unit Crc32;

interface

uses
  classes, Sysutils, Vcl.Dialogs;

function FileCRC32(const FileName: string): Cardinal; overload;
function FileCRC32(const Stream: TStream): Cardinal; overload;
function UpdateCRC32(InitCRC: Cardinal; BufPtr: Pointer; Len: Word): LongInt;

implementation

type
  CRCTable = array [0 .. 255] of Cardinal;

const
  BufLen = 32768;

  CRC32Table: CRCTable = ($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, $04FDFF252, $D1BB67F1, $A6BC5767, $3FB506DD, $048B2364B, $D80D2BDA, $AF0A1B4C, $36034AF6, $041047A60, $DF60EFC3,
    $A867DF55, $316E8EEF, $04669BE79,

    $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);

var
  Buf: array [1 .. BufLen] of Byte;

function UpdateCRC32(InitCRC: Cardinal; BufPtr: Pointer; Len: Word): LongInt;
var
  crc: Cardinal;
  index: Integer;
  i: Cardinal;
begin
  crc := InitCRC;
  for i := 0 to Len - 1 do
  begin
    index := (crc xor Cardinal(Pointer(Cardinal(BufPtr) + i)^)) and $000000FF;
    crc := (crc shr 8) xor CRC32Table[index];
  end;
  Result := crc;
end;

function FileCRC32(const FileName: string): Cardinal;
var
  InFile: TFileStream;
  Crc32: Cardinal;
  Res: Integer;
  BufPtr: Pointer;
begin
  BufPtr := @Buf;
  Crc32 := $FFFFFFFF;
  try
    InFile := TFileStream.Create(FileName, fmShareDenyNone);
    Res := InFile.Read(Buf, BufLen);
    while (Res <> 0) do
    begin
      Crc32 := UpdateCRC32(Crc32, BufPtr, Res);
      Res := InFile.Read(Buf, BufLen);
    end;
    InFile.Destroy;
  except
    on E: Exception do
    begin
      if Assigned(InFile) then InFile.Free;
      ShowMessage(Format('При обработке файла [%s] вышла ' + 'вот такая oшибочка [%s]', [FileName, E.Message]));
    end;
  end;
  Result := not Crc32;
end;

function FileCRC32(const Stream: TStream): Cardinal;
var
  InFile: TFileStream;
  Crc32: Cardinal;
  Res: Integer;
  BufPtr: Pointer;
begin
  BufPtr := @Buf;
  Crc32 := $FFFFFFFF;
  try
    InFile := TFileStream(Stream);
    // TFileStream.Create(FileName, fmShareDenyNone);
    Res := InFile.Read(Buf, BufLen);
    while (Res <> 0) do
    begin
      Crc32 := UpdateCRC32(Crc32, BufPtr, Res);
      Res := InFile.Read(Buf, BufLen);
    end;
    InFile.Destroy;
  except
    on E: Exception do
    begin
      if Assigned(InFile) then InFile.Free;
      ShowMessage(Format('При обработке файла потока вышла ' + 'вот такая oшибочка [%s]', [E.Message]));
    end;
  end;
  Result := not Crc32;
end;

end.
