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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 : */
|