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Навигация: Главная > Программирование под Windows > Pascal, Delphi > FAQ по Delphi

FAQ по Delphi

Как наиболее быстрым способом узнать, сколько файлов с определенным расширением есть в определенной папке?
Как вычислить CRC-32 для файла?
Как подсчитать количество файлов в папке?
Как работать с INI-файлами?
Как прочитать MP3 ID3-Tag?
Работа с TGA файлами

Q: Как наиболее быстрым способом узнать, сколько файлов с определенным расширением есть в определенной папке?

A: Например для HTM файлов:

Function GetFileCount(Dir:string):integer; var fs:TSearchRec; begin
  Result:=0;
  if FindFirst(Dir+'\*.htm',faAnyFile-faDirectory-faVolumeID, fs)=0 then
    repeat
      inc(Result);
    until FindNext(fs)<>0;
  FindClose(fs);
end;

Автор ответа: Vit

вверх

Q: Как вычислить CRC-32 для файла?

// The constants here are for the CRC-32 generator  
// polynomial, as defined in the Microsoft  
// Systems Journal, March 1995, pp. 107 - 108  
const  
  Table: 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);

type  
//----------------------------------crc32----------------------------------  
  {$IFDEF VER130}           // This is a bit awkward  
    // 8-byte integer  
    TInteger8 = Int64;     // Delphi 5  
  {$ELSE}  
  {$IFDEF VER120}  
    TInteger8 = Int64;     // Delphi 4  
  {$ELSE}  
    TInteger8 = COMP;      // Delphi  2 or 3  
  {$ENDIF}  
  {$ENDIF}  
//----------------------------------crc32----------------------------------

// Use CalcCRC32 as a procedure so CRCValue can be passed in but  
  // also returned. This allows multiple calls to CalcCRC32 for  
  // the "same" CRC-32 calculation.  
procedure CalcCRC32(p: Pointer; ByteCount: DWORD; var CRCValue: DWORD);  
  // The following is a little cryptic (but executes very quickly).  
  // The algorithm is as follows:  
  // 1. exclusive-or the input byte with the low-order byte of  
  // the CRC register to get an INDEX  
  // 2. shift the CRC register eight bits to the right  
  // 3. exclusive-or the CRC register with the contents of Table[INDEX]  
  // 4. repeat steps 1 through 3 for all bytes  
var  
  i: DWORD;  
  q: ^BYTE;  
begin  
  q := p;  
  for i := 0 to ByteCount - 1 do  
  begin  
    CRCvalue := (CRCvalue shr 8) xor  
      Table[q^ xor (CRCvalue and $000000FF)];  
    Inc(q)  
  end  
end {CalcCRC32};

function CalcStringCRC32(s: string; out CRC32: DWORD): Boolean;  
var  
  CRC32Table: DWORD;  
begin  
  // Verify the table used to compute the CRCs has not been modified.  
  // Thanks to Gary Williams for this suggestion, Jan. 2003.  
  CRC32Table := $FFFFFFFF;  
  CalcCRC32(Addr(Table[0]), SizeOf(Table), CRC32Table);  
  CRC32Table := not CRC32Table;

if CRC32Table <> $6FCF9E13 then ShowMessage('CRC32 Table CRC32 is ' +  
      IntToHex(Crc32Table, 8) +  
      ', expecting $6FCF9E13')  
  else  
  begin  
    CRC32 := $FFFFFFFF; // To match PKZIP  
    if Length(s) > 0  // Avoid access violation in D4  
      then CalcCRC32(Addr(s[1]), Length(s), CRC32);  
    CRC32 := not CRC32; // To match PKZIP  
  end;  
end;

procedure CalcFileCRC32(FromName: string; var CRCvalue: DWORD;  
  var TotalBytes: TInteger8;  
  var error: Word);  
var  
  Stream: TMemoryStream;  
begin  
  error := 0;  
  CRCValue := $FFFFFFFF;  
  Stream := TMemoryStream.Create;  
  try  
    try  
      Stream.LoadFromFile(FromName);  
      if Stream.Size > 0 then CalcCRC32(Stream.Memory, Stream.Size, CRCvalue)  
      except  
        on E: EReadError do  
          error := 1  
    end;  
    CRCvalue := not CRCvalue  
  finally  
    Stream.Free  
  end;  
end;

procedure TForm1.Button1Click(Sender: TObject);  
var  
  s: string;  
  CRC32: DWORD;  
begin  
  s := 'Test String';  
  if CalcStringCRC32(s, CRC32) then  
    ShowMessage(IntToStr(crc32));  
end;

вверх

Q: Как подсчитать количество файлов в папке?

