[apple/libc.git] / gen / vis.3

.\" Copyright (c) 1989, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     From: @(#)vis.3	8.1 (Berkeley) 6/9/93
.\" $FreeBSD: src/lib/libc/gen/vis.3,v 1.18 2001/10/01 16:08:51 ru Exp $
.\"
.Dd July 25, 1996
.Dt VIS 3
.Os
.Sh NAME
.Nm vis
.Nd visually encode characters
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In vis.h
.Ft char *
.Fn vis "char *dst" "int c" "int flag" "int nextc"
.Ft int
.Fn strvis "char *dst" "const char *src" "int flag"
.Ft int
.Fn strvisx "char *dst" "const char *src" "size_t len" "int flag"
.Sh DESCRIPTION
The
.Fn vis
function
copies into
.Fa dst
a string which represents the character
.Fa c .
If
.Fa c
needs no encoding, it is copied in unaltered.  The string is
null terminated, and a pointer to the end of the string is
returned.  The maximum length of any encoding is four
characters (not including the trailing
.Dv NUL ) ;
thus, when
encoding a set of characters into a buffer, the size of the buffer should
be four times the number of characters encoded, plus one for the trailing
.Dv NUL .
The flag parameter is used for altering the default range of
characters considered for encoding and for altering the visual
representation.
The additional character,
.Fa nextc ,
is only used when selecting the
.Dv VIS_CSTYLE
encoding format (explained below).
.Pp
The
.Fn strvis
and
.Fn strvisx
functions copy into
.Fa dst
a visual representation of
the string
.Fa src .
The
.Fn strvis
function encodes characters from
.Fa src
up to the
first
.Dv NUL .
The
.Fn strvisx
function encodes exactly
.Fa len
characters from
.Fa src
(this
is useful for encoding a block of data that may contain
.Dv NUL Ns 's ) .
Both forms
.Dv NUL
terminate
.Fa dst .
The size of
.Fa dst
must be four times the number
of characters encoded from
.Fa src
(plus one for the
.Dv NUL ) .
Both
forms return the number of characters in dst (not including
the trailing
.Dv NUL ) .
.Pp
The encoding is a unique, invertible representation composed entirely of
graphic characters; it can be decoded back into the original form using
the
.Xr unvis 3
or
.Xr strunvis 3
functions.
.Pp
There are two parameters that can be controlled: the range of
characters that are encoded, and the type
of representation used.
By default, all non-graphic characters
except space, tab, and newline are encoded.
(See
.Xr isgraph 3 . )
The following flags
alter this:
.Bl -tag -width VIS_WHITEX
.It Dv VIS_SP
Also encode space.
.It Dv VIS_TAB
Also encode tab.
.It Dv VIS_NL
Also encode newline.
.It Dv VIS_WHITE
Synonym for
.Dv VIS_SP
\&|
.Dv VIS_TAB
\&|
.Dv VIS_NL .
.It Dv VIS_SAFE
Only encode "unsafe" characters.  Unsafe means control
characters which may cause common terminals to perform
unexpected functions.  Currently this form allows space,
tab, newline, backspace, bell, and return - in addition
to all graphic characters - unencoded.
.El
.Pp
There are four forms of encoding.
Most forms use the backslash character
.Ql \e
to introduce a special
sequence; two backslashes are used to represent a real backslash.
These are the visual formats:
.Bl -tag -width VIS_HTTPSTYLE
.It (default)
Use an
.Ql M
to represent meta characters (characters with the 8th
bit set), and use carat
.Ql ^
to represent control characters see
.Pf ( Xr iscntrl 3 ) .
The following formats are used:
.Bl -tag -width xxxxx
.It Dv \e^C
Represents the control character
.Ql C .
Spans characters
.Ql \e000
through
.Ql \e037 ,
and
.Ql \e177
(as
.Ql \e^? ) .
.It Dv \eM-C
Represents character
.Ql C
with the 8th bit set.
Spans characters
.Ql \e241
through
.Ql \e376 .
.It Dv \eM^C
Represents control character
.Ql C
with the 8th bit set.
Spans characters
.Ql \e200
through
.Ql \e237 ,
and
.Ql \e377
(as
.Ql \eM^? ) .
.It Dv \e040
Represents
.Tn ASCII
space.
.It Dv \e240
Represents Meta-space.
.El
.Pp
.It Dv VIS_CSTYLE
Use C-style backslash sequences to represent standard non-printable
characters.
