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
1 //环形缓冲区实现类 2 //2014-03-20 16:20 3 //QQ 287413288 4 unit uCircleBuffer; 5 6 interface 7 8 uses 9 Windows,Classes; 10 11 type 12 TCircleBuffer=class 13 private 14 FMS:TMemoryStream; 15 FUserData:Pointer; 16 function GetMemory: Pointer; 17 protected 18 FReadPosition:Integer; 19 FWritePosition:Integer; 20 FCanReadCount:Integer; 21 FCanWrieCount:Integer; 22 public 23 constructor Create(const BuffSize:Integer);virtual; 24 destructor Destroy();override; 25 function Write(const Buffer;Count:Integer):integer;virtual; 26 function Read(var Buffer;Count:Integer):Integer;virtual; 27 public 28 property ReadPosition:Integer read FReadPosition; 29 property WritePosition:Integer read FWritePosition; 30 property CanReadCount:Integer read FCanReadCount; 31 property CanWrieCount:Integer read FCanWrieCount; 32 property Memory:Pointer read GetMemory; 33 property UserData:Pointer read FUserData write FUserData; 34 end; 35 36 //线程安全版本 37 TCircleBufferThread=class(TCircleBuffer) 38 private 39 FCS:TRTLCriticalSection; 40 function GetReadPosition():Integer; 41 function GetWritePosition():Integer; 42 function GetCanReadCount():Integer; 43 function GetCanWrieCount():Integer; 44 public 45 constructor Create(const BuffSize:Integer);override; 46 destructor Destroy();override; 47 function Write(const Buffer;Count:Integer):integer;override; 48 function Read(var Buffer;Count:Integer):Integer;override; 49 public 50 property ReadPosition:Integer read GetReadPosition; 51 property WritePosition:Integer read GetWritePosition; 52 property CanReadCount:Integer read GetCanReadCount; 53 property CanWrieCount:Integer read GetCanWrieCount; 54 end; 55 56 implementation 57 58 { TCircleBuffer } 59 60 constructor TCircleBuffer.Create(const BuffSize: Integer); 61 begin 62 FMS := TMemoryStream.Create(); 63 FMS.Size := BuffSize; 64 FMS.Position := 0; 65 FWritePosition := 0; 66 FReadPosition := 0; 67 FCanWrieCount := BuffSize; 68 FCanReadCount := 0; 69 //\ 70 ZeroMemory(FMS.Memory,FMS.Size); 71 end; 72 73 destructor TCircleBuffer.Destroy; 74 begin 75 inherited; 76 FMS.Free(); 77 end; 78 79 function TCircleBuffer.GetMemory: Pointer; 80 begin 81 Result := FMS.Memory; 82 end; 83 84 function TCircleBuffer.Read(var Buffer; Count: Integer): Integer; 85 var 86 P:PAnsiChar; 87 Len,DataLen:Integer; 88 begin 89 Result := 0; 90 //(I) 91 if FCanReadCount <= 0 then 92 begin 93 Exit; 94 end; 95 96 if Count > FCanReadCount then 97 DataLen := FCanReadCount 98 else DataLen := Count; 99 100 FMS.Position := FReadPosition mod FMS.Size; 101 Result := FMS.Read(Buffer,DataLen); 102 Dec(FCanReadCount,Result); 103 Dec(Count,Result); 104 105 //(II) 106 if (Count > 0) and (FCanReadCount > 0) then //继续读 107 begin 108 DataLen := Count; 109 if DataLen > FCanReadCount then DataLen := FCanReadCount; 110 FMS.Position := 0; 111 P := @Buffer; 112 Inc(P,Result); 113 Len := FMS.Read(P^,DataLen); 114 Inc(Result,Len); 115 Dec(FCanReadCount,Len); 116 end; 117 118 //增加可写字节数 119 Inc(FCanWrieCount,Result); 120 if FCanWrieCount > FMS.Size then FCanWrieCount := FMS.Size; 121 122 //调整读指针位置 123 Inc(FReadPosition,Result); 124 if FReadPosition > FMS.Size then Dec(FReadPosition,FMS.Size); 125 126 end; 127 128 function TCircleBuffer.Write(const Buffer; Count: Integer): integer; 129 var 130 Len,DataLen:Integer; 131 P:PAnsiChar; 132 begin 133 Result := 0; 134 //(I) 135 if FCanWrieCount <= 0 then 136 begin 137 Exit; 138 end; 139 140 if Count > FCanWrieCount then DataLen := FCanWrieCount else DataLen := Count; 141 FMS.Position := FWritePosition mod FMS.Size; 142 P := @Buffer; 143 Result := FMS.Write(Buffer,DataLen); 144 P := FMS.Memory; 145 if P = nil then 146 Exit; 147 Dec(Count,Result); 148 Dec(FCanWrieCount,Result); 149 if (Count > 0) and (FCanWrieCount > 0) then 150 