make a "copy file" function

Create a specific function to copy a file from a location to
another location.

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>

src/lxc/Makefile.am

@@ -34,7 +34,7 @@ liblxc_la_SOURCES = \
 	parse.c parse.h \
 	cgroup.c cgroup.h \
 	lxc.h \
-	lxc_utils.h \
+	utils.c utils.h \
 	lock.c lock.h \
 	namespace.h \
 	conf.c conf.h \

src/lxc/utils.c

@@ -0,0 +1,104 @@
+/*
+ * lxc: linux Container library
+ *
+ * (C) Copyright IBM Corp. 2007, 2008
+ *
+ * Authors:
+ * Daniel Lezcano <dlezcano at fr.ibm.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+#include "log.h"
+
+lxc_log_define(lxc_utils, lxc);
+
+int lxc_copy_file(const char *srcfile, const char *dstfile)
+{
+	void *srcaddr = NULL, *dstaddr;
+	struct stat stat;
+	int srcfd, dstfd, ret = -1;
+	char c = '\0';
+
+	dstfd = open(dstfile, O_CREAT | O_EXCL | O_RDWR, 0600);
+	if (dstfd < 0) {
+		SYSERROR("failed to creat '%s'", dstfile);
+		goto out;
+	}
+
+	srcfd = open(srcfile, O_RDONLY);
+	if (srcfd < 0) {
+		SYSERROR("failed to open '%s'", srcfile);
+		goto err;
+	}
+
+	if (fstat(srcfd, &stat)) {
+		SYSERROR("failed to stat '%s'", srcfile);
+		goto err;
+	}
+
+	if (!stat.st_size) {
+		INFO("copy '%s' which is an empty file", srcfile);
+		ret = 0;
+		goto out_close;
+	}
+
+	if (lseek(dstfd, stat.st_size - 1, SEEK_SET) < 0) {
+		SYSERROR("failed to seek dest file '%s'", dstfile);
+		goto err;
+	}
+
+	/* fixup length */
+	if (write(dstfd, &c, 1) < 0) {
+		SYSERROR("failed to write to '%s'", dstfile);
+		goto err;
+	}
+
+	srcaddr = mmap(NULL, stat.st_size, PROT_READ, MAP_SHARED, srcfd, 0L);
+	if (srcaddr == MAP_FAILED) {
+		SYSERROR("failed to mmap '%s'", srcfile);
+		goto err;
+	}
+
+	dstaddr = mmap(NULL, stat.st_size, PROT_WRITE, MAP_SHARED, dstfd, 0L);
+	if (dstaddr == MAP_FAILED) {
+		SYSERROR("failed to mmap '%s'", dstfile);
+		goto err;
+	}
+
+	ret = 0;
+
+	memcpy(dstaddr, srcaddr, stat.st_size);
+
+	munmap(dstaddr, stat.st_size);
+out_mmap:
+	if (srcaddr)
+		munmap(srcaddr, stat.st_size);
+out_close:
+	close(dstfd);
+	close(srcfd);
+out:
+	return ret;
+err:
+	unlink(dstfile);
+	goto out_mmap;
+}

src/lxc/utils.h

@@ -49,3 +49,5 @@
 	} while (0)
 
 #endif
+
+extern int lxc_copy_file(const char *src, const char *dst);