readline.c

/*	$NetBSD: readline.c,v 1.21 2002/03/18 16:20:36 christos Exp $	*/

/*-
 * Copyright (c) 1997 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jaromir Dolecek.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the NetBSD
 *	Foundation, Inc. and its contributors.
 * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, 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 THE FOUNDATION 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.
 */

#include "config.h"
#if !defined(lint) && !defined(SCCSID)
__RCSID("$NetBSD: readline.c,v 1.21 2002/03/18 16:20:36 christos Exp $");
#endif /* not lint && not SCCSID */

#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <dirent.h>
#include <string.h>
#include <pwd.h>
#include <ctype.h>
#include <stdlib.h>
#include <unistd.h>
#include <limits.h>
#include "histedit.h"
#include "readline/readline.h"
#include "el.h"
#include "fcns.h"		/* for EL_NUM_FCNS */

/* for rl_complete() */
#define	TAB		'\r'

/* see comment at the #ifdef for sense of this */
#define	GDB_411_HACK

/* readline compatibility stuff - look at readline sources/documentation */
/* to see what these variables mean */
const char *rl_library_version = "EditLine wrapper";
static char empty[] = { '\0' };
static char expand_chars[] = { ' ', '\t', '\n', '=', '(', '\0' };
static char break_chars[] = { ' ', '\t', '\n', '"', '\\', '\'', '`', '@', '$',
    '>', '<', '=', ';', '|', '&', '{', '(', '\0' };
char *rl_readline_name = empty;
FILE *rl_instream = NULL;
FILE *rl_outstream = NULL;
int rl_point = 0;
int rl_end = 0;
char *rl_line_buffer = NULL;

int history_base = 1;		/* probably never subject to change */
int history_length = 0;
int max_input_history = 0;
char history_expansion_char = '!';
char history_subst_char = '^';
char *history_no_expand_chars = expand_chars;
Function *history_inhibit_expansion_function = NULL;

int rl_inhibit_completion = 0;
int rl_attempted_completion_over = 0;
char *rl_basic_word_break_characters = break_chars;
char *rl_completer_word_break_characters = NULL;
char *rl_completer_quote_characters = NULL;
CPFunction *rl_completion_entry_function = NULL;
CPPFunction *rl_attempted_completion_function = NULL;

/*
 * This is set to character indicating type of completion being done by
 * rl_complete_internal(); this is available for application completion
 * functions.
 */
int rl_completion_type = 0;

/*
 * If more than this number of items results from query for possible
 * completions, we ask user if they are sure to really display the list.
 */
int rl_completion_query_items = 100;

/*
 * List of characters which are word break characters, but should be left
 * in the parsed text when it is passed to the completion function.
 * Shell uses this to help determine what kind of completing to do.
 */
char *rl_special_prefixes = (char *)NULL;

/*
 * This is the character appended to the completed words if at the end of
 * the line. Default is ' ' (a space).
 */
int rl_completion_append_character = ' ';

/* stuff below is used internally by libedit for readline emulation */

/* if not zero, non-unique completions always show list of possible matches */
static int _rl_complete_show_all = 0;

static History *h = NULL;
static EditLine *e = NULL;
static int el_rl_complete_cmdnum = 0;

/* internal functions */
static unsigned char	 _el_rl_complete(EditLine *, int);
static char		*_get_prompt(EditLine *);
static HIST_ENTRY	*_move_history(int);
static int		 _history_search_gen(const char *, int, int);
static int		 _history_expand_command(const char *, size_t, char **);
static char		*_rl_compat_sub(const char *, const char *,
			    const char *, int);
static int		 rl_complete_internal(int);
static int		 _rl_qsort_string_compare(const void *, const void *);

/*
 * needed for prompt switching in readline()
 */
static char *el_rl_prompt = NULL;


/* ARGSUSED */
static char *
_get_prompt(EditLine *el)
{
	return (el_rl_prompt);
}


