环形缓冲区实现类(Delphi)

环形缓冲区的用途及原理可以去百度资料狠多的，这里就不介绍了。直接贴代码.代码分别用D7,XE2编译测试

源码下载 http://files.cnblogs.com/lwm8246/uCircleBuffer.rar

 //环形缓冲区实现类
 //-- :
 //QQ
 unit uCircleBuffer;

 interface

 uses
   Windows,Classes;

 type
   TCircleBuffer=class
   private
     FMS:TMemoryStream;
     FUserData:Pointer;
     function GetMemory: Pointer;
   protected
     FReadPosition:Integer;
     FWritePosition:Integer;
     FCanReadCount:Integer;
     FCanWrieCount:Integer;
   public
     constructor Create(const BuffSize:Integer);virtual;
     destructor  Destroy();override;
     function    Write(const Buffer;Count:Integer):integer;virtual;
     function    Read(var Buffer;Count:Integer):Integer;virtual;
   public
     property ReadPosition:Integer  read FReadPosition;
     property WritePosition:Integer read FWritePosition;
     property CanReadCount:Integer  read FCanReadCount;
     property CanWrieCount:Integer  read FCanWrieCount;
     property Memory:Pointer read GetMemory;
     property UserData:Pointer read FUserData write FUserData;
   end;

   //线程安全版本
   TCircleBufferThread=class(TCircleBuffer)
   private
     FCS:TRTLCriticalSection;
     function GetReadPosition():Integer;
     function GetWritePosition():Integer;
     function GetCanReadCount():Integer;
     function GetCanWrieCount():Integer;
   public
     constructor Create(const BuffSize:Integer);override;
     destructor  Destroy();override;
     function    Write(const Buffer;Count:Integer):integer;override;
     function    Read(var Buffer;Count:Integer):Integer;override;
   public
     property ReadPosition:Integer  read GetReadPosition;
     property WritePosition:Integer read GetWritePosition;
     property CanReadCount:Integer  read GetCanReadCount;
     property CanWrieCount:Integer  read GetCanWrieCount;
   end;

 implementation

 { TCircleBuffer }

 constructor TCircleBuffer.Create(const BuffSize: Integer);
 begin
   FMS := TMemoryStream.Create();
   FMS.Size := BuffSize;
   FMS.Position := ;
   FWritePosition := ;
   FReadPosition  := ;
   FCanWrieCount  := BuffSize;
   FCanReadCount  := ;
   //\\
   ZeroMemory(FMS.Memory,FMS.Size);
 end;

 destructor TCircleBuffer.Destroy;
 begin
   inherited;
   FMS.Free();
 end;

 function TCircleBuffer.GetMemory: Pointer;
 begin
   Result := FMS.Memory;
 end;

 function TCircleBuffer.Read(var Buffer; Count: Integer): Integer;
 var
   P:PAnsiChar;
   Len,DataLen:Integer;
 begin
   Result := ;
   //(I)
   if FCanReadCount <=  then
   begin
     Exit;
   end;

   if Count > FCanReadCount then
     DataLen := FCanReadCount
   else DataLen := Count;

   FMS.Position := FReadPosition mod FMS.Size;
   Result := FMS.Read(Buffer,DataLen);
   Dec(FCanReadCount,Result);
   Dec(Count,Result);

   //(II)
   if (Count > ) and (FCanReadCount > ) then //继续读
   begin
     DataLen := Count;
     if DataLen > FCanReadCount then DataLen := FCanReadCount;
     FMS.Position := ;
     P := @Buffer;
     Inc(P,Result);
     Len := FMS.Read(P^,DataLen);
     Inc(Result,Len);
     Dec(FCanReadCount,Len);
   end;

   //增加可写字节数
   Inc(FCanWrieCount,Result);
   if FCanWrieCount > FMS.Size then FCanWrieCount := FMS.Size;

   //调整读指针位置
   Inc(FReadPosition,Result);
   if FReadPosition > FMS.Size then Dec(FReadPosition,FMS.Size);

 end;

 function TCircleBuffer.Write(const Buffer; Count: Integer): integer;
 var
   Len,DataLen:Integer;
   P:PAnsiChar;
 begin
   Result := ;
   //(I)
   if FCanWrieCount <=  then
   begin
     Exit;
   end;

   if Count > FCanWrieCount then DataLen := FCanWrieCount else DataLen := Count;
   FMS.Position := FWritePosition mod FMS.Size;
   P := @Buffer;
   Result := FMS.Write(Buffer,DataLen);
   P := FMS.Memory;
   if P = nil then
     Exit;
   Dec(Count,Result);
   Dec(FCanWrieCount,Result);
   if (Count > ) and (FCanWrieCount > ) then
   begin
     //(II)
     P := @Buffer;
     Inc(P,Result);
     Len := FReadPosition  - ;
     if Count > Len then DataLen := Len else DataLen := Count;
     FMS.Position := ;
     Len := FMS.Write(P^,DataLen);
     Inc(Result,Len);
     Dec(FCanWrieCount,Len);
   end;

