可以分块计算CRC的，以下是我的CRC32测试代码，其计算结果与WinRar/WinZip一致：
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TForm1 = class(TForm)
lblCRC32: TLabel;
btnFile: TButton;
edtFile: TEdit;
btnCalcCRC32: TButton;
edtCRC32: TEdit;
OpenDialog1: TOpenDialog;
procedure FormCreate(Sender: TObject);
procedure btnFileClick(Sender: TObject);
procedure btnCalcCRC32Click(Sender: TObject);
private
{ Private declarations }
m_bExit: Boolean; //校验过程中用户选“退出”???
m_bCalcing: Boolean; //正在校验???
function CalcCrc32OfFile(const sFileName: string): DWORD;
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
var
crc32table: array[0..255] of DWORD =
(
$00000000, $77073096, $EE0E612C, $990951BA,
$076DC419, $706AF48F, $E963A535, $9E6495A3,
$0EDB8832, $79DCB8A4, $E0D5E91E, $97D2D988,
$09B64C2B, $7EB17CBD, $E7B82D07, $90BF1D91,
$1DB71064, $6AB020F2, $F3B97148, $84BE41DE,
$1ADAD47D, $6DDDE4EB, $F4D4B551, $83D385C7,
$136C9856, $646BA8C0, $FD62F97A, $8A65C9EC,
$14015C4F, $63066CD9, $FA0F3D63, $8D080DF5,
$3B6E20C8, $4C69105E, $D56041E4, $A2677172,
$3C03E4D1, $4B04D447, $D20D85FD, $A50AB56B,
$35B5A8FA, $42B2986C, $DBBBC9D6, $ACBCF940,
$32D86CE3, $45DF5C75, $DCD60DCF, $ABD13D59,
$26D930AC, $51DE003A, $C8D75180, $BFD06116,
$21B4F4B5, $56B3C423, $CFBA9599, $B8BDA50F,
$2802B89E, $5F058808, $C60CD9B2, $B10BE924,
$2F6F7C87, $58684C11, $C1611DAB, $B6662D3D,
$76DC4190, $01DB7106, $98D220BC, $EFD5102A,
$71B18589, $06B6B51F, $9FBFE4A5, $E8B8D433,
$7807C9A2, $0F00F934, $9609A88E, $E10E9818,
$7F6A0DBB, $086D3D2D, $91646C97, $E6635C01,
$6B6B51F4, $1C6C6162, $856530D8, $F262004E,
$6C0695ED, $1B01A57B, $8208F4C1, $F50FC457,
$65B0D9C6, $12B7E950, $8BBEB8EA, $FCB9887C,
$62DD1DDF, $15DA2D49, $8CD37CF3, $FBD44C65,
$4DB26158, $3AB551CE, $A3BC0074, $D4BB30E2,
$4ADFA541, $3DD895D7, $A4D1C46D, $D3D6F4FB,
$4369E96A, $346ED9FC, $AD678846, $DA60B8D0,
$44042D73, $33031DE5, $AA0A4C5F, $DD0D7CC9,
$5005713C, $270241AA, $BE0B1010, $C90C2086,
$5768B525, $206F85B3, $B966D409, $CE61E49F,
$5EDEF90E, $29D9C998, $B0D09822, $C7D7A8B4,
$59B33D17, $2EB40D81, $B7BD5C3B, $C0BA6CAD,
$EDB88320, $9ABFB3B6, $03B6E20C, $74B1D29A,
$EAD54739, $9DD277AF, $04DB2615, $73DC1683,
$E3630B12, $94643B84, $0D6D6A3E, $7A6A5AA8,
$E40ECF0B, $9309FF9D, $0A00AE27, $7D079EB1,
$F00F9344, $8708A3D2, $1E01F268, $6906C2FE,
$F762575D, $806567CB, $196C3671, $6E6B06E7,
$FED41B76, $89D32BE0, $10DA7A5A, $67DD4ACC,
$F9B9DF6F, $8EBEEFF9, $17B7BE43, $60B08ED5,
$D6D6A3E8, $A1D1937E, $38D8C2C4, $4FDFF252,
$D1BB67F1, $A6BC5767, $3FB506DD, $48B2364B,
$D80D2BDA, $AF0A1B4C, $36034AF6, $41047A60,
$DF60EFC3, $A867DF55, $316E8EEF, $4669BE79,
$CB61B38C, $BC66831A, $256FD2A0, $5268E236,
$CC0C7795, $BB0B4703, $220216B9, $5505262F,
$C5BA3BBE, $B2BD0B28, $2BB45A92, $5CB36A04,
$C2D7FFA7, $B5D0CF31, $2CD99E8B, $5BDEAE1D,
$9B64C2B0, $EC63F226, $756AA39C, $026D930A,
$9C0906A9, $EB0E363F, $72076785, $05005713,
$95BF4A82, $E2B87A14, $7BB12BAE, $0CB61B38,
$92D28E9B, $E5D5BE0D, $7CDCEFB7, $0BDBDF21,
$86D3D2D4, $F1D4E242, $68DDB3F8, $1FDA836E,
$81BE16CD, $F6B9265B, $6FB077E1, $18B74777,
$88085AE6, $FF0F6A70, $66063BCA, $11010B5C,
$8F659EFF, $F862AE69, $616BFFD3, $166CCF45,
$A00AE278, $D70DD2EE, $4E048354, $3903B3C2,
$A7672661, $D06016F7, $4969474D, $3E6E77DB,
$AED16A4A, $D9D65ADC, $40DF0B66, $37D83BF0,
$A9BCAE53, $DEBB9EC5, $47B2CF7F, $30B5FFE9,
$BDBDF21C, $CABAC28A, $53B39330, $24B4A3A6,
$BAD03605, $CDD70693, $54DE5729, $23D967BF,
$B3667A2E, $C4614AB8, $5D681B02, $2A6F2B94,
$B40BBE37, $C30C8EA1, $5A05DF1B, $2D02EF8D
);
procedure InitCrc32Table;
var
bOk: Boolean;
i, j: Integer;
dwCrc: DWORD;
begin
for i := 0 to 255 do
begin
dwCrc := i; //必须为DWORD !!!!否则得不到正确的CRC32表
for j := 0 to 7 do
begin
bOk := Boolean(dwCrc and 1);
dwCrc := dwCrc shr 1;
if bOk then
dwCrc := dwCrc xor $EDB88320;
end;
crc32table[i] := dwCrc;
end;
end;
function Crc32(Buf: PChar; Length: DWORD): DWORD;
var //一次计算CRC32值
crc, i, dwTemp: DWORD;
begin
crc := $FFFFFFFF;
for i := 0 to Length -1 do
begin
dwTemp := (crc xor Byte(Buf^)) and $000000FF;
Inc(Buf);
crc := ( crc shr 8) xor crc32table[dwTemp];
end;
Result := not crc;
{
//以下为不用表的算法!!!经过检验的!!! 2003.2.20.
