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authorBob Pearson <rpearson@systemfabricworks.com>2012-03-23 15:02:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-23 16:58:37 -0700
commit9a1dbf6a29694c9d81b498019f103aee0f8b5b6c (patch)
tree1f331fa108ea29ccf06a7b5816da4dbcaa12bf2d /lib/gen_crc32table.c
parentce4320ddda4c2520fe77194d3c801ad4e8a8aa11 (diff)
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crc32: make CRC_*_BITS definition correspond to actual bit counts
crc32.c provides a choice of one of several algorithms for computing the LSB and LSB versions of the CRC32 checksum based on the parameters CRC_LE_BITS and CRC_BE_BITS. In the original version the values 1, 2, 4 and 8 respectively selected versions of the alrogithm that computed the crc 1, 2, 4 and 32 bits as a time. This patch series adds a new version that computes the CRC 64 bits at a time. To make things easier to understand the parameter has been reinterpreted to actually stand for the number of bits processed in each step of the algorithm so that the old value 8 has been replaced with the value 32. This also allows us to add in a widely used crc algorithm that computes the crc 8 bits at a time called the Sarwate algorithm. [djwong@us.ibm.com: Minor changelog tweaks] Signed-off-by: Bob Pearson <rpearson@systemfabricworks.com> Signed-off-by: Darrick J. Wong <djwong@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/gen_crc32table.c')
-rw-r--r--lib/gen_crc32table.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/lib/gen_crc32table.c b/lib/gen_crc32table.c
index eced7696eb7c..99ac744848fb 100644
--- a/lib/gen_crc32table.c
+++ b/lib/gen_crc32table.c
@@ -4,8 +4,17 @@
#define ENTRIES_PER_LINE 4
+#if CRC_LE_BITS <= 8
#define LE_TABLE_SIZE (1 << CRC_LE_BITS)
+#else
+#define LE_TABLE_SIZE 256
+#endif
+
+#if CRC_BE_BITS <= 8
#define BE_TABLE_SIZE (1 << CRC_BE_BITS)
+#else
+#define BE_TABLE_SIZE 256
+#endif
static uint32_t crc32table_le[4][256];
static uint32_t crc32table_be[4][256];
@@ -24,7 +33,7 @@ static void crc32init_le(void)
crc32table_le[0][0] = 0;
- for (i = 1 << (CRC_LE_BITS - 1); i; i >>= 1) {
+ for (i = LE_TABLE_SIZE >> 1; i; i >>= 1) {
crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
crc32table_le[0][i + j] = crc ^ crc32table_le[0][j];