The following sequences are used to represent the indicated characters:
.Bd -unfilled -offset indent
.Li \ea Tn  - BEL No (007)
.Li \eb Tn  - BS No (010)
.Li \ef Tn  - NP No (014)
.Li \en Tn  - NL No (012)
.Li \er Tn  - CR No (015)
.Li \et Tn  - HT No (011)
.Li \ev Tn  - VT No (013)
.Li \e0 Tn  - NUL No (000)
.Ed
.Pp
When using this format, the nextc parameter is looked at to determine
if a
.Dv NUL
character can be encoded as
.Ql \e0
instead of
.Ql \e000 .
If
.Fa nextc
is an octal digit, the latter representation is used to
avoid ambiguity.
.It Dv VIS_HTTPSTYLE
Use URI encoding as described in RFC 1808.
The form is
.Ql %dd
where
.Em d
represents a hexadecimal digit.
.It Dv VIS_OCTAL
Use a three digit octal sequence.  The form is
.Ql \eddd
where
.Em d
represents an octal digit.
.El
.Pp
There is one additional flag,
.Dv VIS_NOSLASH ,
which inhibits the
doubling of backslashes and the backslash before the default
format (that is, control characters are represented by
.Ql ^C
and
meta characters as
.Ql M-C ) .
With this flag set, the encoding is
ambiguous and non-invertible.
.Sh SEE ALSO
.Xr unvis 1 ,
.Xr unvis 3
.Rs
.%A R. Fielding
.%T Relative Uniform Resource Locators
.%O RFC1808
.Re
.Sh HISTORY
These functions first appeared in
.Bx 4.4 .
Commit	Line	Data
5b2abdfb A	1	.\" Copyright (c) 1989, 1991, 1993
	2	.\" The Regents of the University of California. All rights reserved.
	3	.\"
	4	.\" Redistribution and use in source and binary forms, with or without
	5	.\" modification, are permitted provided that the following conditions
	6	.\" are met:
	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.
	19	.\"
	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
	30	.\" SUCH DAMAGE.
	31	.\"
	32	.\" From: @(#)vis.3 8.1 (Berkeley) 6/9/93
	33	.\" $FreeBSD: src/lib/libc/gen/vis.3,v 1.18 2001/10/01 16:08:51 ru Exp $
	34	.\"
	35	.Dd July 25, 1996
	36	.Dt VIS 3
	37	.Os
	38	.Sh NAME
	39	.Nm vis
	40	.Nd visually encode characters
	41	.Sh LIBRARY
	42	.Lb libc
	43	.Sh SYNOPSIS
	44	.In vis.h
	45	.Ft char *
	46	.Fn vis "char *dst" "int c" "int flag" "int nextc"
	47	.Ft int
	48	.Fn strvis "char dst" "const char src" "int flag"
	49	.Ft int
	50	.Fn strvisx "char dst" "const char src" "size_t len" "int flag"
	51	.Sh DESCRIPTION
	52	The
	53	.Fn vis
	54	function
	55	copies into
	56	.Fa dst
	57	a string which represents the character
	58	.Fa c .
	59	If
	60	.Fa c
	61	needs no encoding, it is copied in unaltered. The string is
	62	null terminated, and a pointer to the end of the string is
	63	returned. The maximum length of any encoding is four
	64	characters (not including the trailing
65	.Dv NUL ) ;
66	thus, when
67	encoding a set of characters into a buffer, the size of the buffer should
68	be four times the number of characters encoded, plus one for the trailing
69	.Dv NUL .
70	The flag parameter is used for altering the default range of
71	characters considered for encoding and for altering the visual
72	representation.
73	The additional character,
74	.Fa nextc ,
75	is only used when selecting the
76	.Dv VIS_CSTYLE
77	encoding format (explained below).
78	.Pp
79	The
80	.Fn strvis
81	and
82	.Fn strvisx
83	functions copy into
84	.Fa dst
85	a visual representation of
86	the string
87	.Fa src .
88	The
89	.Fn strvis
90	function encodes characters from
91	.Fa src
92	up to the
93	first
94	.Dv NUL .
95	The
96	.Fn strvisx
97	function encodes exactly
98	.Fa len
99	characters from
100	.Fa src
101	(this
102	is useful for encoding a block of data that may contain
103	.Dv NUL Ns 's ) .
104	Both forms
105	.Dv NUL
106	terminate
107	.Fa dst .
108	The size of
109	.Fa dst
110	must be four times the number
111	of characters encoded from
112	.Fa src
113	(plus one for the
114	.Dv NUL ) .
115	Both
116	forms return the number of characters in dst (not including
117	the trailing
118	.Dv NUL ) .
