Small one-bit array library.

bitarray.c

# include <stdlib.h>
# include <bitarray.h>

struct bit_array* bitarray_init(unsigned int bits)
{
    struct bit_array* new_array = malloc(sizeof(struct bit_array));
    
    new_array->size = (bits % 8 == 0) ? bits / 8 : (bits / 8) + 1;
    
    new_array->array = calloc(new_array->size,sizeof(struct bit_element));
    
    
    return new_array;
}

unsigned char bitarray_get(struct bit_array* b , unsigned int position)
{
    if ( position > (b->size * 8) )
	return 2;
    
    unsigned int array_offset = position / 8;
    unsigned int bit_offset = position - (array_offset*8);
    
    switch (bit_offset)
    {
	case 0 : return b->array[array_offset].a;
	case 1 : return b->array[array_offset].b;
	case 2 : return b->array[array_offset].c;
	case 3 : return b->array[array_offset].d;
	case 4 : return b->array[array_offset].e;
	case 5 : return b->array[array_offset].f;
	case 6 : return b->array[array_offset].g;
	case 7 : return b->array[array_offset].h;
    }
}

unsigned char bitarray_set(struct bit_array* b, unsigned int position, char value)
{
    if ( position > (b->size * 8) )
	return 1;

    if ( value != 0 )
	value = 1;
    
    unsigned int array_offset = position / 8;
    unsigned int bit_offset = position - (array_offset*8);
    
    switch (bit_offset)
    {
	case 0 : b->array[array_offset].a = value;
	case 1 : b->array[array_offset].b = value;
	case 2 : b->array[array_offset].c = value;
	case 3 : b->array[array_offset].d = value;
	case 4 : b->array[array_offset].e = value;
	case 5 : b->array[array_offset].f = value;
	case 6 : b->array[array_offset].g = value;
	case 7 : b->array[array_offset].h = value;
    }
    
    return 0;
}

void bitarray_free(struct bit_array* b)
{
    free(b->array);
    free(b);
}

bitarray.h

# ifndef BITARRAY_H
# define BITARRAY_H

struct bit_element
{
    unsigned char a:1, b:1, c:1, d:1, e:1, f:1, g:1, h:1;
};

struct bit_array
{
    struct bit_element* array; // 8 or 4 bytes.
    unsigned int size; // Size in bytes (n_fields <= size * 8)
		       // 4 bytes -> aligned.
};

typedef struct bit_array bit_array;

/*
 * returns NULL if an error occurred.
 */
struct bit_array* bitarray_init(unsigned int bits);

/*
 * returns 0 or 1 if successful; else 2 is returned.
 */
unsigned char bitarray_get(struct bit_array*, unsigned int position);

/*
 * returns non-zero if an error occurred, else 0.
 */
unsigned char bitarray_set(struct bit_array*, unsigned int position, char value);

/*
 * returns non-zero if an error occurred, else 0.
 */
void bitarray_free(struct bit_array* b);

# endif

CMakeLists.txt

project(libbitarray)
cmake_minimum_required(VERSION 2.8)


set(CMAKE_C_FLAGS ${CMAKE_C_FLAGS} -O3)
include_directories(.)

set(libsources
bitarray.c
)

set(testsources
test.c
)

add_library(bitarray STATIC ${libsources})

add_executable(testlibbitarray ${testsources})
target_link_libraries(testlibbitarray bitarray)

libbitarray.kdev4

[Project]
Name=libbitarray
Manager=KDevCMakeManager
VersionControl=kdevgit

LICENSE

The MIT License (MIT)

Copyright (c) 2014 Lewin Bormann

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

test.c

# include <stdio.h>
# include <bitarray.h>

int main(int argc, char **argv)
{
    bit_array* b = bitarray_init(18);

    bitarray_set(b,0,1);
    bitarray_set(b,1,1);
    bitarray_set(b,2,1);

    char a = bitarray_get(b,0);
    char d = bitarray_get(b,1);
    char c = bitarray_get(b,2);

    printf("%i\n",b->size);

    bitarray_free(b);
    return 0;
}