1.\" $NetBSD: unvis.3,v 1.23 2011/03/17 14:06:29 wiz 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)unvis.3 8.2 (Berkeley) 12/11/93 31.\" 32.Dd March 12, 2011 33.Dt UNVIS 3 34.Os 35.Sh NAME 36.Nm unvis , 37.Nm strunvis 38.Nd decode a visual representation of characters 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In vis.h 43.Ft int 44.Fn unvis "char *cp" "int c" "int *astate" "int flag" 45.Ft int 46.Fn strunvis "char *dst" "const char *src" 47.Ft int 48.Fn strnunvis "char *dst" "size_t dlen" "const char *src" 49.Ft int 50.Fn strunvisx "char *dst" "const char *src" "int flag" 51.Ft int 52.Fn strnunvisx "char *dst" "size_t dlen" "const char *src" "int flag" 53.Sh DESCRIPTION 54The 55.Fn unvis , 56.Fn strunvis 57and 58.Fn strunvisx 59functions 60are used to decode a visual representation of characters, as produced 61by the 62.Xr vis 3 63function, back into 64the original form. 65.Pp 66The 67.Fn unvis 68function is called with successive characters in 69.Ar c 70until a valid sequence is recognized, at which time the decoded 71character is available at the character pointed to by 72.Ar cp . 73.Pp 74The 75.Fn strunvis 76function decodes the characters pointed to by 77.Ar src 78into the buffer pointed to by 79.Ar dst . 80The 81.Fn strunvis 82function simply copies 83.Ar src 84to 85.Ar dst , 86decoding any escape sequences along the way, 87and returns the number of characters placed into 88.Ar dst , 89or \-1 if an 90invalid escape sequence was detected. 91The size of 92.Ar dst 93should be equal to the size of 94.Ar src 95(that is, no expansion takes place during decoding). 96.Pp 97The 98.Fn strunvisx 99function does the same as the 100.Fn strunvis 101function, 102but it allows you to add a flag that specifies the style the string 103.Ar src 104is encoded with. 105Currently, the supported flags are: 106.Dv VIS_HTTPSTYLE 107and 108.Dv VIS_MIMESTYLE . 109.Pp 110The 111.Fn unvis 112function implements a state machine that can be used to decode an 113arbitrary stream of bytes. 114All state associated with the bytes being decoded is stored outside the 115.Fn unvis 116function (that is, a pointer to the state is passed in), so 117calls decoding different streams can be freely intermixed. 118To start decoding a stream of bytes, first initialize an integer to zero. 119Call 120.Fn unvis 121with each successive byte, along with a pointer 122to this integer, and a pointer to a destination character. 123The 124.Fn unvis 125function has several return codes that must be handled properly. 126They are: 127.Bl -tag -width UNVIS_VALIDPUSH 128.It Li \&0 (zero) 129Another character is necessary; nothing has been recognized yet. 130.It Dv UNVIS_VALID 131A valid character has been recognized and is available at the location 132pointed to by cp. 133.It Dv UNVIS_VALIDPUSH 134A valid character has been recognized and is available at the location 135pointed to by cp; however, the character currently passed in should 136be passed in again. 137.It Dv UNVIS_NOCHAR 138A valid sequence was detected, but no character was produced. 139This return code is necessary to indicate a logical break between characters. 140.It Dv UNVIS_SYNBAD 141An invalid escape sequence was detected, or the decoder is in an unknown state. 142The decoder is placed into the starting state. 143.El 144.Pp 145When all bytes in the stream have been processed, call 146.Fn unvis 147one more time with flag set to 148.Dv UNVIS_END 149to extract any remaining character (the character passed in is ignored). 150.Pp 151The 152.Ar flag 153argument is also used to specify the encoding style of the source. 154If set to 155.Dv VIS_HTTPSTYLE 156or 157.Dv VIS_HTTP1808 , 158.Fn unvis 159will decode URI strings as specified in RFC 1808. 160If set to 161.Dv VIS_HTTP1866 , 162.Fn unvis 163will decode URI strings as specified in RFC 1866. 164If set to 165.Dv VIS_MIMESTYLE , 166.Fn unvis 167will decode MIME Quoted-Printable strings as specified in RFC 2045. 168If set to 169.Dv VIS_NOESCAPE , 170.Fn unvis 171will not decode \e quoted characters. 172.Pp 173The following code fragment illustrates a proper use of 174.Fn unvis . 175.Bd -literal -offset indent 176int state = 0; 177char out; 178 179while ((ch = getchar()) != EOF) { 180again: 181 switch(unvis(\*[Am]out, ch, \*[Am]state, 0)) { 182 case 0: 183 case UNVIS_NOCHAR: 184 break; 185 case UNVIS_VALID: 186 (void)putchar(out); 187 break; 188 case UNVIS_VALIDPUSH: 189 (void)putchar(out); 190 goto again; 191 case UNVIS_SYNBAD: 192 errx(EXIT_FAILURE, "Bad character sequence!"); 193 } 194} 195if (unvis(\*[Am]out, '\e0', \*[Am]state, UNVIS_END) == UNVIS_VALID) 196 (void)putchar(out); 197.Ed 198.Sh ERRORS 199The functions 200.Fn strunvis , 201.Fn strnunvis , 202.Fn strunvisx , 203and 204.Fn strnunvisx 205will return \-1 on error and set 206.Va errno 207to: 208.Bl -tag -width Er 209.It Bq Er EINVAL 210An invalid escape sequence was detected, or the decoder is in an unknown state. 211.El 212.Pp 213In addition the functions 214.Fn strnunvis 215and 216.Fn strnunvisx 217will can also set 218.Va errno 219on error to: 220.Bl -tag -width Er 221.It Bq Er ENOSPC 222Not enough space to perform the conversion. 223.El 224.Sh SEE ALSO 225.Xr unvis 1 , 226.Xr vis 1 , 227.Xr vis 3 228.Rs 229.%A R. Fielding 230.%T Relative Uniform Resource Locators 231.%O RFC1808 232.Re 233.Sh HISTORY 234The 235.Fn unvis 236function 237first appeared in 238.Bx 4.4 . 239The 240.Fn strnunvis 241and 242.Fn strnunvisx 243functions appeared in 244.Nx 6.0 . 245