1.\" $NetBSD: vis.3,v 1.45 2016/06/08 15:00:04 wiz Exp $ 2.\" $FreeBSD$ 3.\" 4.\" Copyright (c) 1989, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)vis.3 8.1 (Berkeley) 6/9/93 32.\" 33.Dd January 14, 2015 34.Dt VIS 3 35.Os 36.Sh NAME 37.Nm vis , 38.Nm nvis , 39.Nm strvis , 40.Nm stravis , 41.Nm strnvis , 42.Nm strvisx , 43.Nm strnvisx , 44.Nm strenvisx , 45.Nm svis , 46.Nm snvis , 47.Nm strsvis , 48.Nm strsnvis , 49.Nm strsvisx , 50.Nm strsnvisx , 51.Nm strsenvisx 52.Nd visually encode characters 53.Sh LIBRARY 54.Lb libc 55.Sh SYNOPSIS 56.In vis.h 57.Ft char * 58.Fn vis "char *dst" "int c" "int flag" "int nextc" 59.Ft char * 60.Fn nvis "char *dst" "size_t dlen" "int c" "int flag" "int nextc" 61.Ft int 62.Fn strvis "char *dst" "const char *src" "int flag" 63.Ft int 64.Fn stravis "char **dst" "const char *src" "int flag" 65.Ft int 66.Fn strnvis "char *dst" "size_t dlen" "const char *src" "int flag" 67.Ft int 68.Fn strvisx "char *dst" "const char *src" "size_t len" "int flag" 69.Ft int 70.Fn strnvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag" 71.Ft int 72.Fn strenvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag" "int *cerr_ptr" 73.Ft char * 74.Fn svis "char *dst" "int c" "int flag" "int nextc" "const char *extra" 75.Ft char * 76.Fn snvis "char *dst" "size_t dlen" "int c" "int flag" "int nextc" "const char *extra" 77.Ft int 78.Fn strsvis "char *dst" "const char *src" "int flag" "const char *extra" 79.Ft int 80.Fn strsnvis "char *dst" "size_t dlen" "const char *src" "int flag" "const char *extra" 81.Ft int 82.Fn strsvisx "char *dst" "const char *src" "size_t len" "int flag" "const char *extra" 83.Ft int 84.Fn strsnvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag" "const char *extra" 85.Ft int 86.Fn strsenvisx "char *dst" "size_t dlen" "const char *src" "size_t len" "int flag" "const char *extra" "int *cerr_ptr" 87.Sh DESCRIPTION 88The 89.Fn vis 90function 91copies into 92.Fa dst 93a string which represents the character 94.Fa c . 95If 96.Fa c 97needs no encoding, it is copied in unaltered. 98The string is null terminated, and a pointer to the end of the string is 99returned. 100The maximum length of any encoding is four 101bytes (not including the trailing 102.Dv NUL ) ; 103thus, when 104encoding a set of characters into a buffer, the size of the buffer should 105be four times the number of bytes encoded, plus one for the trailing 106.Dv NUL . 107The flag parameter is used for altering the default range of 108characters considered for encoding and for altering the visual 109representation. 110The additional character, 111.Fa nextc , 112is only used when selecting the 113.Dv VIS_CSTYLE 114encoding format (explained below). 115.Pp 116The 117.Fn strvis , 118.Fn stravis , 119.Fn strnvis , 120.Fn strvisx , 121and 122.Fn strnvisx 123functions copy into 124.Fa dst 125a visual representation of 126the string 127.Fa src . 128The 129.Fn strvis 130and 131.Fn strnvis 132functions encode characters from 133.Fa src 134up to the 135first 136.Dv NUL . 137The 138.Fn strvisx 139and 140.Fn strnvisx 141functions encode exactly 142.Fa len 143characters from 144.Fa src 145(this 146is useful for encoding a block of data that may contain 147.Dv NUL Ns 's ) . 148Both forms 149.Dv NUL 150terminate 151.Fa dst . 152The size of 153.Fa dst 154must be four times the number 155of bytes encoded from 156.Fa src 157(plus one for the 158.Dv NUL ) . 159Both 160forms return the number of characters in 161.Fa dst 162(not including the trailing 163.Dv NUL ) . 164The 165.Fn stravis 166function allocates space dynamically to hold the string. 167The 168.Dq Nm n 169versions of the functions also take an additional argument 170.Fa dlen 171that indicates the length of the 172.Fa dst 173buffer. 174If 175.Fa dlen 176is not large enough to fit the converted string then the 177.Fn strnvis 178and 179.Fn strnvisx 180functions return \-1 and set 181.Va errno 182to 183.Dv ENOSPC . 