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[/] [openrisc/] [tags/] [gnu-src/] [newlib-1.18.0/] [newlib-1.18.0-or32-1.0rc2/] [newlib/] [libc/] [unix/] [pread.c] - Rev 520
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#ifndef _NO_PREAD /* FUNCTION <<pread>>---read a file from specified position INDEX pread INDEX _pread_r ANSI_SYNOPSIS #include <unistd.h> ssize_t pread(int <[fd]>, void *<[buf]>, size_t <[n]>, off_t <[off]>); ssize_t _pread_r(struct _reent *<[rptr]>, int <[fd]>, void *<[buf]>, size_t <[n]>, off_t <[off]>); TRAD_SYNOPSIS #include <unistd.h> ssize_t pread(<[fd]>, <[buf]>, <[n]>, <[off]>) int <[fd]>; void *<[buf]>; size_t <[n]>; off_t <[off]>; ssize_t _pread_r(<[rptr]>, <[fd]>, <[buf]>, <[n]>, <[off]>) struct _reent *<[rptr]>; int <[fd]>; void *<[buf]>; size_t <[n]>; off_t <[off]>; DESCRIPTION The <<pread>> function is similar to <<read>>. One difference is that <<pread>> has an additional parameter <[off]> which is the offset to position in the file before reading. The function also differs in that the file position is unchanged by the function (i.e. the file position is the same before and after a call to <<pread>>). The <<_pread_r>> function is the same as <<pread>>, only a reentrant struct pointer <[rptr]> is provided to preserve reentrancy. RETURNS <<pread>> returns the number of bytes read or <<-1>> if failure occurred. PORTABILITY <<pread>> is non-ANSI and is specified by the Single Unix Specification. Supporting OS subroutine required: <<read>>, <<lseek>>. */ #include <_ansi.h> #include <unistd.h> #include <reent.h> ssize_t _DEFUN (_pread_r, (rptr, fd, buf, n, off), struct _reent *rptr _AND int fd _AND _PTR buf _AND size_t n _AND off_t off) { off_t cur_pos; _READ_WRITE_RETURN_TYPE num_read; if ((cur_pos = _lseek_r (rptr, fd, 0, SEEK_CUR)) == (off_t)-1) return -1; if (_lseek_r (rptr, fd, off, SEEK_SET) == (off_t)-1) return -1; num_read = _read_r (rptr, fd, buf, n); if (_lseek_r (rptr, fd, cur_pos, SEEK_SET) == (off_t)-1) return -1; return (ssize_t)num_read; } #ifndef _REENT_ONLY ssize_t _DEFUN (pread, (fd, buf, n, off), int fd _AND _PTR buf _AND size_t n _AND off_t off) { return _pread_r (_REENT, fd, buf, n, off); } #endif /* !_REENT_ONLY */ #endif /* !_NO_PREAD */