z_bmalloc.c

#include <stdlib.h>
#include <string.h>
#include "m_fixed.h"
#include "z_zone.h"
#include "z_bmalloc.h"
#include "i_system.h"

enum
{

    unused_block = 0,
    used_block = 1

};

typedef struct bmalpool_s
{

    struct bmalpool_s *nextpool;
    size_t blocks;
    byte used[0];

} bmalpool_t;

inline static void *getelem(bmalpool_t *p, size_t size, size_t n)
{

    return (((byte*)p) + sizeof (bmalpool_t) + sizeof (byte) * (p->blocks) + size*n);

}

inline static int iselem(const bmalpool_t *pool, size_t size, const void* p)
{

    int dif = (const char*)p - (const char*)pool;

    dif -= sizeof(bmalpool_t);
    dif -= pool->blocks;

    if (dif < 0)
        return -1;

    dif /= size;

    return (((size_t)dif >= pool->blocks) ? -1 : dif);

}

void *Z_BMalloc(struct block_memory_alloc_s *pzone)
{

    register bmalpool_t **pool = (bmalpool_t **)&(pzone->firstpool);
    bmalpool_t *newpool;

    while (*pool != NULL)
    {

        byte *p = memchr((*pool)->used, unused_block, (*pool)->blocks);

        if (p)
        {

            int n = p - (*pool)->used;

            (*pool)->used[n] = used_block;

            return getelem(*pool, pzone->size, n);

        }

        else
        {

            pool = &((*pool)->nextpool);

        }

    }

    *pool = newpool = Z_Calloc(sizeof(*newpool) + (sizeof(byte) + pzone->size)*(pzone->perpool), 1, pzone->tag, NULL);
    newpool->nextpool = NULL;
    newpool->used[0] = used_block;
    newpool->blocks = pzone->perpool;

    return getelem(newpool, pzone->size, 0);

}

void Z_BFree(struct block_memory_alloc_s *pzone, void *p)
{

    register bmalpool_t **pool = (bmalpool_t**)&(pzone->firstpool);

    while (*pool != NULL)
    {

        int n = iselem(*pool, pzone->size, p);

        if (n >= 0)
        {

            (*pool)->used[n] = unused_block;

            if (memchr(((*pool)->used), used_block, (*pool)->blocks) == NULL)
            {

                bmalpool_t *oldpool = *pool;
                *pool = (*pool)->nextpool;
                Z_Free(oldpool);

            }

            return;

        }

        else
        {

            pool = &((*pool)->nextpool);

        }

    }

    I_Error("Z_BFree: Free not in zone %s", pzone->desc);

}