184The 185.Fn strenvisx 186function takes an additional argument, 187.Fa cerr_ptr , 188that is used to pass in and out a multibyte conversion error flag. 189This is useful when processing single characters at a time when 190it is possible that the locale may be set to something other 191than the locale of the characters in the input data. 192.Pp 193The functions 194.Fn svis , 195.Fn snvis , 196.Fn strsvis , 197.Fn strsnvis , 198.Fn strsvisx , 199.Fn strsnvisx , 200and 201.Fn strsenvisx 202correspond to 203.Fn vis , 204.Fn nvis , 205.Fn strvis , 206.Fn strnvis , 207.Fn strvisx , 208.Fn strnvisx , 209and 210.Fn strenvisx 211but have an additional argument 212.Fa extra , 213pointing to a 214.Dv NUL 215terminated list of characters. 216These characters will be copied encoded or backslash-escaped into 217.Fa dst . 218These functions are useful e.g. to remove the special meaning 219of certain characters to shells. 220.Pp 221The encoding is a unique, invertible representation composed entirely of 222graphic characters; it can be decoded back into the original form using 223the 224.Xr unvis 3 , 225.Xr strunvis 3 226or 227.Xr strnunvis 3 228functions. 229.Pp 230There are two parameters that can be controlled: the range of 231characters that are encoded (applies only to 232.Fn vis , 233.Fn nvis , 234.Fn strvis , 235.Fn strnvis , 236.Fn strvisx , 237and 238.Fn strnvisx ) , 239and the type of representation used. 240By default, all non-graphic characters, 241except space, tab, and newline are encoded (see 242.Xr isgraph 3 ) . 243The following flags 244alter this: 245.Bl -tag -width VIS_WHITEX 246.It Dv VIS_GLOB 247Also encode the magic characters 248.Ql ( * , 249.Ql \&? , 250.Ql \&[ , 251and 252.Ql # ) 253recognized by 254.Xr glob 3 . 255.It Dv VIS_SHELL 256Also encode the meta characters used by shells (in addition to the glob 257characters): 258.Ql ( ' , 259.Ql ` , 260.Ql \&" , 261.Ql \&; , 262.Ql & , 263.Ql < , 264.Ql > , 265.Ql \&( , 266.Ql \&) , 267.Ql \&| , 268.Ql \&] , 269.Ql \e , 270.Ql $ , 271.Ql \&! , 272.Ql \&^ , 273and 274.Ql ~ ) . 275.It Dv VIS_SP 276Also encode space. 277.It Dv VIS_TAB 278Also encode tab. 279.It Dv VIS_NL 280Also encode newline. 281.It Dv VIS_WHITE 282Synonym for 283.Dv VIS_SP | VIS_TAB | VIS_NL . 284.It Dv VIS_META 285Synonym for 286.Dv VIS_WHITE | VIS_GLOB | VIS_SHELL . 287.It Dv VIS_SAFE 288Only encode 289.Dq unsafe 290characters. 291Unsafe means control characters which may cause common terminals to perform 292unexpected functions. 293Currently this form allows space, tab, newline, backspace, bell, and 294return \(em in addition to all graphic characters \(em unencoded. 295.El 296.Pp 297(The above flags have no effect for 298.Fn svis , 299.Fn snvis , 300.Fn strsvis , 301.Fn strsnvis , 302.Fn strsvisx , 303and 304.Fn strsnvisx . 305When using these functions, place all graphic characters to be 306encoded in an array pointed to by 307.Fa extra . 308In general, the backslash character should be included in this array, see the 309warning on the use of the 310.Dv VIS_NOSLASH 311flag below). 312.Pp 313There are four forms of encoding. 314All forms use the backslash character 315.Ql \e 316to introduce a special 317sequence; two backslashes are used to represent a real backslash, 318except 319.Dv VIS_HTTPSTYLE 320that uses 321.Ql % , 322or 323.Dv VIS_MIMESTYLE 324that uses 325.Ql = . 326These are the visual formats: 327.Bl -tag -width VIS_CSTYLE 328.It (default) 329Use an 330.Ql M 331to represent meta characters (characters with the 8th 332bit set), and use caret 333.Ql ^ 334to represent control characters (see 335.Xr iscntrl 3 ) . 336The following formats are used: 337.Bl -tag -width xxxxx 338.It Dv \e^C 339Represents the control character 340.Ql C . 341Spans characters 342.Ql \e000 343through 344.Ql \e037 , 345and 346.Ql \e177 347(as 348.Ql \e^? ) . 349.It Dv \eM-C 350Represents character 351.Ql C 352with the 8th bit set. 353Spans characters 354.Ql \e241 355through 356.Ql \e376 . 357.It Dv \eM^C 358Represents control character 359.Ql C 360with the 8th bit set. 361Spans characters 362.Ql \e200 363through 364.Ql \e237 , 365and 366.Ql \e377 367(as 368.Ql \eM^? ) . 369.It Dv \e040 370Represents 371.Tn ASCII 372space. 373.It Dv \e240 374Represents Meta-space. 375.El 376.It Dv VIS_CSTYLE 377Use C-style backslash sequences to represent standard non-printable 378characters. 