decode.c revision 89019 
1/*
2 * Copyright (C) 1984-2000  Mark Nudelman
3 *
4 * You may distribute under the terms of either the GNU General Public
5 * License or the Less License, as specified in the README file.
6 *
7 * For more information about less, or for information on how to
8 * contact the author, see the README file.
9 */
10
11
12/*
13 * Routines to decode user commands.
14 *
15 * This is all table driven.
16 * A command table is a sequence of command descriptors.
17 * Each command descriptor is a sequence of bytes with the following format:
18 *	<c1><c2>...<cN><0><action>
19 * The characters c1,c2,...,cN are the command string; that is,
20 * the characters which the user must type.
21 * It is terminated by a null <0> byte.
22 * The byte after the null byte is the action code associated
23 * with the command string.
24 * If an action byte is OR-ed with A_EXTRA, this indicates
25 * that the option byte is followed by an extra string.
26 *
27 * There may be many command tables.
28 * The first (default) table is built-in.
29 * Other tables are read in from "lesskey" files.
30 * All the tables are linked together and are searched in order.
31 */
32
33#include "less.h"
34#include "cmd.h"
35#include "lesskey.h"
36
37extern int erase_char, kill_char;
38extern int secure;
39
40#define SK(k) \
41	SK_SPECIAL_KEY, (k), 6, 1, 1, 1
42/*
43 * Command table is ordered roughly according to expected
44 * frequency of use, so the common commands are near the beginning.
45 */
46
47static unsigned char cmdtable[] =
48{
49	'\r',0,				A_F_LINE,
50	'\n',0,				A_F_LINE,
51	'e',0,				A_F_LINE,
52	'j',0,				A_F_LINE,
53	SK(SK_DOWN_ARROW),0,		A_F_LINE,
54	CONTROL('E'),0,			A_F_LINE,
55	CONTROL('N'),0,			A_F_LINE,
56	'k',0,				A_B_LINE,
57	'y',0,				A_B_LINE,
58	CONTROL('Y'),0,			A_B_LINE,
59	SK(SK_CONTROL_K),0,		A_B_LINE,
60	CONTROL('P'),0,			A_B_LINE,
61	SK(SK_UP_ARROW),0,		A_B_LINE,
62	'J',0,				A_FF_LINE,
63	'K',0,				A_BF_LINE,
64	'Y',0,				A_BF_LINE,
65	'd',0,				A_F_SCROLL,
66	CONTROL('D'),0,			A_F_SCROLL,
67	'u',0,				A_B_SCROLL,
68	CONTROL('U'),0,			A_B_SCROLL,
69	' ',0,				A_F_SCREEN,
70	'f',0,				A_F_SCREEN,
71	CONTROL('F'),0,			A_F_SCREEN,
72	CONTROL('V'),0,			A_F_SCREEN,
73	SK(SK_PAGE_DOWN),0,		A_F_SCREEN,
74	'b',0,				A_B_SCREEN,
75	CONTROL('B'),0,			A_B_SCREEN,
76	ESC,'v',0,			A_B_SCREEN,
77	SK(SK_PAGE_UP),0,		A_B_SCREEN,
78	'z',0,				A_F_WINDOW,
79	'w',0,				A_B_WINDOW,
80	ESC,' ',0,			A_FF_SCREEN,
81	'F',0,				A_F_FOREVER,
