1 .\" Copyright (c) 1989, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 3. All advertising materials mentioning features or use of this software
13 .\" must display the following acknowledgement:
14 .\" This product includes software developed by the University of
15 .\" California, Berkeley and its contributors.
16 .\" 4. Neither the name of the University nor the names of its contributors
17 .\" may be used to endorse or promote products derived from this software
18 .\" without specific prior written permission.
20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 .\" @(#)unvis.3 8.2 (Berkeley) 12/11/93
33 .\" $FreeBSD: src/lib/libc/gen/unvis.3,v 1.6.2.5 2001/12/14 18:33:51 ru Exp $
34 .\" $DragonFly: src/lib/libc/gen/unvis.3,v 1.2 2003/06/17 04:26:42 dillon Exp $
42 .Nd decode a visual representation of characters
48 .Fn unvis "char *cp" "int c" "int *astate" "int flag"
50 .Fn strunvis "char *dst" "const char *src"
57 are used to decode a visual representation of characters, as produced
61 the original form. Unvis is called with successive characters in
64 sequence is recognized, at which time the decoded character is
65 available at the character pointed to by
68 characters pointed to by
70 into the buffer pointed to by
80 decoding any escape sequences along the way,
81 and returns the number of characters placed into
84 invalid escape sequence was detected. The size of
89 (that is, no expansion takes place during
95 implements a state machine that can be used to decode an arbitrary
96 stream of bytes. All state associated with the bytes being decoded
99 function (that is, a pointer to the state is passed in), so
100 calls decoding different streams can be freely intermixed. To
101 start decoding a stream of bytes, first initialize an integer
104 with each successive byte, along with a pointer
105 to this integer, and a pointer to a destination character.
109 has several return codes that must be handled properly. They are:
110 .Bl -tag -width UNVIS_VALIDPUSH
112 Another character is necessary; nothing has been recognized yet.
114 A valid character has been recognized and is available at the location
116 .It Dv UNVIS_VALIDPUSH
117 A valid character has been recognized and is available at the location
118 pointed to by cp; however, the character currently passed in should
121 A valid sequence was detected, but no character was produced. This
122 return code is necessary to indicate a logical break between characters.
124 An invalid escape sequence was detected, or the decoder is in an
125 unknown state. The decoder is placed into the starting state.
128 When all bytes in the stream have been processed, call
134 to extract any remaining character (the character passed in is ignored).
136 The following code fragment illustrates a proper use of
138 .Bd -literal -offset indent
142 while ((ch = getchar()) != EOF) {
144 switch(unvis(&out, ch, &state, 0)) {
151 case UNVIS_VALIDPUSH:
155 (void)fprintf(stderr, "bad sequence!\en");
159 if (unvis(&out, (char)0, &state, UNVIS_END) == UNVIS_VALID)