source: vbox/trunk/src/VBox/GuestHost/OpenGL/util/idpool.c@ 71997

/* Copyright (c) 2001, Stanford University
 * All rights reserved
 *
 * See the file LICENSE.txt for information on redistributing this software.
 */

#include "chromium.h"
#include "cr_error.h"
#include "cr_mem.h"
#include "cr_idpool.h"


#define CR_MAXUINT             ((GLuint) 0xFFFFFFFF)

typedef struct FreeElemRec {
        GLuint min;
        GLuint max;
        struct FreeElemRec *next;
        struct FreeElemRec *prev;
} FreeElem;

struct CRIdPoolRec {
        FreeElem *freeList;
};



CRIdPool *crAllocIdPool( void )
{
        CRIdPool *pool = (CRIdPool *) crCalloc(sizeof(CRIdPool));
        pool->freeList = (FreeElem *) crCalloc(sizeof(FreeElem));
        pool->freeList->min = 1;
        pool->freeList->max = CR_MAXUINT;
        pool->freeList->next = NULL;
        pool->freeList->prev = NULL;
        return pool;
}

void crFreeIdPool( CRIdPool *pool )
{
        FreeElem *i, *next;
        for (i = pool->freeList; i; i = next)
        {
                next = i->next;
                crFree(i);
        }
        crFree(pool);
}

/*
 * Allocate a block of <count> IDs.  Return index of first one.
 * Return 0 if we fail.
 */
GLuint crIdPoolAllocBlock( CRIdPool *pool, GLuint count )
{
        FreeElem *f;
        GLuint ret;

        CRASSERT(count > 0);

        f = pool->freeList;
        while (f)
        {
                if (f->max - f->min + 1 >= (GLuint) count)
                {
                        /* found a sufficiently large enough block */
                        ret = f->min;
                        f->min += count;

                        if (f->min == f->max)
                        {
                                /* remove this block from linked list */
                                if (f == pool->freeList) 
                                {
                                        /* remove from head */
                                        pool->freeList = pool->freeList->next;
                                        pool->freeList->prev = NULL;
                                }
                                else 
                                {
                                        /* remove from elsewhere */
                                        f->prev->next = f->next;
                                        f->next->prev = f->prev;
                                }
                                crFree(f);
                        }

#ifdef DEBUG
                        /* make sure the IDs really are allocated */
                        {
                                GLuint i;
                                for (i = 0; i < count; i++)
                                {
                                        CRASSERT(crIdPoolIsIdUsed(pool, ret + i));
                                }
                        }
#endif

                        return ret;
                }
                else {
                        f = f->next;
                }
        }

        /* failed to find free block */
        return 0;
}


/*
 * Free a block of <count> IDs starting at <first>.
 */
void crIdPoolFreeBlock( CRIdPool *pool, GLuint first, GLuint count )
{
        FreeElem *i;
        FreeElem *newelem;

        /*********************************/
        /* Add the name to the freeList  */
        /* Find the bracketing sequences */

        for (i = pool->freeList; i && i->next && i->next->min < first; i = i->next)
        {
                /* EMPTY BODY */
        }

        /* j will always be valid */
        if (!i)
                return;
        if (!i->next && i->max == first)
                return;

        /* Case:  j:(~,first-1) */
        if (i->max + 1 == first) 
        {
                i->max += count;
                if (i->next && i->max+1 >= i->next->min) 
                {
                        /* Collapse */
                        i->next->min = i->min;
                        i->next->prev = i->prev;
                        if (i->prev)
                        {
                                i->prev->next = i->next;
                        }
                        if (i == pool->freeList)
                        {
                                pool->freeList = i->next;
                        }
                        crFree(i);
                }
                return;
        }

        /* Case: j->next: (first+1, ~) */
        if (i->next && i->next->min - count == first) 
        {
                i->next->min -= count;
                if (i->max + 1 >= i->next->min) 
                {
                        /* Collapse */
                        i->next->min = i->min;
                        i->next->prev = i->prev;
                        if (i->prev)
                        {
                                i->prev->next = i->next;
                        }
                        if (i == pool->freeList) 
                        {
                                pool->freeList = i->next;
                        }
                        crFree(i);
                }
                return;
        }

        /* Case: j: (first+1, ~) j->next: null */
        if (!i->next && i->min - count == first) 
        {
                i->min -= count;
                return;
        }

        /* allocate a new FreeElem node */
        newelem = (FreeElem *) crCalloc(sizeof(FreeElem));
        newelem->min = first;
        newelem->max = first + count - 1;

        /* Case: j: (~,first-(2+))  j->next: (first+(2+), ~) or null */
        if (first > i->max) 
        {
                newelem->prev = i;
                newelem->next = i->next;
                if (i->next)
                {
                        i->next->prev = newelem;
                }
                i->next = newelem;
                return;
        }

        /* Case: j: (first+(2+), ~) */
        /* Can only happen if j = t->freeList! */
        if (i == pool->freeList && i->min > first) 
        {
                newelem->next = i;
                newelem->prev = i->prev;
                i->prev = newelem;
                pool->freeList = newelem;
                return;
        }
}



/*
 * Mark the given Id as being allocated.
 */
void crIdPoolAllocId( CRIdPool *pool, GLuint id )
{
        FreeElem *f;

        CRASSERT(id > 0);

        f = pool->freeList;
        while (f)
        {
                if (id >= f->min && id <= f->max)
                {
                        /* found the block */
                        if (id == f->min)
                        {
                                f->min++;
                        }
                        else if (id == f->max)
                        {
                                f->max--;
                        }
                        else
                        {
                                /* somewhere in the middle - split the block */
                                FreeElem *newelem = (FreeElem *) crCalloc(sizeof(FreeElem));
                                newelem->min = id + 1;
                                newelem->max = f->max;
                                f->max = id - 1;
                                newelem->next = f->next;
                                if (f->next)
                                   f->next->prev = newelem;
                                newelem->prev = f;
                                f->next = newelem;
                        }
                        return;
                }
                f = f->next;
        }

        /* if we get here, the ID was already allocated - that's OK */
}


/*
 * Determine if the given id is free.  Return GL_TRUE if so.
 */
GLboolean crIdPoolIsIdFree( const CRIdPool *pool, GLuint id )
{
        FreeElem *i;

        /* First find which region it fits in */
        for (i = pool->freeList; i && !(i->min <= id && id <= i->max); i=i->next)
        {
                /* EMPTY BODY */
        }

        if (i)
                return GL_TRUE;
        else
                return GL_FALSE;
}


/*
 * Determine if the given id is used.  Return GL_TRUE if so.
 */
GLboolean crIdPoolIsIdUsed( const CRIdPool *pool, GLuint id )
{
        return (GLboolean) !crIdPoolIsIdFree( pool, id);
}