1 /* 2 FUNCTION 3 <<pread64>>---read a large file from specified position 4 5 INDEX 6 pread64 7 8 ANSI_SYNOPSIS 9 #include <unistd.h> 10 ssize_t pread64(int <[fd]>, void *<[buf]>, size_t <[n]>, loff_t <[off]>); 11 12 TRAD_SYNOPSIS 13 #include <unistd.h> 14 ssize_t pread64(<[fd]>, <[buf]>, <[n]>, <[off]>) 15 int <[fd]>; 16 void *<[buf]>; 17 size_t <[n]>; 18 loff_t <[off]>; 19 20 DESCRIPTION 21 The <<pread64>> function is similar to <<pread>>. The only difference is 22 that it operates on large files and so takes a 64-bit offset. Like <<pread>>>, 23 the file position is unchanged by the function (i.e. the file position 24 is the same before and after a call to <<pread>>). 25 26 RETURNS 27 <<pread64>> returns the number of bytes read or <<-1>> if failure occurred. 28 29 PORTABILITY 30 <<pread64>> is an EL/IX extension. 31 32 Supporting OS subroutine required: <<read>>, <<lseek64>>. 33 */ 34 35 #include <_ansi.h> 36 #include <unistd.h> 37 #include <reent.h> 38 #include <machine/weakalias.h> 39 40 ssize_t 41 _DEFUN (__libc_pread64, (fd, buf, n, off), 42 int fd _AND 43 _PTR buf _AND 44 size_t n _AND 45 loff_t off) 46 { 47 loff_t cur_pos; 48 _READ_WRITE_RETURN_TYPE num_read; 49 50 if ((cur_pos = lseek64 (fd, 0, SEEK_CUR)) == (loff_t)-1) 51 return -1; 52 53 if (lseek64 (fd, off, SEEK_SET) == (loff_t)-1) 54 return -1; 55 56 num_read = read (fd, buf, n); 57 58 if (lseek64 (fd, cur_pos, SEEK_SET) == (loff_t)-1) 59 return -1; 60 61 return (ssize_t)num_read; 62 } 63 weak_alias(__libc_pread64,pread64); 64 weak_alias(__libc_pread64,__pread64); 65 66