//10次抽样比较，这样速度会快点，不适合特别大的文件，这样容易漏比
function CompFile(const f1,f2: string): Boolean;
var
fs1,fs2: TFileStream;
ms: TMemoryStream;
i,p: Integer;
b1,b2: Byte;
begin
Result := False;
if not (FileExists(f1) and FileExists(f2)) then Exit;
fs1 := TFileStream.Create(f1, fmOpenRead);
fs2 := TFileStream.Create(f2, fmOpenRead);
if fs1.Size <> fs2.Size then
begin
fs1.Free;
fs2.Free;
Exit;
end;
Result := True;
Randomize;
for i := 0 to 9 do
begin
p := Random(fs1.Size);
fs1.Position := p;
fs2.Position := p;
fs1.ReadBuffer(b1,1);
fs2.ReadBuffer(b2,1);
if b1 <> b2 then
begin
Result := False;
Break;
end;
end;
fs1.Free;
fs2.Free;
end;
//随机取10个字节比对的方式并不好，如果差异在随机取得的字节之外，容易误判，MemoryStream加载文件对小文件的处理没
//多少问题，万一是大文件（比如1G）那在LoadFromFile的时候，系统可能会当掉。
function CompareFile(const f1,f2: string; BufferSize: Cardinal = 1024 * 1024 * 64
{默认为 64k 的缓存}): Boolean;
var
ms1,ms2: TStream;
readb1,readb2: Integer;
b1,b2: PByte;
begin
Result := False;
if not (FileExists(f1) and FileExists(f2)) then Exit;
if BufferSize = 0 then BufferSize := 1024 * 1024 * 64;
ms1 := TFileStream.Create(f1, fmOpenRead or fmShareDenyWrite);
try
ms2 := TFileStream.Create(f2, fmOpenRead or fmShareDenyWrite);
try
if ms1.Size <> ms2.Size then Exit;
GetMem(b1, BufferSize);
try
GetMem(b2, BufferSize);
try
repeat
readb1 := ms1.Read(b1^, BufferSize);
readb2 := ms2.Read(b2^, BufferSize);
if readb1 > 0 then
begin
if readb1 = readb2 then
Result := CompareMem(b1, b2, readb1)
else
Result := False;
end;
until (not Result) or (readb1 = 0) or (readb2 = 0);
finally
FreeMem(b2);
end;
finally
FreeMem(b1);
end;
finally
ms1.Free;
end;
finally
ms2.Free;
end;
end;
