对文件、字符串进行 CRC 校验
{*------------------------------------------------
CRC 校验
@author xszlo
@version P72
@todo 1
@History,2010-7-16,1
--------------------------------------------------*}

unit uCRC; interface uses  Windows, SysUtils;  type  TCRC = class(TObject)  private    Table: array[0..255] of DWORD;    procedure MakeTable();  public    procedure GetCRC32File(FileName: string; var CRC32: DWORD);    function GetCrc32Str(s: string; Seed: LongInt): string;    function GetCRC32FileHexStr(FileName: string): string;  end; implementation { TCRC } {-------------------------------------------  过程名:    TCRC.GetCRC32File  作者:      xszlo  日期:      2008.12.09  参数:      FileName: string; var CRC32: DWORD  返回值:    无  作用：     生成文件的CRC32验证码-------------------------------------------}procedure TCRC.GetCRC32File(FileName: string; var CRC32: DWORD);var  F: file;  BytesRead: DWORD;  Buffer: array[1..65521] of Byte;  i: Word;begin  MakeTable;  FileMode := 0;  CRC32 := $FFFFFFFF;{$I-}  AssignFile(F, FileName);  Reset(F, 1);  if IoResult = 0 then  begin    repeat      BlockRead(F, Buffer, Sizeof(Buffer), BytesRead);      for i := 1 to BytesRead do        CRC32 := (CRC32 shr 8) xor Table[Buffer[i] xor (CRC32 and $000000FF)];    until BytesRead = 0;  end;  CloseFile(F);{$I+}  CRC32 := not CRC32;end; {-------------------------------------------  过程名:    TCRC.GetCRC32FileHexStr  作者:      xszlo  日期:      2008.12.09  参数:      FileName: string  返回值:    string  作用：     得到文件的RCR32验证码-------------------------------------------}function TCRC.GetCRC32FileHexStr(FileName: string): string;var  dcrc32: DWORD;begin  GetCRC32File(FileName, dcrc32);  if dcrc32 <> 0 then    result := PChar(IntToHex(dcrc32, 6));end; {*------------------------------------------  生成字符CRC验证  @param    s string     Seed Integer    @throws 无  @return  string------------------------------------------*}function TCRC.GetCrc32Str(s: string; Seed: Integer): string;var  Count: Integer;  CrcVal: LongInt;begin  MakeTable();  CrcVal := Seed;  for Count := 1 to Length(s) do    CrcVal := Table[Byte(CrcVal xor DWORD(Ord(s[Count])))] xor ((CrcVal shr 8) and $00FFFFFF);  Result := IntToHex(not (CrcVal), 8);end; {-------------------------------------------  过程名:    TCRC.MakeTable  作者:      xszlo  日期:      2008.12.09  参数:      无  返回值:    无  作用：     无-------------------------------------------}procedure TCRC.MakeTable;var  i, j, Crc: integer;begin  for i := 0 to 255 do  begin    Crc := i;    for j := 0 to 7 do    begin      if (Crc and 1) <> 0 then        Crc := (Crc shr 1) xor $EDB88320      else        Crc := Crc shr 1;    end;    Table[i] := Crc;  end;end; end.

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使用方法：
var
CRC:TCRC;

CRC:=TCRC.Create;
showmessage(CRC.GetCRC32FileHexStr('d:\a.txt'));
FreeAndNil(CRC);

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