// STM32 CRC32 Test App - sourcer32@gmail.com
// Copyright (C) 2014

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>

//****************************************************************************

DWORD Crc32(DWORD Crc, DWORD Data)
{
 int i;
 Crc = Crc ^ Data;
 for(i=0; i<32; i++)
 if (Crc & 0x80000000)
 Crc = (Crc << 1) ^ 0x04C11DB7; // Polynomial used in STM32
 else
 Crc = (Crc << 1);
 return(Crc);
}

//****************************************************************************

DWORD Crc32Block(DWORD Crc, DWORD Size, DWORD *Buffer) // 32-bit units
{
 while(Size--)
 Crc = Crc32(Crc, *Buffer++);

 return(Crc);
}

//****************************************************************************

DWORD Crc32Fast(DWORD Crc, DWORD Data)
{
 static const DWORD CrcTable[16] = { // Nibble lookup table for 0x04C11DB7 polynomial
 0x00000000,0x04C11DB7,0x09823B6E,0x0D4326D9,0x130476DC,0x17C56B6B,0x1A864DB2,0x1E475005,
 0x2608EDB8,0x22C9F00F,0x2F8AD6D6,0x2B4BCB61,0x350C9B64,0x31CD86D3,0x3C8EA00A,0x384FBDBD };

 Crc = Crc ^ Data; // Apply all 32-bits

 // Process 32-bits, 4 at a time, or 8 rounds
 Crc = (Crc << 4) ^ CrcTable[Crc >> 28]; // Assumes 32-bit reg, masking index to 4-bits
 Crc = (Crc << 4) ^ CrcTable[Crc >> 28]; // 0x04C11DB7 Polynomial used in STM32
 Crc = (Crc << 4) ^ CrcTable[Crc >> 28];
 Crc = (Crc << 4) ^ CrcTable[Crc >> 28];
 Crc = (Crc << 4) ^ CrcTable[Crc >> 28];
 Crc = (Crc << 4) ^ CrcTable[Crc >> 28];
 Crc = (Crc << 4) ^ CrcTable[Crc >> 28];
 Crc = (Crc << 4) ^ CrcTable[Crc >> 28];

 return(Crc);
}

//****************************************************************************

DWORD Crc32FastBlock(DWORD Crc, DWORD Size, DWORD *Buffer) // 32-bit units
{
 while(Size--)
 Crc = Crc32Fast(Crc, *Buffer++);

 return(Crc);
}

//****************************************************************************

void test(void)
{
 BYTE vector[12] = { 0x02,0x07,0x02,0x00,0x18,0x8A,0xD0,0x23,0x25,0x2B,0x09,0x00 }; // ACD7E298
 DWORD Crc;
 int i;

 for(i=0; i<sizeof(vector); i++)
 printf("%02X ",vector[i]);
 putchar('\n');

 Crc = 0xFFFFFFFF; // Initial state

 for(i=0; i<sizeof(vector); i+=4)
 {
 Crc = Crc32Fast(Crc, *((DWORD *)&vector[i]) ); // 4-bytes at a time
 }

 printf("%08X %08X test",Crc, Crc32FastBlock(0xFFFFFFFF, sizeof(vector)/4, (void *)vector));
}

//****************************************************************************

void TestFile(char *Filename)
{
 FILE *f;
 DWORD Size;
 BYTE *Buffer;

 f = fopen (Filename, "rb");
 if (f)
 {
 fseek(f, 0, SEEK_END);

 Size = ftell (f);

 fseek(f, 0, SEEK_SET);

 if (Size & 3)
 printf("WARNING: File must be multiple of 4 bytes (32-bit) for valid results\n");

 Buffer = malloc(Size);

 fread(Buffer, Size, 1, f);

 fclose(f);

 printf("crc=%08X Slow\n", Crc32Block(0xFFFFFFFF, Size >> 2, (void *)Buffer));
 printf("crc=%08X Fast", Crc32FastBlock(0xFFFFFFFF, Size >> 2, (void *)Buffer));

 free(Buffer);
 }
 else
 printf("ERROR: Unable to open file '%s'\n", Filename);
}

//****************************************************************************

int main(int argc, char **argv)
{
 printf("STM32CRC Test\n Usage: STM32CRC [<file>]\n");

 if ((Crc32(0xFFFFFFFF, 0x12345678) != 0xDF8A8A2B) ||
 (Crc32Fast(0xFFFFFFFF, 0x12345678) != 0xDF8A8A2B))
 {
 printf("ERROR: Internal Sanity Check Failed\n");
 }

 if (argc > 1)
 TestFile(argv[1]);
 else
 test();

 return(1);
}

//****************************************************************************