/*
 * jidctred.c
 *
 * This file was part of the Independent JPEG Group's software.
 * Copyright (C) 1994-1998, Thomas G. Lane.
 * libjpeg-turbo Modifications:
 * Copyright (C) 2015, D. R. Commander.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains inverse-DCT routines that produce reduced-size output:
 * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
 *
 * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
 * algorithm used in jidctint.c.  We simply replace each 8-to-8 1-D IDCT step
 * with an 8-to-4 step that produces the four averages of two adjacent outputs
 * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
 * These steps were derived by computing the corresponding values at the end
 * of the normal LL&M code, then simplifying as much as possible.
 *
 * 1x1 is trivial: just take the DC coefficient divided by 8.
 *
 * See jidctint.c for additional comments.
 */

#define JPEG_INTERNALS

#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"               /* Private declarations for DCT subsystem */

#ifdef IDCT_SCALING_SUPPORTED


/*
 * This module is specialized to the case DCTSIZE = 8.
 */

#if DCTSIZE != 8
Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
#endif


/* Scaling is the same as in jidctint.c. */

#if BITS_IN_JSAMPLE == 8
#define CONST_BITS  13
#define PASS1_BITS  2
#else
#define CONST_BITS  13
#define PASS1_BITS  1           /* lose a little precision to avoid overflow */
#endif

/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
 * causing a lot of useless floating-point operations at run time.
 * To get around this we use the following pre-calculated constants.
 * If you change CONST_BITS you may want to add appropriate values.
 * (With a reasonable C compiler, you can just rely on the FIX() macro...)
 */

#if CONST_BITS == 13
#define FIX_0_211164243  ((JLONG)  1730)        /* FIX(0.211164243) */
#define FIX_0_509795579  ((JLONG)  4176)        /* FIX(0.509795579) */
#define FIX_0_601344887  ((JLONG)  4926)        /* FIX(0.601344887) */
#define FIX_0_720959822  ((JLONG)  5906)        /* FIX(0.720959822) */
#define FIX_0_765366865  ((JLONG)  6270)        /* FIX(0.765366865) */
#define FIX_0_850430095  ((JLONG)  6967)        /* FIX(0.850430095) */
#define FIX_0_899976223  ((JLONG)  7373)        /* FIX(0.899976223) */
#define FIX_1_061594337  ((JLONG)  8697)        /* FIX(1.061594337) */
#define FIX_1_272758580  ((JLONG)  10426)       /* FIX(1.272758580) */
#define FIX_1_451774981  ((JLONG)  11893)       /* FIX(1.451774981) */
#define FIX_1_847759065  ((JLONG)  15137)       /* FIX(1.847759065) */
#define FIX_2_172734803  ((JLONG)  17799)       /* FIX(2.172734803) */
#define FIX_2_562915447  ((JLONG)  20995)       /* FIX(2.562915447) */
#define FIX_3_624509785  ((JLONG)  29692)       /* FIX(3.624509785) */
#else
#define FIX_0_211164243  FIX(0.211164243)
#define FIX_0_509795579  FIX(0.509795579)
#define FIX_0_601344887  FIX(0.601344887)
#define FIX_0_720959822  FIX(0.720959822)
#define FIX_0_765366865  FIX(0.765366865)
#define FIX_0_850430095  FIX(0.850430095)
#define FIX_0_899976223  FIX(0.899976223)
#define FIX_1_061594337  FIX(1.061594337)
#define FIX_1_272758580  FIX(1.272758580)
#define FIX_1_451774981  FIX(1.451774981)
#define FIX_1_847759065  FIX(1.847759065)
#define FIX_2_172734803  FIX(2.172734803)
#define FIX_2_562915447  FIX(2.562915447)
#define FIX_3_624509785  FIX(3.624509785)
#endif


/* Multiply a JLONG variable by a JLONG constant to yield a JLONG result.
 * For 8-bit samples with the recommended scaling, all the variable
 * and constant values involved are no more than 16 bits wide, so a
 * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
 * For 12-bit samples, a full 32-bit multiplication will be needed.
 */

#if BITS_IN_JSAMPLE == 8
#define MULTIPLY(var,const)  MULTIPLY16C16(var,const)
#else
#define MULTIPLY(var, const)  ((var) * (const))
#endif


/* Dequantize a coefficient by multiplying it by the multiplier-table
 * entry; produce an int result.  In this module, both inputs and result
 * are 16 bits or less, so either int or short multiply will work.
 */

#define DEQUANTIZE(coef, quantval)  (((ISLOW_MULT_TYPE) (coef)) * (quantval))