/*
 * generic function for moving around history
 */
static HIST_ENTRY *
_move_history(int op)
{
	HistEvent ev;
	static HIST_ENTRY rl_he;

	if (history(h, &ev, op) != 0)
		return (HIST_ENTRY *) NULL;

	rl_he.line = ev.str;
	rl_he.data = "";

	return (&rl_he);
}


/*
 * READLINE compatibility stuff
 */

/*
 * initialize rl compat stuff
 */
int
rl_initialize(void)
{
	HistEvent ev;
	const LineInfo *li;
	int i;
	int editmode = 1;
	struct termios t;

	if (e != NULL)
		el_end(e);
	if (h != NULL)
		history_end(h);

	if (!rl_instream)
		rl_instream = stdin;
	if (!rl_outstream)
		rl_outstream = stdout;

	/*
	 * See if we don't really want to run the editor
	 */
	if (tcgetattr(fileno(rl_instream), &t) != -1 && (t.c_lflag & ECHO) == 0)
		editmode = 0;

	e = el_init(rl_readline_name, rl_instream, rl_outstream, stderr);

	if (!editmode)
		el_set(e, EL_EDITMODE, 0);

	h = history_init();
	if (!e || !h)
		return (-1);

	history(h, &ev, H_SETSIZE, INT_MAX);	/* unlimited */
	history_length = 0;
	max_input_history = INT_MAX;
	el_set(e, EL_HIST, history, h);

	/* for proper prompt printing in readline() */
	el_rl_prompt = strdup("");
	el_set(e, EL_PROMPT, _get_prompt);
	el_set(e, EL_SIGNAL, 1);

	/* set default mode to "emacs"-style and read setting afterwards */
	/* so this can be overriden */
	el_set(e, EL_EDITOR, "emacs");

	/*
	 * Word completition - this has to go AFTER rebinding keys
	 * to emacs-style.
	 */
	el_set(e, EL_ADDFN, "rl_complete",
	    "ReadLine compatible completition function",
	    _el_rl_complete);
	el_set(e, EL_BIND, "^I", "rl_complete", NULL);

	/*
	 * Find out where the rl_complete function was added; this is
	 * used later to detect that lastcmd was also rl_complete.
	 */
	for(i=EL_NUM_FCNS; i < e->el_map.nfunc; i++) {
		if (e->el_map.func[i] == _el_rl_complete) {
			el_rl_complete_cmdnum = i;
			break;
		}
	}
		
	/* read settings from configuration file */
	el_source(e, NULL);

	/*
	 * Unfortunately, some applications really do use rl_point
	 * and rl_line_buffer directly.
	 */
	li = el_line(e);
	/* a cheesy way to get rid of const cast. */
	rl_line_buffer = memchr(li->buffer, *li->buffer, 1);
	rl_point = rl_end = 0;

	return (0);
}


/*
 * read one line from input stream and return it, chomping
 * trailing newline (if there is any)
 */
char *
readline(const char *prompt)
{
	HistEvent ev;
	int count;
	const char *ret;
	char *buf;

	if (e == NULL || h == NULL)
		rl_initialize();

	/* update prompt accordingly to what has been passed */
	if (!prompt)
		prompt = "";
	if (strcmp(el_rl_prompt, prompt) != 0) {
		free(el_rl_prompt);
		el_rl_prompt = strdup(prompt);
	}
	/* get one line from input stream */
	ret = el_gets(e, &count);

	if (ret && count > 0) {
		int lastidx;

		buf = strdup(ret);
		lastidx = count - 1;
		if (buf[lastidx] == '\n')
			buf[lastidx] = '\0';
	} else
		buf = NULL;

	history(h, &ev, H_GETSIZE);
	history_length = ev.num;

	return buf;
}

/*
 * history functions
 */

/*
 * is normally called before application starts to use
 * history expansion functions
 */
void
using_history(void)
{
	if (h == NULL || e == NULL)
		rl_initialize();
}


