/**
 *
 * @File : LittleEndian-->BigEndian
 *
 * @Author : A. Dragut
 *
 * @Synopsis : exo 04 Optionnel
 **/
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>


void bits4_1byte(unsigned char x)
{
	
	int k;
	for(k = 0; k < 8; x <<= 1, k++) {
		putchar('0' + ((x&128)>>7)); /* from MSbit to LSbit, for human readability */
		
	}
	
}

void bits4bytes(unsigned int value)  //bits from an integer=4 bytes 
{
	unsigned int B0,B1,B2,B3; //Bytes 0,1,2,3
	B0=(value>>24) & 0xFF; /* l'octet le plus significatif obtenu avec des shifts*/
	B1=(value>>16) & 0xFF;
	B2=(value>>8) & 0xFF;
	B3=value&0xFF;
	printf("\n");
	printf("-------- | -------- | -------- | -------- |\n"); 
	bits4_1byte(B0);
	printf(" | ");
    bits4_1byte(B1);
	printf(" | ");
	bits4_1byte(B2);
	printf(" | ");
    bits4_1byte(B3);
	printf(" |");
	printf("\n");
}

	unsigned int SwitchBitsInt (unsigned int value )
{	//on renverse une valeur de 32-bit 8 bits=1byte a la fois
	//Algorithme connu comme "Reverse bits in word by lookup table"
	static const unsigned char LookupTable256[] = 
	{
		0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0, 0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0, 
		0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8, 0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8, 
		0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4, 0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4, 
		0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC, 0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC, 
		0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2, 0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2, 
		0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA, 0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA,
		0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6, 0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6, 
		0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE, 0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE,
		0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1, 0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1,
		0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9, 0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9, 
		0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5, 0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5,
		0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED, 0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD,
		0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3, 0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3, 
		0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB, 0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB,
		0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7, 0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7, 
		0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF, 0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF
	};
	// En 2009 Hallvard Furuseth  a suggere une table macro plus efficace.
	//static const unsigned char BitReverseTable256[256] = 
	//{
	//#   define R2(n)     n,     n + 2*64,     n + 1*64,     n + 3*64
	//#   define R4(n) R2(n), R2(n + 2*16), R2(n + 1*16), R2(n + 3*16)
	//#   define R6(n) R4(n), R4(n + 2*4 ), R4(n + 1*4 ), R4(n + 3*4 )
	//	R6(0), R6(2), R6(1), R6(3)
	//};
	
	
	unsigned int c; // la valeur renversee
	
	// Variante 1 : 17 operations CPU
	
	c = (LookupTable256[value & 0xff] << 24) | 
	(LookupTable256[(value >> 8) & 0xff] << 16) | 
	(LookupTable256[(value >> 16) & 0xff] << 8) |
	(LookupTable256[(value >> 24) & 0xff]);
	printf("\n");
	bits4bytes(c);
	printf("\n");
	// Variante 2:12 operations CPU
	unsigned char * p = (unsigned char *) &value;
	unsigned char * q = (unsigned char *) &c;
	q[3] = LookupTable256[p[0]]; 
	q[2] = LookupTable256[p[1]]; 
	q[1] = LookupTable256[p[2]]; 
	q[0] = LookupTable256[p[3]];
	return c;
}




int main(int argc, char * argv [])
{
	printf("Votre nombre\n");
	unsigned int Nombre;
	scanf ("%i",&Nombre);
	unsigned char c=0;
	c   = *(unsigned char *)(&Nombre);
	printf("\n");
	printf("Nombre en binaire \n");
	printf("Lowest memory address ");
	bits4_1byte(c);
	printf("\n");
	bits4bytes(Nombre);
	
	
	printf("\n");
	printf("\n");
	printf("\n");
	printf("Bits renverses\n");
		
		
		
	unsigned int NbRenv = SwitchBitsInt(Nombre);
	printf("Lowest memory address ");
	c=0;
	c   = *(unsigned char *)(&NbRenv);
	printf("\n");
	bits4_1byte(c);
	printf("\n");	
	  
		
	bits4bytes(NbRenv);

  	
    return 0;

}  //  main()