82	'R',0,				A_FREPAINT,
83	'r',0,				A_REPAINT,
84	CONTROL('R'),0,			A_REPAINT,
85	CONTROL('L'),0,			A_REPAINT,
86	ESC,'u',0,			A_UNDO_SEARCH,
87	'g',0,				A_GOLINE,
88	SK(SK_HOME),0,			A_GOLINE,
89	'<',0,				A_GOLINE,
90	ESC,'<',0,			A_GOLINE,
91	'p',0,				A_PERCENT,
92	'%',0,				A_PERCENT,
93	ESC,'[',0,			A_LSHIFT,
94	ESC,']',0,			A_RSHIFT,
95	ESC,'(',0,			A_LSHIFT,
96	ESC,')',0,			A_RSHIFT,
97	SK(SK_RIGHT_ARROW),0,		A_RSHIFT,
98	SK(SK_LEFT_ARROW),0,		A_LSHIFT,
99	'{',0,				A_F_BRACKET|A_EXTRA,	'{','}',0,
100	'}',0,				A_B_BRACKET|A_EXTRA,	'{','}',0,
101	'(',0,				A_F_BRACKET|A_EXTRA,	'(',')',0,
102	')',0,				A_B_BRACKET|A_EXTRA,	'(',')',0,
103	'[',0,				A_F_BRACKET|A_EXTRA,	'[',']',0,
104	']',0,				A_B_BRACKET|A_EXTRA,	'[',']',0,
105	ESC,CONTROL('F'),0,		A_F_BRACKET,
106	ESC,CONTROL('B'),0,		A_B_BRACKET,
107	'G',0,				A_GOEND,
108	ESC,'>',0,			A_GOEND,
109	'>',0,				A_GOEND,
110	SK(SK_END),0,			A_GOEND,
111	'P',0,				A_GOPOS,
112
113	'0',0,				A_DIGIT,
114	'1',0,				A_DIGIT,
115	'2',0,				A_DIGIT,
116	'3',0,				A_DIGIT,
117	'4',0,				A_DIGIT,
118	'5',0,				A_DIGIT,
119	'6',0,				A_DIGIT,
120	'7',0,				A_DIGIT,
121	'8',0,				A_DIGIT,
122	'9',0,				A_DIGIT,
123
124	'=',0,				A_STAT,
125	CONTROL('G'),0,			A_STAT,
126	':','f',0,			A_STAT,
127	'/',0,				A_F_SEARCH,
128	'?',0,				A_B_SEARCH,
129	ESC,'/',0,			A_F_SEARCH|A_EXTRA,	'*',0,
130	ESC,'?',0,			A_B_SEARCH|A_EXTRA,	'*',0,
131	'n',0,				A_AGAIN_SEARCH,
132	ESC,'n',0,			A_T_AGAIN_SEARCH,
133	'N',0,				A_REVERSE_SEARCH,
134	ESC,'N',0,			A_T_REVERSE_SEARCH,
135	'm',0,				A_SETMARK,
136	'\'',0,				A_GOMARK,
137	CONTROL('X'),CONTROL('X'),0,	A_GOMARK,
138	'E',0,				A_EXAMINE,
139	':','e',0,			A_EXAMINE,
140	CONTROL('X'),CONTROL('V'),0,	A_EXAMINE,
141	':','n',0,			A_NEXT_FILE,
142	':','p',0,			A_PREV_FILE,
143	't',0,				A_NEXT_TAG,
144	'T',0,				A_PREV_TAG,
145	':','x',0,			A_INDEX_FILE,
146	':','d',0,			A_REMOVE_FILE,
147	'-',0,				A_OPT_TOGGLE,
148	':','t',0,			A_OPT_TOGGLE|A_EXTRA,	't',0,
149	's',0,				A_OPT_TOGGLE|A_EXTRA,	'o',0,
150	'_',0,				A_DISP_OPTION,
151	'|',0,				A_PIPE,
152	'v',0,				A_VISUAL,
153	'!',0,				A_SHELL,
154	'+',0,				A_FIRSTCMD,
155
156	'H',0,				A_HELP,
157	'h',0,				A_HELP,
158	SK(SK_F1),0,			A_HELP,
159	'V',0,				A_VERSION,
160	'q',0,				A_QUIT,
161	'Q',0,				A_QUIT,
162	':','q',0,			A_QUIT,
163	':','Q',0,			A_QUIT,
164	'Z','Z',0,			A_QUIT
165};
166
167static unsigned char edittable[] =
168{
169	'\t',0,	    			EC_F_COMPLETE,	/* TAB */
