SharedMemoryEx

在前面的SharedMemory中,我们通过P/Invoke完成了Win32中的Mapping File的使用..
通过这个,我们可以很方便的完成.NET应用程序的进程间通讯:)

但是,由于SharedMemory的映射空间的大小是在创建对象的时候固定了的,不能很方便的进行动态修改.
在某些场合就不方便使用..

有一个方法:
1,建立两个内存映射文件.
2,一个用于数据交换,另一个用于消息传送(比如当数据交换的那个内存映射文件的大小发生改变,用于通过另一方).

在这个基础上,我写了一个SharedMemoryEx..
大家可以看看,用用,看看有没有什么问题:)

    SharedMemoryEx#region SharedMemoryEx
    class SharedMemoryEx : SharedMemory
    {

        Private Variable & Property#region Private Variable & Property
        private bool creator;

        private SharedMemory msgmem;
        private string msgmemname;
        private const int msgmemsize = 512;
        private const string CHANGESIZE = "ChangeSize";
        private const char SpliteChar    = ':';

        private int curlpSecuAttrs;
        private ProtectionTypes curProtection;
        private SectionTypes curSection;
        private AccessTypes curAccess;
        private int curOffset;


        public override int Size
        {
            get
            {
                CheckTo();
                return base.Size;
            }
        }

        #endregion

        Constructor & Dispose#region Constructor & Dispose
        public SharedMemoryEx() : base(){}

        public SharedMemoryEx(string MsgMemName):base()
        {
            msgmemname = MsgMemName;
        }

        public SharedMemoryEx(int Size,string Name,string MsgMemName):this(Size,Name,ProtectionTypes.PageReadWrite,SectionTypes.SecCommit,AccessTypes.Full,MsgMemName){}

        public SharedMemoryEx(int Size, string Name, ProtectionTypes Protection, SectionTypes Section, AccessTypes Access,string MsgMemName)
        {
            Create(Size,Name,0,Protection,Section,Access,MsgMemName);                        
        }

        public override void Dispose()
        {
            msgmem.Dispose();
            base.Dispose ();
        }        
        #endregion

        Common Functions#region Common Functions

        Open#region Open
        public override void Open(int Size, string Name, int Offset, AccessTypes Access)
        {
            creator = false;
            if( msgmem == null)
            {
                msgmem = new SharedMemory();
                msgmem.Open(msgmemsize,msgmemname,0,AccessTypes.Full);
            }

            curOffset = Offset;
            curAccess = Access;
            base.Open(Size,Name,Offset,Access);
        }

        public virtual void Open(string Name)
        {
            Open( Name, 0, AccessTypes.Read);
        }

        public virtual void Open(string Name, AccessTypes Access)
        {
            Open( Name, 0, Access);
        }

        public virtual void Open(string Name, int Offset)
        {
            Open(Name, Offset, AccessTypes.Read);
        }

        public virtual void Open(string Name,int Offset,AccessTypes Access)
        {
            Open(Name,Offset,Access,msgmemname);
        }

        public virtual void Open(string Name,string MsgMemName)
        {
            Open( Name, 0, AccessTypes.Read,MsgMemName);
        }

        public virtual void Open(string Name, AccessTypes Access,string MsgMemName)
        {
            Open( Name, 0, Access,MsgMemName);
        }

        public virtual void Open(string Name, int Offset,string MsgMemName)
        {
            Open(Name, Offset, AccessTypes.Read,MsgMemName);
        }

        public virtual void Open( string Name, int Offset, AccessTypes Access,string MsgMemName)
        {
            Open(0,Name,Offset,Access,MsgMemName);
        }

        public virtual void Open(int Size, string Name, int Offset, AccessTypes Access,string MsgMemName)
        {
            msgmemname = MsgMemName;
            Open(Size,Name,Offset,Access);
        }
        #endregion

        Create#region Create
        public override void Create(int Size, string Name, int lpSecurityAttributes, ProtectionTypes Protection, SectionTypes Section, AccessTypes Access)
        {
            creator = true;
            if( msgmem == null)
            {
                msgmem = new SharedMemory();
                msgmem.Create(msgmemsize,msgmemname,ProtectionTypes.PageReadWrite,SectionTypes.SecCommit,AccessTypes.Full);
                SendChangeMsg(Size);
            }
            curlpSecuAttrs = lpSecurityAttributes;
            curProtection = Protection;
            curSection = Section;
            curAccess = Access;
            base.Create (Size, Name, lpSecurityAttributes, Protection, Section, Access);
        }
        
        public void Create(int Size, string Name, int lpSecurityAttributes, ProtectionTypes Protection, SectionTypes Section, AccessTypes Access,string MsgMemName)
        {
            msgmemname = MsgMemName;
            Create(Size,Name,lpSecurityAttributes,Protection,Section,Access);
        }

        #endregion

        CopyXXX#region CopyXXX 
        public override void CopyFrom(byte[] source, int startIndex, int length)
        {
            CheckFrom(length);
            base.CopyFrom (source, startIndex, length);
        }

        private void CheckFrom(int length)
        {
            if( length > Size)
            {
                if( !creator)
                {
                    throw new ApplicationException("Can't Write so many bytes. Writalbe size " + Size + " .Want write size " + length);
                }
                //                byte[] msg = Encoding.Unicode.GetBytes( CHANGESIZE + SpliteChar);
                //                byte[] bysizes = BitConverter.GetBytes(length);
                //                byte[] temp = new byte[msg.Length + bysizes.Length];
                //                Array.Copy(msg,0,temp,0,msg.Length);
                //                Array.Copy(bysizes,0,temp,msg.Length,bysizes.Length);
                SendChangeMsg(length);
                Create(length,Name,curlpSecuAttrs,curProtection,curSection,curAccess);
            }
        }

        private void SendChangeMsg(int length)
        {
            msgmem.CopyFrom( CHANGESIZE + SpliteChar + length);
        }

        public override void CopyTo( byte[] destination, int startIndex, int length)
        {
            CheckTo();
            base.CopyTo (destination, startIndex, length);
        }

        private void CheckTo()
        {
            if( creator )
            {
                return;
            }
            int realsize = ReceiveChangeMsg();
            if( size < realsize)
            {
                Open( realsize,Name,curOffset,curAccess);
            }
        }

        private void ReceiveChangeMsg(out int length)
        {
            length = ReceiveChangeMsg();
        }

        private int ReceiveChangeMsg()
        {
            string[] msgs = msgmem.CopyToString().Split( SpliteChar);
            if( msgs.Length != 2 || msgs[0] != CHANGESIZE)
            {
                return 0;
            }
            return int.Parse( msgs[1]);
        }
        #endregion

        #endregion
    }
    #endregion

注: 在CopyTo和CopyFrom前,都加入了一个检测函数.
CopyFrom前: 如果发现新的数据比申请的要大,就直接将原来的内存映射文件关掉,重新申请一个大的空间,同时修改MsgMem中的数据.
CopyTo前: 如果发现MsgMem中的消息为ChangeSize,而且新的Size大于当前的Size,就把当前的内存映射文件Release,再重新Open.

对于内存映射文件的创建者(用bool creator来标识),才可以重新Create,对于非创建者,才可以重新Open :)

希望大家喜欢:)

ps,代码就不用提供下载了吧??
...还是提供一个吧,最新的:)
SharedMemoryEx.zip