/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 4x4 output block.
 */

GLOBAL(void)
jpeg_idct_4x4(j_decompress_ptr cinfo, jpeg_component_info *compptr,
              JCOEFPTR coef_block,
              JSAMPARRAY output_buf, JDIMENSION output_col) {
	JLONG tmp0, tmp2, tmp10, tmp12;
	JLONG z1, z2, z3, z4;
	JCOEFPTR inptr;
	ISLOW_MULT_TYPE *quantptr;
	int *wsptr;
	JSAMPROW outptr;
	JSAMPLE *range_limit = IDCT_range_limit(cinfo);
	int ctr;
	int workspace[DCTSIZE * 4];     /* buffers data between passes */
	SHIFT_TEMPS

	/* Pass 1: process columns from input, store into work array. */

	inptr = coef_block;
	quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	wsptr = workspace;
	for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
		/* Don't bother to process column 4, because second pass won't use it */
		if (ctr == DCTSIZE - 4)
			continue;
		if (inptr[DCTSIZE * 1] == 0 && inptr[DCTSIZE * 2] == 0 &&
		    inptr[DCTSIZE * 3] == 0 && inptr[DCTSIZE * 5] == 0 &&
		    inptr[DCTSIZE * 6] == 0 && inptr[DCTSIZE * 7] == 0) {
			/* AC terms all zero; we need not examine term 4 for 4x4 output */
			int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]),
			                       PASS1_BITS);

			wsptr[DCTSIZE * 0] = dcval;
			wsptr[DCTSIZE * 1] = dcval;
			wsptr[DCTSIZE * 2] = dcval;
			wsptr[DCTSIZE * 3] = dcval;

			continue;
		}

		/* Even part */

		tmp0 = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]);
		tmp0 = LEFT_SHIFT(tmp0, CONST_BITS + 1);

		z2 = DEQUANTIZE(inptr[DCTSIZE * 2], quantptr[DCTSIZE * 2]);
		z3 = DEQUANTIZE(inptr[DCTSIZE * 6], quantptr[DCTSIZE * 6]);

		tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, -FIX_0_765366865);

		tmp10 = tmp0 + tmp2;
		tmp12 = tmp0 - tmp2;

		/* Odd part */

		z1 = DEQUANTIZE(inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7]);
		z2 = DEQUANTIZE(inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5]);
		z3 = DEQUANTIZE(inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3]);
		z4 = DEQUANTIZE(inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1]);

		tmp0 = MULTIPLY(z1, -FIX_0_211164243) /* sqrt(2) * (c3-c1) */
		       + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
		       + MULTIPLY(z3, -FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
		       + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */

		tmp2 = MULTIPLY(z1, -FIX_0_509795579) /* sqrt(2) * (c7-c5) */
		       + MULTIPLY(z2, -FIX_0_601344887) /* sqrt(2) * (c5-c1) */
		       + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
		       + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

		/* Final output stage */

		wsptr[DCTSIZE * 0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS - PASS1_BITS + 1);
		wsptr[DCTSIZE * 3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS - PASS1_BITS + 1);
		wsptr[DCTSIZE * 1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS - PASS1_BITS + 1);
		wsptr[DCTSIZE * 2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS - PASS1_BITS + 1);
	}

	/* Pass 2: process 4 rows from work array, store into output array. */

	wsptr = workspace;
	for (ctr = 0; ctr < 4; ctr++) {
		outptr = output_buf[ctr] + output_col;
		/* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
		if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
		    wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
			/* AC terms all zero */
			JSAMPLE dcval = range_limit[(int) DESCALE((JLONG) wsptr[0], PASS1_BITS + 3)
			                            & RANGE_MASK];

			outptr[0] = dcval;
			outptr[1] = dcval;
			outptr[2] = dcval;
			outptr[3] = dcval;

			wsptr += DCTSIZE;         /* advance pointer to next row */
			continue;
		}
#endif

		/* Even part */

		tmp0 = LEFT_SHIFT((JLONG) wsptr[0], CONST_BITS + 1);

		tmp2 = MULTIPLY((JLONG) wsptr[2], FIX_1_847759065)
		       + MULTIPLY((JLONG) wsptr[6], -FIX_0_765366865);

		tmp10 = tmp0 + tmp2;
		tmp12 = tmp0 - tmp2;

		/* Odd part */

		z1 = (JLONG) wsptr[7];
		z2 = (JLONG) wsptr[5];
		z3 = (JLONG) wsptr[3];
		z4 = (JLONG) wsptr[1];

		tmp0 = MULTIPLY(z1, -FIX_0_211164243) /* sqrt(2) * (c3-c1) */
		       + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
		       + MULTIPLY(z3, -FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
		       + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */

		tmp2 = MULTIPLY(z1, -FIX_0_509795579) /* sqrt(2) * (c7-c5) */
		       + MULTIPLY(z2, -FIX_0_601344887) /* sqrt(2) * (c5-c1) */
		       + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
		       + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