170	'\17',0,			EC_B_COMPLETE,	/* BACKTAB */
171	SK(SK_BACKTAB),0,		EC_B_COMPLETE,	/* BACKTAB */
172	ESC,'\t',0,			EC_B_COMPLETE,	/* ESC TAB */
173	CONTROL('L'),0,			EC_EXPAND,	/* CTRL-L */
174	CONTROL('V'),0,			EC_LITERAL,	/* BACKSLASH */
175	CONTROL('A'),0,			EC_LITERAL,	/* BACKSLASH */
176   	ESC,'l',0,			EC_RIGHT,	/* ESC l */
177	SK(SK_RIGHT_ARROW),0,		EC_RIGHT,	/* RIGHTARROW */
178	ESC,'h',0,			EC_LEFT,	/* ESC h */
179	SK(SK_LEFT_ARROW),0,		EC_LEFT,	/* LEFTARROW */
180	ESC,'b',0,			EC_W_LEFT,	/* ESC b */
181	ESC,SK(SK_LEFT_ARROW),0,	EC_W_LEFT,	/* ESC LEFTARROW */
182	SK(SK_CTL_LEFT_ARROW),0,	EC_W_LEFT,	/* CTRL-LEFTARROW */
183	ESC,'w',0,			EC_W_RIGHT,	/* ESC w */
184	ESC,SK(SK_RIGHT_ARROW),0,	EC_W_RIGHT,	/* ESC RIGHTARROW */
185	SK(SK_CTL_RIGHT_ARROW),0,	EC_W_RIGHT,	/* CTRL-RIGHTARROW */
186	ESC,'i',0,			EC_INSERT,	/* ESC i */
187	SK(SK_INSERT),0,		EC_INSERT,	/* INSERT */
188	ESC,'x',0,			EC_DELETE,	/* ESC x */
189	SK(SK_DELETE),0,		EC_DELETE,	/* DELETE */
190	ESC,'X',0,			EC_W_DELETE,	/* ESC X */
191	ESC,SK(SK_DELETE),0,		EC_W_DELETE,	/* ESC DELETE */
192	SK(SK_CTL_DELETE),0,		EC_W_DELETE,	/* CTRL-DELETE */
193	SK(SK_CTL_BACKSPACE),0,		EC_W_BACKSPACE, /* CTRL-BACKSPACE */
194	ESC,'\b',0,			EC_W_BACKSPACE,	/* ESC BACKSPACE */
195	ESC,'0',0,			EC_HOME,	/* ESC 0 */
196	SK(SK_HOME),0,			EC_HOME,	/* HOME */
197	ESC,'$',0,			EC_END,		/* ESC $ */
198	SK(SK_END),0,			EC_END,		/* END */
199	ESC,'k',0,			EC_UP,		/* ESC k */
200	SK(SK_UP_ARROW),0,		EC_UP,		/* UPARROW */
201	ESC,'j',0,			EC_DOWN,	/* ESC j */
202	SK(SK_DOWN_ARROW),0,		EC_DOWN,	/* DOWNARROW */
203};
204
205/*
206 * Structure to support a list of command tables.
207 */
208struct tablelist
209{
210	struct tablelist *t_next;
211	char *t_start;
212	char *t_end;
213};
214
215/*
216 * List of command tables and list of line-edit tables.
217 */
218static struct tablelist *list_fcmd_tables = NULL;
219static struct tablelist *list_ecmd_tables = NULL;
220static struct tablelist *list_var_tables = NULL;
221static struct tablelist *list_sysvar_tables = NULL;
222
223
224/*
225 * Expand special key abbreviations in a command table.
226 */
227	static void
228expand_special_keys(table, len)
229	char *table;
230	int len;
231{
232	register char *fm;
233	register char *to;
234	register int a;
235	char *repl;
236	int klen;
237
238	for (fm = table;  fm < table + len; )
239	{
240		/*
241		 * Rewrite each command in the table with any
242		 * special key abbreviations expanded.
