bits.h - Bits management unit

This file contains basic routines necessary to access single or multiple bits in a number.

The routines are implemented as macros. In this way they do not introduce overhead. But be aware that the expressions are not evaluated before the call and there is no type checking.

bits_get_bit
bits_get_bits
bits_get_bits_mask

bits_pos_bit
bits_pos_bits
bits_pos_bits_mask

bits_set_bit
bits_set_bits
bits_set_bits_mask

bits_get_bit(nr,shift)

Parameters:

Name	IN/OUT	Recomended type	Description	Acesses
nr	IN	unsigned int unsigned short unsigned char	Input value	1 read
shift	IN	unsigned char	Bit number	1 read

Returns:

Result bit value

Example:

bit=bits_get_bit(16,4);
/* bit==1 */
bit=bits_get_bit(16,3);
/* bit==0 */
bit=bits_get_bit(16,5);
/* bit==0 */

bits_get_bits(nr,shift,nrbits)

Parameters:

Name	IN/OUT	Recomended type	Description	Acesses
nr	IN	unsigned int unsigned short unsigned char	Input value	1 read
shift	IN	unsigned char	Rightmost bit	1 read
nrbits	IN	unsigned char, <32	Nr of bits	1 read

Returns:

Result bits value

Example:

bits=bits_get_bits(16,4,2);
/* bits==1 */
bits=bits_get_bits(16,3,2);
/* bits==2 */
bits=bits_get_bits(16,5,2);
/* bits==0 */
bits=bits_get_bits(16,0,4);
/* bits==0 */
bits=bits_get_bits(16,0,5);
/* bits==16 */

bits_get_bits_mask(nr,shift,mask)

Parameters:

Name	IN/OUT	Recomended type	Description	Acesses
nr	IN	unsigned int unsigned short unsigned char	Input value	1 read
shift	IN	unsigned char	Rightmost bit	1 read
mask	IN	same as nr	Mask of bits	1 read

Returns:

Result bits value

Example:

bits=bits_get_bits_mask(16,4,1);
/* bits==1 */
bits=bits_get_bits_mask(16,3,1);
/* bits==2 */
bits=bits_get_bits_mask(16,5,1);
/* bits==0 */
bits=bits_get_bits_mask(16,0,15);
/* bits==0 */
bits=bits_get_bits_mask(16,0,31);
/* bits==16 */
bits=bits_get_bits_mask(16,0,16);
/* bits==16 */
bits=bits_get_bits_mask(16,1,16);
/* bits==0 */

bits_pos_bit(bit,shift)

Parameters:

Name	IN/OUT	Recomended type	Description	Acesses
bit	IN	unsigned char	Bit value	1 read
shift	IN	unsigned char	Bit number	1 read

Returns:

Value with the bit on the right place

Example:

nr=bits_pos_bit(1,4);
/* nr==16 */
nr=bits_pos_bit(1,3);
/* nr=8 */
nr=bits_pos_bit(1,5);
/* nr=32 */
nr=bits_pos_bit(0,<any value>);
/* nr==0 */

bits_pos_bits(bits,shift,nrbits)

Parameters:

Name	IN/OUT	Recomended type	Description	Acesses
bits	IN	unsigned int unsigned short unsigned char	Bits value	1 read
shift	IN	unsigned char	Rightmost bit	1 read
nrbits	IN	unsigned char, <32	Nr of bits	1 read

Returns:

Value with the bit on the right place

Example:

nr=bits_pos_bits(0,<any value>,<any value>);
/* nr==0 */
nr=bits_pos_bits(<any value>,<any value>,0);
/* nr==0 */
nr=bits_pos_bits(3,3,2);
/* bits==24 */
nr=bits_pos_bits(4,3,2);
/* nr==0 , 4&3=0 => ==bits_pos_bits(0,3,2)*/
nr=bits_pos_bits(2,5,2);
/* nr==64 */
nr=bits_pos_bits(1,5,2);
/* nr==32 */

bits_pos_bits_mask(bits,shift,mask)

Parameters:

