Merge pull request #7735 from deepikabhavnani/crc_lfs

Optimized CRC implementation - (32-bit ANSI polynomial)

Author: Nir Sonnenschein

drivers/MbedCRC.h

@@ -95,7 +95,14 @@ namespace mbed {
 template <uint32_t polynomial = POLY_32BIT_ANSI, uint8_t width = 32>
 class MbedCRC {
 public:
-    enum CrcMode { HARDWARE = 0, TABLE, BITWISE };
+    enum CrcMode
+    {
+#ifdef DEVICE_CRC
+        HARDWARE = 0,
+#endif
+        TABLE = 1,
+        BITWISE
+    };
 
 public:
     typedef uint64_t crc_data_size_t;
@@ -170,12 +177,12 @@ class MbedCRC {
     int32_t compute_partial(void *buffer, crc_data_size_t size, uint32_t *crc)
     {
         switch (_mode) {
-            case HARDWARE:
 #ifdef DEVICE_CRC
+            case HARDWARE:
                 hal_crc_compute_partial((uint8_t *)buffer, size);
-#endif // DEVICE_CRC
                 *crc = 0;
                 return 0;
+#endif
             case TABLE:
                 return table_compute_partial(buffer, size, crc);
             case BITWISE:
@@ -229,20 +236,22 @@ class MbedCRC {
     {
         MBED_ASSERT(crc != NULL);
 
-        if (_mode == HARDWARE) {
 #ifdef DEVICE_CRC
+        if (_mode == HARDWARE) {
             *crc = hal_crc_get_result();
             return 0;
-#else
-            return -1;
-#endif
         }
-
+#endif
         uint32_t p_crc = *crc;
         if ((width < 8) && (NULL == _crc_table)) {
             p_crc = (uint32_t)(p_crc << (8 - width));
         }
-        *crc = (reflect_remainder(p_crc) ^ _final_xor) & get_crc_mask();
+        // Optimized algorithm for 32BitANSI does not need additional reflect_remainder
+        if ((TABLE == _mode) && (POLY_32BIT_ANSI == polynomial)) {
+            *crc = (p_crc ^ _final_xor) & get_crc_mask();
+        } else {
+            *crc = (reflect_remainder(p_crc) ^ _final_xor) & get_crc_mask();
+        }
         return 0;
     }
 
@@ -420,9 +429,9 @@ class MbedCRC {
             }
         } else {
             uint32_t *crc_table = (uint32_t *)_crc_table;
-            for (crc_data_size_t byte = 0; byte < size; byte++) {
-                data_byte = reflect_bytes(data[byte]) ^ (p_crc >> (width - 8));
-                p_crc = crc_table[data_byte] ^ (p_crc << 8);
+            for (crc_data_size_t i = 0; i < size; i++) {
+                p_crc = (p_crc >> 4) ^ crc_table[(p_crc ^ (data[i] >> 0)) & 0xf];
+                p_crc = (p_crc >> 4) ^ crc_table[(p_crc ^ (data[i] >> 4)) & 0xf];
             }
         }
         *crc = p_crc & get_crc_mask();

drivers/TableCRC.cpp

@@ -108,39 +108,11 @@ extern const uint16_t Table_CRC_16bit_IBM[MBED_CRC_TABLE_SIZE] = {
     0x220,  0x8225, 0x822f, 0x22a,  0x823b, 0x23e,  0x234,  0x8231, 0x8213, 0x216,  0x21c,  0x8219
 };
 
