/*
 * jdcoefct.c
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1994-1997, Thomas G. Lane.
 * libjpeg-turbo Modifications:
 * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
 * Copyright (C) 2010, 2015-2016, D. R. Commander.
 * Copyright (C) 2015, Google, Inc.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains the coefficient buffer controller for decompression.
 * This controller is the top level of the JPEG decompressor proper.
 * The coefficient buffer lies between entropy decoding and inverse-DCT steps.
 *
 * In buffered-image mode, this controller is the interface between
 * input-oriented processing and output-oriented processing.
 * Also, the input side (only) is used when reading a file for transcoding.
 */

#include "jinclude.h"
#include "jdcoefct.h"
#include "jpegcomp.h"


/* Forward declarations */
METHODDEF(int) decompress_onepass
		(j_decompress_ptr cinfo, JSAMPIMAGE output_buf);

#ifdef D_MULTISCAN_FILES_SUPPORTED

METHODDEF(int) decompress_data
		(j_decompress_ptr cinfo, JSAMPIMAGE output_buf);

#endif
#ifdef BLOCK_SMOOTHING_SUPPORTED

LOCAL(boolean) smoothing_ok(j_decompress_ptr cinfo);

METHODDEF(int) decompress_smooth_data
		(j_decompress_ptr cinfo, JSAMPIMAGE output_buf);

#endif


/*
 * Initialize for an input processing pass.
 */

METHODDEF(void)
start_input_pass(j_decompress_ptr cinfo) {
	cinfo->input_iMCU_row = 0;
	start_iMCU_row(cinfo);
}


/*
 * Initialize for an output processing pass.
 */

METHODDEF(void)
start_output_pass(j_decompress_ptr cinfo) {
#ifdef BLOCK_SMOOTHING_SUPPORTED
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

	/* If multipass, check to see whether to use block smoothing on this pass */
	if (coef->pub.coef_arrays != NULL) {
		if (cinfo->do_block_smoothing && smoothing_ok(cinfo))
			coef->pub.decompress_data = decompress_smooth_data;
		else
			coef->pub.decompress_data = decompress_data;
	}
#endif
	cinfo->output_iMCU_row = 0;
}


/*
 * Decompress and return some data in the single-pass case.
 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
 * Input and output must run in lockstep since we have only a one-MCU buffer.
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 *
 * NB: output_buf contains a plane for each component in image,
 * which we index according to the component's SOF position.
 */

METHODDEF(int)
decompress_onepass(j_decompress_ptr cinfo, JSAMPIMAGE output_buf) {
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
	JDIMENSION MCU_col_num;       /* index of current MCU within row */
	JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
	JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
	int blkn, ci, xindex, yindex, yoffset, useful_width;
	JSAMPARRAY output_ptr;
	JDIMENSION start_col, output_col;
	jpeg_component_info *compptr;
	inverse_DCT_method_ptr inverse_DCT;

	/* Loop to process as much as one whole iMCU row */
	for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
	     yoffset++) {
		for (MCU_col_num = coef->MCU_ctr; MCU_col_num <= last_MCU_col;
		     MCU_col_num++) {
			/* Try to fetch an MCU.  Entropy decoder expects buffer to be zeroed. */
			jzero_far((void *) coef->MCU_buffer[0],
			          (size_t) (cinfo->blocks_in_MCU * sizeof(JBLOCK)));
			if (!(*cinfo->entropy->decode_mcu)(cinfo, coef->MCU_buffer)) {
				/* Suspension forced; update state counters and exit */
				coef->MCU_vert_offset = yoffset;
				coef->MCU_ctr = MCU_col_num;
				return JPEG_SUSPENDED;
			}

