UNVIS(3) | Library Functions Manual | UNVIS(3) |
unvis
, strunvis
,
strnunvis
, strunvisx
,
strnunvisx
—
#include <vis.h>
int
unvis
(char
*cp, int c,
int *astate,
int flag);
int
strunvis
(char
*dst, const char
*src);
int
strnunvis
(char
*dst, size_t dlen,
const char *src);
int
strunvisx
(char
*dst, const char
*src, int
flag);
int
strnunvisx
(char
*dst, size_t dlen,
const char *src,
int flag);
unvis
(), strunvis
() and
strunvisx
() functions are used to decode a visual
representation of characters, as produced by the
vis(3) function, back into the
original form.
The unvis
() function is called with
successive characters in c until a valid sequence is
recognized, at which time the decoded character is available at the
character pointed to by cp.
The strunvis
() function decodes the
characters pointed to by src into the buffer pointed
to by dst. The strunvis
()
function simply copies src to
dst, decoding any escape sequences along the way, and
returns the number of characters placed into dst, or
-1 if an invalid escape sequence was detected. The size of
dst should be equal to the size of
src (that is, no expansion takes place during
decoding).
The strunvisx
() and
strnunvisx
() functions do the same as the
strunvis
() and strnunvis
()
functions, but take a flag that specifies the style the string
src is encoded with. The meaning of the flag is the
same as explained below for unvis
().
The 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
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
unvis
() with each successive byte, along with a
pointer to this integer, and a pointer to a destination character. The
unvis
() function has several return codes that must
be handled properly. They are:
0
(zero)UNVIS_VALID
UNVIS_VALIDPUSH
UNVIS_NOCHAR
UNVIS_SYNBAD
When all bytes in the stream have been processed, call
unvis
() one more time with flag set to
UNVIS_END
to extract any remaining character (the
character passed in is ignored).
The flag argument is also used to specify
the encoding style of the source. If set to
VIS_NOESCAPE
unvis
() will
not decode backslash escapes. If set to
VIS_HTTPSTYLE
or
VIS_HTTP1808
, unvis
() will
decode URI strings as specified in RFC 1808. If set to
VIS_HTTP1866
, unvis
() will
decode entity references and numeric character references as specified in
RFC 1866. If set to VIS_MIMESTYLE
,
unvis
() will decode MIME Quoted-Printable strings as
specified in RFC 2045. If set to VIS_NOESCAPE
,
unvis
() will not decode
‘\
’ quoted characters.
The following code fragment illustrates a proper use of
unvis
().
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: errx(EXIT_FAILURE, "Bad character sequence!"); } } if (unvis(&out, '\0', &state, UNVIS_END) == UNVIS_VALID) (void)putchar(out);
strunvis
(),
strnunvis
(), strunvisx
(), and
strnunvisx
() will return -1 on error and set
errno to:
EINVAL
]In addition the functions strnunvis
() and
strnunvisx
() will can also set
errno on error to:
ENOSPC
]R. Fielding, Relative Uniform Resource Locators, RFC1808.
unvis
() function first appeared in
4.4BSD. The strnunvis
() and
strnunvisx
() functions appeared in
NetBSD 6.0.
VIS_HTTP1808
and
VIS_HTTP1866
are wrong. Percent-encoding was defined
in RFC 1738, the original RFC for URL. RFC 1866 defines HTML 2.0, an
application of SGML, from which it inherits concepts of numeric character
references and entity references.
May 8, 2019 | NetBSD 9.0 |