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%%	options

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


%%	header

/**	@file	dk4membuf.h	Memory buffer.
*/

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

/**	One cell of a memory buffer.
*/
typedef struct _dk4_membuf_cell_t_ {
  struct _dk4_membuf_cell_t_	*next;	/**< Next element in linked list. */
  char				*buf;	/**< Buffer for data storage. */
  size_t			 max;	/**< Number of bytes available. */
  size_t			 used;	/**< Number of bytes used. */
} dk4_membuf_cell_t;

/**	Memory buffer object.
*/
typedef struct {
  dk4_membuf_cell_t	*first;		/**< First cell (head of list). */
  dk4_membuf_cell_t	*last;		/**< Last cell (end of list). */
  int			 he;		/**< Flag: Had allocation error. */
} dk4_membuf_t;

#ifdef __cplusplus
extern "C" {
#endif

/**	Create new buffer, allocate initial memory.
	@param	erp	Error report, may be NULL.
	@return	Pointer on success, NULL on error.
*/
dk4_membuf_t *
dk4membuf_open(dk4_er_t *erp);

/**	Destroy buffer, release memory.
	@param	mbptr	Buffer to destroy.
*/
void
dk4membuf_close(dk4_membuf_t *mbptr);

/**	Store data in buffer.
	@param	mbptr	Buffer object.
	@param	src	Address of data to store.
	@param	sz	Number of bytes to store.
	@param	erp	Error report, may be NULL.
	@return	1 on success, 0 on error.
	
	Error code:
	- DK4_E_INVALID_ARGUMENTS<br>
	  if mbptr or src is NULL or sz is 0,
	- DK4_E_MATH_OVERFLOW<br>
	  if a mathematical overflow occured in size calculation,
	- DK4_E_MEMORY_ALLOCATION_FAILED<br>
	  with mem.elsize and mem.nelem set
	  if there is not enough memory available.

*/
int
dk4membuf_store(dk4_membuf_t *mbptr, const void *src, size_t sz, dk4_er_t *erp);

/**	Retrieve size of data stored in memory buffer.
	@param	szptr	Address of result variable.
	@param	mbptr	Buffer to find size for.
	@param	erp	Error report, may be NULL.
	@return	1 on success, 0 on error.

	Error code:
	- DK4_E_INVALID_ARGUMENTS<br>
	  if szptr or mbptr is NULL.
	- DK4_E_MATH_OVERFLOW<br>
	  if a mathematical overflow occured in size calculation.
*/
int
dk4membuf_size(size_t *szptr, dk4_membuf_t *mbptr, dk4_er_t *erp);

#ifdef __cplusplus
}
#endif

/**	Default chunk size.
*/
#define	DK4MEMBUF_CHUNK_SIZE	4096U

%%	module

#include "dk4membuf.h"
#include "dk4mem.h"
#include "dk4maasz.h"



$!trace-include



static
void
dk4membuf_cell_close(dk4_membuf_cell_t *mcptr)
{
  if (NULL != mcptr) {
    dk4mem_release(mcptr->buf);
    mcptr->next = NULL;
    mcptr->max = mcptr->used = 0;
    dk4mem_free(mcptr);
  }
}



static
dk4_membuf_cell_t *
dk4membuf_cell_open(size_t sz, dk4_er_t *erp)
{
  dk4_er_t		 er;
  dk4_membuf_cell_t	*back	= NULL;
  size_t		 nb;

  /*	Ensure number of bytes is a multiple of the chunk size.
  */
  nb = sz / DK4MEMBUF_CHUNK_SIZE;
  if (0 != (sz % DK4MEMBUF_CHUNK_SIZE)) { nb++; }
  dk4error_init(&er);
  nb = dk4ma_size_t_mul(nb, (size_t)(DK4MEMBUF_CHUNK_SIZE), &er);
  if (0 != er.ec) { nb = sz; }

  /*	Allocate
  */
  back = dk4mem_new(dk4_membuf_cell_t,1,erp);
  if (NULL != back) {
    back->next = NULL;
    back->max  = nb;
    back->used = 0;
    back->buf = dk4mem_new(char,nb,erp);
    if (NULL == back->buf) {
      dk4mem_free(back);
      back = NULL;
    }
  }
  return back;
}



dk4_membuf_t *
dk4membuf_open(dk4_er_t *erp)
{
  dk4_membuf_t		*back	= NULL;
  back = dk4mem_new(dk4_membuf_t,1,erp);
  if (NULL != back) {
    back->he = 0;
    back->last = NULL;
    back->first = dk4membuf_cell_open(DK4MEMBUF_CHUNK_SIZE, erp);
    if (NULL != back->first) {
      back->last = back->first;
    } else {
      dk4mem_free(back);
      back = NULL;
    }
  }
  return back;
}



void
dk4membuf_close(dk4_membuf_t *mbptr)
{
  dk4_membuf_cell_t	*pc;
  dk4_membuf_cell_t	*pn;

  if (NULL != mbptr) {
    pc = mbptr->first;
    while (NULL != pc) {
      pn = pc->next;
      dk4membuf_cell_close(pc);
      pc = pn;
    }
    dk4mem_free(mbptr);
  }
}



int
dk4membuf_store(dk4_membuf_t *mbptr, const void *src, size_t sz, dk4_er_t *erp)
{
  dk4_membuf_cell_t	*pc	= NULL;
  dk4_membuf_cell_t	*pn	= NULL;
  const char		*psrc	= NULL;
  size_t		 bl	= 0;
  int			 back	= 0;

  if ((NULL != mbptr) && (NULL != src) && (0 < sz)) {
    /*	Initialize variables.
    */
    back = 1;
    pc   = mbptr->last;
    psrc = (const char *)src;
    /*	Attempt to fill current cell.
    */
    if (pc->max > pc->used) {
      bl = pc->max - pc->used;
      if (sz < bl) { bl = sz; }
      DK4_MEMCPY(&((pc->buf)[pc->used]), psrc, bl);
      pc->used += bl;
      sz -= bl;
      psrc = &(psrc[bl]);
    }
    /*	Use new cell if necessary.
    */
    if (0 < sz) {
      back = 0;
      pn = dk4membuf_cell_open(sz, erp);
      if (NULL != pn) {
        pc->next = pn;
	mbptr->last = pn;
	DK4_MEMCPY(pn->buf, psrc, sz);
	back = 1;
	pn->used = sz;
      } else {
        mbptr->he = 1;
      }
    }
  } else {
    dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS);
  }
  return back;
}



int
dk4membuf_size(size_t *szptr, dk4_membuf_t *mbptr, dk4_er_t *erp)
{
  dk4_er_t		 er;
  dk4_membuf_cell_t	*cp	= NULL;
  size_t		 result	= (size_t)0U;
  int			 back	= 0;

  if ((NULL != szptr) && (NULL != mbptr)) {
    back = 1;
    cp = mbptr->first;
    dk4error_init(&er);
    while (NULL != cp) {
      result = dk4ma_size_t_add(result, cp->used, &er);
      cp = cp->next;
    }
    if (DK4_E_NONE == er.ec) {
      back = 1;
      *szptr = result;
    }
  } else {
    dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS);
  }
  return back;
}