Messages in this thread | | | Subject | Re: [patch v3 5/7] crc32: add-real-8-bit.diff | From | Joakim Tjernlund <> | Date | Tue, 9 Aug 2011 19:09:55 +0200 |
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Bob Pearson <rpearson@systemfabricworks.com> wrote on 2011/08/09 07:25:49:
> From: Bob Pearson <rpearson@systemfabricworks.com> > To: linux-kernel@vger.kernel.org, linux@horizon.com, joakim.tjernlund@transmode.se, fzago@systemfabricworks.com, rpearson@systemfabricworks.com, akpm@linux-foundation.org > Date: 2011/08/09 07:25 > Subject: [patch v3 5/7] crc32: add-real-8-bit.diff > > crc32.c encodes an algorithm that processes 32 bits at a time > with the value BITS = 8 and leaves out the most common 8 bit algorithm > for computing the crc. This patch reencodes the 32 bit algorithm > with the value 32 and adds back the 'standard' 8 bit algorithm. > > Signed-off-by: Bob Pearson <rpearson@systemfabricworks.com> > > --- > lib/crc32.c | 17 ++++++++++++++--- > lib/crc32defs.h | 18 ++++++++++-------- > lib/gen_crc32table.c | 27 ++++++++++++++++++--------- > 3 files changed, 42 insertions(+), 20 deletions(-) >
...
> =================================================================== > --- infiniband.orig/lib/gen_crc32table.c > +++ infiniband/lib/gen_crc32table.c > @@ -4,11 +4,20 @@ > > #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][LE_TABLE_SIZE]; > -static uint32_t crc32table_be[4][BE_TABLE_SIZE]; > +static uint32_t crc32table_le[8][256]; > +static uint32_t crc32table_be[8][256];
Above is wrong as only 32 bits is supported at this point.
> > /** > * crc32init_le() - allocate and initialize LE table data > @@ -24,14 +33,14 @@ 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]; > } > for (i = 0; i < LE_TABLE_SIZE; i++) { > crc = crc32table_le[0][i]; > - for (j = 1; j < 4; j++) { > + for (j = 1; j < 8; j++) { > crc = crc32table_le[0][crc & 0xff] ^ (crc >> 8); > crc32table_le[j][i] = crc; > } > @@ -55,18 +64,18 @@ static void crc32init_be(void) > } > for (i = 0; i < BE_TABLE_SIZE; i++) { > crc = crc32table_be[0][i]; > - for (j = 1; j < 4; j++) { > + for (j = 1; j < 8; j++) { > crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8); > crc32table_be[j][i] = crc; > } > } > } > > -static void output_table(uint32_t table[4][256], int len, char *trans) > +static void output_table(uint32_t table[8][256], int len, char *trans) > { > int i, j; > > - for (j = 0 ; j < 4; j++) { > + for (j = 0 ; j < 8; j++) { > printf("{"); > for (i = 0; i < len - 1; i++) { > if (i % ENTRIES_PER_LINE == 0) > @@ -83,14 +92,14 @@ int main(int argc, char** argv) > > if (CRC_LE_BITS > 1) { > crc32init_le(); > - printf("static const u32 crc32table_le[4][256] = {"); > + printf("static const u32 crc32table_le[8][256] = {");
This makes the table way to big.
> output_table(crc32table_le, LE_TABLE_SIZE, "tole"); > printf("};\n"); > } > > if (CRC_BE_BITS > 1) { > crc32init_be(); > - printf("static const u32 crc32table_be[4][256] = {"); > + printf("static const u32 crc32table_be[8][256] = {"); Ditto.
> output_table(crc32table_be, BE_TABLE_SIZE, "tobe"); > printf("};\n"); > }
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