Btrfs-progs: add btrfs-crc tool

This tool can be used to compute btrfs' style crc32c checksums for filenames
as done by the kernel. Additionally, there is -c mode to do a brute force
search for file names with a given checksum.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>

diff --git a/Makefile b/Makefile
index a270e9c..dcd3a0e 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -174,6 +174,10 @@ btrfs-image: $(objects) $(libs) btrfs-image.o
        @echo "    [LD]     $@"
        $(Q)$(CC) $(CFLAGS) -o btrfs-image $(objects) btrfs-image.o -lpthread -lz $(LDFLAGS) $(LIBS)
 
+btrfs-crc: btrfs-crc.o $(libs)
+       @echo "    [LD]     $@"
+       $(Q)$(CC) $(CFLAGS) -o btrfs-crc btrfs-crc.o $(LDFLAGS) $(LIBS)
+
 dir-test: $(objects) $(libs) dir-test.o
        @echo "    [LD]     $@"
        $(Q)$(CC) $(CFLAGS) -o dir-test $(objects) dir-test.o $(LDFLAGS) $(LIBS)

diff --git a/btrfs-crc.c b/btrfs-crc.c
new file mode 100644 (file)
index 0000000..6e21a0e
--- /dev/null
+++ b/btrfs-crc.c
@@ -0,0 +1,89 @@
+/*
+ * Copyright (C) 2013 STRATO.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * 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 021110-1307, USA.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include "crc32c.h"
+
+void usage(void)
+{
+       printf("usage: btrfs-crc filename\n");
+       printf("    print out the btrfs crc for \"filename\"\n");
+       printf("usage: btrfs-crc filename -c crc [-s seed] [-l length]\n");
+       printf("    brute force search for file names with the given crc\n");
+       printf("      -s seed    the random seed (default: random)\n");
+       printf("      -l length  the length of the file names (default: 10)\n");
+       exit(1);
+}
+
+int main(int argc, char **argv)
+{
+       char c;
+       unsigned long checksum = 0;
+       char *str;
+       char *buf;
+       int length = 10;
+       int seed = getpid() ^ getppid();
+       int loop = 0;
+       int i;
+
+       while ((c = getopt(argc, argv, "l:c:s:h")) != -1) {
+               switch (c) {
+               case 'l':
+                       length = atol(optarg);
+                       break;
+               case 'c':
+                       checksum = atol(optarg);
+                       loop = 1;
+                       break;
+               case 's':
+                       seed = atol(optarg);
+                       break;
+               case 'h':
+                       usage();
+               case '?':
+                       return 255;
+               }
+       }
+
+       str = argv[optind];
+
+       if (!loop) {
+               if (optind >= argc) {
+                       fprintf(stderr, "not enough arguments\n");
+                       return 255;
+               }
+               printf("%12u - %s\n", crc32c(~1, str, strlen(str)), str);
+               return 0;
+       }
+
+       buf = malloc(length);
+       if (!buf)
+               return -ENOMEM;
+       srand(seed);
+
+       while (1) {
+               for (i = 0; i < length; i++)
+                       buf[i] = rand() % 94 + 33;
+               if (crc32c(~1, buf, length) == checksum)
+                       printf("%12lu - %.*s\n", checksum, length, buf);
+       }
+
+       return 0;
+}