Diff: mbed-os/features/storage/FEATURE_STORAGE/flash-journal/flash-journal-strategy-sequential/flash_journal_crc.c

Revision:

0:02dd72d1d465

diff -r 000000000000 -r 02dd72d1d465 mbed-os/features/storage/FEATURE_STORAGE/flash-journal/flash-journal-strategy-sequential/flash_journal_crc.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os/features/storage/FEATURE_STORAGE/flash-journal/flash-journal-strategy-sequential/flash_journal_crc.c	Tue Apr 24 11:45:18 2018 +0000
@@ -0,0 +1,220 @@
+/**********************************************************************
+ *
+ * Filename:    flash_journal_crc.c
+ *
+ * Description: Slow and fast implementations of the CRC standards.
+ *
+ * Notes:       The parameters for each supported CRC standard are
+ *              defined in the header file crc.h.  The implementations
+ *              here should stand up to further additions to that list.
+ *
+ *
+ * Copyright (c) 2000 by Michael Barr.  This software is placed into
+ * the public domain and may be used for any purpose.  However, this
+ * notice must not be changed or removed and no warranty is either
+ * expressed or implied by its publication or distribution.
+ **********************************************************************/
+
+#include "flash-journal-strategy-sequential/flash_journal_crc.h"
+
+#define FALSE   0
+#define TRUE    !FALSE
+
+#define CRC_NAME            "CRC-32"
+#define POLYNOMIAL          0x04C11DB7
+#define INITIAL_REMAINDER   0xFFFFFFFF
+#define FINAL_XOR_VALUE     0xFFFFFFFF
+#define REFLECT_DATA        TRUE
+#define REFLECT_REMAINDER   TRUE
+#define CHECK_VALUE         0xCBF43926
+
+
+/*
+ * Derive parameters from the standard-specific parameters in crc.h.
+ */
+#define WIDTH    (8 * sizeof(flash_journal_crc32_t))
+/* U postfix required to suppress the following warning with TOOLCHAIN_ARM:
+ * #61-D: integer operation result is out of range
+ */
+#define TOPBIT   0x80000000U
+
+#if (REFLECT_DATA == TRUE)
+#undef  REFLECT_DATA
+#define REFLECT_DATA(X)         ((unsigned char) reflect((X), 8))
+#else
+#undef  REFLECT_DATA
+#define REFLECT_DATA(X)         (X)
+#endif
+
+#if (REFLECT_REMAINDER == TRUE)
+#undef  REFLECT_REMAINDER
+#define REFLECT_REMAINDER(X)    ((flash_journal_crc32_t) reflect((X), WIDTH))
+#else
+#undef  REFLECT_REMAINDER
+#define REFLECT_REMAINDER(X)    (X)
+#endif
+
+
+/*********************************************************************
+ *
+ * Function:    reflect()
+ *
+ * Description: Reorder the bits of a binary sequence, by reflecting
+ *              them about the middle position.
+ *
+ * Notes:       No checking is done that nBits <= 32.
+ *
+ * Returns:     The reflection of the original data.
+ *
+ *********************************************************************/
+static uint32_t
+reflect(uint32_t data, unsigned char nBits)
+{
+    uint32_t  reflection = 0x00000000;
+    unsigned char  bit;
+
+    /*
+     * Reflect the data about the center bit.
+     */
+    for (bit = 0; bit < nBits; ++bit)
+    {
+        /*
+         * If the LSB bit is set, set the reflection of it.
+         */
+        if (data & 0x01)
+        {
+            reflection |= (1 << ((nBits - 1) - bit));
+        }
+
+        data = (data >> 1);
+    }
+
+    return (reflection);
+
+}   /* reflect() */
+
+
+static flash_journal_crc32_t  crcTable[256];
+static flash_journal_crc32_t  crcEngineRemainder = INITIAL_REMAINDER;
+
+/*********************************************************************
+ *
+ * Function:    flashJournalCrcInit()
+ *
+ * Description: Populate the partial CRC lookup table.
+ *
+ * Notes:       This function must be rerun any time the CRC standard
+ *              is changed.  If desired, it can be run "offline" and
+ *              the table results stored in an embedded system's ROM.
+ *
+ * Returns:     None defined.
+ *
+ *********************************************************************/
+void
+flashJournalCrcInit(void)
+{
+    flash_journal_crc32_t            remainder;
+    int            dividend;
+    unsigned char  bit;
+
+
+    /*
+     * Compute the remainder of each possible dividend.
+     */
+    for (dividend = 0; dividend < 256; ++dividend)
+    {
+        /*
+         * Start with the dividend followed by zeros.
+         */
+        remainder = dividend << (WIDTH - 8);
+
+        /*
+         * Perform modulo-2 division, a bit at a time.
+         */
+        for (bit = 8; bit > 0; --bit)
+        {
+            /*
+             * Try to divide the current data bit.
+             */
+            if (remainder & TOPBIT)
+            {
+                remainder = (remainder << 1) ^ POLYNOMIAL;
+            }
+            else
+            {
+                remainder = (remainder << 1);
+            }
+        }
+
+        /*
+         * Store the result into the table.
+         */
+        crcTable[dividend] = remainder;
+    }
+
+}   /* flashJournalCrcInit() */
+
+/*********************************************************************
+ *
+ * Function:    flashJournalCrcReset()
+ *
+ * Description: Resets internal state before calling crcCummulative().
+ *
+ * Notes: See the notes to crcCummulative().
+ *
+ * Returns:     None defined.
+ *
+ *********************************************************************/
+void
+flashJournalCrcReset(void)
+{
+    static unsigned initCalled = 0;
+    if (!initCalled) {
+        flashJournalCrcInit();
+        initCalled = 1;
+    }
+
+    crcEngineRemainder = INITIAL_REMAINDER;
+
+}   /* flashJournalCrcReset() */
+
+/*********************************************************************
+ *
+ * Function:    crcCummulative()
+ *
+ * Description: Compute the CRC of a group of messages.
+ *
+ * Notes:
+ * This function is intended to be used in the following way:
+ *  - crcReset() is called first to reset internal state before the first
+ *    fragment of a new message is processed with crcCummulative().
+ *  - crcCummulative() called successfully appending additional message
+ *    fragments to those previously supplied (in order), and returning
+ *    the current crc for the message payload so far.
+ *
+ * Returns:     The CRC of the message.
+ *
+ *********************************************************************/
+flash_journal_crc32_t
+flashJournalCrcCummulative(unsigned char const message[], int nBytes)
+{
+    unsigned char  data;
+    int            byte;
+
+
+    /*
+     * Divide the message by the polynomial, a byte at a time.
+     */
+    for (byte = 0; byte < nBytes; ++byte)
+    {
+        data = REFLECT_DATA(message[byte]) ^ (crcEngineRemainder >> (WIDTH - 8));
+        crcEngineRemainder = crcTable[data] ^ (crcEngineRemainder << 8);
+    }
+
+    /*
+     * The final remainder is the CRC.
+     */
+    return (REFLECT_REMAINDER(crcEngineRemainder) ^ FINAL_XOR_VALUE);
+
+}   /* crcCummulative() */
+