/*
 * jdpostct.c
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * It was modified by The libjpeg-turbo Project to include only code relevant
 * to libjpeg-turbo.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains the decompression postprocessing controller.
 * This controller manages the upsampling, color conversion, and color
 * quantization/reduction steps; specifically, it controls the buffering
 * between upsample/color conversion and color quantization/reduction.
 *
 * If no color quantization/reduction is required, then this module has no
 * work to do, and it just hands off to the upsample/color conversion code.
 * An integrated upsample/convert/quantize process would replace this module
 * entirely.
 */

#define JPEG_INTERNALS

#include "jinclude.h"
#include "jpeglib.h"


/* Private buffer controller object */

typedef struct {
	struct jpeg_d_post_controller pub; /* public fields */

	/* Color quantization source buffer: this holds output data from
	 * the upsample/color conversion step to be passed to the quantizer.
	 * For two-pass color quantization, we need a full-image buffer;
	 * for one-pass operation, a strip buffer is sufficient.
	 */
	jvirt_sarray_ptr whole_image; /* virtual array, or NULL if one-pass */
	JSAMPARRAY buffer;            /* strip buffer, or current strip of virtual */
	JDIMENSION strip_height;      /* buffer size in rows */
	/* for two-pass mode only: */
	JDIMENSION starting_row;      /* row # of first row in current strip */
	JDIMENSION next_row;          /* index of next row to fill/empty in strip */
} my_post_controller;

typedef my_post_controller *my_post_ptr;


/* Forward declarations */
METHODDEF(void) post_process_1pass
		(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
		 JDIMENSION *in_row_group_ctr, JDIMENSION in_row_groups_avail,
		 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
		 JDIMENSION out_rows_avail);

#ifdef QUANT_2PASS_SUPPORTED

METHODDEF(void) post_process_prepass
		(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
		 JDIMENSION *in_row_group_ctr, JDIMENSION in_row_groups_avail,
		 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
		 JDIMENSION out_rows_avail);

METHODDEF(void) post_process_2pass
		(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
		 JDIMENSION *in_row_group_ctr, JDIMENSION in_row_groups_avail,
		 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
		 JDIMENSION out_rows_avail);

#endif


/*
 * Initialize for a processing pass.
 */

METHODDEF(void)
start_pass_dpost(j_decompress_ptr cinfo, J_BUF_MODE pass_mode) {
	my_post_ptr post = (my_post_ptr) cinfo->post;

	switch (pass_mode) {
		case JBUF_PASS_THRU:
			if (cinfo->quantize_colors) {
				/* Single-pass processing with color quantization. */
				post->pub.post_process_data = post_process_1pass;
				/* We could be doing buffered-image output before starting a 2-pass
				 * color quantization; in that case, jinit_d_post_controller did not
				 * allocate a strip buffer.  Use the virtual-array buffer as workspace.
				 */
				if (post->buffer == NULL) {
					post->buffer = (*cinfo->mem->access_virt_sarray)
							((j_common_ptr) cinfo, post->whole_image,
							 (JDIMENSION) 0, post->strip_height, TRUE);
				}
			} else {
				/* For single-pass processing without color quantization,
				 * I have no work to do; just call the upsampler directly.
				 */
				post->pub.post_process_data = cinfo->upsample->upsample;
			}
			break;
#ifdef QUANT_2PASS_SUPPORTED
		case JBUF_SAVE_AND_PASS:
			/* First pass of 2-pass quantization */
			if (post->whole_image == NULL)
				ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
			post->pub.post_process_data = post_process_prepass;
			break;
		case JBUF_CRANK_DEST:
			/* Second pass of 2-pass quantization */
			if (post->whole_image == NULL)
				ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
			post->pub.post_process_data = post_process_2pass;
			break;
#endif /* QUANT_2PASS_SUPPORTED */
		default:
			ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
			break;
	}
	post->starting_row = post->next_row = 0;
}


/*
 * Process some data in the one-pass (strip buffer) case.
 * This is used for color precision reduction as well as one-pass quantization.
 */

METHODDEF(void)
post_process_1pass(j_decompress_ptr cinfo,
                   JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
                   JDIMENSION in_row_groups_avail,
                   JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
                   JDIMENSION out_rows_avail) {
	my_post_ptr post = (my_post_ptr) cinfo->post;
	JDIMENSION num_rows, max_rows;

	/* Fill the buffer, but not more than what we can dump out in one go. */
	/* Note we rely on the upsampler to detect bottom of image. */
	max_rows = out_rows_avail - *out_row_ctr;
	if (max_rows > post->strip_height)
		max_rows = post->strip_height;
	num_rows = 0;
	(*cinfo->upsample->upsample)(cinfo,
	                             input_buf, in_row_group_ctr, in_row_groups_avail,
	                             post->buffer, &num_rows, max_rows);
	/* Quantize and emit data. */
	(*cinfo->cquantize->color_quantize)(cinfo,
	                                    post->buffer, output_buf + *out_row_ctr, (int) num_rows);
	*out_row_ctr += num_rows;
}