			/* Only perform the IDCT on blocks that are contained within the desired
			 * cropping region.
			 */
			if (MCU_col_num >= cinfo->master->first_iMCU_col &&
			    MCU_col_num <= cinfo->master->last_iMCU_col) {
				/* Determine where data should go in output_buf and do the IDCT thing.
				 * We skip dummy blocks at the right and bottom edges (but blkn gets
				 * incremented past them!).  Note the inner loop relies on having
				 * allocated the MCU_buffer[] blocks sequentially.
				 */
				blkn = 0;                 /* index of current DCT block within MCU */
				for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
					compptr = cinfo->cur_comp_info[ci];
					/* Don't bother to IDCT an uninteresting component. */
					if (!compptr->component_needed) {
						blkn += compptr->MCU_blocks;
						continue;
					}
					inverse_DCT = cinfo->idct->inverse_DCT[compptr->component_index];
					useful_width = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
					                                            : compptr->last_col_width;
					output_ptr = output_buf[compptr->component_index] +
					             yoffset * compptr->_DCT_scaled_size;
					start_col = (MCU_col_num - cinfo->master->first_iMCU_col) *
					            compptr->MCU_sample_width;
					for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
						if (cinfo->input_iMCU_row < last_iMCU_row ||
						    yoffset + yindex < compptr->last_row_height) {
							output_col = start_col;
							for (xindex = 0; xindex < useful_width; xindex++) {
								(*inverse_DCT)(cinfo, compptr,
								               (JCOEFPTR) coef->MCU_buffer[blkn + xindex],
								               output_ptr, output_col);
								output_col += compptr->_DCT_scaled_size;
							}
						}
						blkn += compptr->MCU_width;
						output_ptr += compptr->_DCT_scaled_size;
					}
				}
			}
		}
		/* Completed an MCU row, but perhaps not an iMCU row */
		coef->MCU_ctr = 0;
	}
	/* Completed the iMCU row, advance counters for next one */
	cinfo->output_iMCU_row++;
	if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
		start_iMCU_row(cinfo);
		return JPEG_ROW_COMPLETED;
	}
	/* Completed the scan */
	(*cinfo->inputctl->finish_input_pass)(cinfo);
	return JPEG_SCAN_COMPLETED;
}


/*
 * Dummy consume-input routine for single-pass operation.
 */

METHODDEF(int)
dummy_consume_data(j_decompress_ptr cinfo) {
	return JPEG_SUSPENDED;        /* Always indicate nothing was done */
}


#ifdef D_MULTISCAN_FILES_SUPPORTED

/*
 * Consume input data and store it in the full-image coefficient buffer.
 * We read as much as one fully interleaved MCU row ("iMCU" row) per call,
 * ie, v_samp_factor block rows for each component in the scan.
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 */

METHODDEF(int)
consume_data(j_decompress_ptr cinfo) {
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
	JDIMENSION MCU_col_num;       /* index of current MCU within row */
	int blkn, ci, xindex, yindex, yoffset;
	JDIMENSION start_col;
	JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
	JBLOCKROW buffer_ptr;
	jpeg_component_info *compptr;

	/* Align the virtual buffers for the components used in this scan. */
	for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
		compptr = cinfo->cur_comp_info[ci];
		buffer[ci] = (*cinfo->mem->access_virt_barray)
				((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
				 cinfo->input_iMCU_row * compptr->v_samp_factor,
				 (JDIMENSION) compptr->v_samp_factor, TRUE);
		/* Note: entropy decoder expects buffer to be zeroed,
		 * but this is handled automatically by the memory manager
		 * because we requested a pre-zeroed array.
		 */
	}

	/* Loop to process one whole iMCU row */
	for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
	     yoffset++) {
		for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row;
		     MCU_col_num++) {
			/* Construct list of pointers to DCT blocks belonging to this MCU */
			blkn = 0;                 /* index of current DCT block within MCU */
			for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
				compptr = cinfo->cur_comp_info[ci];
				start_col = MCU_col_num * compptr->MCU_width;
				for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
					buffer_ptr = buffer[ci][yindex + yoffset] + start_col;
					for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
						coef->MCU_buffer[blkn++] = buffer_ptr++;
					}
				}
			}
			/* Try to fetch the MCU. */
			if (!(*cinfo->entropy->decode_mcu)(cinfo, coef->MCU_buffer)) {
				/* Suspension forced; update state counters and exit */
				coef->MCU_vert_offset = yoffset;
				coef->MCU_ctr = MCU_col_num;
				return JPEG_SUSPENDED;
			}
		}
		/* Completed an MCU row, but perhaps not an iMCU row */
		coef->MCU_ctr = 0;
	}
	/* Completed the iMCU row, advance counters for next one */
	if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
		start_iMCU_row(cinfo);
		return JPEG_ROW_COMPLETED;
	}
	/* Completed the scan */
	(*cinfo->inputctl->finish_input_pass)(cinfo);
	return JPEG_SCAN_COMPLETED;
}


/*
 * Decompress and return some data in the multi-pass case.
 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 *
 * NB: output_buf contains a plane for each component in image.
 */

