[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.
.\" 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 1.30 2007/01/09 00:27:56 imp Exp $
.\"
.Dd April 9, 2006
.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:
.Pp
.Bl -tag -width ".Li \e0" -offset indent -compact
.It Li \ea
.Dv BEL No (007)
.It Li \eb
.Dv BS No (010)
.It Li \ef
.Dv NP No (014)
.It Li \en
.Dv NL No (012)
.It Li \er
.Dv CR No (015)
.It Li \es
.Dv SP No (040)
.It Li \et
.Dv HT No (011)
.It Li \ev
.Dv VT No (013)
.It Li \e0
.Dv NUL No (000)
.El
.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.
5b2abdfb A	12	.\" 4. Neither the name of the University nor the names of its contributors
	13	.\" may be used to endorse or promote products derived from this software
	14	.\" without specific prior written permission.
	15	.\"
	16	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	17	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	18	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	19	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	20	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	21	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	22	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	23	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	24	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	25	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	26	.\" SUCH DAMAGE.
	27	.\"
	28	.\" From: @(#)vis.3 8.1 (Berkeley) 6/9/93
1f2f436a	29	.\" $FreeBSD: src/lib/libc/gen/vis.3,v 1.30 2007/01/09 00:27:56 imp Exp $
5b2abdfb	30	.\"
1f2f436a	31	.Dd April 9, 2006
5b2abdfb A	32	.Dt VIS 3
	33	.Os
	34	.Sh NAME
	35	.Nm vis
	36	.Nd visually encode characters
	37	.Sh LIBRARY
	38	.Lb libc
	39	.Sh SYNOPSIS
	40	.In vis.h
	41	.Ft char *
	42	.Fn vis "char *dst" "int c" "int flag" "int nextc"
	43	.Ft int
	44	.Fn strvis "char dst" "const char src" "int flag"
	45	.Ft int
	46	.Fn strvisx "char dst" "const char src" "size_t len" "int flag"
	47	.Sh DESCRIPTION
	48	The
	49	.Fn vis
	50	function
	51	copies into
	52	.Fa dst
	53	a string which represents the character
	54	.Fa c .
	55	If
	56	.Fa c
3d9156a7 A	57	needs no encoding, it is copied in unaltered.
3d9156a7 A	58	The string is
5b2abdfb	59	null terminated, and a pointer to the end of the string is
3d9156a7 A	60	returned.
3d9156a7 A	61	The maximum length of any encoding is four
5b2abdfb A	62	characters (not including the trailing
	63	.Dv NUL ) ;
	64	thus, when
	65	encoding a set of characters into a buffer, the size of the buffer should
	66	be four times the number of characters encoded, plus one for the trailing
	67	.Dv NUL .
9385eb3d A	68	The
	69	.Fa flag
	70	argument is used for altering the default range of
5b2abdfb A	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
3d9156a7 A	138	.It Dv VIS_GLOB
	139	Also encode magic characters
	140	.Ql ( * ,
	141	.Ql \&? ,
	142	.Ql \&[
	143	and
	144	.Ql # )
	145	recognized by
	146	.Xr glob 3 .
5b2abdfb A	147	.It Dv VIS_SP
	148	Also encode space.
	149	.It Dv VIS_TAB
	150	Also encode tab.
	151	.It Dv VIS_NL
	152	Also encode newline.
	153	.It Dv VIS_WHITE
	154	Synonym for
	155	.Dv VIS_SP
	156	\&\|
	157	.Dv VIS_TAB
	158	\&\|
	159	.Dv VIS_NL .
	160	.It Dv VIS_SAFE
3d9156a7 A	161	Only encode "unsafe" characters.
3d9156a7 A	162	Unsafe means control
5b2abdfb	163	characters which may cause common terminals to perform
3d9156a7 A	164	unexpected functions.
3d9156a7 A	165	Currently this form allows space,
5b2abdfb A	166	tab, newline, backspace, bell, and return - in addition
	167	to all graphic characters - unencoded.
	168	.El
	169	.Pp
	170	There are four forms of encoding.
	171	Most forms use the backslash character
	172	.Ql \e
	173	to introduce a special
	174	sequence; two backslashes are used to represent a real backslash.