		/* Final output stage */

		outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2,
		                                      CONST_BITS + PASS1_BITS + 3 + 1)
		                        & RANGE_MASK];
		outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2,
		                                      CONST_BITS + PASS1_BITS + 3 + 1)
		                        & RANGE_MASK];
		outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0,
		                                      CONST_BITS + PASS1_BITS + 3 + 1)
		                        & RANGE_MASK];
		outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0,
		                                      CONST_BITS + PASS1_BITS + 3 + 1)
		                        & RANGE_MASK];

		wsptr += DCTSIZE;           /* advance pointer to next row */
	}
}


/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 2x2 output block.
 */

GLOBAL(void)
jpeg_idct_2x2(j_decompress_ptr cinfo, jpeg_component_info *compptr,
              JCOEFPTR coef_block,
              JSAMPARRAY output_buf, JDIMENSION output_col) {
	JLONG tmp0, tmp10, z1;
	JCOEFPTR inptr;
	ISLOW_MULT_TYPE *quantptr;
	int *wsptr;
	JSAMPROW outptr;
	JSAMPLE *range_limit = IDCT_range_limit(cinfo);
	int ctr;
	int workspace[DCTSIZE * 2];     /* buffers data between passes */
	SHIFT_TEMPS

	/* Pass 1: process columns from input, store into work array. */

	inptr = coef_block;
	quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	wsptr = workspace;
	for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
		/* Don't bother to process columns 2,4,6 */
		if (ctr == DCTSIZE - 2 || ctr == DCTSIZE - 4 || ctr == DCTSIZE - 6)
			continue;
		if (inptr[DCTSIZE * 1] == 0 && inptr[DCTSIZE * 3] == 0 &&
		    inptr[DCTSIZE * 5] == 0 && inptr[DCTSIZE * 7] == 0) {
			/* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
			int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]),
			                       PASS1_BITS);

			wsptr[DCTSIZE * 0] = dcval;
			wsptr[DCTSIZE * 1] = dcval;

			continue;
		}

		/* Even part */

		z1 = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]);
		tmp10 = LEFT_SHIFT(z1, CONST_BITS + 2);

		/* Odd part */

		z1 = DEQUANTIZE(inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7]);
		tmp0 = MULTIPLY(z1, -FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
		z1 = DEQUANTIZE(inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5]);
		tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
		z1 = DEQUANTIZE(inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3]);
		tmp0 += MULTIPLY(z1, -FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
		z1 = DEQUANTIZE(inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1]);
		tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

		/* Final output stage */

		wsptr[DCTSIZE * 0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS - PASS1_BITS + 2);
		wsptr[DCTSIZE * 1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS - PASS1_BITS + 2);
	}

	/* Pass 2: process 2 rows from work array, store into output array. */

	wsptr = workspace;
	for (ctr = 0; ctr < 2; ctr++) {
		outptr = output_buf[ctr] + output_col;
		/* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
		if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
			/* AC terms all zero */
			JSAMPLE dcval = range_limit[(int) DESCALE((JLONG) wsptr[0], PASS1_BITS + 3)
			                            & RANGE_MASK];

			outptr[0] = dcval;
			outptr[1] = dcval;

			wsptr += DCTSIZE;         /* advance pointer to next row */
			continue;
		}
#endif

		/* Even part */

		tmp10 = LEFT_SHIFT((JLONG) wsptr[0], CONST_BITS + 2);

		/* Odd part */

		tmp0 = MULTIPLY((JLONG) wsptr[7], -FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
		       + MULTIPLY((JLONG) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
		       + MULTIPLY((JLONG) wsptr[3], -FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
		       + MULTIPLY((JLONG) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

		/* Final output stage */

		outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0,
		                                      CONST_BITS + PASS1_BITS + 3 + 2)
		                        & RANGE_MASK];
		outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0,
		                                      CONST_BITS + PASS1_BITS + 3 + 2)
		                        & RANGE_MASK];

		wsptr += DCTSIZE;           /* advance pointer to next row */
	}
}


/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 1x1 output block.
 */

GLOBAL(void)
jpeg_idct_1x1(j_decompress_ptr cinfo, jpeg_component_info *compptr,
              JCOEFPTR coef_block,
              JSAMPARRAY output_buf, JDIMENSION output_col) {
	int dcval;
	ISLOW_MULT_TYPE *quantptr;
	JSAMPLE *range_limit = IDCT_range_limit(cinfo);
	SHIFT_TEMPS

	/* We hardly need an inverse DCT routine for this: just take the
	 * average pixel value, which is one-eighth of the DC coefficient.
	 */
	quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
	dcval = (int) DESCALE((JLONG) dcval, 3);

	output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
}

#endif /* IDCT_SCALING_SUPPORTED */
