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Diffstat (limited to 'lib/libc/gen/unvis.3')
| -rw-r--r-- | lib/libc/gen/unvis.3 | 162 |
1 files changed, 162 insertions, 0 deletions
diff --git a/lib/libc/gen/unvis.3 b/lib/libc/gen/unvis.3 new file mode 100644 index 0000000..807a851 --- /dev/null +++ b/lib/libc/gen/unvis.3 @@ -0,0 +1,162 @@ +.\" 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. +.\" +.\" @(#)unvis.3 8.2 (Berkeley) 12/11/93 +.\" +.Dd December 11, 1993 +.Dt UNVIS 3 +.Os +.Sh NAME +.Nm unvis , +.Nm strunvis +.Nd decode a visual representation of characters +.Sh SYNOPSIS +.Fd #include <vis.h> +.Ft int +.Fn unvis "u_char *cp" "u_char c" "int *astate" "int flag" +.Ft int +.Fn strunvis "char *dst" "char *src" +.Sh DESCRIPTION +The +.Fn unvis +and +.Fn strunvis +functions +are used to decode a visual representation of characters, as produced +by the +.Xr vis 3 +function, back into +the original form. Unvis is called with successive characters in +.Ar c +until a valid +sequence is recognized, at which time the decoded character is +available at the character pointed to by +.Ar cp . +Strunvis decodes the +characters pointed to by +.Ar src +into the buffer pointed to by +.Ar dst . +.Pp +The +.Fn strunvis +function +simply copies +.Ar src +to +.Ar dst , +decoding any escape sequences along the way, +and returns the number of characters placed into +.Ar dst , +or \-1 if an +invalid escape sequence was detected. The size of +.Ar dst +should be +equal to the size of +.Ar src +(that is, no expansion takes place during +decoding). +.Pp +The +.Fn unvis +function +implements a state machine that can be used to decode an arbitrary +stream of bytes. All state associated with the bytes being decoded +is stored outside the +.Fn unvis +function (that is, a pointer to the state is passed in), so +calls decoding different streams can be freely intermixed. To +start decoding a stream of bytes, first initialize an integer +to zero. Call +.Fn unvis +with each successive byte, along with a pointer +to this integer, and a pointer to a destination character. +The +.Xr unvis +function +has several return codes that must be handled properly. They are: +.Bl -tag -width UNVIS_VALIDPUSH +.It Li \&0 (zero) +Another character is necessary; nothing has been recognized yet. +.It Dv UNVIS_VALID +A valid character has been recognized and is available at the location +pointed to by cp. +.It Dv UNVIS_VALIDPUSH +A valid character has been recognized and is available at the location +pointed to by cp; however, the character currently passed in should +be passed in again. +.It Dv UNVIS_NOCHAR +A valid sequence was detected, but no character was produced. This +return code is necessary to indicate a logical break between characters. +.It Dv UNVIS_SYNBAD +An invalid escape sequence was detected, or the decoder is in an +unknown state. The decoder is placed into the starting state. +.El +.Pp +When all bytes in the stream have been processed, call +.Fn unvis +one more time with flag set to +.Dv UNVIS_END +to extract any remaining character (the character passed in is ignored). +.Pp +The following code fragment illustrates a proper use of +.Fn unvis . +.Bd -literal -offset indent +int state = 0; +char out; + +while ((ch = getchar()) != EOF) { +again: + switch(unvis(&out, ch, &state, 0)) { + case 0: + case UNVIS_NOCHAR: + break; + case UNVIS_VALID: + (void) putchar(out); + break; + case UNVIS_VALIDPUSH: + (void) putchar(out); + goto again; + case UNVIS_SYNBAD: + (void)fprintf(stderr, "bad sequence!\n"); + exit(1); + } +} +if (unvis(&out, (char)0, &state, UNVIS_END) == UNVIS_VALID) + (void) putchar(out); +.Ed +.Sh SEE ALSO +.Xr vis 1 +.Sh HISTORY +The +.Nm unvis +function +first appeared in 4.4BSD. |
