sfmemcap.c

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/*
  sfmemcap.c

  These functions wrap the malloc & free functions. They enforce a memory cap using
  the MEMCAP structure.  The MEMCAP structure tracks memory usage.  Each allocation
  has 4 bytes added to it so we can store the allocation size.  This allows us to 
  free a block and accurately track how much memory was recovered.
  
  Marc Norton  
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include "sfmemcap.h"

/*
*   Set max # bytes & init other variables.
*/
void sfmemcap_init( MEMCAP * mc, unsigned nbytes )
{
        mc->memcap = nbytes;
        mc->memused= 0;
        mc->nblocks= 0;
}

/*
*   Create and Init a MEMCAP -  use free to release it
*/
MEMCAP * sfmemcap_new( unsigned nbytes )
{
         MEMCAP * mc;

         mc = (MEMCAP*)calloc(1,sizeof(MEMCAP));

         if( mc ) sfmemcap_init( mc, nbytes );
         
         return mc;
}

/*
*  Release the memcap structure
*/
void sfmemcap_delete( MEMCAP * p )
{
     if(p)free( p );
}

/*
*  Allocate some memory
*/
void * sfmemcap_alloc( MEMCAP * mc, unsigned nbytes )
{
   long * data;

   //printf("sfmemcap_alloc: %d bytes requested, memcap=%d, used=%d\n",nbytes,mc->memcap,mc->memused);

   nbytes += sizeof(long);


   /* Check if we are limiting memory use */
   if( mc->memcap > 0 )
   {
      /* Check if we've maxed out our memory - if we are tracking memory */
      if( (mc->memused + nbytes) > mc->memcap )
      {
              return 0;
      }
   }

   data = (long *) malloc( nbytes );
   if( data == NULL )
   {
        return 0;
   }

   *data++ = (long)nbytes;

   mc->memused += nbytes;
   mc->nblocks++;

   return data;
}

/*
*   Free some memory
*/
void sfmemcap_free( MEMCAP * mc, void * p )
{
   long * q;

   q = (long*)p;
   q--;
   mc->memused -= (unsigned)(*q);
   mc->nblocks--;

   free(q);
}

/*
*   For debugging.
*/
void sfmemcap_showmem( MEMCAP * mc )
{
     fprintf(stderr, "memcap: memcap = %u bytes,",mc->memcap);
     fprintf(stderr, " memused= %u bytes,",mc->memused);
     fprintf(stderr, " nblocks= %d blocks\n",mc->nblocks);
}

/*
*  String Dup Some memory.
*/
char * sfmemcap_strdup( MEMCAP * mc, const char *str )
{
    char * data = (char *)sfmemcap_alloc( mc, strlen(str) + 1 );
    if(data == NULL)
    {
        return  0 ;
    }
    strcpy(data,str);
    return data;
}

/*
*  Dup Some memory.
*/
void * sfmemcap_dupmem( MEMCAP * mc, void * src, int n )
{
    void * data = (char *)sfmemcap_alloc( mc, n );
    if(data == NULL)
    {
        return  0;
    }

    memcpy( data, src, n );

    return data;
}

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