   //增加可读字节数
   Inc(FCanReadCount,Result);
   if FCanReadCount > FMS.Size then FCanReadCount := FMS.Size;

   //调整写指针位置
   Inc(FWritePosition,Result);
   if FWritePosition > FMS.Size then
     FWritePosition := FWritePosition - FMS.Size;
 end;

 { TCircleBufferThread }

 constructor TCircleBufferThread.Create(const BuffSize: Integer);
 begin
   InitializeCriticalSection(FCS);  //初始化
   inherited Create(BuffSize);
 end;

 destructor TCircleBufferThread.Destroy;
 begin
   DeleteCriticalSection(FCS);
   inherited;
 end;

 function TCircleBufferThread.GetCanReadCount: Integer;
 begin
   EnterCriticalSection(FCS);
   Result := FCanReadCount;
   LeaveCriticalSection(FCS);
 end;

 function TCircleBufferThread.GetCanWrieCount: Integer;
 begin
   EnterCriticalSection(FCS);
   Result := FCanWrieCount;
   LeaveCriticalSection(FCS);
 end;

 function TCircleBufferThread.GetReadPosition: Integer;
 begin
   EnterCriticalSection(FCS);
   Result := FReadPosition;
   LeaveCriticalSection(FCS);
 end;

 function TCircleBufferThread.GetWritePosition: Integer;
 begin
   EnterCriticalSection(FCS);
   Result := FWritePosition;
   LeaveCriticalSection(FCS);
 end;

 function TCircleBufferThread.Read(var Buffer; Count: Integer): Integer;
 begin
   EnterCriticalSection(FCS);
   try
     Result := inherited read(Buffer,Count);
   finally
     LeaveCriticalSection(FCS);
   end;
 end;

 function TCircleBufferThread.Write(const Buffer; Count: Integer): integer;
 begin
   EnterCriticalSection(FCS);
   try
     Result := inherited Write(Buffer,Count);
   finally
     LeaveCriticalSection(FCS);
   end;
 end;

 end.

测试代码段：

 procedure TForm1.btn1Click(Sender: TObject);
 var
   obj:TCircleBuffer;
   TmpStr:AnsiString;
   Len:Integer;
   Buf:array[..] of AnsiChar;
   ASize,APosition:Integer;
   P:PAnsiChar;
 begin

   obj := TCircleBuffer.Create();
   ZeroMemory(@Buf,SizeOf(Buf));

   TmpStr := '';
   Len := obj.Write(TmpStr[],Length(TmpStr));
   P := Obj.Memory;
   if P = nil then
     Exit;

   TmpStr := 'ABCD';
   Len := obj.Write(TmpStr[],Length(TmpStr));
   if Len <  then
     Exit;
   P := Obj.Memory;
   if P = nil then
     Exit;

   TmpStr := '';
   Len := obj.Read(Buf,);
   if Len <  then
     Exit;

     P := Obj.Memory;
   if P = nil then
     Exit;

   Len := obj.Read(Buf,);
   if Len <  then
     Exit;

   P := Obj.Memory;
   if P = nil then
     Exit;

   tmpStr := 'ABC';
   Len := Obj.Write(TmpStr[],);
   if Len <  then
     Exit;

   tmpStr := '123456#';
   Len := Obj.Write(TmpStr[],Length(TmpStr));
   if Len <  then
     Exit;

   P := Obj.Memory;
   if P = nil then
     Exit;

   FillChar(Buf,SizeOf(Buf),$);
  // ZeroMemory(@Buf,SizeOf(Buf));
   Len := obj.Read(Buf,);
     if Len <  then
     Exit;

   ZeroMemory(@Buf,SizeOf(Buf));
   Len := obj.Read(Buf,);
     if Len <  then
     Exit;

    P := Obj.Memory;
   if P = nil then
     Exit;

   TmpStr := 'AB';
   Len := obj.Write(TmpStr[],);
   if Len <  then
    Exit;

      P := Obj.Memory;
   if P = nil then
     Exit;

   TmpStr := 'abcdefghijklmnopqrst';
   Len := obj.Write(TmpStr[],Length(TmpStr));
   if Len <  then
    Exit;

    ZeroMemory(@Buf,SizeOf(Buf));
   Len := obj.Read(Buf,);
     if Len <  then
     Exit;

   if obj <> nil then
     obj.Free();

      P := Obj.Memory;
   if P = nil then
     Exit;

 end;