--- a/ChangeLog	Wed May 05 20:53:05 2010 +0200
+++ b/ChangeLog	Wed May 05 21:09:38 2010 +0200
@@ -1,3 +1,18 @@
+2010-05-05  Peter O'Gorman  <pogma@thewrittenword.com>
+
+	New module pwrite.
+	* lib/unistd.in.h (pwrite): New declaration.
+	* lib/pwrite.c: New file, from glibc with modifications.
+	* m4/pwrite.m4: New file.
+	* m4/unistd_h.m4 (gl_UNISTD_H): Test whether pwrite is declared.
+	(gl_UNISTD_H_DEFAULTS): Initialize GNULIB_PWRITE, HAVE_PWRITE,
+	REPLACE_PWRITE.
+	* modules/pwrite: New file.
+	* modules/unistd (Makefile.am): Substitute GNULIB_PWRITE, HAVE_PWRITE,
+	REPLACE_PWRITE.
+	* tests/test-unistd-c++.cc: Check GNULIB_NAMESPACE::pwrite.
+	* doc/posix-functions/pwrite.texi: Mention the new module.
+
 2010-05-05  Peter O'Gorman  <pogma@thewrittenword.com>
 
 	pread: Update documentation.

--- a/doc/posix-functions/pwrite.texi	Wed May 05 20:53:05 2010 +0200
+++ b/doc/posix-functions/pwrite.texi	Wed May 05 21:09:38 2010 +0200
@@ -4,15 +4,15 @@
 
 POSIX specification: @url{http://www.opengroup.org/onlinepubs/9699919799/functions/pwrite.html}
 
-Gnulib module: ---
+Gnulib module: pwrite
 
 Portability problems fixed by Gnulib:
 @itemize
+@item
+This function is missing on some platforms:
+HP-UX 10, mingw, BeOS.
 @end itemize
 
 Portability problems not fixed by Gnulib:
 @itemize
-@item
-This function is missing on some platforms:
-mingw, BeOS.
 @end itemize

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/pwrite.c	Wed May 05 21:09:38 2010 +0200
@@ -0,0 +1,64 @@
+/* Write block to given position in file without changing file pointer.
+   POSIX version.
+   Copyright (C) 1997, 1998, 1999, 2002 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <unistd.h>
+
+#include <errno.h>
+
+#define __libc_lseek(f,o,w) lseek (f, o, w)
+#define __set_errno(Val) errno = (Val)
+#define __libc_write(f,b,n) write (f, b, n)
+
+/* Note: This implementation of pwrite is not multithread-safe.  */
+
+ssize_t
+pwrite (int fd, const void *buf, size_t nbyte, off_t offset)
+{
+  /* Since we must not change the file pointer preserve the value so that
+     we can restore it later.  */
+  int save_errno;
+  ssize_t result;
+  off_t old_offset = __libc_lseek (fd, 0, SEEK_CUR);
+  if (old_offset == (off_t) -1)
+    return -1;
+
+  /* Set to wanted position.  */
+  if (__libc_lseek (fd, offset, SEEK_SET) == (off_t) -1)
+    return -1;
+
+  /* Write out the data.  */
+  result = __libc_write (fd, buf, nbyte);
+
+  /* Now we have to restore the position.  If this fails we have to
+     return this as an error.  But if the writing also failed we
+     return this error.  */
+  save_errno = errno;
+  if (__libc_lseek (fd, old_offset, SEEK_SET) == (off_t) -1)
+    {
+      if (result == -1)
+	__set_errno (save_errno);
+      return -1;
+    }
+  __set_errno (save_errno);
+
+  return result;
+}

--- a/lib/unistd.in.h	Wed May 05 20:53:05 2010 +0200
+++ b/lib/unistd.in.h	Wed May 05 21:09:38 2010 +0200
@@ -86,7 +86,7 @@
 #endif
 
 #if (@GNULIB_WRITE@ || @GNULIB_READLINK@ || @GNULIB_READLINKAT@ \
-     || @GNULIB_PREAD@ || defined GNULIB_POSIXCHECK)
+     || @GNULIB_PREAD@ || @GNULIB_PWRITE@ || defined GNULIB_POSIXCHECK)
 /* Get ssize_t.  */
 # include <sys/types.h>
 #endif
@@ -1016,6 +1016,40 @@
 #endif
 
