plan9fox/sys/man/2/rune

.TH RUNE 2
.SH NAME
runetochar, chartorune, runelen, runenlen, fullrune, utfecpy, utflen, utfnlen, utfrune, utfrrune, utfutf \- rune/UTF conversion
.SH SYNOPSIS
.ta \w'\fLchar*xx'u
.B #include <u.h>
.br
.B #include <libc.h>
.PP
.B
int	runetochar(char *s, Rune *r)
.PP
.B
int	chartorune(Rune *r, char *s)
.PP
.B
int	runelen(long r)
.PP
.B
int	runenlen(Rune *r, int n)
.PP
.B
int	fullrune(char *s, int n)
.PP
.B
char*	utfecpy(char *s1, char *es1, char *s2)
.PP
.B
int	utflen(char *s)
.PP
.B
int	utfnlen(char *s, long n)
.PP
.B
char*	utfrune(char *s, long c)
.PP
.B
char*	utfrrune(char *s, long c)
.PP
.B
char*	utfutf(char *s1, char *s2)
.SH DESCRIPTION
These routines convert to and from a
.SM UTF
byte stream and runes.
.PP
.I Runetochar
copies one rune at
.I r
to at most
.B UTFmax
bytes starting at
.I s
and returns the number of bytes copied.
.BR UTFmax ,
defined as
.B 4
in
.BR <libc.h> ,
is the maximum number of bytes required to represent a rune.
.PP
.I Chartorune
copies at most
.B UTFmax
bytes starting at
.I s
to one rune at
.I r
and returns the number of bytes copied.
If the input is not exactly in
.SM UTF
format,
.I chartorune
will convert to
.B Runeerror
(0xFFFD)
and return 1.
.PP
.I Runelen
returns the number of bytes
required to convert
.I r
into
.SM UTF.
.PP
.I Runenlen
returns the number of bytes
required to convert the
.I n
runes pointed to by
.I r
into
.SM UTF.
.PP
.I Fullrune
returns 1 if the string
.I s
of length
.I n
is long enough to be decoded by
.I chartorune
and 0 otherwise.
This does not guarantee that the string
contains a legal
.SM UTF
encoding.
This routine is used by programs that
obtain input a byte at
a time and need to know when a full rune
has arrived.
.PP
The following routines are analogous to the
corresponding string routines with
.B utf
substituted for
.B str
and
.B rune
substituted for
.BR chr .
.PP
.I Utfecpy
copies UTF sequences until a null sequence has been copied, but writes no 
sequences beyond
.IR es1 .
If any sequences are copied,
.I s1
is terminated by a null sequence, and a pointer to that sequence is returned.
Otherwise, the original
.I s1
is returned.
.PP
.I Utflen
returns the number of runes that
are represented by the
.SM UTF
string
.IR s .
.PP
.I Utfnlen
returns the number of complete runes that
are represented by the first
.I n
bytes of
.SM UTF
string
.IR s .
If the last few bytes of the string contain an incompletely coded rune,
.I utfnlen
will not count them; in this way, it differs from
.IR utflen ,
which includes every byte of the string.
.PP
.I Utfrune
.RI ( utfrrune )
returns a pointer to the first (last)
occurrence of rune
.I c
in the
.SM UTF
string
.IR s ,
or 0 if
.I c
does not occur in the string.
The NUL byte terminating a string is considered to
be part of the string
.IR s .
.PP
.I Utfutf
returns a pointer to the first occurrence of
the
.SM UTF
string
.I s2
as a
.SM UTF
substring of
.IR s1 ,
or 0 if there is none.
If
.I s2
is the null string,
.I utfutf
returns
.IR s1 .
.SH SOURCE
.B /sys/src/libc/port/rune.c
.br
.B /sys/src/libc/port/utfecpy.c
.br
.B /sys/src/libc/port/utfrune.c
.br
.B /sys/src/libc/port/utfrrune.c
.br
.B /sys/src/libc/port/utflen.c
.br
.B /sys/src/libc/port/utfnlen.c
.br
.B /sys/src/libc/port/utfutf.c
.SH SEE ALSO
.IR utf (6),
.IR tcs (1)
.SH BUGS
When re-encoding UTF strings with
.I chartorune
and
.I runetochar
one has to consider that encoding a
.I Runeerror
(0xFFFD)
that resulted from invalid encoded input can yield
a longer UTF sequence on the output.