crc32: major optimization

[thirdparty/linux.git] / lib / gen_crc32table.c

diff --git a/lib/gen_crc32table.c b/lib/gen_crc32table.c
index bea5d97df99162f5bb8b1d3122a60dc07d6bb8b7..85d0e412a04f966a187fac0a5f8c7ff16c9a49c8 100644 (file)
--- a/lib/gen_crc32table.c
+++ b/lib/gen_crc32table.c
@@ -7,8 +7,8 @@
 #define LE_TABLE_SIZE (1 << CRC_LE_BITS)
 #define BE_TABLE_SIZE (1 << CRC_BE_BITS)
 
-static uint32_t crc32table_le[LE_TABLE_SIZE];
-static uint32_t crc32table_be[BE_TABLE_SIZE];
+static uint32_t crc32table_le[4][LE_TABLE_SIZE];
+static uint32_t crc32table_be[4][BE_TABLE_SIZE];
 
 /**
  * crc32init_le() - allocate and initialize LE table data
@@ -22,12 +22,19 @@ static void crc32init_le(void)
        unsigned i, j;
        uint32_t crc = 1;
 
-       crc32table_le[0] = 0;
+       crc32table_le[0][0] = 0;
 
        for (i = 1 << (CRC_LE_BITS - 1); i; i >>= 1) {
                crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
                for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
-                       crc32table_le[i + j] = crc ^ crc32table_le[j];
+                       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++) {
+                       crc = crc32table_le[0][crc & 0xff] ^ (crc >> 8);
+                       crc32table_le[j][i] = crc;
+               }
        }
 }
 
@@ -39,25 +46,35 @@ static void crc32init_be(void)
        unsigned i, j;
        uint32_t crc = 0x80000000;
 
-       crc32table_be[0] = 0;
+       crc32table_be[0][0] = 0;
 
        for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
                crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
                for (j = 0; j < i; j++)
-                       crc32table_be[i + j] = crc ^ crc32table_be[j];
+                       crc32table_be[0][i + j] = crc ^ crc32table_be[0][j];
+       }
+       for (i = 0; i < BE_TABLE_SIZE; i++) {
+               crc = crc32table_be[0][i];
+               for (j = 1; j < 4; j++) {
+                       crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
+                       crc32table_be[j][i] = crc;
+               }
        }
 }
 
-static void output_table(uint32_t table[], int len, char *trans)
+static void output_table(uint32_t table[4][256], int len, char *trans)
 {
-       int i;
+       int i, j;
 
-       for (i = 0; i < len - 1; i++) {
-               if (i % ENTRIES_PER_LINE == 0)
-                       printf("\n");
-               printf("%s(0x%8.8xL), ", trans, table[i]);
+       for (j = 0 ; j < 4; j++) {
+               printf("{");
+               for (i = 0; i < len - 1; i++) {
+                       if (i % ENTRIES_PER_LINE == 0)
+                               printf("\n");
+                       printf("%s(0x%8.8xL), ", trans, table[j][i]);
+               }
+               printf("%s(0x%8.8xL)},\n", trans, table[j][len - 1]);
        }
-       printf("%s(0x%8.8xL)\n", trans, table[len - 1]);
 }
 
 int main(int argc, char** argv)
@@ -66,14 +83,14 @@ int main(int argc, char** argv)
 
        if (CRC_LE_BITS > 1) {
                crc32init_le();
-               printf("static const u32 crc32table_le[] = {");
+               printf("static const u32 crc32table_le[4][256] = {");
                output_table(crc32table_le, LE_TABLE_SIZE, "tole");
                printf("};\n");
        }
 
        if (CRC_BE_BITS > 1) {
                crc32init_be();
-               printf("static const u32 crc32table_be[] = {");
+               printf("static const u32 crc32table_be[4][256] = {");
                output_table(crc32table_be, BE_TABLE_SIZE, "tobe");
                printf("};\n");
        }