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%%	options

copyright owner	=	Dirk Krause
copyright year	=	2016-xxxx
SPDX-License-Identifier:	BSD-3-Clause

%%	module

#include "dk4conf.h"

#ifndef	DK4TYPES_H_INCLUDED
#include "dk4types.h"
#endif

#ifndef	DK4MAASZ_H_INCLUDED
#include "dk4maasz.h"
#endif

#ifndef	DK4PX_H_INCLUDED
#include "dk4px.h"
#endif

#ifndef	DK4BIFTY_H_INCLUDED
#include "dk4bifty.h"
#endif

#ifndef	BIF_H_INCLUDED
#include "bif.h"
#endif

#if DK4_HAVE_ASSERT_H
#ifndef	ASSERT_H_INCLUDED
#include <assert.h>
#define	ASSERT_H_INCLUDED 1
#endif
#endif


$!trace-include



static const size_t shift_1bpp[] = {
	7, 6, 5, 4, 3, 2, 1, 0
};


static const size_t shift_2bpp[] = {
	6, 4, 2, 0
};

static const size_t shift_4bpp[] = {
	4, 0
};




dk4_px_t
dk4bifpackedbits_get_element(
	unsigned char	const	*buffer,
	size_t					 elin,
	size_t					 bd,
	size_t					 nbytes
)
{
	dk4_er_t	 er;			/* Error report for index calculation */
	size_t		 bytei	= 0;	/* Byte index */
	size_t		 elno	= 0;	/* Element number within the byte */
	size_t		 shv	= 0;	/* Number of bits for right shift operation */
	dk4_px_t	 mask	= 0;	/* Mask value to apply after bit shifting */
	dk4_px_t	 back	= 0;	/* Result */

	$? "+ dk4bifpackedbits_get_element"
#if	DK4_USE_ASSERT
	assert(NULL != buffer);
#endif
	/*
		Check buffer pointer
	*/
	if (NULL == buffer) {
		goto finished;
	}
	/*	Check bit depth
	*/
	if (8 != bd) {
		if (16 != bd) {
			if (1 != bd) {
				if (4 != bd) {
					if (2 != bd) {
						goto finished;
					}
				}
			}
		}
	}
	switch ( (int)bd ) {
		case 16 : {
			dk4error_init(&er);
			bytei = dk4ma_size_t_mul(elin, 2, &er);
			if ((DK4_E_NONE == er.ec) && (nbytes > bytei)) {
				back = ((((dk4_px_t)(buffer[bytei])) << 8) & (dk4_px_t)0xFF00U)
					 | (((dk4_px_t)(buffer[bytei+1])) & (dk4_px_t)0x00FFU);
			}
		} break;
		case 8 : {
			if (nbytes > elin) {
				back = (dk4_px_t)(buffer[elin]);
			}
		} break;
		default : {
			switch ( (int)bd ) {
				case 1 : {
					bytei = elin / 8;
					elno  = elin % 8;
					shv   = shift_1bpp[elno];
					mask  = 1U;
				} break;
				case 2 : {
					bytei = elin / 4;
					elno  = elin % 4;
					shv   = shift_2bpp[elno];
					mask  = 3U;
				} break;
				case 4 : {
					bytei = elin / 2;
					elno  = elin % 2;
					shv   = shift_4bpp[elno];
					mask  = 15U;
				} break;
			}
			if (nbytes > bytei) {
				back = buffer[bytei];
				if (0 < shv) {
					back = back >> shv;
				}
				back &= mask;
			}
		} break;
	}
	finished:
	$? "- dk4bifpackedbits_get_element %u", (unsigned)back
	return back;
}



/* vim: set ai sw=4 ts=4 : */