/*
 * substitute ``what'' with ``with'', returning resulting string; if
 * globally == 1, substitutes all occurences of what, otherwise only the
 * first one
 */
static char *
_rl_compat_sub(const char *str, const char *what, const char *with,
    int globally)
{
	char *result;
	const char *temp, *new;
	int len, with_len, what_len, add;
	size_t size, i;

	result = malloc((size = 16));
	temp = str;
	with_len = strlen(with);
	what_len = strlen(what);
	len = 0;
	do {
		new = strstr(temp, what);
		if (new) {
			i = new - temp;
			add = i + with_len;
			if (i + add + 1 >= size) {
				size += add + 1;
				result = realloc(result, size);
			}
			(void) strncpy(&result[len], temp, i);
			len += i;
			(void) strcpy(&result[len], with);	/* safe */
			len += with_len;
			temp = new + what_len;
		} else {
			add = strlen(temp);
			if (len + add + 1 >= size) {
				size += add + 1;
				result = realloc(result, size);
			}
			(void) strcpy(&result[len], temp);	/* safe */
			len += add;
			temp = NULL;
		}
	} while (temp && globally);
	result[len] = '\0';

	return (result);
}


/*
 * the real function doing history expansion - takes as argument command
 * to do and data upon which the command should be executed
 * does expansion the way I've understood readline documentation
 * word designator ``%'' isn't supported (yet ?)
 *
 * returns 0 if data was not modified, 1 if it was and 2 if the string
 * should be only printed and not executed; in case of error,
 * returns -1 and *result points to NULL
 * it's callers responsibility to free() string returned in *result
 */
static int
_history_expand_command(const char *command, size_t cmdlen, char **result)
{
	char **arr, *tempcmd, *line, *search = NULL, *cmd;
	const char *event_data = NULL;
	static char *from = NULL, *to = NULL;
	int start = -1, end = -1, max, i, idx;
	int h_on = 0, t_on = 0, r_on = 0, e_on = 0, p_on = 0, g_on = 0;
	int event_num = 0, retval;
	size_t cmdsize;

	*result = NULL;

	cmd = alloca(cmdlen + 1);
	(void) strncpy(cmd, command, cmdlen);
	cmd[cmdlen] = 0;

	idx = 1;
	/* find out which event to take */
	if (cmd[idx] == history_expansion_char) {
		event_num = history_length;
		idx++;
	} else {
		int off, num;
		size_t len;
		off = idx;
		while (cmd[off] && !strchr(":^$*-%", cmd[off]))
			off++;
		num = atoi(&cmd[idx]);
		if (num != 0) {
			event_num = num;
			if (num < 0)
				event_num += history_length + 1;
		} else {
			int prefix = 1, curr_num;
			HistEvent ev;

			len = off - idx;
			if (cmd[idx] == '?') {
				idx++, len--;
				if (cmd[off - 1] == '?')
					len--;
				else if (cmd[off] != '\n' && cmd[off] != '\0')
					return (-1);
				prefix = 0;
			}
			search = alloca(len + 1);
			(void) strncpy(search, &cmd[idx], len);
			search[len] = '\0';

			if (history(h, &ev, H_CURR) != 0)
				return (-1);
			curr_num = ev.num;

			if (prefix)
				retval = history_search_prefix(search, -1);
			else
				retval = history_search(search, -1);

			if (retval == -1) {
				fprintf(rl_outstream, "%s: Event not found\n",
				    search);
				return (-1);
			}
			if (history(h, &ev, H_CURR) != 0)
				return (-1);
			event_data = ev.str;

			/* roll back to original position */
			history(h, &ev, H_NEXT_EVENT, curr_num);
		}
		idx = off;
	}

	if (!event_data && event_num >= 0) {
		HIST_ENTRY *rl_he;
		rl_he = history_get(event_num);
		if (!rl_he)
			return (0);
		event_data = rl_he->line;
	} else
		return (-1);

	if (cmd[idx] != ':')
		return (-1);
	cmd += idx + 1;

	/* recognize cmd */
	if (*cmd == '^')
		start = end = 1, cmd++;
	else if (*cmd == '$')
		start = end = -1, cmd++;
	else if (*cmd == '*')
		start = 1, end = -1, cmd++;
	else if (isdigit((unsigned char) *cmd)) {
		const char *temp;
		int shifted = 0;

		start = atoi(cmd);
		temp = cmd;
		for (; isdigit((unsigned char) *cmd); cmd++);
		if (temp != cmd)
			shifted = 1;
		if (shifted && *cmd == '-') {
			if (!isdigit((unsigned char) *(cmd + 1)))
				end = -2;
			else {
				end = atoi(cmd + 1);
				for (; isdigit((unsigned char) *cmd); cmd++);
			}
		} else if (shifted && *cmd == '*')
			end = -1, cmd++;
		else if (shifted)
			end = start;
	}
	if (*cmd == ':')
		cmd++;

