mbed 5.15 CRC update

Author: pilotak

LittleFileSystem2.cpp

@@ -24,8 +24,9 @@ namespace mbed {
 
 extern "C" uint32_t lfs2_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);
+    uint32_t initial_xor = lfs2_rbit(crc);
+    MbedCRC<POLY_32BIT_ANSI, 32, CrcMode::TABLE> ct(initial_xor, 0x0, true, true);
+
     ct.compute((void *)buffer, size, &crc);
     return crc;
 }

littlefs/lfs2_util.h

@@ -51,6 +51,7 @@ extern "C"
 #ifdef __MBED__
 #include "mbed_debug.h"
 #include "mbed_assert.h"
+#include "cmsis_compiler.h"
 #else
 #define MBED_LFS2_ENABLE_INFO    false
 #define MBED_LFS2_ENABLE_DEBUG   true
@@ -211,6 +212,21 @@ static inline uint32_t lfs2_tole32(uint32_t a) {
     return lfs2_fromle32(a);
 }
 
+// Reverse the bits in a
+static inline uint32_t lfs2_rbit(uint32_t a) {
+#if !defined(LFS2_NO_INTRINSICS) && MBED_LFS2_INTRINSICS && \
+    defined(__MBED__)
+    return __RBIT(a);
+#else
+    a = ((a & 0xaaaaaaaa) >> 1) | ((a & 0x55555555) << 1);
+    a = ((a & 0xcccccccc) >> 2) | ((a & 0x33333333) << 2);
+    a = ((a & 0xf0f0f0f0) >> 4) | ((a & 0x0f0f0f0f) << 4);
+    a = ((a & 0xff00ff00) >> 8) | ((a & 0x00ff00ff) << 8);
+    a = (a >> 16) | (a << 16);
+    return a;
+#endif
+}
+
 // Convert between 32-bit big-endian and native order
 static inline uint32_t lfs2_frombe32(uint32_t a) {
 #if !defined(LFS2_NO_INTRINSICS) && MBED_LFS2_INTRINSICS && ( \