METHODDEF(int)
decompress_data(j_decompress_ptr cinfo, JSAMPIMAGE output_buf) {
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
	JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
	JDIMENSION block_num;
	int ci, block_row, block_rows;
	JBLOCKARRAY buffer;
	JBLOCKROW buffer_ptr;
	JSAMPARRAY output_ptr;
	JDIMENSION output_col;
	jpeg_component_info *compptr;
	inverse_DCT_method_ptr inverse_DCT;

	/* Force some input to be done if we are getting ahead of the input. */
	while (cinfo->input_scan_number < cinfo->output_scan_number ||
	       (cinfo->input_scan_number == cinfo->output_scan_number &&
	        cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) {
		if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
			return JPEG_SUSPENDED;
	}

	/* OK, output from the virtual arrays. */
	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	     ci++, compptr++) {
		/* Don't bother to IDCT an uninteresting component. */
		if (!compptr->component_needed)
			continue;
		/* Align the virtual buffer for this component. */
		buffer = (*cinfo->mem->access_virt_barray)
				((j_common_ptr) cinfo, coef->whole_image[ci],
				 cinfo->output_iMCU_row * compptr->v_samp_factor,
				 (JDIMENSION) compptr->v_samp_factor, FALSE);
		/* Count non-dummy DCT block rows in this iMCU row. */
		if (cinfo->output_iMCU_row < last_iMCU_row)
			block_rows = compptr->v_samp_factor;
		else {
			/* NB: can't use last_row_height here; it is input-side-dependent! */
			block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
			if (block_rows == 0) block_rows = compptr->v_samp_factor;
		}
		inverse_DCT = cinfo->idct->inverse_DCT[ci];
		output_ptr = output_buf[ci];
		/* Loop over all DCT blocks to be processed. */
		for (block_row = 0; block_row < block_rows; block_row++) {
			buffer_ptr = buffer[block_row] + cinfo->master->first_MCU_col[ci];
			output_col = 0;
			for (block_num = cinfo->master->first_MCU_col[ci];
			     block_num <= cinfo->master->last_MCU_col[ci]; block_num++) {
				(*inverse_DCT)(cinfo, compptr, (JCOEFPTR) buffer_ptr,
				               output_ptr, output_col);
				buffer_ptr++;
				output_col += compptr->_DCT_scaled_size;
			}
			output_ptr += compptr->_DCT_scaled_size;
		}
	}

	if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
		return JPEG_ROW_COMPLETED;
	return JPEG_SCAN_COMPLETED;
}

#endif /* D_MULTISCAN_FILES_SUPPORTED */


#ifdef BLOCK_SMOOTHING_SUPPORTED

/*
 * This code applies interblock smoothing as described by section K.8
 * of the JPEG standard: the first 5 AC coefficients are estimated from
 * the DC values of a DCT block and its 8 neighboring blocks.
 * We apply smoothing only for progressive JPEG decoding, and only if
 * the coefficients it can estimate are not yet known to full precision.
 */

/* Natural-order array positions of the first 5 zigzag-order coefficients */
#define Q01_POS  1
#define Q10_POS  8
#define Q20_POS  16
#define Q11_POS  9
#define Q02_POS  2

/*
 * Determine whether block smoothing is applicable and safe.
 * We also latch the current states of the coef_bits[] entries for the
 * AC coefficients; otherwise, if the input side of the decompressor
 * advances into a new scan, we might think the coefficients are known
 * more accurately than they really are.
 */

LOCAL(boolean)
smoothing_ok(j_decompress_ptr cinfo) {
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
	boolean smoothing_useful = FALSE;
	int ci, coefi;
	jpeg_component_info *compptr;
	JQUANT_TBL *qtable;
	int *coef_bits;
	int *coef_bits_latch;

	if (!cinfo->progressive_mode || cinfo->coef_bits == NULL)
		return FALSE;

	/* Allocate latch area if not already done */
	if (coef->coef_bits_latch == NULL)
		coef->coef_bits_latch = (int *)
				(*cinfo->mem->alloc_small)((j_common_ptr) cinfo, JPOOL_IMAGE,
				                           cinfo->num_components *
				                           (SAVED_COEFS * sizeof(int)));
	coef_bits_latch = coef->coef_bits_latch;