#ifdef QUANT_2PASS_SUPPORTED

/*
 * Process some data in the first pass of 2-pass quantization.
 */

METHODDEF(void)
post_process_prepass(j_decompress_ptr cinfo,
                     JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
                     JDIMENSION in_row_groups_avail,
                     JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
                     JDIMENSION out_rows_avail) {
	my_post_ptr post = (my_post_ptr) cinfo->post;
	JDIMENSION old_next_row, num_rows;

	/* Reposition virtual buffer if at start of strip. */
	if (post->next_row == 0) {
		post->buffer = (*cinfo->mem->access_virt_sarray)
				((j_common_ptr) cinfo, post->whole_image,
				 post->starting_row, post->strip_height, TRUE);
	}

	/* Upsample some data (up to a strip height's worth). */
	old_next_row = post->next_row;
	(*cinfo->upsample->upsample)(cinfo,
	                             input_buf, in_row_group_ctr, in_row_groups_avail,
	                             post->buffer, &post->next_row, post->strip_height);

	/* Allow quantizer to scan new data.  No data is emitted, */
	/* but we advance out_row_ctr so outer loop can tell when we're done. */
	if (post->next_row > old_next_row) {
		num_rows = post->next_row - old_next_row;
		(*cinfo->cquantize->color_quantize)(cinfo, post->buffer + old_next_row,
		                                    (JSAMPARRAY) NULL, (int) num_rows);
		*out_row_ctr += num_rows;
	}

	/* Advance if we filled the strip. */
	if (post->next_row >= post->strip_height) {
		post->starting_row += post->strip_height;
		post->next_row = 0;
	}
}


/*
 * Process some data in the second pass of 2-pass quantization.
 */

METHODDEF(void)
post_process_2pass(j_decompress_ptr cinfo,
                   JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
                   JDIMENSION in_row_groups_avail,
                   JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
                   JDIMENSION out_rows_avail) {
	my_post_ptr post = (my_post_ptr) cinfo->post;
	JDIMENSION num_rows, max_rows;

	/* Reposition virtual buffer if at start of strip. */
	if (post->next_row == 0) {
		post->buffer = (*cinfo->mem->access_virt_sarray)
				((j_common_ptr) cinfo, post->whole_image,
				 post->starting_row, post->strip_height, FALSE);
	}

	/* Determine number of rows to emit. */
	num_rows = post->strip_height - post->next_row; /* available in strip */
	max_rows = out_rows_avail - *out_row_ctr; /* available in output area */
	if (num_rows > max_rows)
		num_rows = max_rows;
	/* We have to check bottom of image here, can't depend on upsampler. */
	max_rows = cinfo->output_height - post->starting_row;
	if (num_rows > max_rows)
		num_rows = max_rows;

	/* Quantize and emit data. */
	(*cinfo->cquantize->color_quantize)(cinfo,
	                                    post->buffer + post->next_row, output_buf + *out_row_ctr,
	                                    (int) num_rows);
	*out_row_ctr += num_rows;

	/* Advance if we filled the strip. */
	post->next_row += num_rows;
	if (post->next_row >= post->strip_height) {
		post->starting_row += post->strip_height;
		post->next_row = 0;
	}
}

#endif /* QUANT_2PASS_SUPPORTED */


/*
 * Initialize postprocessing controller.
 */

GLOBAL(void)
jinit_d_post_controller(j_decompress_ptr cinfo, boolean need_full_buffer) {
	my_post_ptr post;

	post = (my_post_ptr)
			(*cinfo->mem->alloc_small)((j_common_ptr) cinfo, JPOOL_IMAGE,
			                           sizeof(my_post_controller));
	cinfo->post = (struct jpeg_d_post_controller *) post;
	post->pub.start_pass = start_pass_dpost;
	post->whole_image = NULL;     /* flag for no virtual arrays */
	post->buffer = NULL;          /* flag for no strip buffer */

	/* Create the quantization buffer, if needed */
	if (cinfo->quantize_colors) {
		/* The buffer strip height is max_v_samp_factor, which is typically
		 * an efficient number of rows for upsampling to return.
		 * (In the presence of output rescaling, we might want to be smarter?)
		 */
		post->strip_height = (JDIMENSION) cinfo->max_v_samp_factor;
		if (need_full_buffer) {
			/* Two-pass color quantization: need full-image storage. */
			/* We round up the number of rows to a multiple of the strip height. */
#ifdef QUANT_2PASS_SUPPORTED
			post->whole_image = (*cinfo->mem->request_virt_sarray)
					((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
					 cinfo->output_width * cinfo->out_color_components,
					 (JDIMENSION) jround_up((long) cinfo->output_height,
					                        (long) post->strip_height),
					 post->strip_height);
#else
			ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
#endif /* QUANT_2PASS_SUPPORTED */
		} else {
			/* One-pass color quantization: just make a strip buffer. */
			post->buffer = (*cinfo->mem->alloc_sarray)
					((j_common_ptr) cinfo, JPOOL_IMAGE,
					 cinfo->output_width * cinfo->out_color_components,
					 post->strip_height);
		}
	}
}
