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1.1 root 1: .\" Copyright (c) 1989 The Regents of the University of California.
2: .\" All rights reserved.
3: .\"
4: .\" Redistribution and use in source and binary forms are permitted provided
5: .\" that: (1) source distributions retain this entire copyright notice and
6: .\" comment, and (2) distributions including binaries display the following
7: .\" acknowledgement: ``This product includes software developed by the
8: .\" University of California, Berkeley and its contributors'' in the
9: .\" documentation or other materials provided with the distribution and in
10: .\" all advertising materials mentioning features or use of this software.
11: .\" Neither the name of the University nor the names of its contributors may
12: .\" be used to endorse or promote products derived from this software without
13: .\" specific prior written permission.
14: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
15: .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
16: .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
17: .\"
18: .\" @(#)unvis.3 1.2 (Berkeley) 6/27/90
19: .\"
20: .TH UNVIS 3 "June 27, 1990"
21: .UC 7
22: .SH NAME
23: unvis, strunvis - decode a visual representation of characters
24: .SH SYNOPSIS
25: .nf
26: .ft B
27: #include <vis.h>
28:
29: int unvis(cp, c, astate, flag)
30: u_char *cp, c;
31: int *astate, flag;
32:
33: int strunvis(dst, src)
34: char *dst, *src;
35:
36: .ft R
37: .fi
38: .SH DESCRIPTION
39: .I Unvis
40: and
41: .I strunvis
42: are used to decode a visual representation of characters, as produced
43: by the vis(3) function, back into
44: its original form. Unvis is called with successive characters in c
45: until a valid
46: sequence is recognized, at which time the decoded character is
47: available at the character pointed to by cp. Strunvis decodes the
48: characters pointed to by src into the buffer pointed to by dst.
49: .LP
50: .I Strunvis
51: simply copies src to dst, decoding any escape sequences along the way,
52: and returns the number of characters placed into dst, or -1 if an
53: invalid escape sequence was detected. The size of dst should be
54: equal to the size of src (that is, no expansion takes place during
55: decoding).
56: .LP
57: .I Unvis
58: implements a state machine that can be used to decode an arbitrary
59: stream of bytes. All state associated with the bytes being decoded
60: is stored outside the
61: .I unvis
62: function (that is, a pointer to the state is passed in), so
63: calls decoding different streams can be freely intermixed. To
64: start decoding a stream of bytes, first initialize an integer
65: to zero. Call unvis with each successive byte, along with a pointer
66: to this integer, and a pointer to an destination character.
67: .I Vis
68: has several return codes that must be handled properly. They are:
69: .TP
70: 0 (zero)
71: Another character is necessary; nothing has been recognized yet.
72: .TP
73: UNVIS_VALID
74: A valid character has been recognized and is available at the location
75: pointed to by cp.
76: .TP
77: UNVIS_VALIDPUSH
78: A valid character has been recognized and is available at the location
79: pointed to by cp; however, the character currently passed in should
80: be passed in again.
81: .TP
82: UNVIS_NOCHAR
83: A valid sequence was detected, but no character was produced. This
84: return code is necessary to indicate a logical break between characters.
85: .TP
86: UNVIS_SYNBAD
87: An invalid esacpe sequence was detected, or the decoder is in an
88: unknown state. The decoder is placed into the starting state.
89: .LP
90: When all bytes in the stream have been processed, call
91: .I unvis
92: one more time with flag set to
93: .B UNVIS_END
94: to extract any remaining character (the character passed in is ignored).
95: .LP
96: The following code fragment illustrates a proper use of
97: .IR unvis .
98: .PP
99: .nf
100: int state = 0;
101: char out;
102:
103: while ((ch = getchar()) != EOF) {
104: again:
105: switch(unvis(&out, ch, &state, 0)) {
106: case 0:
107: case UNVIS_NOCHAR:
108: break;
109: case UNVIS_VALID:
110: (void) putchar(out);
111: break;
112: case UNVIS_VALIDPUSH:
113: (void) putchar(out);
114: goto again;
115: case UNVIS_SYNBAD:
116: (void)fprintf(stderr, "bad sequence!\n");
117: exit(1);
118: }
119: }
120: if (unvis(&out, (char)0, &state, UNVIS_END) == UNVIS_VALID)
121: (void) putchar(out);
122: .fi
123: .SH "SEE ALSO"
124: vis(1)
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