	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	     ci++, compptr++) {
		/* All components' quantization values must already be latched. */
		if ((qtable = compptr->quant_table) == NULL)
			return FALSE;
		/* Verify DC & first 5 AC quantizers are nonzero to avoid zero-divide. */
		if (qtable->quantval[0] == 0 ||
		    qtable->quantval[Q01_POS] == 0 ||
		    qtable->quantval[Q10_POS] == 0 ||
		    qtable->quantval[Q20_POS] == 0 ||
		    qtable->quantval[Q11_POS] == 0 ||
		    qtable->quantval[Q02_POS] == 0)
			return FALSE;
		/* DC values must be at least partly known for all components. */
		coef_bits = cinfo->coef_bits[ci];
		if (coef_bits[0] < 0)
			return FALSE;
		/* Block smoothing is helpful if some AC coefficients remain inaccurate. */
		for (coefi = 1; coefi <= 5; coefi++) {
			coef_bits_latch[coefi] = coef_bits[coefi];
			if (coef_bits[coefi] != 0)
				smoothing_useful = TRUE;
		}
		coef_bits_latch += SAVED_COEFS;
	}

	return smoothing_useful;
}


/*
 * Variant of decompress_data for use when doing block smoothing.
 */

METHODDEF(int)
decompress_smooth_data(j_decompress_ptr cinfo, JSAMPIMAGE output_buf) {
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
	JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
	JDIMENSION block_num, last_block_column;
	int ci, block_row, block_rows, access_rows;
	JBLOCKARRAY buffer;
	JBLOCKROW buffer_ptr, prev_block_row, next_block_row;
	JSAMPARRAY output_ptr;
	JDIMENSION output_col;
	jpeg_component_info *compptr;
	inverse_DCT_method_ptr inverse_DCT;
	boolean first_row, last_row;
	JCOEF *workspace;
	int *coef_bits;
	JQUANT_TBL *quanttbl;
	JLONG Q00, Q01, Q02, Q10, Q11, Q20, num;
	int DC1, DC2, DC3, DC4, DC5, DC6, DC7, DC8, DC9;
	int Al, pred;

	/* Keep a local variable to avoid looking it up more than once */
	workspace = coef->workspace;

	/* Force some input to be done if we are getting ahead of the input. */
	while (cinfo->input_scan_number <= cinfo->output_scan_number &&
	       !cinfo->inputctl->eoi_reached) {
		if (cinfo->input_scan_number == cinfo->output_scan_number) {
			/* If input is working on current scan, we ordinarily want it to
			 * have completed the current row.  But if input scan is DC,
			 * we want it to keep one row ahead so that next block row's DC
			 * values are up to date.
			 */
			JDIMENSION delta = (cinfo->Ss == 0) ? 1 : 0;
			if (cinfo->input_iMCU_row > cinfo->output_iMCU_row + delta)
				break;
		}
		if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
			return JPEG_SUSPENDED;
	}