379The following sequences are used to represent the indicated characters: 380.Bd -unfilled -offset indent 381.Li \ea Tn \(em BEL No (007) 382.Li \eb Tn \(em BS No (010) 383.Li \ef Tn \(em NP No (014) 384.Li \en Tn \(em NL No (012) 385.Li \er Tn \(em CR No (015) 386.Li \es Tn \(em SP No (040) 387.Li \et Tn \(em HT No (011) 388.Li \ev Tn \(em VT No (013) 389.Li \e0 Tn \(em NUL No (000) 390.Ed 391.Pp 392When using this format, the 393.Fa nextc 394parameter is looked at to determine if a 395.Dv NUL 396character can be encoded as 397.Ql \e0 398instead of 399.Ql \e000 . 400If 401.Fa nextc 402is an octal digit, the latter representation is used to 403avoid ambiguity. 404.It Dv VIS_OCTAL 405Use a three digit octal sequence. 406The form is 407.Ql \eddd 408where 409.Em d 410represents an octal digit. 411.It Dv VIS_HTTPSTYLE 412Use URI encoding as described in RFC 1738. 413The form is 414.Ql %xx 415where 416.Em x 417represents a lower case hexadecimal digit. 418.It Dv VIS_MIMESTYLE 419Use MIME Quoted-Printable encoding as described in RFC 2045, only don't 420break lines and don't handle CRLF. 421The form is 422.Ql =XX 423where 424.Em X 425represents an upper case hexadecimal digit. 426.El 427.Pp 428There is one additional flag, 429.Dv VIS_NOSLASH , 430which inhibits the 431doubling of backslashes and the backslash before the default 432format (that is, control characters are represented by 433.Ql ^C 434and 435meta characters as 436.Ql M-C ) . 437With this flag set, the encoding is 438ambiguous and non-invertible. 439.Sh MULTIBYTE CHARACTER SUPPORT 440These functions support multibyte character input. 441The encoding conversion is influenced by the setting of the 442.Ev LC_CTYPE 443environment variable which defines the set of characters 444that can be copied without encoding. 445.Pp 446If 447.Dv VIS_NOLOCALE 448is set, processing is done assuming the C locale and overriding 449any other environment settings. 450.Pp 451When 8-bit data is present in the input, 452.Ev LC_CTYPE 453must be set to the correct locale or to the C locale. 454If the locales of the data and the conversion are mismatched, 455multibyte character recognition may fail and encoding will be performed 456byte-by-byte instead. 457.Pp 458As noted above, 459.Fa dst 460must be four times the number of bytes processed from 461.Fa src . 462But note that each multibyte character can be up to 463.Dv MB_LEN_MAX 464bytes 465.\" (see 466.\" .Xr multibyte 3 ) 467so in terms of multibyte characters, 468.Fa dst 469must be four times 470.Dv MB_LEN_MAX 471times the number of characters processed from 472.Fa src . 473.Sh ENVIRONMENT 474.Bl -tag -width ".Ev LC_CTYPE" 475.It Ev LC_CTYPE 476Specify the locale of the input data. 477Set to C if the input data locale is unknown. 478.El 479.Sh ERRORS 480The functions 481.Fn nvis 482and 483.Fn snvis 484will return 485.Dv NULL 486and the functions 487.Fn strnvis , 488.Fn strnvisx , 489.Fn strsnvis , 490and 491.Fn strsnvisx , 492will return \-1 when the 493.Fa dlen 494destination buffer size is not enough to perform the conversion while 495setting 496.Va errno 497to: 498.Bl -tag -width ".Bq Er ENOSPC" 499.It Bq Er ENOSPC 500The destination buffer size is not large enough to perform the conversion. 501.El 502.Sh SEE ALSO 503.Xr unvis 1 , 504.Xr vis 1 , 505.Xr glob 3 , 506.\" .Xr multibyte 3 , 507.Xr unvis 3 508.Rs 509.%A T. Berners-Lee 510.%T Uniform Resource Locators (URL) 511.%O "RFC 1738" 512.Re 513.Rs 514.%T "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies" 515.%O "RFC 2045" 516.Re 517.Sh HISTORY 518The 519.Fn vis , 520.Fn strvis , 521and 522.Fn strvisx 523functions first appeared in 524.Bx 4.4 . 525The 526.Fn svis , 527.Fn strsvis , 528and 529.Fn strsvisx 530functions appeared in 531.Nx 1.5 532and 533.Fx 9.2 . 534The buffer size limited versions of the functions 535.Po Fn nvis , 536.Fn strnvis , 537.Fn strnvisx , 538.Fn snvis , 539.Fn strsnvis , 540and 541.Fn strsnvisx Pc 542appeared in 543.Nx 6.0 544and 545.Fx 9.2 . 546Multibyte character support was added in 547.Nx 7.0 548and 549.Fx 9.2 . 550