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/* alloc.c - memory allocator for fixed size blocks */

This code is replacement for malloc() and free(). It takes advantage

of the fact that all of my memory allocation is of known fixed-size

blocks. This particular implementation, however, is extremely general

and will do allocation of any number of different fixed-size blocks.

I will just give a simple example here. To allocate struct foo's, declare a handle to the foo space as:

struct freelist_head foo_freelist;

Initialize it:

memory_init(&foo_freelist,sizeof(struct foo),1000,200);

Here we have asked for an initial allocation of 1000 foo's. When that

runs out, further allocations will automatically be performed 200

foo's at a time. (Each allocation calls sbrk() so you want to

minimize them.)

To actually allocate and deallocate foo's, it helps to define two

macros as follow:

#define foo_new() (struct foo *)new(&foo_freelist)

#define foo_destroy(x) destroy(&oct_freelist_head,(Freelist *)(char *)x)

Now you can say things like:

foo1 = foo_new();

foo_destroy(foo1);

#include <stdlib.h>

#include <string.h>

#include "express/alloc.h"

#include "express/error.h"

/* just in case we are compiling by hand */

#ifndef ALLOC

#define ALLOC

#endif /*ALLOC*/

/** chop up big block into linked list of small blocks

* return 0 for failure

* \param flh freelist head

* \param bytes new memory size

Freelist * create_freelist( struct freelist_head * flh, int bytes ) {

Freelist * current = ( Freelist * )malloc( bytes );

if( current == 0 ) {

return( 0 );

}

flh->freelist = current;

#ifndef NOSTAT

flh->create++;

/* set max to point to end of freelist */

if( ( char * )flh->freelist + bytes > ( char * )flh->max ) {

flh->max = ( char * )flh->freelist + bytes;

}

#endif

while( ( char * )current + flh->size <

( ( char * )flh->freelist + bytes ) ) {

current->next = ( Freelist * )( &current->memory + flh->size );

current = current->next;

}

current->next = NULL;

return( current );

}

void

_ALLOCinitialize(void) {

#ifdef DEBUG_MALLOC

malloc_debug( 2 );

#endif

}

/**

* \param flh freelist head

* \param size size of a single element

* \param alloc1 number to allocate initially

* \param alloc2 number to allocate if we run out

void ALLOCinitialize( struct freelist_head * flh, unsigned int size, int alloc1, int alloc2 ) {

flh->size_elt = size; /* kludge for calloc-like behavior */

#ifndef NOSTAT

flh->alloc = flh->dealloc = flh->create = 0;

flh->max = 0;

#endif

/* make block large enough to hold the linked list pointer */

flh->size = ( size > sizeof( Freelist * ) ? size : sizeof( Freelist * ) );

/* set up for future allocations */

flh->bytes = flh->size * alloc2;

#ifdef REAL_MALLOC

return;

/*NOTREACHED*/

#else

if( 0 == create_freelist( flh, flh->size * alloc1 ) ) {

ERRORnospace();

}

#ifdef SPACE_PROFILE

flh->count = 0;

#endif /*SPACE_PROFILE*/

#endif

}

void * ALLOC_new( struct freelist_head * flh ) {

void *obj;

#ifndef NOSTAT

flh->alloc++;

#endif

#ifdef REAL_MALLOC

return( calloc( 1, flh->size_elt ) );

/*NOTREACHED*/

#else

if( flh->freelist == NULL && 0 == create_freelist( flh, flh->bytes ) ) {

ERRORnospace();

}

obj = &flh->freelist->memory;

flh->freelist = flh->freelist->next;

#ifndef NOSTAT

if( obj > flh->max ) {

abort();

}

#endif

#ifdef SPACE_PROFILE

flh->count++;

#endif /*SPACE_PROFILE*/

/* calloc-like */

memset( obj, 0, flh->size_elt );

return( obj );

#endif

}

void ALLOC_destroy( struct freelist_head * flh, Freelist * link ) {

#ifndef NOSTAT

flh->dealloc++;

#endif

#ifdef REAL_MALLOC

free( link );

return;

/*NOTREACHED*/

#else

link->next = flh->freelist;

flh->freelist = link;

#ifdef SPACE_PROFILE

flh->count--;

#endif /*SPACE_PROFILE*/

#endif

}

#ifdef ALLOC_MAIN

struct freelist_head oct_freelist;

#define new_oct() (struct oct *)new(&oct_freelist)

#define destroy_oct(oct) (destroy(&oct_freelist,(Freelist *)(char *)oct))

struct oct {

char a[16];

};

main() {

struct oct * o1, *o2, *o3, *o4, *o5, *o6;

memory_init( &oct_freelist, sizeof( struct oct ), 5, 2 );

o1 = new_oct();

fprintf( stderr, "o1 = %x\n", o1 );

o2 = new_oct();

fprintf( stderr, "o2 = %x\n", o2 );

o3 = new_oct();

fprintf( stderr, "o3 = %x\n", o3 );

o4 = new_oct();

fprintf( stderr, "o4 = %x\n", o4 );

o5 = new_oct();

fprintf( stderr, "o5 = %x\n", o5 );

o6 = new_oct();

fprintf( stderr, "o6 = %x\n", o6 );

destroy_oct( o1 );

destroy_oct( o2 );

o1 = new_oct();

fprintf( stderr, "o1 = %x\n", o1 );

o2 = new_oct();

fprintf( stderr, "o2 = %x\n", o2 );

o3 = new_oct();

fprintf( stderr, "o3 = %x\n", o3 );

o4 = new_oct();

fprintf( stderr, "o4 = %x\n", o4 );

o5 = new_oct();

fprintf( stderr, "o5 = %x\n", o5 );

}

#endif /*ALLOC_MAIN*/