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>
---
Makefile | 4 ++
btrfs-crc.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 93 insertions(+), 0 deletions(-)
create mode 100644 btrfs-crc.c
diff --git a/Makefile b/Makefile
index 9c195b3..145e2ea 100644
--- a/Makefile
+++ b/Makefile
@@ -184,6 +184,10 @@ 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
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;
+}
--
1.7.1
--
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