[apple/libc.git] / gen / FreeBSD / 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 1.26 2004/07/17 12:27:25 tjr Exp $
.\"
.Dd March 21, 2004
.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
.Fa flag
argument 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_GLOB
Also encode magic characters
.Ql ( * ,
.Ql \&? ,
.Ql \&[
and
.Ql # )
recognized by
.Xr glob 3 .
.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 caret
.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
.Fa nextc
argument 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
.Ar d
represents a hexadecimal digit.
.It Dv VIS_OCTAL
Use a three digit octal sequence.
The form is
.Ql \eddd
where
.Ar 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 .
.Sh BUGS
The
.Nm
family of functions do not recognize multibyte characters, and thus
may consider them to be non-printable when they are in fact printable
(and vice versa.)
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
3d9156a7	33	.\" $FreeBSD: src/lib/libc/gen/vis.3,v 1.26 2004/07/17 12:27:25 tjr Exp $
5b2abdfb	34	.\"
3d9156a7	35	.Dd March 21, 2004
5b2abdfb A	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
3d9156a7 A	61	needs no encoding, it is copied in unaltered.
3d9156a7 A	62	The string is
5b2abdfb	63	null terminated, and a pointer to the end of the string is
3d9156a7 A	64	returned.
3d9156a7 A	65	The maximum length of any encoding is four
5b2abdfb A	66	characters (not including the trailing
	67	.Dv NUL ) ;
	68	thus, when
	69	encoding a set of characters into a buffer, the size of the buffer should
	70	be four times the number of characters encoded, plus one for the trailing
	71	.Dv NUL .
9385eb3d A	72	The
	73	.Fa flag
	74	argument is used for altering the default range of
5b2abdfb A	75	characters considered for encoding and for altering the visual
	76	representation.
	77	The additional character,
	78	.Fa nextc ,
	79	is only used when selecting the
	80	.Dv VIS_CSTYLE
	81	encoding format (explained below).
	82	.Pp
	83	The
	84	.Fn strvis
	85	and
	86	.Fn strvisx
	87	functions copy into
	88	.Fa dst
	89	a visual representation of
	90	the string
	91	.Fa src .
	92	The
	93	.Fn strvis
	94	function encodes characters from
	95	.Fa src
	96	up to the
	97	first
	98	.Dv NUL .
	99	The
	100	.Fn strvisx
	101	function encodes exactly
	102	.Fa len
	103	characters from
	104	.Fa src
	105	(this
	106	is useful for encoding a block of data that may contain
	107	.Dv NUL Ns 's ) .
	108	Both forms
	109	.Dv NUL
	110	terminate
	111	.Fa dst .
	112	The size of
	113	.Fa dst
	114	must be four times the number
	115	of characters encoded from
	116	.Fa src
	117	(plus one for the
	118	.Dv NUL ) .
	119	Both
	120	forms return the number of characters in dst (not including
	121	the trailing
	122	.Dv NUL ) .
	123	.Pp
	124	The encoding is a unique, invertible representation composed entirely of
	125	graphic characters; it can be decoded back into the original form using
	126	the
	127	.Xr unvis 3
	128	or
	129	.Xr strunvis 3
	130	functions.
	131	.Pp
	132	There are two parameters that can be controlled: the range of
	133	characters that are encoded, and the type
	134	of representation used.
	135	By default, all non-graphic characters
	136	except space, tab, and newline are encoded.
	137	(See
	138	.Xr isgraph 3 . )
139	The following flags
140	alter this:
141	.Bl -tag -width VIS_WHITEX
3d9156a7 A	142	.It Dv VIS_GLOB
	143	Also encode magic characters
	144	.Ql ( * ,
	145	.Ql \&? ,
	146	.Ql \&[
	147	and
	148	.Ql # )
	149	recognized by
	150	.Xr glob 3 .
5b2abdfb A	151	.It Dv VIS_SP
	152	Also encode space.
	153	.It Dv VIS_TAB
	154	Also encode tab.
	155	.It Dv VIS_NL
	156	Also encode newline.
	157	.It Dv VIS_WHITE
	158	Synonym for
	159	.Dv VIS_SP
	160	\&\|
	161	.Dv VIS_TAB
	162	\&\|
	163	.Dv VIS_NL .
	164	.It Dv VIS_SAFE
3d9156a7 A	165	Only encode "unsafe" characters.
3d9156a7 A	166	Unsafe means control
5b2abdfb	167	characters which may cause common terminals to perform
3d9156a7 A	168	unexpected functions.
