_complete(int action)
{
	char *s;

	if (!in_completion || action == EC_EXPAND) {
		/*
		 * Expand the word under the cursor and
		 * use the first word in the expansion
		 * (or the entire expansion if we're doing EC_EXPAND).
		 */
		init_compl();
		if (tk_text == NULL) {
			ring_bell();
			return (CC_OK);
		}
		if (action == EC_EXPAND) {
			/*
			 * Use the whole list.
			 */
			tk_trial = tk_text;
		} else {
			/*
			 * Use the first filename in the list.
			 */
			in_completion = 1;
			init_textlist(&tk_tlist, tk_text);
			tk_trial = next_compl(action, NULL);
		}
	} else {
		/*
		 * We already have a completion list.
		 * Use the next/previous filename from the list.
		 */
		tk_trial = next_compl(action, tk_trial);
	}

	/*
	 * Remove the original word, or the previous trial completion.
	 */
	while (cp > tk_ipoint)
		(void) cmd_erase();

	if (tk_trial == NULL) {
		/*
		 * There are no more trial completions.
		 * Insert the original (uncompleted) filename.
		 */
		in_completion = 0;
		if (cmd_istr(tk_original) != CC_OK)
			goto fail;
	} else {
		/*
		 * Insert trial completion.
		 */
		if (cmd_istr(tk_trial) != CC_OK)
			goto fail;
		/*
		 * If it is a directory, append a slash.
		 */
		if (is_dir(tk_trial)) {
			if (cp > cmdbuf && cp[-1] == closequote)
				(void) cmd_erase();
			s = lgetenv("LESSSEPARATOR");
			if (s == NULL)
				s = "/";
			if (cmd_istr(s) != CC_OK)
				goto fail;
		}
	}

	return (CC_OK);

fail:
	in_completion = 0;
	ring_bell();
	return (CC_OK);
}

/*
 * Process a single character of a multi-character command, such as
 * a number, or the pattern of a search command.
 * Returns:
 *	CC_OK		The char was accepted.
 *	CC_QUIT		The char requests the command to be aborted.
 *	CC_ERROR	The char could not be accepted due to an error.
 */
int
cmd_char(int c)
{
	int action;
	int len;

	if (!utf_mode) {
		cmd_mbc_buf[0] = c & 0xff;
		len = 1;
	} else {
		/* Perform strict validation in all possible cases.  */
		if (cmd_mbc_buf_len == 0) {
retry:
			cmd_mbc_buf_index = 1;
			*cmd_mbc_buf = c & 0xff;
			if (isascii((unsigned char)c))
				cmd_mbc_buf_len = 1;
			else if (IS_UTF8_LEAD(c)) {
				cmd_mbc_buf_len = utf_len(c);
				return (CC_OK);
			} else {
				/* UTF8_INVALID or stray UTF8_TRAIL */
				ring_bell();
				return (CC_ERROR);
			}
		} else if (IS_UTF8_TRAIL(c)) {
			cmd_mbc_buf[cmd_mbc_buf_index++] = c & 0xff;
			if (cmd_mbc_buf_index < cmd_mbc_buf_len)
				return (CC_OK);
			if (!is_utf8_well_formed(cmd_mbc_buf)) {
				/*
				 * complete, but not well formed
				 * (non-shortest form), sequence
				 */
				cmd_mbc_buf_len = 0;
				ring_bell();
				return (CC_ERROR);
			}
		} else {
			/* Flush incomplete (truncated) sequence.  */
			cmd_mbc_buf_len = 0;
			ring_bell();
			/* Handle new char.  */
			goto retry;
		}

		len = cmd_mbc_buf_len;
		cmd_mbc_buf_len = 0;
	}

	if (literal) {
		/*
		 * Insert the char, even if it is a line-editing char.
		 */
		literal = 0;
		return (cmd_ichar(cmd_mbc_buf, len));
	}

	/*
	 * See if it is a line-editing character.
	 */
	if (in_mca() && len == 1) {
		action = cmd_edit(c);
		switch (action) {
		case CC_OK:
		case CC_QUIT:
			return (action);
		case CC_PASS:
			break;
		}
	}

	/*
	 * Insert the char into the command buffer.
	 */
	return (cmd_ichar(cmd_mbc_buf, len));
}

