Diff: CRC32/crc32.cpp

Revision:

2:c174f9ee414a

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/CRC32/crc32.cpp	Tue Jul 22 04:33:47 2014 +0000
@@ -0,0 +1,65 @@
+#include "crc32.h"
+
+#define CRC32_POLYNOMIAL 0xEDB88320L
+ 
+void CRC32Value(unsigned long &CRC, unsigned char c)
+{
+    /////////////////////////////////////////////////////////////////////////////////////
+    //CRC must be initialized as zero 
+    //c is a character from the sequence that is used to form the CRC
+    //this code is a modification of the code from the Novatel OEM615 specification
+    /////////////////////////////////////////////////////////////////////////////////////
+    unsigned long ulTemp1 = ( CRC >> 8 ) & 0x00FFFFFFL;
+    unsigned long ulCRC = ((int) CRC ^ c ) & 0xff ;
+    for (int  j = 8 ; j > 0; j-- )
+    {
+        if ( ulCRC & 1 )
+        {
+            ulCRC = ( ulCRC >> 1 ) ^ CRC32_POLYNOMIAL;
+        }
+        else
+        {
+            ulCRC >>= 1;
+        }
+    }
+    CRC = ulTemp1 ^ ulCRC;
+} 
+ 
+/* --------------------------------------------------------------------------
+Calculates the CRC-32 of a block of data all at once
+//the CRC is from the complete message (header plus data) 
+//but excluding (of course) the CRC at the end
+-------------------------------------------------------------------------- */
+unsigned long CRC32(const void *data, int len)
+{
+    //////////////////////////////////////////////////////////////////////
+    //the below code tests the CRC32Value procedure used in a markov form
+    //////////////////////////////////////////////////////////////////////
+    unsigned long CRC = 0;
+    const unsigned char *p = (const unsigned char *)data;
+    for (int i = 0 ; i < len ; i++)
+        CRC32Value(CRC, *p++);
+
+    return CRC;
+}
+ 
+/*
+unsigned long CalculateBlockCRC32(
+        unsigned long ulCount, 
+        unsigned char *ucBuffer )
+{
+////////////////////////////////////////////
+//original code from the OEM615 manual
+////////////////////////////////////////////
+    unsigned long ulTemp1;
+    unsigned long ulTemp2;
+    unsigned long ulCRC = 0;
+    while ( ulCount-- != 0 )
+    {
+        ulTemp1 = ( ulCRC >> 8 ) & 0x00FFFFFFL;
+        ulTemp2 = CRC32Value( ((int) ulCRC ^ *ucBuffer++ ) & 0xff );
+        ulCRC = ulTemp1 ^ ulTemp2;
+    }
+    return( ulCRC );
+}
+*/
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