3d9156a7 A	169	Currently this form allows space,
5b2abdfb A	170	tab, newline, backspace, bell, and return - in addition
	171	to all graphic characters - unencoded.
	172	.El
	173	.Pp
	174	There are four forms of encoding.
	175	Most forms use the backslash character
	176	.Ql \e
	177	to introduce a special
	178	sequence; two backslashes are used to represent a real backslash.
	179	These are the visual formats:
	180	.Bl -tag -width VIS_HTTPSTYLE
	181	.It (default)
	182	Use an
	183	.Ql M
	184	to represent meta characters (characters with the 8th
3d9156a7	185	bit set), and use caret
5b2abdfb A	186	.Ql ^
	187	to represent control characters see
	188	.Pf ( Xr iscntrl 3 ) .
	189	The following formats are used:
	190	.Bl -tag -width xxxxx
	191	.It Dv \e^C
	192	Represents the control character
	193	.Ql C .
	194	Spans characters
	195	.Ql \e000
	196	through
	197	.Ql \e037 ,
	198	and
	199	.Ql \e177
	200	(as
	201	.Ql \e^? ) .
	202	.It Dv \eM-C
	203	Represents character
	204	.Ql C
	205	with the 8th bit set.
	206	Spans characters
	207	.Ql \e241
	208	through
	209	.Ql \e376 .
	210	.It Dv \eM^C
	211	Represents control character
	212	.Ql C
	213	with the 8th bit set.
	214	Spans characters
	215	.Ql \e200
	216	through
	217	.Ql \e237 ,
	218	and
	219	.Ql \e377
	220	(as
	221	.Ql \eM^? ) .
	222	.It Dv \e040
	223	Represents
	224	.Tn ASCII
	225	space.
	226	.It Dv \e240
	227	Represents Meta-space.
	228	.El
	229	.Pp
	230	.It Dv VIS_CSTYLE
	231	Use C-style backslash sequences to represent standard non-printable
	232	characters.
	233	The following sequences are used to represent the indicated characters:
	234	.Bd -unfilled -offset indent
	235	.Li \ea Tn - BEL No (007)
	236	.Li \eb Tn - BS No (010)
	237	.Li \ef Tn - NP No (014)
	238	.Li \en Tn - NL No (012)
	239	.Li \er Tn - CR No (015)
	240	.Li \et Tn - HT No (011)
	241	.Li \ev Tn - VT No (013)
	242	.Li \e0 Tn - NUL No (000)
	243	.Ed
	244	.Pp
9385eb3d A	245	When using this format, the
	246	.Fa nextc
	247	argument is looked at to determine
5b2abdfb A	248	if a
	249	.Dv NUL
	250	character can be encoded as
	251	.Ql \e0
	252	instead of
	253	.Ql \e000 .
	254	If
	255	.Fa nextc
	256	is an octal digit, the latter representation is used to
	257	avoid ambiguity.
	258	.It Dv VIS_HTTPSTYLE
	259	Use URI encoding as described in RFC 1808.
	260	The form is
	261	.Ql %dd
	262	where
9385eb3d	263	.Ar d
5b2abdfb A	264	represents a hexadecimal digit.
5b2abdfb A	265	.It Dv VIS_OCTAL
3d9156a7 A	266	Use a three digit octal sequence.
3d9156a7 A	267	The form is
5b2abdfb A	268	.Ql \eddd
5b2abdfb A	269	where
9385eb3d	270	.Ar d
5b2abdfb A	271	represents an octal digit.
	272	.El
	273	.Pp
	274	There is one additional flag,
	275	.Dv VIS_NOSLASH ,
	276	which inhibits the
	277	doubling of backslashes and the backslash before the default
	278	format (that is, control characters are represented by
	279	.Ql ^C
	280	and
	281	meta characters as
	282	.Ql M-C ) .
	283	With this flag set, the encoding is
	284	ambiguous and non-invertible.
	285	.Sh SEE ALSO
	286	.Xr unvis 1 ,
	287	.Xr unvis 3
	288	.Rs
	289	.%A R. Fielding
	290	.%T Relative Uniform Resource Locators
	291	.%O RFC1808
	292	.Re
	293	.Sh HISTORY
	294	These functions first appeared in
	295	.Bx 4.4 .
3d9156a7 A	296	.Sh BUGS
	297	The
	298	.Nm
	299	family of functions do not recognize multibyte characters, and thus
	300	may consider them to be non-printable when they are in fact printable
	301	(and vice versa.)