243		 */
244		for (to = fm;  *fm != '\0'; )
245		{
246			if (*fm != SK_SPECIAL_KEY)
247			{
248				*to++ = *fm++;
249				continue;
250			}
251			/*
252			 * After SK_SPECIAL_KEY, next byte is the type
253			 * of special key (one of the SK_* contants),
254			 * and the byte after that is the number of bytes,
255			 * N, reserved by the abbreviation (including the
256			 * SK_SPECIAL_KEY and key type bytes).
257			 * Replace all N bytes with the actual bytes
258			 * output by the special key on this terminal.
259			 */
260			repl = special_key_str(fm[1]);
261			klen = fm[2] & 0377;
262			fm += klen;
263			if (repl == NULL || strlen(repl) > klen)
264				repl = "\377";
265			while (*repl != '\0')
266				*to++ = *repl++;
267		}
268		*to++ = '\0';
269		/*
270		 * Fill any unused bytes between end of command and
271		 * the action byte with A_SKIP.
272		 */
273		while (to <= fm)
274			*to++ = A_SKIP;
275		fm++;
276		a = *fm++ & 0377;
277		if (a & A_EXTRA)
278		{
279			while (*fm++ != '\0')
280				continue;
281		}
282	}
283}
284
285/*
286 * Initialize the command lists.
287 */
288	public void
289init_cmds()
290{
291	/*
292	 * Add the default command tables.
293	 */
294	add_fcmd_table((char*)cmdtable, sizeof(cmdtable));
295	add_ecmd_table((char*)edittable, sizeof(edittable));
296#if USERFILE
297	/*
298	 * For backwards compatibility,
299	 * try to add tables in the OLD system lesskey file.
300	 */
301#ifdef BINDIR
302	add_hometable(NULL, BINDIR "/.sysless", 1);
303#endif
304	/*
305	 * Try to add the tables in the system lesskey file.
306	 */
307	add_hometable("LESSKEY_SYSTEM", LESSKEYFILE_SYS, 1);
308	/*
309	 * Try to add the tables in the standard lesskey file "$HOME/.less".
310	 */
311	add_hometable("LESSKEY", LESSKEYFILE, 0);
312#endif
313}
314
315/*
316 * Add a command table.
317 */
318	static int
319add_cmd_table(tlist, buf, len)
320	struct tablelist **tlist;
321	char *buf;
322	int len;
323{
324	register struct tablelist *t;
325
326	if (len == 0)
327		return (0);
328	/*
329	 * Allocate a tablelist structure, initialize it,
330	 * and link it into the list of tables.
331	 */
332	if ((t = (struct tablelist *)
333			calloc(1, sizeof(struct tablelist))) == NULL)
334	{
335		return (-1);
336	}
337	expand_special_keys(buf, len);
338	t->t_start = buf;
339	t->t_end = buf + len;
340	t->t_next = *tlist;
341	*tlist = t;
342	return (0);
343}
344
345/*
346 * Add a command table.
347 */
348	public void
349add_fcmd_table(buf, len)
350	char *buf;
351	int len;
352{
353	if (add_cmd_table(&list_fcmd_tables, buf, len) < 0)
354		error("Warning: some commands disabled", NULL_PARG);
355}
356
357/*
358 * Add an editing command table.
359 */
360	public void
361add_ecmd_table(buf, len)
362	char *buf;
363	int len;
364{
365	if (add_cmd_table(&list_ecmd_tables, buf, len) < 0)
366		error("Warning: some edit commands disabled", NULL_PARG);
367}
368
369/*
370 * Add an environment variable table.
371 */
372	static void
373add_var_table(tlist, buf, len)
374	struct tablelist **tlist;
375	char *buf;
376	int len;
377{
378	if (add_cmd_table(tlist, buf, len) < 0)
379		error("Warning: environment variables from lesskey file unavailable", NULL_PARG);
380}
381
382/*
383 * Search a single command table for the command string in cmd.
