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lib - a pwrite() implementation (Contributed by Buccapatnam Tirumala, Gautam)

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This commit is contained in:
Ben Gras 2010-06-22 22:04:43 +00:00
parent d78ae27865
commit 24a5f48921
3 changed files with 28 additions and 0 deletions
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1
include/unistd.h
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@ -147,6 +147,7 @@ _PROTOTYPE( int tcsetpgrp, (int _fd, pid_t _pgrp_id) );
_PROTOTYPE( char *ttyname, (int _fd) );
_PROTOTYPE( int unlink, (const char *_path) );
_PROTOTYPE( ssize_t write, (int _fd, const void *_buf, size_t _n) );
_PROTOTYPE( ssize_t pwrite, (int _fd, const void *_buf, size_t _n, off_t _offset));
_PROTOTYPE( int truncate, (const char *_path, off_t _length) );
_PROTOTYPE( int ftruncate, (int _fd, off_t _length) );
_PROTOTYPE( int nice, (int _incr) );

1
lib/libc/posix/Makefile.inc
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@ -107,4 +107,5 @@ SRCS+= \
nice.c \
priority.c \
pread.c \
pwrite.c \
usleep.c

26
lib/libc/posix/pwrite.c Normal file
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@ -0,0 +1,26 @@
#include <lib.h>
#include <unistd.h>
ssize_t pwrite(int fd, const void *buffer, size_t nbytes, off_t where)
{
off_t here;
ssize_t w;
if((here = lseek(fd, 0, SEEK_CUR)) < 0)
return -1;
if(lseek(fd, where, SEEK_SET) < 0)
return -1;
if((w=write(fd, buffer, nbytes)) < 0) {
int e = errno;
lseek(fd, here, SEEK_SET);
errno = e;
return -1;
}
if(lseek(fd, here, SEEK_SET) < 0)
return -1;
return w;
}