begin 151 //(II) 152 P := @Buffer; 153 Inc(P,Result); 154 Len := FReadPosition - 0; 155 if Count > Len then DataLen := Len else DataLen := Count; 156 FMS.Position := 0; 157 Len := FMS.Write(P^,DataLen); 158 Inc(Result,Len); 159 Dec(FCanWrieCount,Len); 160 end; 161 162 //增加可读字节数 163 Inc(FCanReadCount,Result); 164 if FCanReadCount > FMS.Size then FCanReadCount := FMS.Size; 165 166 //调整写指针位置 167 Inc(FWritePosition,Result); 168 if FWritePosition > FMS.Size then 169 FWritePosition := FWritePosition - FMS.Size; 170 end; 171 172 { TCircleBufferThread } 173 174 constructor TCircleBufferThread.Create(const BuffSize: Integer); 175 begin 176 InitializeCriticalSection(FCS); //初始化 177 inherited Create(BuffSize); 178 end; 179 180 destructor TCircleBufferThread.Destroy; 181 begin 182 DeleteCriticalSection(FCS); 183 inherited; 184 end; 185 186 function TCircleBufferThread.GetCanReadCount: Integer; 187 begin 188 EnterCriticalSection(FCS); 189 Result := FCanReadCount; 190 LeaveCriticalSection(FCS); 191 end; 192 193 function TCircleBufferThread.GetCanWrieCount: Integer; 194 begin 195 EnterCriticalSection(FCS); 196 Result := FCanWrieCount; 197 LeaveCriticalSection(FCS); 198 end; 199 200 function TCircleBufferThread.GetReadPosition: Integer; 201 begin 202 EnterCriticalSection(FCS); 203 Result := FReadPosition; 204 LeaveCriticalSection(FCS); 205 end; 206 207 function TCircleBufferThread.GetWritePosition: Integer; 208 begin 209 EnterCriticalSection(FCS); 210 Result := FWritePosition; 211 LeaveCriticalSection(FCS); 212 end; 213 214 function TCircleBufferThread.Read(var Buffer; Count: Integer): Integer; 215 begin 216 EnterCriticalSection(FCS); 217 try 218 Result := inherited read(Buffer,Count); 219 finally 220 LeaveCriticalSection(FCS); 221 end; 222 end; 223 224 function TCircleBufferThread.Write(const Buffer; Count: Integer): integer; 225 begin 226 EnterCriticalSection(FCS); 227 try 228 Result := inherited Write(Buffer,Count); 229 finally 230 LeaveCriticalSection(FCS); 231 end; 232 end; 233 234 end.
测试代码段：
1 procedure TForm1.btn1Click(Sender: TObject); 2 var 3 obj:TCircleBuffer; 4 TmpStr:AnsiString; 5 Len:Integer; 6 Buf:array[1..4096] of AnsiChar; 7 ASize,APosition:Integer; 8 P:PAnsiChar; 9 begin 10 11 obj := TCircleBuffer.Create(10); 12 ZeroMemory(@Buf,SizeOf(Buf)); 13 14 TmpStr := '0123456789'; 15 Len := obj.Write(TmpStr[1],Length(TmpStr)); 16 P := Obj.Memory; 17 if P = nil then 18 Exit; 19 20 TmpStr := 'ABCD'; 21 Len := obj.Write(TmpStr[1],Length(TmpStr)); 22 if Len < 0 then 23 Exit; 24 P := Obj.Memory; 25 if P = nil then 26 Exit; 27 28 TmpStr := '0123456789'; 29 Len := obj.Read(Buf,10); 30 if Len < 0 then 31 Exit; 32 33 P := Obj.Memory; 34 if P = nil then 35 Exit; 36 37 Len := obj.Read(Buf,10); 38 if Len < 0 then 39 Exit; 40 41 42 P := Obj.Memory; 43 if P = nil then 44 Exit; 45 46 47 tmpStr := 'ABC'; 48 Len := Obj.Write(TmpStr[1],3); 49 if Len < 0 then 50 Exit; 51 52 tmpStr := '123456#'; 53 Len := Obj.Write(TmpStr[1],Length(TmpStr)); 54 if Len < 0 then 55 Exit; 56 57 58 P := Obj.Memory; 59 if P = nil then 60 Exit; 61 62 63 FillChar(Buf,SizeOf(Buf),$32); 64 // ZeroMemory(@Buf,SizeOf(Buf)); 65 Len := obj.Read(Buf,3); 66 if Len < 0 then 67 Exit; 68 69 ZeroMemory(@Buf,SizeOf(Buf)); 70 Len := obj.Read(Buf,10); 71 if Len < 0 then 72 Exit; 73 74 75 P := Obj.Memory; 76 if P = nil then 77 Exit; 78 79 TmpStr := 'AB'; 80 Len := obj.Write(TmpStr[1],2); 81 if Len < 0 then 82 Exit; 83 84 P := Obj.Memory; 85 if P = nil then 86 Exit; 87 88 89 TmpStr := 'abcdefghijklmnopqrst'; 90 Len := obj.Write(TmpStr[1],Length(TmpStr)); 91 if Len < 0 then 92 Exit; 93 94 95 96 97 ZeroMemory(@Buf,SizeOf(Buf)); 98 Len := obj.Read(Buf,10); 99 if Len < 0 then 100 Exit; 101 102 if obj <> nil then 103 obj.Free(); 104 105 P := Obj.Memory; 106 if P = nil then 107 Exit; 108 109 end;