-extern const uint32_t Table_CRC_32bit_ANSI[MBED_CRC_TABLE_SIZE] = {
-    0x0,        0x4c11db7,  0x9823b6e,  0xd4326d9,  0x130476dc, 0x17c56b6b, 0x1a864db2, 0x1e475005,
-    0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61, 0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd,
-    0x4c11db70, 0x48d0c6c7, 0x4593e01e, 0x4152fda9, 0x5f15adac, 0x5bd4b01b, 0x569796c2, 0x52568b75,
-    0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011, 0x791d4014, 0x7ddc5da3, 0x709f7b7a, 0x745e66cd,
-    0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039, 0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5,
-    0xbe2b5b58, 0xbaea46ef, 0xb7a96036, 0xb3687d81, 0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d,
-    0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49, 0xc7361b4c, 0xc3f706fb, 0xceb42022, 0xca753d95,
-    0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1, 0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d,
-    0x34867077, 0x30476dc0, 0x3d044b19, 0x39c556ae, 0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072,
-    0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16, 0x18aeb13,  0x54bf6a4,  0x808d07d,  0xcc9cdca,
-    0x7897ab07, 0x7c56b6b0, 0x71159069, 0x75d48dde, 0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02,
-    0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1, 0x53dc6066, 0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
-    0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e, 0xbfa1b04b, 0xbb60adfc, 0xb6238b25, 0xb2e29692,
-    0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6, 0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a,
-    0xe0b41de7, 0xe4750050, 0xe9362689, 0xedf73b3e, 0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2,
-    0xc6bcf05f, 0xc27dede8, 0xcf3ecb31, 0xcbffd686, 0xd5b88683, 0xd1799b34, 0xdc3abded, 0xd8fba05a,
-    0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637, 0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb,
-    0x4f040d56, 0x4bc510e1, 0x46863638, 0x42472b8f, 0x5c007b8a, 0x58c1663d, 0x558240e4, 0x51435d53,
-    0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47, 0x36194d42, 0x32d850f5, 0x3f9b762c, 0x3b5a6b9b,
-    0x315d626,  0x7d4cb91,  0xa97ed48,  0xe56f0ff,  0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623,
-    0xf12f560e, 0xf5ee4bb9, 0xf8ad6d60, 0xfc6c70d7, 0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b,
-    0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f, 0xc423cd6a, 0xc0e2d0dd, 0xcda1f604, 0xc960ebb3,
-    0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7, 0xae3afba2, 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b,
-    0x9b3660c6, 0x9ff77d71, 0x92b45ba8, 0x9675461f, 0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3,
-    0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640, 0x4e8ee645, 0x4a4ffbf2, 0x470cdd2b, 0x43cdc09c,
-    0x7b827d21, 0x7f436096, 0x7200464f, 0x76c15bf8, 0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24,
-    0x119b4be9, 0x155a565e, 0x18197087, 0x1cd86d30, 0x29f3d35,  0x65e2082,  0xb1d065b,  0xfdc1bec,
-    0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088, 0x2497d08d, 0x2056cd3a, 0x2d15ebe3, 0x29d4f654,
-    0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0, 0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c,
-    0xe3a1cbc1, 0xe760d676, 0xea23f0af, 0xeee2ed18, 0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4,
-    0x89b8fd09, 0x8d79e0be, 0x803ac667, 0x84fbdbd0, 0x9abc8bd5, 0x9e7d9662, 0x933eb0bb, 0x97ffad0c,
-    0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668, 0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4
+extern const uint32_t Table_CRC_32bit_ANSI[MBED_OPTIMIZED_CRC_TABLE_SIZE] = {
+    0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
+    0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
+    0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
+    0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c
 };
 
 /** @}*/

drivers/TableCRC.h

@@ -23,13 +23,14 @@ namespace mbed {
 /** \addtogroup drivers */
 /** @{*/
 
-#define MBED_CRC_TABLE_SIZE     256
+#define MBED_CRC_TABLE_SIZE             256
+#define MBED_OPTIMIZED_CRC_TABLE_SIZE   16
 
 extern const uint8_t Table_CRC_7Bit_SD[MBED_CRC_TABLE_SIZE];
 extern const uint8_t Table_CRC_8bit_CCITT[MBED_CRC_TABLE_SIZE];
 extern const uint16_t Table_CRC_16bit_CCITT[MBED_CRC_TABLE_SIZE];
 extern const uint16_t Table_CRC_16bit_IBM[MBED_CRC_TABLE_SIZE];
-extern const uint32_t Table_CRC_32bit_ANSI[MBED_CRC_TABLE_SIZE];
+extern const uint32_t Table_CRC_32bit_ANSI[MBED_OPTIMIZED_CRC_TABLE_SIZE];
 
 /** @}*/
 } // namespace mbed