Name	IN/OUT	Recomended type	Description	Acesses
bits	IN	unsigned int unsigned short unsigned char	Bits value	1 read
shift	IN	unsigned char	Rightmost bit	1 read
mask	IN	same as nr	Mask of bits	1 read

Returns:

Value with the bit on the right place

Example:

nr=bits_pos_bits_mask(0,<any value>,<any value>);
/* nr==0 */
nr=bits_pos_bits_mask(<any value>,<any value>,0);
/* nr==0 */
nr=bits_pos_bits_mask(0xff,1,0xff);
/* nr==0x1fe */
nr=bits_pos_bits_mask(0xff,8,0xef);
/* nr==0xef00 == bits_pos_bits_mask(0xef,8,0xff)*/

bits_set_bit(nr,shift,bit)

Parameters:

Name	IN/OUT	Recomended type	Description	Acesses
nr	IN	unsigned int unsigned short unsigned char	Value to be modified	1 read
shift	IN	unsigned char	Bit number	2 reads
bit	IN	unsigned char	New bit value	1 read

Returns:

Modified value

Example:

nr=bits_set_bit(16,4,0);
/* nr==0 */

nr=bits_set_bit(16,4,1);
/* nr==16 */

nr=16;
nr1=bits_set_bit(nr,3,0);
/* nr1==16 */

nr=16;
nr=bits_set_bit(nr,3,1);
/* nr==24 */

bits_set_bits(nr,shift,nrbits,bits)

Parameters:

Name	IN/OUT	Recomended type	Description	Acesses
nr	IN	unsigned int unsigned short unsigned char	Value to be modified	1 read
shift	IN	unsigned char	Rightmost bit	2 reads
nrbits	IN	unsigned char, <32	Nr of bits	2 reads
bits	IN	unsigned char	New bit value	1 read

Returns:

Modified value

Example:

nr=16;
nr1=bits_set_bits(nr,4,1,0);
/* nr1==0 */

nr=16;
nr1=bits_set_bits(nr,4,1,1);
/* nr1==1 */

nr=16;
nr=bits_set_bits(nr,3,1,0);
/* nr==16 */

nr=16;
nr=bits_set_bits(nr,3,1,1);
/* nr==24 */

nr=bits_set_bits(16,3,2,0);
/* nr==0 */

nr=16;
nr1=bits_set_bits(nr,3,2,1);
/* nr1==8 */

nr=16;
nr1=bits_set_bits(nr,3,2,2);
/* nr1==16 */

bits_set_bits_mask(nr,shift,mask,bits)

Parameters:

Name	IN/OUT	Recomended type	Description	Acesses
nr	IN	unsigned int unsigned short unsigned char	Value to be modified	1 read
shift	IN	unsigned char	Rightmost bit	2 reads
mask	IN	unsigned char, <32	Mask of bits	2 reads
bits	IN	unsigned char	New bit value	1 read

Returns:

Modified value

Example:

nr=16;
nr1=bits_set_bits_mask(nr,4,1,0);
/* nr1==0 */

nr=16;
nr1=bits_set_bits_mask(nr,4,1,1);
/* nr1==16 */

nr=16;
nr1=bits_set_bits_mask(nr,3,1,0);
/* nr1==16 */

nr=16;
nr1=bits_set_bits_mask(nr,3,1,1);
/* nr1==24 */

nr=16;
nr1=bits_set_bits_mask(nr,3,3,0);
/* nr1==0 */

nr=16;
nr1=bits_set_bits_mask(nr,3,3,1);
/* nr1==8 */

nr=16;
nr1=bits_set_bits_mask(nr,3,3,2);
/* nr1==16 */

nr=16;
nr1=bits_set_bits_mask(nr,3,5,0);
/* nr1==16 */

nr=bits_set_bits_mask(16,3,5,1);
/* nr==24 */

nr=bits_set_bits_mask(16,3,5,4);
/* nr==48 */

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Send comments to: Igor Sfiligoi

Created	:	17.1.1997
Last modified	:	10.2.1997