高分求教校验文件的算法？(200分)

怎样校验一文件，算出一定长的校验码，如果文件被修改则校验码也改变。

CRC32算法
自己到google找
www.playicq.com也有

MD5

校验文件?我也很想学习相关知识,帮你向上提!

给你贴个主程序。pascal的。把相关代码换换就是md5,crc16...
要完整程序留mail

{$A+,B-,G+,R-,X+}

{$DEFINE COMPLETE}
{$IFDEF COMPLETE}
{$D-,E-,I-,L-,N-,S-,V-}
{$ENDIF}
Program CRCheck;

Uses CRC,DOS,OS,TOOLSTPU;

Type
Buffer=Array[1..1] Of Byte;

Var
Buf:^Buffer;
FileSpec:String;
Avail:Longint;
Result:Boolean;

Function TestCRC(FileName:String):Longint;
Var
Fin:File;
CRC32:Longint;
RealRead:Word;
Begin
CRC32:=$FFFFFFFF;
Result:=False;
Assign(Fin,FileName);
{$I-}
Reset(Fin,1);
{$I+}
If IOResult<>0 Then Exit;
Repeat
BlockRead(Fin,Buf^,Avail,RealRead)
{ 从文件中读 Avail 个字节 }
CRC32:=UpdateCRC32(CRC32,Buf^,RealRead)
{ 计算这部分的 CRC }
Until RealRead<>Avail
{ 直到文件结束 }
Close(Fin);
CRC32:=Not CRC32;
TestCRC:=CRC32;
Result:=True;
End;

Procedure Work;
Var
CRC32:Longint;
Files:SearchRec;
DirirStr;
Name:NameStr;
Ext:ExtStr;
Begin
FSplit(FileSpec,Dir,Name,Ext);
FindFirst(FileSpec,ReadOnly+Hidden+SysFile+Archive,Files);
{ 查找所有符合 FileSpec 的文件 }
If DosError<>0 Then { 如果没有, 则所给的 FileSpec 有错误 }
Begin
Writeln('File does not exist! Program halt.');
Halt(1);
End;
Avail:=MaxAvail;
If Avail>65500 Then Avail:=65500
{ 限定缓冲区的最大尺寸 }
GetMem(Buf,Avail)
{ 申请缓冲区 }
Writeln('Directory:',Dir);
Writeln('FileName CRC');
Writeln('=========================');
Repeat
CRC32:=TestCRC(Dir+Files.Name)
{ 计算文件的 CRC 值 }
If Result Then Writeln(Files.Name,HexStr(CRC32,4):25-Ord(Files.Name[0]));
{ 如果在计算 CRC 的过程中没有出错, 则输出文件的 CRC }
FindNext(Files)
{ 寻找下一个文件 }
Until DosError<>0
{ 直到找不到符合条件的文件为止 }
FreeMem(Buf,Avail)
{ 释放缓冲区 }
Writeln('=========================');
End;

Procedure Help;
Begin
Writeln('Usage: CRCHECK [Drive:][Path][FileSpec] [/Option | -Option]');
Writeln;
Writeln(' [Drive:][Path][FileSpec] The files to be checked.(Support wildcard)');
Writeln;
Writeln(' /I Information of the program.');
Writeln(' /S Save the CRC code into file CRCHECK.TXT');
Halt(0);
End;

Procedure Information;
Begin
Writeln(' Hello Guy! I am a computer fan. I like writing programs very much. Do you');
Writeln('think it well?');
Writeln(' This program can give you a CRC value of a file. If you find any bugs,');
Writeln('please let me know.');
Writeln;
Writeln('NOTE: This program used CRC.TPU from Edwin T. Floyd');
Writeln;
Writeln('Thanks to : Stephen Satchell, Satchell Evaluations, Chuck Forsberg');
Writeln(' and Edwin T. Floyd.');
Writeln;
Writeln('Thank you for support!');
Halt(0);
End;

Procedure AnalyzerCMDLine;
Begin
If ParamCount<>1 Then Help;
FileSpec:=StringUp(ParamStr(1));
If FileSpec='/I' Then Information;
If ValidFileName(FileSpec) Then Work
Else Help;
End;

Begin
Writeln('[? CRC Checker Version 1.00?Freeware Programmed By Eagle');
Writeln('(C) Copyright Titanic Soft. All rights Reserved');
Writeln('Compiled Date : 02-01-99');
Writeln;
AnalyzerCMDLine;
End.