384 */
385	static int
386cmd_search(cmd, table, endtable, sp)
387	char *cmd;
388	char *table;
389	char *endtable;
390	char **sp;
391{
392	register char *p;
393	register char *q;
394	register int a;
395
396	*sp = NULL;
397	for (p = table, q = cmd;  p < endtable;  p++, q++)
398	{
399		if (*p == *q)
400		{
401			/*
402			 * Current characters match.
403			 * If we're at the end of the string, we've found it.
404			 * Return the action code, which is the character
405			 * after the null at the end of the string
406			 * in the command table.
407			 */
408			if (*p == '\0')
409			{
410				a = *++p & 0377;
411				while (a == A_SKIP)
412					a = *++p & 0377;
413				if (a == A_END_LIST)
414				{
415					/*
416					 * We get here only if the original
417					 * cmd string passed in was empty ("").
418					 * I don't think that can happen,
419					 * but just in case ...
420					 */
421					return (A_UINVALID);
422				}
423				/*
424				 * Check for an "extra" string.
425				 */
426				if (a & A_EXTRA)
427				{
428					*sp = ++p;
429					a &= ~A_EXTRA;
430				}
431				return (a);
432			}
433		} else if (*q == '\0')
434		{
435			/*
436			 * Hit the end of the user's command,
437			 * but not the end of the string in the command table.
438			 * The user's command is incomplete.
439			 */
440			return (A_PREFIX);
441		} else
442		{
443			/*
444			 * Not a match.
445			 * Skip ahead to the next command in the
446			 * command table, and reset the pointer
447			 * to the beginning of the user's command.
448			 */
449			if (*p == '\0' && p[1] == A_END_LIST)
450			{
451				/*
452				 * A_END_LIST is a special marker that tells
453				 * us to abort the cmd search.
454				 */
455				return (A_UINVALID);
456			}
457			while (*p++ != '\0')
458				continue;
459			while (*p == A_SKIP)
460				p++;
461			if (*p & A_EXTRA)
462				while (*++p != '\0')
463					continue;
464			q = cmd-1;
465		}
466	}
467	/*
468	 * No match found in the entire command table.
469	 */
470	return (A_INVALID);
471}
472
473/*
474 * Decode a command character and return the associated action.
475 * The "extra" string, if any, is returned in sp.
476 */
477	static int
478cmd_decode(tlist, cmd, sp)
479	struct tablelist *tlist;
480	char *cmd;
481	char **sp;
482{
483	register struct tablelist *t;
484	register int action = A_INVALID;
485
486	/*
487	 * Search thru all the command tables.
488	 * Stop when we find an action which is not A_INVALID.
489	 */
490	for (t = tlist;  t != NULL;  t = t->t_next)
491	{
492		action = cmd_search(cmd, t->t_start, t->t_end, sp);
493		if (action != A_INVALID)
494			break;
495	}
496	if (action == A_UINVALID)
497		action = A_INVALID;
498	return (action);
499}
500
501/*
502 * Decode a command from the cmdtables list.
503 */
504	public int
505fcmd_decode(cmd, sp)
506	char *cmd;
507	char **sp;
508{
509	return (cmd_decode(list_fcmd_tables, cmd, sp));
510}
511
512/*
513 * Decode a command from the edittables list.
514 */
515	public int
516ecmd_decode(cmd, sp)
517	char *cmd;
518	char **sp;
519{
520	return (cmd_decode(list_ecmd_tables, cmd, sp));
521}
522
523/*
524 * Get the value of an environment variable.
525 * Looks first in the lesskey file, then in the real environment.
526 */
527	public char *
528lgetenv(var)
529	char *var;
530{
531	int a;
532	char *s;
533
534	a = cmd_decode(list_var_tables, var, &s);
535	if (a == EV_OK)
536		return (s);
537	s = getenv(var);
538	if (s != NULL && *s != '\0')
539		return (s);
540	a = cmd_decode(list_sysvar_tables, var, &s);
541	if (a == EV_OK)
542		return (s);
543	return (NULL);
544}
545
546#if USERFILE
547/*
548 * Get an "integer" from a lesskey file.
