/**
* Função que lê uma imagem pgm e retorna uma matriz de ints
*
* @param arq Caminho para o arquivo pbm
* @param tabuleiro Ponteiro para a matriz de ints
* @param nlin Ponteiro para o número de linhas
* @param ncol Ponteiro para o número de colunas
*/
void pbm(char *arq, int ***tabuleiro, int *nlin, int *ncol)
{
FILE *img;
bit **tab;
img = fopen(arq, "r");
if(img)
{
//void bit** pbm_readpbm(FILE * fp, int *colsP, int *rowsP);
tab = pbm_readpbm(img, ncol, nlin);
bit2int(tab, nlin, ncol, tabuleiro);
pbm_freearray(tab, *nlin);
fclose(img);
return;
}
else
{
// Erro na leitura
printf("Arquivo não encontrado\n");
exit(0);
}
}
//This function performs the SBox substitution
//The input is a 48 bits array, and the output is a 32 bits array
void SBox_Function(unsigned int *oldBlock, unsigned int *compressedBlock)
{
int beg,end,row,col,index;
unsigned int aux[4]; //Auxiliary array that stored the Sbox value in binary
beg = 0; //flag to the beginning of the 48 bits array
end = 5; //flag to the end of the 48 bits array
index = 0; //flag that controls the array that stores substitutions
unsigned int rowBin[2], colBin[4]; // arrays that store both row and column of Sbox in binary
//Execute this until the end of 48 bits array
while(end<48)
{
//Extract both first and last bits in a range of 6 bits
rowBin[0] = oldBlock[beg];
rowBin[1] = oldBlock[end];
//Extract the 4 bits in the middle of beg and end
for(int i=beg+1,j=0;i<end;i++,j++)
{
colBin[j] = oldBlock[i];
}
//Convert Row and Col to numbers
row = bit2int(rowBin,2);
col = bit2int(colBin,4);
//Select the correspondent Sbox number and transforms it in binary
switch(end)
{
case 5:
int2bin(aux,(int)S1[row][col],4);
break;
case 11:
int2bin(aux,(int)S2[row][col],4);
break;
case 17:
int2bin(aux,(int)S3[row][col],4);
break;
case 23:
int2bin(aux,(int)S4[row][col],4);
break;
case 29:
int2bin(aux,(int)S5[row][col],4);
break;
case 35:
int2bin(aux,(int)S6[row][col],4);
break;
case 41:
int2bin(aux,(int)S7[row][col],4);
break;
case 47:
int2bin(aux,(int)S8[row][col],4);
break;
}
//Append the 4 bits array generated to the 32 bits array
for(int j=0;j<4;j++,index++)
compressedBlock[index] = aux[j];
beg+=6;
end+=6;
}
}