转自hash.pas

function CRC32(CRC: LongWord
Data: Pointer
DataSize: LongWord): LongWord
assembler;
asm
AND EDX,EDX
JZ @Exit
JCXZ @Exit
PUSH EBX
@Start:
MOVZX EBX,AL
XOR BL,[EDX]
SHR EAX,8
XOR EAX,CS:[EBX * 4 + OFFSET @CRC32]
INC EDX
DEC ECX
JNZ @Start
POP EBX
@Exit: RET

@CRC32: DD 000000000h, 077073096h, 0EE0E612Ch, 0990951BAh
DD 0076DC419h, 0706AF48Fh, 0E963A535h, 09E6495A3h
DD 00EDB8832h, 079DCB8A4h, 0E0D5E91Eh, 097D2D988h
DD 009B64C2Bh, 07EB17CBDh, 0E7B82D07h, 090BF1D91h
DD 01DB71064h, 06AB020F2h, 0F3B97148h, 084BE41DEh
DD 01ADAD47Dh, 06DDDE4EBh, 0F4D4B551h, 083D385C7h
DD 0136C9856h, 0646BA8C0h, 0FD62F97Ah, 08A65C9ECh
DD 014015C4Fh, 063066CD9h, 0FA0F3D63h, 08D080DF5h
DD 03B6E20C8h, 04C69105Eh, 0D56041E4h, 0A2677172h
DD 03C03E4D1h, 04B04D447h, 0D20D85FDh, 0A50AB56Bh
DD 035B5A8FAh, 042B2986Ch, 0DBBBC9D6h, 0ACBCF940h
DD 032D86CE3h, 045DF5C75h, 0DCD60DCFh, 0ABD13D59h
DD 026D930ACh, 051DE003Ah, 0C8D75180h, 0BFD06116h
DD 021B4F4B5h, 056B3C423h, 0CFBA9599h, 0B8BDA50Fh
DD 02802B89Eh, 05F058808h, 0C60CD9B2h, 0B10BE924h
DD 02F6F7C87h, 058684C11h, 0C1611DABh, 0B6662D3Dh
DD 076DC4190h, 001DB7106h, 098D220BCh, 0EFD5102Ah
DD 071B18589h, 006B6B51Fh, 09FBFE4A5h, 0E8B8D433h
DD 07807C9A2h, 00F00F934h, 09609A88Eh, 0E10E9818h
DD 07F6A0DBBh, 0086D3D2Dh, 091646C97h, 0E6635C01h
DD 06B6B51F4h, 01C6C6162h, 0856530D8h, 0F262004Eh
DD 06C0695EDh, 01B01A57Bh, 08208F4C1h, 0F50FC457h
DD 065B0D9C6h, 012B7E950h, 08BBEB8EAh, 0FCB9887Ch
DD 062DD1DDFh, 015DA2D49h, 08CD37CF3h, 0FBD44C65h
DD 04DB26158h, 03AB551CEh, 0A3BC0074h, 0D4BB30E2h
DD 04ADFA541h, 03DD895D7h, 0A4D1C46Dh, 0D3D6F4FBh
DD 04369E96Ah, 0346ED9FCh, 0AD678846h, 0DA60B8D0h
DD 044042D73h, 033031DE5h, 0AA0A4C5Fh, 0DD0D7CC9h
DD 05005713Ch, 0270241AAh, 0BE0B1010h, 0C90C2086h
DD 05768B525h, 0206F85B3h, 0B966D409h, 0CE61E49Fh
DD 05EDEF90Eh, 029D9C998h, 0B0D09822h, 0C7D7A8B4h
DD 059B33D17h, 02EB40D81h, 0B7BD5C3Bh, 0C0BA6CADh
DD 0EDB88320h, 09ABFB3B6h, 003B6E20Ch, 074B1D29Ah
DD 0EAD54739h, 09DD277AFh, 004DB2615h, 073DC1683h
DD 0E3630B12h, 094643B84h, 00D6D6A3Eh, 07A6A5AA8h
DD 0E40ECF0Bh, 09309FF9Dh, 00A00AE27h, 07D079EB1h
DD 0F00F9344h, 08708A3D2h, 01E01F268h, 06906C2FEh
DD 0F762575Dh, 0806567CBh, 0196C3671h, 06E6B06E7h