	175	These are the visual formats:
	176	.Bl -tag -width VIS_HTTPSTYLE
	177	.It (default)
	178	Use an
	179	.Ql M
	180	to represent meta characters (characters with the 8th
3d9156a7	181	bit set), and use caret
5b2abdfb A	182	.Ql ^
	183	to represent control characters see
	184	.Pf ( Xr iscntrl 3 ) .
	185	The following formats are used:
	186	.Bl -tag -width xxxxx
	187	.It Dv \e^C
	188	Represents the control character
	189	.Ql C .
	190	Spans characters
	191	.Ql \e000
	192	through
	193	.Ql \e037 ,
	194	and
	195	.Ql \e177
	196	(as
	197	.Ql \e^? ) .
	198	.It Dv \eM-C
	199	Represents character
	200	.Ql C
	201	with the 8th bit set.
	202	Spans characters
	203	.Ql \e241
	204	through
	205	.Ql \e376 .
	206	.It Dv \eM^C
	207	Represents control character
	208	.Ql C
	209	with the 8th bit set.
	210	Spans characters
	211	.Ql \e200
	212	through
	213	.Ql \e237 ,
	214	and
	215	.Ql \e377
	216	(as
	217	.Ql \eM^? ) .
	218	.It Dv \e040
	219	Represents
	220	.Tn ASCII
	221	space.
	222	.It Dv \e240
	223	Represents Meta-space.
	224	.El
	225	.Pp
	226	.It Dv VIS_CSTYLE
	227	Use C-style backslash sequences to represent standard non-printable
	228	characters.
	229	The following sequences are used to represent the indicated characters:
1f2f436a A	230	.Pp
	231	.Bl -tag -width ".Li \e0" -offset indent -compact
	232	.It Li \ea
	233	.Dv BEL No (007)
	234	.It Li \eb
	235	.Dv BS No (010)
	236	.It Li \ef
	237	.Dv NP No (014)
	238	.It Li \en
	239	.Dv NL No (012)
	240	.It Li \er
	241	.Dv CR No (015)
	242	.It Li \es
	243	.Dv SP No (040)
	244	.It Li \et
	245	.Dv HT No (011)
	246	.It Li \ev
	247	.Dv VT No (013)
	248	.It Li \e0
	249	.Dv NUL No (000)
	250	.El
5b2abdfb	251	.Pp
9385eb3d A	252	When using this format, the
	253	.Fa nextc
	254	argument is looked at to determine
5b2abdfb A	255	if a
	256	.Dv NUL
	257	character can be encoded as
	258	.Ql \e0
	259	instead of
	260	.Ql \e000 .
	261	If
	262	.Fa nextc
	263	is an octal digit, the latter representation is used to
	264	avoid ambiguity.
	265	.It Dv VIS_HTTPSTYLE
	266	Use URI encoding as described in RFC 1808.
	267	The form is
	268	.Ql %dd
	269	where
9385eb3d	270	.Ar d
5b2abdfb A	271	represents a hexadecimal digit.
5b2abdfb A	272	.It Dv VIS_OCTAL
3d9156a7 A	273	Use a three digit octal sequence.
3d9156a7 A	274	The form is
5b2abdfb A	275	.Ql \eddd
5b2abdfb A	276	where
9385eb3d	277	.Ar d
5b2abdfb A	278	represents an octal digit.
	279	.El
	280	.Pp
	281	There is one additional flag,
	282	.Dv VIS_NOSLASH ,
	283	which inhibits the
	284	doubling of backslashes and the backslash before the default
	285	format (that is, control characters are represented by
	286	.Ql ^C
	287	and
	288	meta characters as
	289	.Ql M-C ) .
	290	With this flag set, the encoding is
	291	ambiguous and non-invertible.
	292	.Sh SEE ALSO
	293	.Xr unvis 1 ,
	294	.Xr unvis 3
	295	.Rs
	296	.%A R. Fielding
	297	.%T Relative Uniform Resource Locators
	298	.%O RFC1808
	299	.Re
	300	.Sh HISTORY
	301	These functions first appeared in
	302	.Bx 4.4 .
3d9156a7 A	303	.Sh BUGS
	304	The
	305	.Nm
	306	family of functions do not recognize multibyte characters, and thus
	307	may consider them to be non-printable when they are in fact printable
	308	(and vice versa.)