Add writev() to libc

This function is needed by perror(3).

Closes #239.

libports/lib/mk/libc.mk

@@ -14,7 +14,7 @@ SRC_CC = atexit.cc dummies.cc rlimit.cc sysctl.cc readlink.cc munmap.cc \
          issetugid.cc errno.cc gai_strerror.cc clock_gettime.cc \
          gettimeofday.cc malloc.cc progname.cc fd_alloc.cc file_operations.cc \
          plugin.cc plugin_registry.cc select.cc exit.cc environ.cc nanosleep.cc \
-         libc_mem_alloc.cc
+         libc_mem_alloc.cc writev.cc
 
 #
 # Files from string library that are not included in libc-raw_string because

libports/src/lib/libc/dummies.cc

@@ -137,7 +137,6 @@ DUMMY(-1, utimes)
 DUMMY(-1, utrace)
 DUMMY(-1, vfork)
 DUMMY(-1, _wait4)
-DUMMY(-1, _writev)
 
 void ksem_init(void)
 {

libports/src/lib/libc/writev.cc

@@ -0,0 +1,75 @@
+/*
+ * \brief  Plugin implementation
+ * \author Josef Soentgen 
+ * \date   2012-04-10
+ */
+
+/*
+ * Copyright (C) 2010-2012 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+
+#include <sys/uio.h>
+#include <limits.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+
+#include <stdio.h>
+
+enum { MAX_BUFFER_LEN = 2048 };
+
+extern "C" int _writev(int d, const struct iovec *iov, int iovcnt)
+{
+	char buffer[MAX_BUFFER_LEN];
+	char *v, *b;
+	ssize_t written;
+	size_t v_len, _len;
+	int i;
+
+	if (iovcnt < 1 || iovcnt > IOV_MAX) {
+		return -EINVAL;
+	}
+
+	for (i = 0; i < iovcnt; i++)
+		v_len += iov->iov_len;
+
+	if (v_len > SSIZE_MAX) {
+		return -EINVAL;
+	}
+
+	b = buffer;
+	while (iovcnt) {
+		v = static_cast<char *>(iov->iov_base);
+		v_len = iov->iov_len;
+
+		while (v_len > 0) {
+			if (v_len < sizeof(buffer))
+				_len = v_len;
+			else
+				_len = sizeof(buffer);
+
+			// TODO error check
+			memmove(b, v, _len);
+			i = write(d, b, _len);
+			v += _len;
+			v_len -= _len;
+
+			written += i;
+		}
+
+		iov++;
+		iovcnt--;
+	}
+
+        return written;
+}
+
+extern "C" ssize_t writev(int d, const struct iovec *iov, int iovcnt)
+{
+	return _writev(d, iov, iovcnt);
+}
+