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/*
FUNCTION
<<pread64>>---read a large file from specified position
INDEX
pread64
ANSI_SYNOPSIS
#include <unistd.h>
ssize_t pread64(int <[fd]>, void *<[buf]>, size_t <[n]>, loff_t <[off]>);
TRAD_SYNOPSIS
#include <unistd.h>
ssize_t pread64(<[fd]>, <[buf]>, <[n]>, <[off]>)
int <[fd]>;
void *<[buf]>;
size_t <[n]>;
loff_t <[off]>;
DESCRIPTION
The <<pread64>> function is similar to <<pread>>. The only difference is
that it operates on large files and so takes a 64-bit offset. Like <<pread>>>,
the file position is unchanged by the function (i.e. the file position
is the same before and after a call to <<pread>>).
RETURNS
<<pread64>> returns the number of bytes read or <<-1>> if failure occurred.
PORTABILITY
<<pread64>> is an EL/IX extension.
Supporting OS subroutine required: <<read>>, <<lseek64>>.
*/
#include <_ansi.h>
#include <unistd.h>
#include <reent.h>
#include <machine/weakalias.h>
ssize_t
_DEFUN (__libc_pread64, (fd, buf, n, off),
int fd _AND
_PTR buf _AND
size_t n _AND
loff_t off)
{
loff_t cur_pos;
_READ_WRITE_RETURN_TYPE num_read;
if ((cur_pos = lseek64 (fd, 0, SEEK_CUR)) == (loff_t)-1)
return -1;
if (lseek64 (fd, off, SEEK_SET) == (loff_t)-1)
return -1;
num_read = read (fd, buf, n);
if (lseek64 (fd, cur_pos, SEEK_SET) == (loff_t)-1)
return -1;
return (ssize_t)num_read;
}
weak_alias(__libc_pread64,pread64);
weak_alias(__libc_pread64,__pread64);
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