	/* OK, output from the virtual arrays. */
	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	     ci++, compptr++) {
		/* Don't bother to IDCT an uninteresting component. */
		if (!compptr->component_needed)
			continue;
		/* Count non-dummy DCT block rows in this iMCU row. */
		if (cinfo->output_iMCU_row < last_iMCU_row) {
			block_rows = compptr->v_samp_factor;
			access_rows = block_rows * 2; /* this and next iMCU row */
			last_row = FALSE;
		} else {
			/* NB: can't use last_row_height here; it is input-side-dependent! */
			block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
			if (block_rows == 0) block_rows = compptr->v_samp_factor;
			access_rows = block_rows; /* this iMCU row only */
			last_row = TRUE;
		}
		/* Align the virtual buffer for this component. */
		if (cinfo->output_iMCU_row > 0) {
			access_rows += compptr->v_samp_factor; /* prior iMCU row too */
			buffer = (*cinfo->mem->access_virt_barray)
					((j_common_ptr) cinfo, coef->whole_image[ci],
					 (cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,
					 (JDIMENSION) access_rows, FALSE);
			buffer += compptr->v_samp_factor; /* point to current iMCU row */
			first_row = FALSE;
		} else {
			buffer = (*cinfo->mem->access_virt_barray)
					((j_common_ptr) cinfo, coef->whole_image[ci],
					 (JDIMENSION) 0, (JDIMENSION) access_rows, FALSE);
			first_row = TRUE;
		}
		/* Fetch component-dependent info */
		coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);
		quanttbl = compptr->quant_table;
		Q00 = quanttbl->quantval[0];
		Q01 = quanttbl->quantval[Q01_POS];
		Q10 = quanttbl->quantval[Q10_POS];
		Q20 = quanttbl->quantval[Q20_POS];
		Q11 = quanttbl->quantval[Q11_POS];
		Q02 = quanttbl->quantval[Q02_POS];
		inverse_DCT = cinfo->idct->inverse_DCT[ci];
		output_ptr = output_buf[ci];
		/* Loop over all DCT blocks to be processed. */
		for (block_row = 0; block_row < block_rows; block_row++) {
			buffer_ptr = buffer[block_row] + cinfo->master->first_MCU_col[ci];
			if (first_row && block_row == 0)
				prev_block_row = buffer_ptr;
			else
				prev_block_row = buffer[block_row - 1];
			if (last_row && block_row == block_rows - 1)
				next_block_row = buffer_ptr;
			else
				next_block_row = buffer[block_row + 1];
			/* We fetch the surrounding DC values using a sliding-register approach.
			 * Initialize all nine here so as to do the right thing on narrow pics.
			 */
			DC1 = DC2 = DC3 = (int) prev_block_row[0][0];
			DC4 = DC5 = DC6 = (int) buffer_ptr[0][0];
			DC7 = DC8 = DC9 = (int) next_block_row[0][0];
			output_col = 0;
			last_block_column = compptr->width_in_blocks - 1;
			for (block_num = cinfo->master->first_MCU_col[ci];
			     block_num <= cinfo->master->last_MCU_col[ci]; block_num++) {
				/* Fetch current DCT block into workspace so we can modify it. */
				jcopy_block_row(buffer_ptr, (JBLOCKROW) workspace, (JDIMENSION) 1);
				/* Update DC values */
				if (block_num < last_block_column) {
					DC3 = (int) prev_block_row[1][0];
					DC6 = (int) buffer_ptr[1][0];
					DC9 = (int) next_block_row[1][0];
				}
				/* Compute coefficient estimates per K.8.
				 * An estimate is applied only if coefficient is still zero,
				 * and is not known to be fully accurate.
				 */
				/* AC01 */
				if ((Al = coef_bits[1]) != 0 && workspace[1] == 0) {
					num = 36 * Q00 * (DC4 - DC6);
					if (num >= 0) {
						pred = (int) (((Q01 << 7) + num) / (Q01 << 8));
						if (Al > 0 && pred >= (1 << Al))
							pred = (1 << Al) - 1;
					} else {
						pred = (int) (((Q01 << 7) - num) / (Q01 << 8));
						if (Al > 0 && pred >= (1 << Al))
							pred = (1 << Al) - 1;
						pred = -pred;
					}
					workspace[1] = (JCOEF) pred;
				}
				/* AC10 */
				if ((Al = coef_bits[2]) != 0 && workspace[8] == 0) {
					num = 36 * Q00 * (DC2 - DC8);
					if (num >= 0) {
						pred = (int) (((Q10 << 7) + num) / (Q10 << 8));
						if (Al > 0 && pred >= (1 << Al))
							pred = (1 << Al) - 1;
					} else {
						pred = (int) (((Q10 << 7) - num) / (Q10 << 8));
						if (Al > 0 && pred >= (1 << Al))
							pred = (1 << Al) - 1;
						pred = -pred;
					}
					workspace[8] = (JCOEF) pred;
				}
				/* AC20 */
				if ((Al = coef_bits[3]) != 0 && workspace[16] == 0) {
					num = 9 * Q00 * (DC2 + DC8 - 2 * DC5);
					if (num >= 0) {
						pred = (int) (((Q20 << 7) + num) / (Q20 << 8));
						if (Al > 0 && pred >= (1 << Al))
							pred = (1 << Al) - 1;
					} else {
						pred = (int) (((Q20 << 7) - num) / (Q20 << 8));
						if (Al > 0 && pred >= (1 << Al))
							pred = (1 << Al) - 1;
						pred = -pred;
					}
					workspace[16] = (JCOEF) pred;
				}
				/* AC11 */
				if ((Al = coef_bits[4]) != 0 && workspace[9] == 0) {
					num = 5 * Q00 * (DC1 - DC3 - DC7 + DC9);
					if (num >= 0) {
						pred = (int) (((Q11 << 7) + num) / (Q11 << 8));
						if (Al > 0 && pred >= (1 << Al))
							pred = (1 << Al) - 1;
					} else {
						pred = (int) (((Q11 << 7) - num) / (Q11 << 8));
						if (Al > 0 && pred >= (1 << Al))
							pred = (1 << Al) - 1;
						pred = -pred;
					}
					workspace[9] = (JCOEF) pred;
				}
				/* AC02 */
				if ((Al = coef_bits[5]) != 0 && workspace[2] == 0) {
					num = 9 * Q00 * (DC4 + DC6 - 2 * DC5);
					if (num >= 0) {
						pred = (int) (((Q02 << 7) + num) / (Q02 << 8));
						if (Al > 0 && pred >= (1 << Al))
							pred = (1 << Al) - 1;
					} else {
						pred = (int) (((Q02 << 7) - num) / (Q02 << 8));
						if (Al > 0 && pred >= (1 << Al))
							pred = (1 << Al) - 1;
						pred = -pred;
					}
					workspace[2] = (JCOEF) pred;
				}
				/* OK, do the IDCT */
				(*inverse_DCT)(cinfo, compptr, (JCOEFPTR) workspace,
				               output_ptr, output_col);
				/* Advance for next column */
				DC1 = DC2;
				DC2 = DC3;
				DC4 = DC5;
				DC5 = DC6;
				DC7 = DC8;
				DC8 = DC9;
				buffer_ptr++, prev_block_row++, next_block_row++;
				output_col += compptr->_DCT_scaled_size;
			}
			output_ptr += compptr->_DCT_scaled_size;
		}
	}

