Function init_des

src/common/enc.cpp:765–896

* Initialize various tables. This need only be done once. It could even be * done at compile time, if the compiler were capable of that sort of thing. */

 * done at compile time, if the compiler were capable of that sort of thing.
 */
STATIC void init_des()
{
	SLONG k;
	static unsigned char perm[64];	// "static" for speed

	// table that converts chars "./0-9A-Za-z"to integers 0-63.

	for (int i = 0; i < 64; i++)
		a64toi[itoa64[i]] = i;

	// PC1ROT - bit reverse, then PC1, then Rotate, then PC2.

	for (int i = 0; i < 64; i++)
		perm[i] = 0;

	for (int i = 0; i < 64; i++)
	{
		if ((k = PC2[i]) == 0)
			continue;
		k += Rotates[0] - 1;
		if ((k % 28) < Rotates[0])
			k -= 28;
		k = PC1[k];
		if (k > 0)
		{
			k--;
			k = (k | 07) - (k & 07);
			k++;
		}
		perm[i] = (unsigned char) k;
	}
	init_perm(PC1ROT, perm, 8);

	// PC2ROT - PC2 inverse, then Rotate (once or twice), then PC2.

	for (int j = 0; j < 2; j++)
	{
		unsigned char pc2inv[64];
		for (int i = 0; i < 64; i++)
			perm[i] = pc2inv[i] = 0;

		for (int i = 0; i < 64; i++)
		{
			if ((k = PC2[i]) == 0)
				continue;
			pc2inv[k - 1] = i + 1;
		}

		for (int i = 0; i < 64; i++)
		{
			if ((k = PC2[i]) == 0)
				continue;
			k += j;
			if ((k % 28) <= j)
				k -= 28;
			perm[i] = pc2inv[k];
		}
		init_perm(PC2ROT[j], perm, 8);