%%	options

copyright owner	=	Dirk Krause
copyright year	=	2015-xxxx
license		=	bsd



%%	header

/**	@file	dk4bf.h	Bit fields.
*/

#ifndef DK4ERROR_H_INCLUDED
#include "dk4error.h"
#endif

/**	Bit field structure.
*/
typedef struct {
  unsigned char	*d;	/**< Data buffer. */
  size_t	 s;	/**< Number of bits in the array. */
} dk4_bit_field_t;

#ifdef __cplusplus
extern "C" {
#endif

/**	Open bit field.
	@param	sz	Size of the bit field (number of bits).
	@param	erp	Error report, may be NULL.
	@return	Pointer to new bit field on success, NULL on error.

	Error codes:
	- DK4_E_INVALID_ARGUMENTS<br>
	  if sz is 0,
	- DK4_E_MEMORY_ALLOCATION_FAILED<br>
	  if not enough memory was available.
*/
dk4_bit_field_t *
dk4bf_open(size_t sz, dk4_er_t *erp);

/**	Set one bit in a bit field.
	@param	dptr	Bit field.
	@param	bitno	Index of bit to modify.
	@param	val	Bit value.
	@param	erp	Error report, may be NULL.
	@return	1 on success, 0 on error.

	Error codes:
	- DK4_E_INVALID_ARGUMENTS<br>
	  if dptr is 0 or bitno is outside the bit field size.
*/
int
dk4bf_set(dk4_bit_field_t *dptr, size_t bitno, int val, dk4_er_t *erp);

/**	Retrieve one value from bit field.
	@param	dptr	Address of result variable.
	@param	bfptr	Bit field.
	@param	bitno	Number of bit to obtain.
	@param	erp	Error report, may be NULL.
	@return	1 on success (dptr set), 0 on error (dptr unchanged).

	Error codes:
	- DK4_E_INVALID_ARGUMENTS<br>
	  if dptr or bfptr is NULL or bitno is outside the bit field size.
*/
int
dk4bf_get(int *dptr, dk4_bit_field_t *bfptr, size_t bitno, dk4_er_t *erp);

/**	Close bit field.
	@param	ptr	Pointer to bit field previously opened using
			dk4bf_open().
*/
void
dk4bf_close(dk4_bit_field_t *ptr);

#ifdef __cplusplus
}
#endif



%%	module


#include "dk4bf.h"
#include "dk4mem.h"



$!trace-include



/**	Position of single bits within a byte.
*/
static const unsigned char dk4bf_bits_in_byte[] = {
  0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01
};



dk4_bit_field_t *
dk4bf_open(size_t sz, dk4_er_t *erp)
{
  dk4_bit_field_t	*back	=	NULL;
  size_t		 bsz;
  if (0 < sz) {
    back = dk4mem_new(dk4_bit_field_t,1,erp);
    if (NULL != back) {
      back->s = sz;
      bsz = sz / 8;
      if (0 != (sz % 8)) {
        bsz++;
      }
      back->d = dk4mem_new(unsigned char,bsz,erp);
      if (NULL == back->d) {
        dk4bf_close(back);
	back = NULL;
      }
    }
  } else {
    dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS);
  }
  return back;
}



int
dk4bf_set(dk4_bit_field_t *dptr, size_t bitno, int val, dk4_er_t *erp)
{
  size_t	 bytei;			/* Byte index */
  size_t	 biti;			/* Bit index */
  int		 back	=	0;
  if (NULL != dptr) {
    if (bitno < dptr->s) {
      bytei = bitno / 8;
      biti  = bitno % 8;
      if (0 != val) {
        (dptr->d)[bytei] |= dk4bf_bits_in_byte[biti];
      } else {
        (dptr->d)[bytei] &= (~(dk4bf_bits_in_byte[biti]));
      }
      back = 1;
    } else {
      dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS);
    }
  } else {
    dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS);
  }
  return back;
}



int
dk4bf_get(int *dptr, dk4_bit_field_t *bfptr, size_t bitno, dk4_er_t *erp)
{
  size_t	 bytei;			/* Byte index */
  size_t	 biti;			/* Bit index within byte */
  int		 back	=	0;
  if ((NULL != dptr) && (NULL != bfptr)) {
    if (bitno < bfptr->s) {
      bytei = bitno / 8;
      biti  = bitno % 8;
      if (0x00 != (((bfptr->d)[bytei]) & (dk4bf_bits_in_byte[biti]))) {
        *dptr = 1;
      } else {
        *dptr = 0;
      }
      back = 1;
    } else {
      dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS);
    }
  } else {
    dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS);
  }
  return back;
}



void
dk4bf_close(dk4_bit_field_t *ptr)
{
  if (NULL != ptr) {
    dk4mem_release(ptr->d);
    dk4mem_free(ptr);
  }
}