1.\" $OpenBSD: unvis.3,v 1.7 1999/06/03 10:03:24 aaron Exp $ 2.\" 3.\" Copyright (c) 1989, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.Dd December 11, 1993 35.Dt UNVIS 3 36.Os 37.Sh NAME 38.Nm unvis , 39.Nm strunvis 40.Nd decode a visual representation of characters 41.Sh SYNOPSIS 42.Fd #include <vis.h> 43.Ft int 44.Fn unvis "char *cp" "char c" "int *astate" "int flag" 45.Ft int 46.Fn strunvis "char *dst" "char *src" 47.Sh DESCRIPTION 48The 49.Fn unvis 50and 51.Fn strunvis 52functions 53are used to decode a visual representation of characters, as produced 54by the 55.Xr vis 3 56function, back into 57the original form. 58.Fn unvis 59is called with successive characters in 60.Fa c 61until a valid 62sequence is recognized, at which time the decoded character is 63available at the character pointed to by 64.Fa cp . 65.Pp 66.Fn strunvis 67decodes the characters pointed to by 68.Fa src 69into the buffer pointed to by 70.Fa dst . 71.Pp 72The 73.Fn strunvis 74function 75simply copies 76.Fa src 77to 78.Fa dst , 79decoding any escape sequences along the way, 80and returns the number of characters placed into 81.Fa dst , 82or \-1 if an 83invalid escape sequence was detected. The size of 84.Fa dst 85should be 86equal to the size of 87.Fa src 88(that is, no expansion takes place during decoding). 89.Pp 90The 91.Fn unvis 92function 93implements a state machine that can be used to decode an arbitrary 94stream of bytes. All state associated with the bytes being decoded 95is stored outside the 96.Fn unvis 97function (that is, a pointer to the state is passed in), so 98calls decoding different streams can be freely intermixed. To 99start decoding a stream of bytes, first initialize an integer 100to zero. Call 101.Fn unvis 102with each successive byte, along with a pointer 103to this integer, and a pointer to a destination character. 104The 105.Fn unvis 106function 107has several return codes that must be handled properly. They are: 108.Bl -tag -width UNVIS_VALIDPUSH 109.It Li \&0 (zero) 110Another character is necessary; nothing has been recognized yet. 111.It Dv UNVIS_VALID 112A valid character has been recognized and is available at the location 113pointed to by 114.Fa cp . 115.It Dv UNVIS_VALIDPUSH 116A valid character has been recognized and is available at the location 117pointed to by 118.Fa cp ; 119however, the character currently passed in should be passed in again. 120.It Dv UNVIS_NOCHAR 121A valid sequence was detected, but no character was produced. This 122return code is necessary to indicate a logical break between characters. 123.It Dv UNVIS_SYNBAD 124An invalid escape sequence was detected, or the decoder is in an 125unknown state. The decoder is placed into the starting state. 126.El 127.Pp 128When all bytes in the stream have been processed, call 129.Fn unvis 130one more time with flag set to 131.Dv UNVIS_END 132to extract any remaining character (the character passed in is ignored). 133.Pp 134.Sh EXAMPLES 135The following code fragment illustrates a proper use of 136.Fn unvis . 137.Bd -literal -offset indent 138int state = 0; 139char out; 140 141while ((ch = getchar()) != EOF) { 142again: 143 switch(unvis(&out, ch, &state, 0)) { 144 case 0: 145 case UNVIS_NOCHAR: 146 break; 147 case UNVIS_VALID: 148 (void) putchar(out); 149 break; 150 case UNVIS_VALIDPUSH: 151 (void) putchar(out); 152 goto again; 153 case UNVIS_SYNBAD: 154 (void)fprintf(stderr, "bad sequence!\n"); 155 exit(1); 156 } 157} 158if (unvis(&out, (char)0, &state, UNVIS_END) == UNVIS_VALID) 159 (void) putchar(out); 160.Ed 161.Sh SEE ALSO 162.Xr unvis 1 , 163.Xr vis 1 , 164.Xr vis 3 165.Sh HISTORY 166The 167.Fn unvis 168function first appeared in 169.Bx 4.4 . 170