Use MbedCRC for LittleFS (0xEDB88320)

CRC used in LittleFS is Reversed ANSI, hence new polynomial added.
Reversed polynomials perform shift in reverse direction of standard
polynomial, and we do not have option to notify reverse shift to hardware.
Hence this option is available in software only.

Author: Deepika

drivers/MbedCRC.cpp

@@ -34,6 +34,14 @@ MbedCRC<POLY_32BIT_ANSI, 32>::MbedCRC():
     mbed_crc_ctor();
 }
 
+template<>
+MbedCRC<POLY_32BIT_REV_ANSI, 32>::MbedCRC():
+    _initial_value(~(0x0)), _final_xor(~(0x0)), _reflect_data(false), _reflect_remainder(false),
+    _crc_table((uint32_t *)Table_CRC_32bit_Rev_ANSI)
+{
+    mbed_crc_ctor();
+}
+
 template<>
 MbedCRC<POLY_16BIT_IBM, 16>::MbedCRC():
     _initial_value(0), _final_xor(0), _reflect_data(true), _reflect_remainder(true),

drivers/MbedCRC.h

@@ -275,7 +275,7 @@ class MbedCRC {
             p_crc = (uint32_t)(p_crc << (8 - width));
         }
         // Optimized algorithm for 32BitANSI does not need additional reflect_remainder
-        if ((TABLE == _mode) && (POLY_32BIT_ANSI == polynomial)) {
+        if ((TABLE == _mode) && (POLY_32BIT_REV_ANSI == polynomial)) {
             *crc = (p_crc ^ _final_xor) & get_crc_mask();
         } else {
             *crc = (reflect_remainder(p_crc) ^ _final_xor) & get_crc_mask();
@@ -480,9 +480,17 @@ class MbedCRC {
             }
         } else {
             uint32_t *crc_table = (uint32_t *)_crc_table;
-            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];
+            if (POLY_32BIT_REV_ANSI == polynomial) {
+                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];
+                }
+            }
+            else {
+                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);
+                }
             }
         }
         *crc = p_crc & get_crc_mask();
@@ -497,6 +505,11 @@ class MbedCRC {
         MBED_STATIC_ASSERT(width <= 32, "Max 32-bit CRC supported");
 
 #ifdef DEVICE_CRC
+        if (POLY_32BIT_REV_ANSI == polynomial) {
+            _crc_table = (uint32_t *)Table_CRC_32bit_Rev_ANSI;
+            _mode = TABLE;
+            return;
+        }
         crc_mbed_config_t config;
         config.polynomial  = polynomial;
         config.width       = width;
@@ -510,10 +523,14 @@ class MbedCRC {
             return;
         }
 #endif
+
         switch (polynomial) {
             case POLY_32BIT_ANSI:
                 _crc_table = (uint32_t *)Table_CRC_32bit_ANSI;
                 break;
+            case POLY_32BIT_REV_ANSI:
+                _crc_table = (uint32_t *)Table_CRC_32bit_Rev_ANSI;
+                break;
             case POLY_8BIT_CCITT:
                 _crc_table = (uint32_t *)Table_CRC_8bit_CCITT;
                 break;

drivers/TableCRC.cpp

@@ -108,12 +108,48 @@ 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_OPTIMIZED_CRC_TABLE_SIZE] = {
+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_Rev_ANSI[MBED_OPTIMIZED_CRC_TABLE_SIZE] = {
     0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
     0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
     0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
     0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c
 };
 
+
 /** @}*/
 } // namespace mbed

drivers/TableCRC.h

@@ -30,7 +30,8 @@ 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_OPTIMIZED_CRC_TABLE_SIZE];
+extern const uint32_t Table_CRC_32bit_ANSI[MBED_CRC_TABLE_SIZE];
+extern const uint32_t Table_CRC_32bit_Rev_ANSI[MBED_OPTIMIZED_CRC_TABLE_SIZE];
 
 /** @}*/
 } // namespace mbed

features/storage/filesystem/littlefs/LittleFileSystem.cpp

@@ -18,7 +18,14 @@
 #include "errno.h"
 #include "lfs.h"
 #include "lfs_util.h"
+#include "MbedCRC.h"
 
+extern "C" void mbed_lfs_crc(uint32_t *crc, const void *buffer, size_t size)
+{
+    uint32_t initial_xor = *crc;    
+    MbedCRC<POLY_32BIT_REV_ANSI, 32> ct(initial_xor, 0x0, true, false);
+    ct.compute((void *)buffer, size, (uint32_t *) crc);
+}
 
 ////// Conversion functions //////
 static int lfs_toerror(int err)

features/storage/filesystem/littlefs/littlefs/lfs_util.c

@@ -6,11 +6,19 @@
  */
 #include "lfs_util.h"
 
+
 // Only compile if user does not provide custom config
 #ifndef LFS_CONFIG
 
+#ifdef __MBED__
+extern void mbed_lfs_crc(uint32_t *crc, const void *buffer, size_t size);
 
 // Software CRC implementation with small lookup table
+void lfs_crc(uint32_t *restrict crc, const void *buffer, size_t size) {
+    mbed_lfs_crc(crc, buffer, size);
+}
+
+#else
 void lfs_crc(uint32_t *restrict crc, const void *buffer, size_t size) {
     static const uint32_t rtable[16] = {
         0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
@@ -20,12 +28,11 @@ void lfs_crc(uint32_t *restrict crc, const void *buffer, size_t size) {
     };
 
     const uint8_t *data = buffer;
-
     for (size_t i = 0; i < size; i++) {
         *crc = (*crc >> 4) ^ rtable[(*crc ^ (data[i] >> 0)) & 0xf];
         *crc = (*crc >> 4) ^ rtable[(*crc ^ (data[i] >> 4)) & 0xf];
     }
 }
-
-
 #endif
+
+#endif

hal/crc_api.h

@@ -33,6 +33,7 @@ typedef enum crc_polynomial {
     POLY_16BIT_CCITT = 0x1021,     // x16+x12+x5+1
     POLY_16BIT_IBM   = 0x8005,     // x16+x15+x2+1
     POLY_32BIT_ANSI  = 0x04C11DB7, // x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x+1
+    POLY_32BIT_REV_ANSI = 0xEDB88320
 } crc_polynomial_t;
 
 typedef struct crc_mbed_config {