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authorLinus Torvalds <torvalds@linux-foundation.org>2018-08-22 22:34:08 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-08-22 22:34:08 +0300
commitcd9b44f90763c3367e8dd0601849ffb028e8ba52 (patch)
treed1da0c2d49e3622fe51584a154ab383b3e783c1b /lib/crc64.c
parentdf2def49c57b4146520a1f4ca37bc3f494e2cd67 (diff)
parent2a9d6481004215da8e93edb588cf448f2af80303 (diff)
downloadlinux-cd9b44f90763c3367e8dd0601849ffb028e8ba52.tar.xz
Merge branch 'akpm' (patches from Andrew)
Merge more updates from Andrew Morton: - the rest of MM - procfs updates - various misc things - more y2038 fixes - get_maintainer updates - lib/ updates - checkpatch updates - various epoll updates - autofs updates - hfsplus - some reiserfs work - fatfs updates - signal.c cleanups - ipc/ updates * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (166 commits) ipc/util.c: update return value of ipc_getref from int to bool ipc/util.c: further variable name cleanups ipc: simplify ipc initialization ipc: get rid of ids->tables_initialized hack lib/rhashtable: guarantee initial hashtable allocation lib/rhashtable: simplify bucket_table_alloc() ipc: drop ipc_lock() ipc/util.c: correct comment in ipc_obtain_object_check ipc: rename ipcctl_pre_down_nolock() ipc/util.c: use ipc_rcu_putref() for failues in ipc_addid() ipc: reorganize initialization of kern_ipc_perm.seq ipc: compute kern_ipc_perm.id under the ipc lock init/Kconfig: remove EXPERT from CHECKPOINT_RESTORE fs/sysv/inode.c: use ktime_get_real_seconds() for superblock stamp adfs: use timespec64 for time conversion kernel/sysctl.c: fix typos in comments drivers/rapidio/devices/rio_mport_cdev.c: remove redundant pointer md fork: don't copy inconsistent signal handler state to child signal: make get_signal() return bool signal: make sigkill_pending() return bool ...
Diffstat (limited to 'lib/crc64.c')
-rw-r--r--lib/crc64.c56
1 files changed, 56 insertions, 0 deletions
diff --git a/lib/crc64.c b/lib/crc64.c
new file mode 100644
index 000000000000..0ef8ae6ac047
--- /dev/null
+++ b/lib/crc64.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Normal 64-bit CRC calculation.
+ *
+ * This is a basic crc64 implementation following ECMA-182 specification,
+ * which can be found from,
+ * http://www.ecma-international.org/publications/standards/Ecma-182.htm
+ *
+ * Dr. Ross N. Williams has a great document to introduce the idea of CRC
+ * algorithm, here the CRC64 code is also inspired by the table-driven
+ * algorithm and detail example from this paper. This paper can be found
+ * from,
+ * http://www.ross.net/crc/download/crc_v3.txt
+ *
+ * crc64table[256] is the lookup table of a table-driven 64-bit CRC
+ * calculation, which is generated by gen_crc64table.c in kernel build
+ * time. The polynomial of crc64 arithmetic is from ECMA-182 specification
+ * as well, which is defined as,
+ *
+ * x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
+ * x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
+ * x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
+ * x^7 + x^4 + x + 1
+ *
+ * Copyright 2018 SUSE Linux.
+ * Author: Coly Li <colyli@suse.de>
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include "crc64table.h"
+
+MODULE_DESCRIPTION("CRC64 calculations");
+MODULE_LICENSE("GPL v2");
+
+/**
+ * crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
+ * @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
+ or the previous crc64 value if computing incrementally.
+ * @p: pointer to buffer over which CRC64 is run
+ * @len: length of buffer @p
+ */
+u64 __pure crc64_be(u64 crc, const void *p, size_t len)
+{
+ size_t i, t;
+
+ const unsigned char *_p = p;
+
+ for (i = 0; i < len; i++) {
+ t = ((crc >> 56) ^ (*_p++)) & 0xFF;
+ crc = crc64table[t] ^ (crc << 8);
+ }
+
+ return crc;
+}
+EXPORT_SYMBOL_GPL(crc64_be);