 
+#if @GNULIB_PWRITE@
+/* Write at most BUFSIZE bytes from BUF into FD, starting at OFFSET.
+   Return the number of bytes written if successful, otherwise
+   set errno and return -1.  0 indicates nothing written.  See the
+   POSIX:2001 specification
+   <http://www.opengroup.org/susv3xsh/pwrite.html>.  */
+# if @REPLACE_PWRITE@
+#  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
+#   define pwrite rpl_pwrite
+#  endif
+_GL_FUNCDECL_RPL (pwrite, ssize_t,
+                  (int fd, const void *buf, size_t bufsize, off_t offset)
+                  _GL_ARG_NONNULL ((2)));
+_GL_CXXALIAS_RPL (pwrite, ssize_t,
+                  (int fd, const void *buf, size_t bufsize, off_t offset));
+# else
+#  if !@HAVE_PWRITE@
+_GL_FUNCDECL_SYS (pwrite, ssize_t,
+                  (int fd, const void *buf, size_t bufsize, off_t offset)
+                  _GL_ARG_NONNULL ((2)));
+#  endif
+_GL_CXXALIAS_SYS (pwrite, ssize_t,
+                  (int fd, const void *buf, size_t bufsize, off_t offset));
+# endif
+_GL_CXXALIASWARN (pwrite);
+#elif defined GNULIB_POSIXCHECK
+# undef pwrite
+# if HAVE_RAW_DECL_PWRITE
+_GL_WARN_ON_USE (pwrite, "pwrite is unportable - "
+                 "use gnulib module pwrite for portability");
+# endif
+#endif
+
+
 #if @GNULIB_READLINK@
 /* Read the contents of the symbolic link FILE and place the first BUFSIZE
    bytes of it into BUF.  Return the number of bytes placed into BUF if

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m4/pwrite.m4	Wed May 05 21:09:38 2010 +0200
@@ -0,0 +1,19 @@
+# pwrite.m4 serial 1
+dnl Copyright (C) 2010 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_PWRITE],
+[
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+
+  dnl Persuade glibc <unistd.h> to declare pwrite().
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
+  AC_CHECK_FUNCS_ONCE([pwrite])
+  if test $ac_cv_func_pwrite = no; then
+    HAVE_PWRITE=0
+    AC_LIBOBJ([pwrite])
+  fi
+])

--- a/m4/unistd_h.m4	Wed May 05 20:53:05 2010 +0200
+++ b/m4/unistd_h.m4	Wed May 05 21:09:38 2010 +0200
@@ -38,8 +38,9 @@
     ]], [chown dup2 dup3 environ euidaccess faccessat fchdir fchownat
     fsync ftruncate getcwd getdomainname getdtablesize getgroups
     gethostname getlogin getlogin_r getpagesize getusershell setusershell
-    endusershell lchown link linkat lseek pipe2 pread readlink readlinkat
-    rmdir sleep symlink symlinkat ttyname_r unlink unlinkat usleep])
+    endusershell lchown link linkat lseek pipe2 pread pwrite readlink
+    readlinkat rmdir sleep symlink symlinkat ttyname_r unlink unlinkat
+    usleep])
 ])
 
 AC_DEFUN([gl_UNISTD_MODULE_INDICATOR],
@@ -79,6 +80,7 @@
   GNULIB_LSEEK=0;            AC_SUBST([GNULIB_LSEEK])
   GNULIB_PIPE2=0;            AC_SUBST([GNULIB_PIPE2])
   GNULIB_PREAD=0;            AC_SUBST([GNULIB_PREAD])
+  GNULIB_PWRITE=0;           AC_SUBST([GNULIB_PWRITE])
   GNULIB_READLINK=0;         AC_SUBST([GNULIB_READLINK])
   GNULIB_READLINKAT=0;       AC_SUBST([GNULIB_READLINKAT])
   GNULIB_RMDIR=0;            AC_SUBST([GNULIB_RMDIR])
@@ -113,6 +115,7 @@
   HAVE_LINKAT=1;          AC_SUBST([HAVE_LINKAT])
   HAVE_PIPE2=1;           AC_SUBST([HAVE_PIPE2])
   HAVE_PREAD=1;           AC_SUBST([HAVE_PREAD])
+  HAVE_PWRITE=1;          AC_SUBST([HAVE_PWRITE])
   HAVE_READLINK=1;        AC_SUBST([HAVE_READLINK])
   HAVE_READLINKAT=1;      AC_SUBST([HAVE_READLINKAT])
   HAVE_SLEEP=1;           AC_SUBST([HAVE_SLEEP])
@@ -140,6 +143,7 @@
   REPLACE_LINKAT=0;       AC_SUBST([REPLACE_LINKAT])
   REPLACE_LSEEK=0;        AC_SUBST([REPLACE_LSEEK])
   REPLACE_PREAD=0;        AC_SUBST([REPLACE_PREAD])
+  REPLACE_PWRITE=0;       AC_SUBST([REPLACE_PWRITE])
   REPLACE_READLINK=0;     AC_SUBST([REPLACE_READLINK])
   REPLACE_RMDIR=0;        AC_SUBST([REPLACE_RMDIR])
   REPLACE_SLEEP=0;        AC_SUBST([REPLACE_SLEEP])

