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Diffstat (limited to 'newlib/libc/unix/pread.c')
-rw-r--r--newlib/libc/unix/pread.c91
1 files changed, 91 insertions, 0 deletions
diff --git a/newlib/libc/unix/pread.c b/newlib/libc/unix/pread.c
new file mode 100644
index 000000000..68ed68eb1
--- /dev/null
+++ b/newlib/libc/unix/pread.c
@@ -0,0 +1,91 @@
+/*
+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