是否有一种优雅的方法可以用Delphi(6)删除文件中的奇偶校验位?在这种情况下,奇偶校验位是第9位。
最佳答案
假设您的文件是包含9位块的长位流,并且您想输出相同的流但包含8位块(即,每第9位丢弃一次)。
您可以一次读取9个字节(72位=八个9位块),然后使用移位将它们放入八个8位块中。
您将需要一些特殊处理来处理不是9字节倍数的文件,因此这只是一个粗略的指导。
procedure TForm1.Button1Click(Sender: TObject);
var
FSIn: TFileStream;
FSOut: TFileStream;
InBuffer: array[0..8] of Byte;
OutBuffer: array[0..7] of Byte;
X: Integer;
BytesRead: Integer;
BytesToWrite: Integer;
begin
FSIn := TFileStream.Create('Input.dat', fmOpenRead);
FSOut := TFileStream.Create('Output.dat', fmCreate);
try
for X := 1 to FSIn.Size div 9 do
begin
FillChar(InBuffer[0], 9, 0);
BytesRead := FSIn.Read(InBuffer[0], 9);
OutBuffer[0] := InBuffer[0];
OutBuffer[1] := (InBuffer[1] and 127) shl 1 + (InBuffer[2] and 128) shr 7;
OutBuffer[2] := (InBuffer[2] and 63) shl 2 + (InBuffer[3] and 192) shr 6;
OutBuffer[3] := (InBuffer[3] and 31) shl 3 + (InBuffer[4] and 224) shr 5;
OutBuffer[4] := (InBuffer[4] and 15) shl 4 + (InBuffer[5] and 240) shr 4;
OutBuffer[5] := (InBuffer[5] and 7) shl 5 + (InBuffer[6] and 248) shr 3;
OutBuffer[6] := (InBuffer[6] and 3) shl 6 + (InBuffer[7] and 252) shr 2;
OutBuffer[7] := (InBuffer[7] and 1) shl 7 + (InBuffer[8] and 254) shr 1;
if BytesRead < 9 then
begin
// To do - handle case where 9 bytes could not be read from input
BytesToWrite := 8;
end else
BytesToWrite := 8;
FSOut.Write(OutBuffer[0], BytesToWrite);
end;
finally
FSIn.Free;
FSOut.Free;
end;
end;
关于file - 使用Delphi从文件中删除奇偶校验位(每9位),我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/970155/