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/modules/pwrite	Wed May 05 21:09:38 2010 +0200
@@ -0,0 +1,25 @@
+Description:
+pwrite() function: write without changing file offset
+
+Files:
+lib/pwrite.c
+m4/pwrite.m4
+
+Depends-on:
+lseek
+unistd
+
+configure.ac:
+gl_FUNC_PWRITE
+gl_UNISTD_MODULE_INDICATOR([pwrite])
+
+Makefile.am:
+
+Include:
+<unistd.h>
+
+License:
+LGPLv2+
+
+Maintainer:
+Peter O'Gorman

--- a/modules/unistd	Wed May 05 20:53:05 2010 +0200
+++ b/modules/unistd	Wed May 05 21:09:38 2010 +0200
@@ -53,6 +53,7 @@
 	      -e 's|@''GNULIB_LSEEK''@|$(GNULIB_LSEEK)|g' \
 	      -e 's|@''GNULIB_PIPE2''@|$(GNULIB_PIPE2)|g' \
 	      -e 's|@''GNULIB_PREAD''@|$(GNULIB_PREAD)|g' \
+	      -e 's|@''GNULIB_PWRITE''@|$(GNULIB_PWRITE)|g' \
 	      -e 's|@''GNULIB_READLINK''@|$(GNULIB_READLINK)|g' \
 	      -e 's|@''GNULIB_READLINKAT''@|$(GNULIB_READLINKAT)|g' \
 	      -e 's|@''GNULIB_RMDIR''@|$(GNULIB_RMDIR)|g' \
@@ -87,6 +88,7 @@
 	      -e 's|@''HAVE_LINKAT''@|$(HAVE_LINKAT)|g' \
 	      -e 's|@''HAVE_PIPE2''@|$(HAVE_PIPE2)|g' \
 	      -e 's|@''HAVE_PREAD''@|$(HAVE_PREAD)|g' \
+	      -e 's|@''HAVE_PWRITE''@|$(HAVE_PWRITE)|g' \
 	      -e 's|@''HAVE_READLINK''@|$(HAVE_READLINK)|g' \
 	      -e 's|@''HAVE_READLINKAT''@|$(HAVE_READLINKAT)|g' \
 	      -e 's|@''HAVE_SLEEP''@|$(HAVE_SLEEP)|g' \
@@ -114,6 +116,7 @@
 	      -e 's|@''REPLACE_LINKAT''@|$(REPLACE_LINKAT)|g' \
 	      -e 's|@''REPLACE_LSEEK''@|$(REPLACE_LSEEK)|g' \
 	      -e 's|@''REPLACE_PREAD''@|$(REPLACE_PREAD)|g' \
+	      -e 's|@''REPLACE_PWRITE''@|$(REPLACE_PWRITE)|g' \
 	      -e 's|@''REPLACE_READLINK''@|$(REPLACE_READLINK)|g' \
 	      -e 's|@''REPLACE_RMDIR''@|$(REPLACE_RMDIR)|g' \
 	      -e 's|@''REPLACE_SLEEP''@|$(REPLACE_SLEEP)|g' \

--- a/tests/test-unistd-c++.cc	Wed May 05 20:53:05 2010 +0200
+++ b/tests/test-unistd-c++.cc	Wed May 05 21:09:38 2010 +0200
@@ -138,6 +138,11 @@
                  (int, void *, size_t, off_t));
 #endif
 
+#if GNULIB_TEST_PWRITE
+SIGNATURE_CHECK (GNULIB_NAMESPACE::pwrite, ssize_t,
+                 (int, const void *, size_t, off_t));
+#endif
+
 #if GNULIB_TEST_READLINK
 SIGNATURE_CHECK (GNULIB_NAMESPACE::readlink, ssize_t,
                  (const char *, char *, size_t));