119	.Pp
120	The encoding is a unique, invertible representation composed entirely of
121	graphic characters; it can be decoded back into the original form using
122	the
123	.Xr unvis 3
124	or
125	.Xr strunvis 3
126	functions.
127	.Pp
128	There are two parameters that can be controlled: the range of
129	characters that are encoded, and the type
130	of representation used.
131	By default, all non-graphic characters
132	except space, tab, and newline are encoded.
133	(See
134	.Xr isgraph 3 . )
135	The following flags
136	alter this:
137	.Bl -tag -width VIS_WHITEX
138	.It Dv VIS_SP
139	Also encode space.
140	.It Dv VIS_TAB
141	Also encode tab.
142	.It Dv VIS_NL
143	Also encode newline.
144	.It Dv VIS_WHITE
145	Synonym for
146	.Dv VIS_SP
147	\&\|
148	.Dv VIS_TAB
149	\&\|
150	.Dv VIS_NL .
151	.It Dv VIS_SAFE
152	Only encode "unsafe" characters. Unsafe means control
153	characters which may cause common terminals to perform
154	unexpected functions. Currently this form allows space,
155	tab, newline, backspace, bell, and return - in addition
156	to all graphic characters - unencoded.
157	.El
158	.Pp
159	There are four forms of encoding.
160	Most forms use the backslash character
161	.Ql \e
162	to introduce a special
163	sequence; two backslashes are used to represent a real backslash.
164	These are the visual formats:
165	.Bl -tag -width VIS_HTTPSTYLE
166	.It (default)
167	Use an
168	.Ql M
169	to represent meta characters (characters with the 8th
170	bit set), and use carat
171	.Ql ^
172	to represent control characters see
173	.Pf ( Xr iscntrl 3 ) .
174	The following formats are used:
175	.Bl -tag -width xxxxx
176	.It Dv \e^C
177	Represents the control character
178	.Ql C .
179	Spans characters
180	.Ql \e000
181	through
182	.Ql \e037 ,
183	and
184	.Ql \e177
185	(as
186	.Ql \e^? ) .
187	.It Dv \eM-C
188	Represents character
189	.Ql C
190	with the 8th bit set.
191	Spans characters
192	.Ql \e241
193	through
194	.Ql \e376 .
195	.It Dv \eM^C
196	Represents control character
197	.Ql C
198	with the 8th bit set.
199	Spans characters
200	.Ql \e200
201	through
202	.Ql \e237 ,
203	and
204	.Ql \e377
205	(as
206	.Ql \eM^? ) .
207	.It Dv \e040
208	Represents
209	.Tn ASCII
210	space.
211	.It Dv \e240
212	Represents Meta-space.
213	.El
214	.Pp
215	.It Dv VIS_CSTYLE
216	Use C-style backslash sequences to represent standard non-printable
217	characters.
218	The following sequences are used to represent the indicated characters:
219	.Bd -unfilled -offset indent
220	.Li \ea Tn - BEL No (007)
221	.Li \eb Tn - BS No (010)
222	.Li \ef Tn - NP No (014)
223	.Li \en Tn - NL No (012)
224	.Li \er Tn - CR No (015)
225	.Li \et Tn - HT No (011)
226	.Li \ev Tn - VT No (013)
227	.Li \e0 Tn - NUL No (000)
228	.Ed
229	.Pp
230	When using this format, the nextc parameter is looked at to determine
231	if a
232	.Dv NUL
233	character can be encoded as
234	.Ql \e0
235	instead of
236	.Ql \e000 .
237	If
238	.Fa nextc
239	is an octal digit, the latter representation is used to
240	avoid ambiguity.
241	.It Dv VIS_HTTPSTYLE
242	Use URI encoding as described in RFC 1808.
243	The form is
244	.Ql %dd
245	where
246	.Em d
247	represents a hexadecimal digit.
248	.It Dv VIS_OCTAL
249	Use a three digit octal sequence. The form is
250	.Ql \eddd
251	where
252	.Em d
253	represents an octal digit.
254	.El
255	.Pp
256	There is one additional flag,
257	.Dv VIS_NOSLASH ,
258	which inhibits the
259	doubling of backslashes and the backslash before the default
260	format (that is, control characters are represented by
261	.Ql ^C
262	and
263	meta characters as
264	.Ql M-C ) .
265	With this flag set, the encoding is
266	ambiguous and non-invertible.
267	.Sh SEE ALSO
268	.Xr unvis 1 ,
269	.Xr unvis 3
270	.Rs
271	.%A R. Fielding
272	.%T Relative Uniform Resource Locators
273	.%O RFC1808
274	.Re
275	.Sh HISTORY
276	These functions first appeared in
277	.Bx 4.4 .