	if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
		return JPEG_ROW_COMPLETED;
	return JPEG_SCAN_COMPLETED;
}

#endif /* BLOCK_SMOOTHING_SUPPORTED */


/*
 * Initialize coefficient buffer controller.
 */

GLOBAL(void)
jinit_d_coef_controller(j_decompress_ptr cinfo, boolean need_full_buffer) {
	my_coef_ptr coef;

	coef = (my_coef_ptr)
			(*cinfo->mem->alloc_small)((j_common_ptr) cinfo, JPOOL_IMAGE,
			                           sizeof(my_coef_controller));
	cinfo->coef = (struct jpeg_d_coef_controller *) coef;
	coef->pub.start_input_pass = start_input_pass;
	coef->pub.start_output_pass = start_output_pass;
#ifdef BLOCK_SMOOTHING_SUPPORTED
	coef->coef_bits_latch = NULL;
#endif

	/* Create the coefficient buffer. */
	if (need_full_buffer) {
#ifdef D_MULTISCAN_FILES_SUPPORTED
		/* Allocate a full-image virtual array for each component, */
		/* padded to a multiple of samp_factor DCT blocks in each direction. */
		/* Note we ask for a pre-zeroed array. */
		int ci, access_rows;
		jpeg_component_info *compptr;

		for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
		     ci++, compptr++) {
			access_rows = compptr->v_samp_factor;
#ifdef BLOCK_SMOOTHING_SUPPORTED
			/* If block smoothing could be used, need a bigger window */
			if (cinfo->progressive_mode)
				access_rows *= 3;
#endif
			coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
					((j_common_ptr) cinfo, JPOOL_IMAGE, TRUE,
					 (JDIMENSION) jround_up((long) compptr->width_in_blocks,
					                        (long) compptr->h_samp_factor),
					 (JDIMENSION) jround_up((long) compptr->height_in_blocks,
					                        (long) compptr->v_samp_factor),
					 (JDIMENSION) access_rows);
		}
		coef->pub.consume_data = consume_data;
		coef->pub.decompress_data = decompress_data;
		coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */
#else
		ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
	} else {
		/* We only need a single-MCU buffer. */
		JBLOCKROW buffer;
		int i;

		buffer = (JBLOCKROW)
				(*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE,
				                           D_MAX_BLOCKS_IN_MCU * sizeof(JBLOCK));
		for (i = 0; i < D_MAX_BLOCKS_IN_MCU; i++) {
			coef->MCU_buffer[i] = buffer + i;
		}
		coef->pub.consume_data = dummy_consume_data;
		coef->pub.decompress_data = decompress_onepass;
		coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */
	}

	/* Allocate the workspace buffer */
	coef->workspace = (JCOEF *)
			(*cinfo->mem->alloc_small)((j_common_ptr) cinfo, JPOOL_IMAGE,
			                           sizeof(JCOEF) * DCTSIZE2);
}
