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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);