/*
 * Return the number currently in the command buffer.
 */
off_t
cmd_int(long *frac)
{
	char *p;
	off_t n = 0;
	int err;

	for (p = cmdbuf; *p >= '0' && *p <= '9'; p++)
		n = (n * 10) + (*p - '0');
	*frac = 0;
	if (*p++ == '.') {
		*frac = getfraction(&p, NULL, &err);
		/* {{ do something if err is set? }} */
	}
	return (n);
}

/*
 * Return a pointer to the command buffer.
 */
char *
get_cmdbuf(void)
{
	return (cmdbuf);
}

/*
 * Return the last (most recent) string in the current command history.
 */
char *
cmd_lastpattern(void)
{
	if (curr_mlist == NULL)
		return (NULL);
	return (curr_mlist->curr_mp->prev->string);
}

/*
 * Get the name of the history file.
 */
static char *
histfile_name(void)
{
	char *home;
	char *name;

	/* See if filename is explicitly specified by $LESSHISTFILE. */
	name = lgetenv("LESSHISTFILE");
	if (name != NULL && *name != '\0') {
		if (strcmp(name, "-") == 0 || strcmp(name, "/dev/null") == 0)
			/* $LESSHISTFILE == "-" means don't use history file */
			return (NULL);
		return (estrdup(name));
	}

	/* Otherwise, file is in $HOME if enabled. */
	if (strcmp(LESSHISTFILE, "-") == 0)
		return (NULL);
	home = lgetenv("HOME");
	if (home == NULL || *home == '\0') {
		return (NULL);
	}
	return (easprintf("%s/%s", home, LESSHISTFILE));
}

/*
 * Initialize history from a .lesshist file.
 */
void
init_cmdhist(void)
{
	struct mlist *ml = NULL;
	char line[CMDBUF_SIZE];
	char *filename;
	FILE *f;
	char *p;

	filename = histfile_name();
	if (filename == NULL)
		return;
	f = fopen(filename, "r");
	free(filename);
	if (f == NULL)
		return;
	if (fgets(line, sizeof (line), f) == NULL ||
	    strncmp(line, HISTFILE_FIRST_LINE,
	    strlen(HISTFILE_FIRST_LINE)) != 0) {
		(void) fclose(f);
		return;
	}
	while (fgets(line, sizeof (line), f) != NULL) {
		for (p = line; *p != '\0'; p++) {
			if (*p == '\n' || *p == '\r') {
				*p = '\0';
				break;
			}
		}
		if (strcmp(line, HISTFILE_SEARCH_SECTION) == 0)
			ml = &mlist_search;
		else if (strcmp(line, HISTFILE_SHELL_SECTION) == 0) {
			ml = &mlist_shell;
		} else if (*line == '"') {
			if (ml != NULL)
				cmd_addhist(ml, line+1);
		}
	}
	(void) fclose(f);
}

/*
 *
 */
static void
save_mlist(struct mlist *ml, FILE *f)
{
	int histsize = 0;
	int n;
	char *s;

	s = lgetenv("LESSHISTSIZE");
	if (s != NULL)
		histsize = atoi(s);
	if (histsize == 0)
		histsize = 100;

	ml = ml->prev;
	for (n = 0; n < histsize; n++) {
		if (ml->string == NULL)
			break;
		ml = ml->prev;
	}
	for (ml = ml->next; ml->string != NULL; ml = ml->next)
		(void) fprintf(f, "\"%s\n", ml->string);
}

/*
 *
 */
void
save_cmdhist(void)
{
	char *filename;
	FILE *f;
	int modified = 0;
	int do_chmod = 1;
	struct stat statbuf;
	int r;

	if (mlist_search.modified)
		modified = 1;
	if (mlist_shell.modified)
		modified = 1;
	if (!modified)
		return;
	filename = histfile_name();
	if (filename == NULL)
		return;
	f = fopen(filename, "w");
	free(filename);
	if (f == NULL)
		return;

	/* Make history file readable only by owner. */
	r = fstat(fileno(f), &statbuf);
	if (r == -1 || !S_ISREG(statbuf.st_mode))
		/* Don't chmod if not a regular file. */
		do_chmod = 0;
	if (do_chmod)
		(void) fchmod(fileno(f), 0600);

	(void) fprintf(f, "%s\n", HISTFILE_FIRST_LINE);

	(void) fprintf(f, "%s\n", HISTFILE_SEARCH_SECTION);
	save_mlist(&mlist_search, f);

	(void) fprintf(f, "%s\n", HISTFILE_SHELL_SECTION);
	save_mlist(&mlist_shell, f);

	(void) fclose(f);
}