可变分区最先适应算法.doc

文档介绍：#include ""
#include ""

#define ERR_NOFREEAREA 1
#define ERR_NOADEQUACYAREA 2
#define ERR_ALLOCATED 4

#define ERR_NOJOBS 1
#define ERR_NOSUCHJOB 2
#define ERR_RECLAIMED 4


typedef struct tagUsedNode
{
long address;
long length;
int flag; //作业名
struct tagUsedNode *next;
} USED_AREA , *USED_TABLE;

typedef struct tagFreeNode
{
long address;
long length;
struct tagFreeNode *next;
} FREE_AREA , *FREE_TABLE;

//空闲区、作业区链表
USED_TABLE usedTable = NULL;
FREE_TABLE freeTable = NULL;


//给作业分配空间
//jobname: 作业名
//jobsize: 作业所需空间大小
int Allocate( int jobname , long jobsize )
{
//如果没有空闲区
if( freeTable == NULL )
return ERR_NOFREEAREA;
FREE_TABLE p = freeTable;
FREE_TABLE q = p;
//找首次适应空闲区
while( p != NULL && p->length jobsize )
{
q = p;
p = p->next;
}
//如果找不到有足够空间的分区
if( p == NULL )
return ERR_NOADEQUACYAREA;

USED_TABLE x = new USED_AREA;
x->address = p->address;
x->length = jobsize;
x->flag = jobname;
x->next = NULL;

//如果该分区大于作业需求,空间大小减去作业大小
if( p->length > jobsize )
{
p->length -= jobsize;
p->address += jobsize;
}
//如果该分区等于作业大小,删除该分区
else
{
if( p == freeTable )
freeTable = NULL;
else
q->next = p->next;
delete p;
}
//作业加入“作业表”中
USED_TABLE r = usedTable;
USED_TABLE t = r;

while( r !=