关于内存流的的CopyFrom速度问题

h98458 2009-07-24 11:49:04

vMemoryStream:=TMemoryStream.Create;
vFileStream:=TFileStream.Create(mFileName,fmOpenRead or fmShareDenyNone);
...
...
...
vMemoryStream.Clear;
vMemoryStream.CopyFrom(vFileStream,StrToIntDef(StrRight(StrRight(vFileInfo[I],'|'),'|'), 0));
vMemoryStream.Position:=0;
---------------------------------------------------------------------------------------
当StrToIntDef(StrRight(StrRight(vFileInfo[I],'|'),'|'), 0)数值很大时发现速度很慢很慢，请问如何解决？
有什么好的办法吗?
或者如果用文件流替代会不会好点，怎么用？

...全文

265 12 打赏收藏转发到动态举报

写回复

用AI写文章

12 条回复

切换为时间正序

请发表友善的回复…

发表回复

h98458 2009-07-27

打赏
举报

自己再顶顶，看看高人们有什么好办法

h98458 2009-07-27

打赏
举报

解决了：
rSize := StrToIntDef(StrRight(StrRight(vFileInfo[I],'|'),'|'), 0);
vMemoryStream.setsize(rSize);//加上这句
vMemoryStream.CopyFrom(vFileStream,rSize);
vMemoryStream.Position:=0;

谢谢二楼

minizhuxianchun 2009-07-27

打赏
举报

哦,忘了先分配内存了:
vMemoryStream:=TMemoryStream.Create;
vFileStream:=TFileStream.Create(mFileName,fmOpenRead or fmShareDenyNone);
...
...
...
vMemoryStream.Clear;
vMemoryStream.Size:=size;
vFileStream.ReadBuffer(vMemoryStream.Memory^,size);
//CopyMemory(vMemoryStream.Memory,vFileStream.Memory,size);//有可能要判断一下文件不能太巨大
//vMemoryStream.CopyFrom(vFileStream,StrToIntDef(StrRight(StrRight(vFileInfo[I],'|'),'|'), 0));
vMemoryStream.Position:=0;

飞天揽月 2009-07-26

打赏
举报

呵呵

minizhuxianchun 2009-07-24

打赏
举报

哦,忘了先分配内存了:
vMemoryStream:=TMemoryStream.Create;
vFileStream:=TFileStream.Create(mFileName,fmOpenRead or fmShareDenyNone);
...
...
...
vMemoryStream.Clear;
vMemoryStream.Size:=size;
CopyMemory(vMemoryStream.Memory,vFileStream.Memory,size);//有可能要判断一下文件不能太巨大
//vMemoryStream.CopyFrom(vFileStream,StrToIntDef(StrRight(StrRight(vFileInfo[I],'|'),'|'), 0));
vMemoryStream.Position:=0;

minizhuxianchun 2009-07-24

打赏
举报

{不要用CopyFrom这个函数,效率不高.
下面的函数体有每次拷贝的大小:
MaxBufSize = $F000;
先读出到缓冲区,再拷贝到内存流,有两次动作.
所以文件比较小时无所谓,大时就很慢的原因
}
function TStream.CopyFrom(Source: TStream; Count: Int64): Int64;
const
MaxBufSize = $F000;
var
BufSize, N: Integer;
Buffer: PChar;
begin
if Count = 0 then
begin
Source.Position := 0;
Count := Source.Size;
end;
Result := Count;
if Count > MaxBufSize then BufSize := MaxBufSize else BufSize := Count;
GetMem(Buffer, BufSize);
try
while Count <> 0 do
begin
if Count > BufSize then N := BufSize else N := Count;
Source.ReadBuffer(Buffer^, N);
WriteBuffer(Buffer^, N);
Dec(Count, N);
end;
finally
FreeMem(Buffer, BufSize);
end;
end;

vMemoryStream:=TMemoryStream.Create;
vFileStream:=TFileStream.Create(mFileName,fmOpenRead or fmShareDenyNone);
...
...
...
vMemoryStream.Clear;
CopyMemory(vMemoryStream.Memory,vFileStream.Memory,size);//有可能要判断一下文件不能太巨大
//vMemoryStream.CopyFrom(vFileStream,StrToIntDef(StrRight(StrRight(vFileInfo[I],'|'),'|'), 0));
vMemoryStream.Position:=0;

ahjoe 2009-07-24

打赏
举报

先分配好空间试试



rSize := StrToIntDef(StrRight(StrRight(vFileInfo[I],'|'),'|'), 0);

vMemoryStream.Size := rSize;

vMemoryStream.Position:=0;

vMemoryStream.CopyFrom(vFileStream,rSize);

...