	line = strdup(event_data);
	for (; *cmd; cmd++) {
		if (*cmd == ':')
			continue;
		else if (*cmd == 'h')
			h_on = 1 | g_on, g_on = 0;
		else if (*cmd == 't')
			t_on = 1 | g_on, g_on = 0;
		else if (*cmd == 'r')
			r_on = 1 | g_on, g_on = 0;
		else if (*cmd == 'e')
			e_on = 1 | g_on, g_on = 0;
		else if (*cmd == 'p')
			p_on = 1 | g_on, g_on = 0;
		else if (*cmd == 'g')
			g_on = 2;
		else if (*cmd == 's' || *cmd == '&') {
			char *what, *with, delim;
			int len, from_len;
			size_t size;

			if (*cmd == '&' && (from == NULL || to == NULL))
				continue;
			else if (*cmd == 's') {
				delim = *(++cmd), cmd++;
				size = 16;
				what = realloc(from, size);
				len = 0;
				for (; *cmd && *cmd != delim; cmd++) {
					if (*cmd == '\\'
					    && *(cmd + 1) == delim)
						cmd++;
					if (len >= size)
						what = realloc(what,
						    (size <<= 1));
					what[len++] = *cmd;
				}
				what[len] = '\0';
				from = what;
				if (*what == '\0') {
					free(what);
					if (search)
						from = strdup(search);
					else {
						from = NULL;
						return (-1);
					}
				}
				cmd++;	/* shift after delim */
				if (!*cmd)
					continue;

				size = 16;
				with = realloc(to, size);
				len = 0;
				from_len = strlen(from);
				for (; *cmd && *cmd != delim; cmd++) {
					if (len + from_len + 1 >= size) {
						size += from_len + 1;
						with = realloc(with, size);
					}
					if (*cmd == '&') {
						/* safe */
						(void) strcpy(&with[len], from);
						len += from_len;
						continue;
					}
					if (*cmd == '\\'
					    && (*(cmd + 1) == delim
						|| *(cmd + 1) == '&'))
						cmd++;
					with[len++] = *cmd;
				}
				with[len] = '\0';
				to = with;

				tempcmd = _rl_compat_sub(line, from, to,
				    (g_on) ? 1 : 0);
				free(line);
				line = tempcmd;
				g_on = 0;
			}
		}
	}

	arr = history_tokenize(line);
	free(line);		/* no more needed */
	if (arr && *arr == NULL)
		free(arr), arr = NULL;
	if (!arr)
		return (-1);

	/* find out max valid idx to array of array */
	max = 0;
	for (i = 0; arr[i]; i++)
		max++;
	max--;

	/* set boundaries to something relevant */
	if (start < 0)
		start = 1;
	if (end < 0)
		end = max - ((end < -1) ? 1 : 0);

	/* check boundaries ... */
	if (start > max || end > max || start > end)
		return (-1);

	for (i = 0; i <= max; i++) {
		char *temp;
		if (h_on && (i == 1 || h_on > 1) &&
		    (temp = strrchr(arr[i], '/')))
			*(temp + 1) = '\0';
		if (t_on && (i == 1 || t_on > 1) &&
		    (temp = strrchr(arr[i], '/')))
			(void) strcpy(arr[i], temp + 1);
		if (r_on && (i == 1 || r_on > 1) &&
		    (temp = strrchr(arr[i], '.')))
			*temp = '\0';
		if (e_on && (i == 1 || e_on > 1) &&
		    (temp = strrchr(arr[i], '.')))
			(void) strcpy(arr[i], temp);
	}

	cmdsize = 1, cmdlen = 0;
	tempcmd = malloc(cmdsize);
	for (i = start; start <= i && i <= end; i++) {
		int arr_len;

		arr_len = strlen(arr[i]);
		if (cmdlen + arr_len + 1 >= cmdsize) {
			cmdsize += arr_len + 1;
			tempcmd = realloc(tempcmd, cmdsize);
		}
		(void) strcpy(&tempcmd[cmdlen], arr[i]);	/* safe */
		cmdlen += arr_len;
		tempcmd[cmdlen++] = ' ';	/* add a space */
	}
	while (cmdlen > 0 && isspace((unsigned char) tempcmd[cmdlen - 1]))
		cmdlen--;
	tempcmd[cmdlen] = '\0';