DD 0FED41B76h, 089D32BE0h, 010DA7A5Ah, 067DD4ACCh
DD 0F9B9DF6Fh, 08EBEEFF9h, 017B7BE43h, 060B08ED5h
DD 0D6D6A3E8h, 0A1D1937Eh, 038D8C2C4h, 04FDFF252h
DD 0D1BB67F1h, 0A6BC5767h, 03FB506DDh, 048B2364Bh
DD 0D80D2BDAh, 0AF0A1B4Ch, 036034AF6h, 041047A60h
DD 0DF60EFC3h, 0A867DF55h, 0316E8EEFh, 04669BE79h
DD 0CB61B38Ch, 0BC66831Ah, 0256FD2A0h, 05268E236h
DD 0CC0C7795h, 0BB0B4703h, 0220216B9h, 05505262Fh
DD 0C5BA3BBEh, 0B2BD0B28h, 02BB45A92h, 05CB36A04h
DD 0C2D7FFA7h, 0B5D0CF31h, 02CD99E8Bh, 05BDEAE1Dh
DD 09B64C2B0h, 0EC63F226h, 0756AA39Ch, 0026D930Ah
DD 09C0906A9h, 0EB0E363Fh, 072076785h, 005005713h
DD 095BF4A82h, 0E2B87A14h, 07BB12BAEh, 00CB61B38h
DD 092D28E9Bh, 0E5D5BE0Dh, 07CDCEFB7h, 00BDBDF21h
DD 086D3D2D4h, 0F1D4E242h, 068DDB3F8h, 01FDA836Eh
DD 081BE16CDh, 0F6B9265Bh, 06FB077E1h, 018B74777h
DD 088085AE6h, 0FF0F6A70h, 066063BCAh, 011010B5Ch
DD 08F659EFFh, 0F862AE69h, 0616BFFD3h, 0166CCF45h
DD 0A00AE278h, 0D70DD2EEh, 04E048354h, 03903B3C2h
DD 0A7672661h, 0D06016F7h, 04969474Dh, 03E6E77DBh
DD 0AED16A4Ah, 0D9D65ADCh, 040DF0B66h, 037D83BF0h
DD 0A9BCAE53h, 0DEBB9EC5h, 047B2CF7Fh, 030B5FFE9h
DD 0BDBDF21Ch, 0CABAC28Ah, 053B39330h, 024B4A3A6h
DD 0BAD03605h, 0CDD70693h, 054DE5729h, 023D967BFh
DD 0B3667A2Eh, 0C4614AB8h, 05D681B02h, 02A6F2B94h
DD 0B40BBE37h, 0C30C8EA1h, 05A05DF1Bh, 02D02EF8Dh
DD 074726F50h, 0736E6F69h, 0706F4320h, 067697279h
DD 028207468h, 031202963h, 020393939h, 048207962h
DD 06E656761h, 064655220h, 06E616D64h, 06FBBA36Eh
end;

function FileCRC32(FileName: string
var FileSize: Integer): LongWord
overload;
const
BufferSize = 102400
// 100k
var
Buffer: Pointer;
RetLen, Count: Cardinal;
begin
with TFileStream.Create(FileName, fmShareDenyNone) do
try
Result := $FFFFFFFF;
Count := Size;
FileSize := Count

GetMem(Buffer, BufferSize);
try
while Count > 0 do
begin
RetLen := Read(Buffer^, BufferSize);
if RetLen > 0 then
begin
Result := CRC32(Result, Buffer, RetLen);
Dec(Count, RetLen);
end

end;
finally
FreeMem(Buffer);
end;
Result := not Result;
finally
Free;
end;
end;

function FileCRC32(FileName: string): LongWord
overload;
var
FileSize: Integer;
begin
Result := FileCRC32(FileName, FileSize);
end;

校验文件
我也很想学习相关知识，樓上的可以給一份來參考參考嗎？webcolonel@163.com

多人接受答案了。