lib: Move generic file-handling code to lib/

[petitboot] / lib / file / file.c

diff --git a/lib/file/file.c b/lib/file/file.c
new file mode 100644 (file)
index 0000000..1bde9fb
--- /dev/null
+++ b/lib/file/file.c
@@ -0,0 +1,123 @@
+/*
+ *  Copyright (C) 2013 Jeremy Kerr <jk@ozlabs.org>
+ *
+ *  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; version 2 of the License.
+ *
+ *  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, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <talloc/talloc.h>
+
+#include "file.h"
+
+static const int max_file_size = 1024 * 1024;
+
+int read_file(void *ctx, const char *filename, char **bufp, int *lenp)
+{
+       struct stat statbuf;
+       int rc, fd, i, len;
+       char *buf;
+
+       fd = open(filename, O_RDONLY);
+       if (fd < 0)
+               return -1;
+
+       rc = fstat(fd, &statbuf);
+       if (rc < 0)
+               goto err_close;
+
+       len = statbuf.st_size;
+       if (len > max_file_size)
+               goto err_close;
+
+       buf = talloc_array(ctx, char, len + 1);
+       if (!buf)
+               goto err_close;
+
+       for (i = 0; i < len; i += rc) {
+               rc = read(fd, buf + i, len - i);
+
+               /* unexpected EOF: trim and return */
+               if (rc == 0) {
+                       len = i;
+                       break;
+               }
+
+               if (rc < 0)
+                       goto err_free;
+
+       }
+
+       buf[len] = '\0';
+
+       close(fd);
+       *bufp = buf;
+       *lenp = len;
+       return 0;
+
+err_free:
+       talloc_free(buf);
+err_close:
+       close(fd);
+       return -1;
+}
+
+static int write_fd(int fd, char *buf, int len)
+{
+       int i, rc;
+
+       for (i = 0; i < len; i += rc) {
+               rc = write(fd, buf + i, len - i);
+               if (rc < 0 && errno != -EINTR)
+                       return rc;
+       }
+
+       return 0;
+}
+
+int replace_file(const char *filename, char *buf, int len)
+{
+       char *tempfile;
+       mode_t oldmask;
+       int rc, fd;
+
+       tempfile = talloc_asprintf(NULL, "%s.XXXXXX", filename);
+
+       oldmask = umask(0644);
+       fd = mkstemp(tempfile);
+       umask(oldmask);
+       if (fd < 0) {
+               talloc_free(tempfile);
+               return fd;
+       }
+
+       rc = write_fd(fd, buf, len);
+       if (rc) {
+               unlink(tempfile);
+       } else {
+               rc = rename(tempfile, filename);
+       }
+
+       talloc_free(tempfile);
+
+       fchmod(fd, 0644);
+
+       close(fd);
+       return rc;
+}