549 * Integers are stored in a funny format:
550 * two bytes, low order first, in radix KRADIX.
551 */
552	static int
553gint(sp)
554	char **sp;
555{
556	int n;
557
558	n = *(*sp)++;
559	n += *(*sp)++ * KRADIX;
560	return (n);
561}
562
563/*
564 * Process an old (pre-v241) lesskey file.
565 */
566	static int
567old_lesskey(buf, len)
568	char *buf;
569	int len;
570{
571	/*
572	 * Old-style lesskey file.
573	 * The file must end with either
574	 *     ...,cmd,0,action
575	 * or  ...,cmd,0,action|A_EXTRA,string,0
576	 * So the last byte or the second to last byte must be zero.
577	 */
578	if (buf[len-1] != '\0' && buf[len-2] != '\0')
579		return (-1);
580	add_fcmd_table(buf, len);
581	return (0);
582}
583
584/*
585 * Process a new (post-v241) lesskey file.
586 */
587	static int
588new_lesskey(buf, len, sysvar)
589	char *buf;
590	int len;
591	int sysvar;
592{
593	char *p;
594	register int c;
595	register int n;
596
597	/*
598	 * New-style lesskey file.
599	 * Extract the pieces.
600	 */
601	if (buf[len-3] != C0_END_LESSKEY_MAGIC ||
602	    buf[len-2] != C1_END_LESSKEY_MAGIC ||
603	    buf[len-1] != C2_END_LESSKEY_MAGIC)
604		return (-1);
605	p = buf + 4;
606	for (;;)
607	{
608		c = *p++;
609		switch (c)
610		{
611		case CMD_SECTION:
612			n = gint(&p);
613			add_fcmd_table(p, n);
614			p += n;
615			break;
616		case EDIT_SECTION:
617			n = gint(&p);
618			add_ecmd_table(p, n);
619			p += n;
620			break;
621		case VAR_SECTION:
622			n = gint(&p);
623			add_var_table((sysvar) ?
624				&list_sysvar_tables : &list_var_tables, p, n);
625			p += n;
626			break;
627		case END_SECTION:
628			return (0);
629		default:
630			/*
631			 * Unrecognized section type.
632			 */
633			return (-1);
634		}
635	}
636}
637
638/*
639 * Set up a user command table, based on a "lesskey" file.
640 */
641	public int
642lesskey(filename, sysvar)
643	char *filename;
644	int sysvar;
645{
646	register char *buf;
647	register POSITION len;
648	register long n;
649	register int f;
650
651	if (secure)
652		return (1);
653	/*
654	 * Try to open the lesskey file.
655	 */
656	filename = unquote_file(filename);
657	f = open(filename, OPEN_READ);
658	free(filename);
659	if (f < 0)
660		return (1);
661
662	/*
663	 * Read the file into a buffer.
664	 * We first figure out the size of the file and allocate space for it.
665	 * {{ Minimal error checking is done here.
666	 *    A garbage .less file will produce strange results.
667	 *    To avoid a large amount of error checking code here, we
668	 *    rely on the lesskey program to generate a good .less file. }}
669	 */
670	len = filesize(f);
671	if (len == NULL_POSITION || len < 3)
672	{
673		/*
674		 * Bad file (valid file must have at least 3 chars).
675		 */
676		close(f);
677		return (-1);
678	}
679	if ((buf = (char *) calloc((int)len, sizeof(char))) == NULL)
680	{
681		close(f);
682		return (-1);
683	}
684	if (lseek(f, (off_t)0, 0) == BAD_LSEEK)
685	{
686		free(buf);
687		close(f);
688		return (-1);
689	}
690	n = read(f, buf, (unsigned int) len);
691	close(f);
692	if (n != len)
693	{
694		free(buf);
695		return (-1);
696	}
697
698	/*
699	 * Figure out if this is an old-style (before version 241)
700	 * or new-style lesskey file format.
