xnu-2782.1.97.tar.gz

[apple/xnu.git] / SETUP / replacecontents / replacecontents.c

diff --git a/SETUP/replacecontents/replacecontents.c b/SETUP/replacecontents/replacecontents.c
new file mode 100644 (file)
index 0000000..3e72b2d
--- /dev/null
+++ b/SETUP/replacecontents/replacecontents.c
@@ -0,0 +1,137 @@
+/*
+ * Copyright (c) 2013 Apple Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdbool.h>
+#include <errno.h>
+#include <err.h>
+#include <sysexits.h>
+
+#include <sys/stat.h>
+#include <sys/fcntl.h>
+#include <sys/param.h>
+#include <sys/time.h>
+
+void usage(void);
+
+int main(int argc, char * argv[])
+{
+       struct stat sb;
+       char *newcontent = NULL;
+       size_t newcontentlength = 0;
+       char *oldcontent = NULL;
+       int ret;
+       int dstfd;
+       const char *dst = NULL;
+       ssize_t readsize, writesize;
+       int i;
+
+       if (argc < 2) {
+               usage();
+       }
+
+       dst = argv[1];
+
+       for (i=2; i < argc; i++) {
+               newcontentlength += strlen(argv[i]) + 1 /* space or newline */;
+       }
+       newcontentlength += 1; /* NUL */
+
+       newcontent = malloc(newcontentlength);
+       if (newcontent == NULL)
+               err(EX_UNAVAILABLE, "malloc() failed");
+
+       newcontent[0] = '\0';
+
+       for (i=2; i < argc; i++) {
+               strlcat(newcontent, argv[i], newcontentlength);
+               if (i < argc - 1) {
+                       strlcat(newcontent, " ", newcontentlength);
+               } else {
+                       strlcat(newcontent, "\n", newcontentlength);
+               }
+       }
+
+       dstfd = open(dst, O_RDWR | O_CREAT | O_APPEND, DEFFILEMODE);
+       if (dstfd < 0)
+               err(EX_NOINPUT, "open(%s)", dst);
+
+       ret = fstat(dstfd, &sb);
+       if (ret < 0)
+               err(EX_NOINPUT, "fstat(%s)", dst);
+
+       if (!S_ISREG(sb.st_mode))
+               err(EX_USAGE, "%s is not a regular file", dst);
+
+       if (sb.st_size != newcontentlength) {
+               /* obvious new content must be different than old */
+               goto replace;
+       }
+
+       oldcontent = malloc(newcontentlength);
+       if (oldcontent == NULL)
+               err(EX_UNAVAILABLE, "malloc(%lu) failed", newcontentlength);
+
+       readsize = read(dstfd, oldcontent, newcontentlength);
+       if (readsize == -1)
+               err(EX_UNAVAILABLE, "read() failed");
+       else if (readsize != newcontentlength)
+               errx(EX_UNAVAILABLE, "short read of file");
+
+       if (0 == memcmp(oldcontent, newcontent, newcontentlength)) {
+               /* binary comparison succeeded, just exit */
+               free(oldcontent);
+               ret = close(dstfd);
+               if (ret < 0)
+                       err(EX_UNAVAILABLE, "close() failed");
+
+               exit(0);
+       }
+
+replace:
+       ret = ftruncate(dstfd, 0);
+       if (ret < 0)
+               err(EX_UNAVAILABLE, "ftruncate() failed");
+
+       writesize = write(dstfd, newcontent, newcontentlength);
+       if (writesize == -1)
+               err(EX_UNAVAILABLE, "write() failed");
+       else if (writesize != newcontentlength)
+               errx(EX_UNAVAILABLE, "short write of file");
+
+       ret = close(dstfd);
+       if (ret < 0)
+               err(EX_NOINPUT, "close(dst)");
+
+       return 0;
+}
+
+void usage(void)
+{
+       fprintf(stderr, "Usage: %s <dst> <new> <contents> <...>\n",
+                       getprogname());
+       exit(EX_USAGE);
+}