	*result = tempcmd;

	for (i = 0; i <= max; i++)
		free(arr[i]);
	free(arr), arr = (char **) NULL;
	return (p_on) ? 2 : 1;
}


/*
 * csh-style history expansion
 */
int
history_expand(char *str, char **output)
{
	int i, retval = 0, idx;
	size_t size;
	char *temp, *result;

	if (h == NULL || e == NULL)
		rl_initialize();

	*output = strdup(str);	/* do it early */

	if (str[0] == history_subst_char) {
		/* ^foo^foo2^ is equivalent to !!:s^foo^foo2^ */
		temp = alloca(4 + strlen(str) + 1);
		temp[0] = temp[1] = history_expansion_char;
		temp[2] = ':';
		temp[3] = 's';
		(void) strcpy(temp + 4, str);
		str = temp;
	}
#define	ADD_STRING(what, len) 						\
	{								\
		if (idx + len + 1 > size)				\
			result = realloc(result, (size += len + 1));	\
		(void)strncpy(&result[idx], what, len);			\
		idx += len;						\
		result[idx] = '\0';					\
	}

	result = NULL;
	size = idx = 0;
	for (i = 0; str[i];) {
		int start, j, loop_again;
		size_t len;

		loop_again = 1;
		start = j = i;
loop:
		for (; str[j]; j++) {
			if (str[j] == '\\' &&
			    str[j + 1] == history_expansion_char) {
				(void) strcpy(&str[j], &str[j + 1]);
				continue;
			}
			if (!loop_again) {
				if (str[j] == '?') {
					while (str[j] && str[++j] != '?');
					if (str[j] == '?')
						j++;
				} else if (isspace((unsigned char) str[j]))
					break;
			}
			if (str[j] == history_expansion_char
			    && !strchr(history_no_expand_chars, str[j + 1])
			    && (!history_inhibit_expansion_function ||
			    (*history_inhibit_expansion_function)(str, j) == 0))
				break;
		}

		if (str[j] && str[j + 1] != '#' && loop_again) {
			i = j;
			j++;
			if (str[j] == history_expansion_char)
				j++;
			loop_again = 0;
			goto loop;
		}
		len = i - start;
		temp = &str[start];
		ADD_STRING(temp, len);

		if (str[i] == '\0' || str[i] != history_expansion_char
		    || str[i + 1] == '#') {
			len = j - i;
			temp = &str[i];
			ADD_STRING(temp, len);
			if (start == 0)
				retval = 0;
			else
				retval = 1;
			break;
		}
		retval = _history_expand_command(&str[i], (size_t) (j - i),
		    &temp);
		if (retval != -1) {
			len = strlen(temp);
			ADD_STRING(temp, len);
		}
		i = j;
	}			/* for(i ...) */

	if (retval == 2) {
		add_history(temp);
#ifdef GDB_411_HACK
		/* gdb 4.11 has been shipped with readline, where */
		/* history_expand() returned -1 when the line	  */
		/* should not be executed; in readline 2.1+	  */
		/* it should return 2 in such a case		  */
		retval = -1;
#endif
	}
	free(*output);
	*output = result;

	return (retval);
}


/*
 * Parse the string into individual tokens, similarily to how shell would do it.
 */
char **
history_tokenize(const char *str)
{
	int size = 1, result_idx = 0, i, start;
	size_t len;
	char **result = NULL, *temp, delim = '\0';

	for (i = 0; str[i]; i++) {
		while (isspace((unsigned char) str[i]))
			i++;
		start = i;
		for (; str[i]; i++) {
			if (str[i] == '\\') {
				if (str[i+1] != '\0')
					i++;
			} else if (str[i] == delim)
				delim = '\0';
			else if (!delim &&
				    (isspace((unsigned char) str[i]) ||
				strchr("()<>;&|$", str[i])))
				break;
			else if (!delim && strchr("'`\"", str[i]))
				delim = str[i];
		}