/* crc polynomial for Ethernet */
//const unsigned long poly = 0xedb88320;
/* crc value - preinitialized to all 1's */
/*unsigned long crc_value = 0xffffffff;
for (unsigned int perByte = 0; perByte < length; perByte ++ )
begin
unsigned char c = *(s++);
for (int perBit = 0; perBit < 8; perBit++ )
begin
crc_value = (crc_value>>1)^
(((crc_value^c)&0x01)?poly:0);
c >>= 1;
end;
end;
return ~crc_value;*/
}
end;
function CalcCRC32(dwCrc32: DWORD; Buf: PChar; dwLen: DWORD): DWORD;
var //分块计算CRC32校验值(每次计算一小块)
i, dwTemp: DWORD; //查看算比不用表直接算速度要快得多 2005.8.28
begin
for i := 0 to dwLen -1 do
begin
dwTemp := (dwCrc32 xor Byte(Buf^)) and $000000FF;
Inc(Buf);
dwCrc32 := (dwCrc32 shr 8) xor crc32table[dwTemp];
end;
Result := dwCrc32;
end;
function CalcCRC32Direct(dwCrc32: DWORD; Buf: PChar; dwLen: DWORD): DWORD;
const //分块计算CRC32校验值(每次计算一小块)
dwPoly: DWORD = $EDB88320; //<不用表直接算,经过检验的 2005.8.28>
var
bXor: Boolean;
i, j: DWORD;
btNow: Byte;
begin
for i := 0 to dwLen - 1 do //按字节算
begin
btNow := Byte(Buf^);
for j := 0 to 7 do //按位算
begin
bXor := ((dwCrc32 xor btNow)and $1) <> 0;
dwCrc32 := dwCrc32 shr 1;
if bXor then
dwCrc32 := dwCrc32 xor dwPoly;
btNow := btNow shr 1;
end;
Inc(Buf);
end;
Result := dwCrc32;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
Application.Title := Caption;
end;
function TForm1.CalcCrc32OfFile(const sFileName: string): DWORD;
const //分块计算CRC32校验值
BlockSize = 4096; //每次计算一小块
var
pCache, pp: PChar;
dwCrc: DWORD;
iPos: int64;
iLen: Integer;
sInfo: String;
begin
Result := 0;
if FileExists(sFileName) then
begin
with TFileStream.Create(sFileName, fmOpenRead) do
try
GetMem(pCache, BlockSize);
try
pp := pCache;
dwCrc := $FFFFFFFF;
iPos := 0;
while iPos < Size do //本循环计算CRC32校验值
begin
sInfo := Format('%d%%', [Trunc(iPos*100.0 / Size)]);
if sInfo <> edtCRC32.Text then //计算大文件时减少刷新
edtCRC32.Text := sInfo;
iLen := Read(pCache^, BlockSize);
if iLen > 0 then
dwCrc := CalcCRC32{Direct}(dwCrc, pp, iLen);
Inc(iPos, BlockSize);
Application.ProcessMessages();
if m_bExit then //退出
break;
end;
Result := not dwCrc; //取一下反，使得其值与WinZip,WinRAR一致
finally
FreeMem(pCache, BlockSize);
end;
finally
Free;
end;
end;
end;
procedure TForm1.btnFileClick(Sender: TObject);
begin
if OpenDialog1.Execute then
edtFile.Text := OpenDialog1.FileName;
end;
procedure TForm1.btnCalcCRC32Click(Sender: TObject);
var
sCap: string;
begin
Screen.Cursor := crHourGlass;
sCap := lblCRC32.Caption;
lblCRC32.Caption := '校验进度：';
m_bCalcing := true;
edtCRC32.Text := '$' + IntToHex(integer(CalcCRC32OfFile(edtFile.Text)), 8);
m_bCalcing := false;
lblCRC32.Caption := sCap;
Screen.Cursor := crDefault;
end;
end. |
