Delphi,FileStream和MemoryStream

Question

我想将FileStream的一部分复制到内存流.

FileStream.Write(Pointer(MemoryStream)^, MemoryStream.Size);
FileStream.Read(Pointer(MemoryStream)^, count);

是对的吗？它不适合我.

Answer 1

你必须从FileStream中将Read()放入一个单独的缓冲区,然后将Write()放到MemoryStream中,即:

var
  Buffer: PByte;

GetMem(Buffer, NumberOfBytes);
try
  FileStream.ReadBuffer(Buffer^, NumberOfBytes);
  MemoryStream.WriteBuffer(Buffer^, NumberOfBytes);
finally
  FreeMem(Buffer);
end;

由于您正在处理两个TStream对象,因此使用TStream.CopyFrom()方法会更容易,即:

MemoryStream.CopyFrom(FileStream, NumberOfBytes);