TH MEMORY 2
SH NAME
memccpy, memchr, memcmp, memcpy, memmove, memset \- memory operations
SH SYNOPSIS
B #include <u.h>
br
B #include <libc.h>
PP
ta \w'\fLvoid* 'u
B
void* memccpy(void *s1, void *s2, int c, long n)
PP
B
void* memchr(void *s, int c, long n)
PP
B
int memcmp(void *s1, void *s2, long n)
PP
B
void* memcpy(void *s1, void *s2, long n)
PP
B
void* memmove(void *s1, void *s2, long n)
PP
B
void* memset(void *s, int c, long n)
SH DESCRIPTION
These functions operate efficiently on memory areas
(arrays of bytes bounded by a count, not terminated by a zero byte).
They do not check for the overflow of any receiving memory area.
PP
I Memccpy
copies bytes from memory area
I s2
into
IR s1 ,
stopping after the first occurrence of byte
I c
has been copied, or after
I n
bytes have been copied, whichever comes first.
It returns a pointer to the byte after
the copy of
I c
in
IR s1 ,
or zero if
I c
was not found in the first
I n
bytes of
IR s2 .
PP
I Memchr
returns a pointer to the first
occurrence of byte
I c
in the first
I n
bytes of memory area
IR s,
or zero if
I c
does not occur.
PP
I Memcmp
compares its arguments, looking at the first
I n
bytes only, and returns an integer
less than, equal to, or greater than 0,
according as
I s1
is lexicographically less than, equal to, or
greater than
IR s2 .
The comparison is bytewise unsigned.
PP
I Memcpy
copies
I n
bytes from memory area
I s2
to
IR s1 .
It returns
IR s1 .
PP
I Memmove
works like
IR memcpy ,
except that it is guaranteed to work if
I s1
and
IR s2
overlap.
PP
I Memset
sets the first
I n
bytes in memory area
I s
to the value of byte
IR c .
It returns
IR s .
SH SOURCE
All these routines have portable C implementations in
BR /sys/src/libc/port .
Most also have machine-dependent assembly language implementations in
BR /sys/src/libc/$objtype .
SH SEE ALSO
IR strcat (2)
SH BUGS
ANSI C does not require
I memcpy
to handle overlapping source and destination; on Plan 9, it does, so
I memmove
and
I memcpy
behave identically.
PP
If
I memcpy
and
I memmove
are handed a negative count, they abort.
