#include "dct.h"

#define FIX_0_382683433  (98)		/* FIX(0.382683433) */
#define FIX_0_541196100  (139)		/* FIX(0.541196100) */
#define FIX_0_707106781  (181)		/* FIX(0.707106781) */
#define FIX_1_306562965  (334)		/* FIX(1.306562965) */

/*
 * Perform the forward DCT on one block of samples.
 */
void fdct(int *data) {
	int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
	int tmp10, tmp11, tmp12, tmp13;
	int z1, z2, z3, z4, z5, z11, z13;
	int *dataptr;
	int ctr;
//	SHIFT_TEMPS

	/* Pass 1: process rows. */

	dataptr = data;
	for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
		tmp0 = dataptr[0] + dataptr[7];
		tmp7 = dataptr[0] - dataptr[7];
		tmp1 = dataptr[1] + dataptr[6];
		tmp6 = dataptr[1] - dataptr[6];
		tmp2 = dataptr[2] + dataptr[5];
		tmp5 = dataptr[2] - dataptr[5];
		tmp3 = dataptr[3] + dataptr[4];
		tmp4 = dataptr[3] - dataptr[4];
    
		/* Even part */
    
		tmp10 = tmp0 + tmp3;	/* phase 2 */
		tmp13 = tmp0 - tmp3;
		tmp11 = tmp1 + tmp2;
		tmp12 = tmp1 - tmp2;
    
		dataptr[0] = tmp10 + tmp11; /* phase 3 */
		dataptr[4] = tmp10 - tmp11;

		z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
		dataptr[2] = tmp13 + z1;	/* phase 5 */
		dataptr[6] = tmp13 - z1;
   
		/* Odd part */

		tmp10 = tmp4 + tmp5;	/* phase 2 */
		tmp11 = tmp5 + tmp6;
		tmp12 = tmp6 + tmp7;
		
		/* The rotator is modified from fig 4-8 to avoid extra negations. */
		z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
		z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */
		z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */
		z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */

		z11 = tmp7 + z3;		/* phase 5 */
		z13 = tmp7 - z3;

		dataptr[5] = z13 + z2;	/* phase 6 */
		dataptr[3] = z13 - z2;
		dataptr[1] = z11 + z4;
		dataptr[7] = z11 - z4;
		
		dataptr += DCTSIZE;		/* advance pointer to next row */
	}

	/* Pass 2: process columns. */

	dataptr = data;
	for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
		tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7];
		tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7];
		tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6];
		tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6];
		tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5];
		tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5];
		tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4];
		tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4];
    
		/* Even part */

		tmp10 = tmp0 + tmp3;	/* phase 2 */
		tmp13 = tmp0 - tmp3;
		tmp11 = tmp1 + tmp2;
		tmp12 = tmp1 - tmp2;
    
		dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */
		dataptr[DCTSIZE*4] = tmp10 - tmp11;
    
		z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
		dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */
		dataptr[DCTSIZE*6] = tmp13 - z1;

		/* Odd part */

		tmp10 = tmp4 + tmp5;	/* phase 2 */
		tmp11 = tmp5 + tmp6;
		tmp12 = tmp6 + tmp7;
		
		/* The rotator is modified from fig 4-8 to avoid extra negations. */
		z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
		z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */
		z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */
		z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */

		z11 = tmp7 + z3;		/* phase 5 */
		z13 = tmp7 - z3;

		dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */
		dataptr[DCTSIZE*3] = z13 - z2;
		dataptr[DCTSIZE*1] = z11 + z4;
		dataptr[DCTSIZE*7] = z11 - z4;

		dataptr++;			/* advance pointer to next column */
	}
}