701	 */
702	if (buf[0] != C0_LESSKEY_MAGIC || buf[1] != C1_LESSKEY_MAGIC ||
703	    buf[2] != C2_LESSKEY_MAGIC || buf[3] != C3_LESSKEY_MAGIC)
704		return (old_lesskey(buf, (int)len));
705	return (new_lesskey(buf, (int)len, sysvar));
706}
707
708/*
709 * Add the standard lesskey file "$HOME/.less"
710 */
711	public void
712add_hometable(envname, def_filename, sysvar)
713	char *envname;
714	char *def_filename;
715	int sysvar;
716{
717	char *filename;
718	PARG parg;
719
720	if (envname != NULL && (filename = lgetenv(envname)) != NULL)
721		filename = save(filename);
722	else if (sysvar)
723		filename = save(def_filename);
724	else
725		filename = homefile(def_filename);
726	if (filename == NULL)
727		return;
728	if (lesskey(filename, sysvar) < 0)
729	{
730		parg.p_string = filename;
731		error("Cannot use lesskey file \"%s\"", &parg);
732	}
733	free(filename);
734}
735#endif
736
737/*
738 * See if a char is a special line-editing command.
739 */
740	public int
741editchar(c, flags)
742	int c;
743	int flags;
744{
745	int action;
746	int nch;
747	char *s;
748	char usercmd[MAX_CMDLEN+1];
749
750	/*
751	 * An editing character could actually be a sequence of characters;
752	 * for example, an escape sequence sent by pressing the uparrow key.
753	 * To match the editing string, we use the command decoder
754	 * but give it the edit-commands command table
755	 * This table is constructed to match the user's keyboard.
756	 */
757	if (c == erase_char)
758		return (EC_BACKSPACE);
759	if (c == kill_char)
760		return (EC_LINEKILL);
761
762	/*
763	 * Collect characters in a buffer.
764	 * Start with the one we have, and get more if we need them.
765	 */
766	nch = 0;
767	do {
768	  	if (nch > 0)
769			c = getcc();
770		usercmd[nch] = c;
771		usercmd[nch+1] = '\0';
772		nch++;
773		action = ecmd_decode(usercmd, &s);
774	} while (action == A_PREFIX);
775
776	if (flags & EC_NORIGHTLEFT)
777	{
778		switch (action)
779		{
780		case EC_RIGHT:
781		case EC_LEFT:
782			action = A_INVALID;
783			break;
784		}
785	}
786#if CMD_HISTORY
787	if (flags & EC_NOHISTORY)
788	{
789		/*
790		 * The caller says there is no history list.
791		 * Reject any history-manipulation action.
792		 */
793		switch (action)
794		{
795		case EC_UP:
796		case EC_DOWN:
797			action = A_INVALID;
798			break;
799		}
800	}
801#endif
802#if TAB_COMPLETE_FILENAME
803	if (flags & EC_NOCOMPLETE)
804	{
805		/*
806		 * The caller says we don't want any filename completion cmds.
807		 * Reject them.
808		 */
809		switch (action)
810		{
811		case EC_F_COMPLETE:
812		case EC_B_COMPLETE:
813		case EC_EXPAND:
814			action = A_INVALID;
815			break;
816		}
817	}
818#endif
819	if ((flags & EC_PEEK) || action == A_INVALID)
820	{
821		/*
822		 * We're just peeking, or we didn't understand the command.
823		 * Unget all the characters we read in the loop above.
824		 * This does NOT include the original character that was
825		 * passed in as a parameter.
826		 */
827		while (nch > 1)
828		{
829			ungetcc(usercmd[--nch]);
830		}
831	} else
832	{
833		if (s != NULL)
834			ungetsc(s);
835	}
836	return action;
837}
838
839