		if (result_idx + 2 >= size) {
			size <<= 1;
			result = realloc(result, size * sizeof(char *));
		}
		len = i - start;
		temp = malloc(len + 1);
		(void) strncpy(temp, &str[start], len);
		temp[len] = '\0';
		result[result_idx++] = temp;
		result[result_idx] = NULL;
	}

	return (result);
}


/*
 * limit size of history record to ``max'' events
 */
void
stifle_history(int max)
{
	HistEvent ev;

	if (h == NULL || e == NULL)
		rl_initialize();

	if (history(h, &ev, H_SETSIZE, max) == 0)
		max_input_history = max;
}


/*
 * "unlimit" size of history - set the limit to maximum allowed int value
 */
int
unstifle_history(void)
{
	HistEvent ev;
	int omax;

	history(h, &ev, H_SETSIZE, INT_MAX);
	omax = max_input_history;
	max_input_history = INT_MAX;
	return (omax);		/* some value _must_ be returned */
}


int
history_is_stifled(void)
{

	/* cannot return true answer */
	return (max_input_history != INT_MAX);
}


/*
 * read history from a file given
 */
int
read_history(const char *filename)
{
	HistEvent ev;

	if (h == NULL || e == NULL)
		rl_initialize();
	return (history(h, &ev, H_LOAD, filename));
}


/*
 * write history to a file given
 */
int
write_history(const char *filename)
{
	HistEvent ev;

	if (h == NULL || e == NULL)
		rl_initialize();
	return (history(h, &ev, H_SAVE, filename));
}


/*
 * returns history ``num''th event
 *
 * returned pointer points to static variable
 */
HIST_ENTRY *
history_get(int num)
{
	static HIST_ENTRY she;
	HistEvent ev;
	int i = 1, curr_num;

	if (h == NULL || e == NULL)
		rl_initialize();

	/* rewind to beginning */
	if (history(h, &ev, H_CURR) != 0)
		return (NULL);
	curr_num = ev.num;
	if (history(h, &ev, H_LAST) != 0)
		return (NULL);	/* error */
	while (i < num && history(h, &ev, H_PREV) == 0)
		i++;
	if (i != num)
		return (NULL);	/* not so many entries */

	she.line = ev.str;
	she.data = NULL;

	/* rewind history to the same event it was before */
	(void) history(h, &ev, H_FIRST);
	(void) history(h, &ev, H_NEXT_EVENT, curr_num);

	return (&she);
}


/*
 * add the line to history table
 */
int
add_history(const char *line)
{
	HistEvent ev;

	if (h == NULL || e == NULL)
		rl_initialize();

	(void) history(h, &ev, H_ENTER, line);
	if (history(h, &ev, H_GETSIZE) == 0)
		history_length = ev.num;

	return (!(history_length > 0));	/* return 0 if all is okay */
}


/*
 * clear the history list - delete all entries
 */
void
clear_history(void)
{
	HistEvent ev;

	history(h, &ev, H_CLEAR);
}


/*
 * returns offset of the current history event
 */
int
where_history(void)
{
	HistEvent ev;
	int curr_num, off;

	if (history(h, &ev, H_CURR) != 0)
		return (0);
	curr_num = ev.num;

	history(h, &ev, H_FIRST);
	off = 1;
	while (ev.num != curr_num && history(h, &ev, H_NEXT) == 0)
		off++;

	return (off);
}


/*
 * returns current history event or NULL if there is no such event
 */
HIST_ENTRY *
current_history(void)
{

	return (_move_history(H_CURR));
}


/*
 * returns total number of bytes history events' data are using
 */
int
history_total_bytes(void)
{
	HistEvent ev;
	int curr_num, size;

	if (history(h, &ev, H_CURR) != 0)
		return (-1);
	curr_num = ev.num;

	history(h, &ev, H_FIRST);
	size = 0;
	do
		size += strlen(ev.str);
	while (history(h, &ev, H_NEXT) == 0);

	/* get to the same position as before */
	history(h, &ev, H_PREV_EVENT, curr_num);

	return (size);