uses
  Windows, { ... }

function FileCount(const aFolder: string): Integer;
var
  H: THandle;
  Data: TWin32FindData;
begin
  Result := 0;
  H := FindFirstFile(PCHAR(aFolder + '*.*'), Data);
  if H <> INVALID_HANDLE_VALUE then
    repeat
      Inc(Result, Ord(Data.dwFileAttributes and FILE_ATTRIBUTE_DIRECTORY = 0));
    until
      not FindNextFile(H, Data);
  Windows.FindClose(H);
end;

вверх

Q: Как работать с INI-файлами?

function ReadIni(ASection, AString: string): string;
var
  sIniFile: TIniFile;
  sPath: string[60];
const
  S = 'xyz'; { стандартная строка для выдачи ошибок чтения }
begin
  GetDir(0, sPath);
  sIniFile := TIniFile.Create(sPath + '\Name.INI');
  Result := sIniFile.ReadString(ASection, AString, S); { [Section] String=Value}
  sIniFile.Free;
end;

procedure WriteIni(ASection, AString, AValue: string);
var
  sIniFile: TIniFile;
  sPath: string[60];
begin
  GetDir(0, sPath);
  sIniFile := TIniFile.Create(sPath + '\Name.INI');
  sIniFile.WriteString(ASection, AString, AValue); { [Section] String=Value }
  sIniFile.Free;
end;

{ReadSection считывает все пункты
указанной секции - т.е.
ключи перед знаком "="
ReadSectionValues полностью считывает все
строки указанной секции,
т.е. Punkt=xyz }

вверх

Q: Как прочитать MP3 ID3-Tag?

{  
  Byte 1-3 = ID 'TAG'  
  Byte 4-33 = Titel / Title  
  Byte 34-63 = Artist  
  Byte 64-93 = Album  
  Byte 94-97 = Jahr / Year  
  Byte 98-127 = Kommentar / Comment  
  Byte 128 = Genre  
}

type  
  TID3Tag = record  
    ID: string[3];  
    Titel: string[30];  
    Artist: string[30];  
    Album: string[30];  
    Year: string[4];  
    Comment: string[30];  
    Genre: Byte;  
  end;

const  
 Genres : array[0..146] of string =  
    ('Blues','Classic Rock','Country','Dance','Disco','Funk','Grunge',  
    'Hip- Hop','Jazz','Metal','New Age','Oldies','Other','Pop','R&B',  
    'Rap','Reggae','Rock','Techno','Industrial','Alternative','Ska',  
    'Death Metal','Pranks','Soundtrack','Euro-Techno','Ambient',  
    'Trip-Hop','Vocal','Jazz+Funk','Fusion','Trance','Classical',  
    'Instrumental','Acid','House','Game','Sound Clip','Gospel','Noise',  
    'Alternative Rock','Bass','Punk','Space','Meditative','Instrumental Pop',  
    'Instrumental Rock','Ethnic','Gothic','Darkwave','Techno-Industrial','Electronic',  
    'Pop-Folk','Eurodance','Dream','Southern Rock','Comedy','Cult','Gangsta',  
    'Top 40','Christian Rap','Pop/Funk','Jungle','Native US','Cabaret','New Wave',  
    'Psychadelic','Rave','Showtunes','Trailer','Lo-Fi','Tribal','Acid Punk',  
    'Acid Jazz','Polka','Retro','Musical','Rock & Roll','Hard Rock','Folk',  
    'Folk-Rock','National Folk','Swing','Fast Fusion','Bebob','Latin','Revival',  
    'Celtic','Bluegrass','Avantgarde','Gothic Rock','Progressive Rock',  
    'Psychedelic Rock','Symphonic Rock','Slow Rock','Big Band','Chorus',  
    'Easy Listening','Acoustic','Humour','Speech','Chanson','Opera',  
    'Chamber Music','Sonata','Symphony','Booty Bass','Primus','Porn Groove',  
    'Satire','Slow Jam','Club','Tango','Samba','Folklore','Ballad',  
    'Power Ballad','Rhytmic Soul','Freestyle','Duet','Punk Rock','Drum Solo',  
    'Acapella','Euro-House','Dance Hall','Goa','Drum & Bass','Club-House',  
    'Hardcore','Terror','Indie','BritPop','Negerpunk','Polsk Punk','Beat',  
    'Christian Gangsta','Heavy Metal','Black Metal','Crossover','Contemporary C',  
    'Christian Rock','Merengue','Salsa','Thrash Metal','Anime','JPop','SynthPop');

var  
  Form1: TForm1;

implementation

{$R *.dfm}

function readID3Tag(FileName: string): TID3Tag;  
var  
  FS: TFileStream;  
  Buffer: array [1..128] of Char;  
begin  
  FS := TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);  
  try  
    FS.Seek(-128, soFromEnd);  
    FS.Read(Buffer, 128);  
    with Result do  
    begin  
      ID := Copy(Buffer, 1, 3);  
      Titel := Copy(Buffer, 4, 30);  
      Artist := Copy(Buffer, 34, 30);  
      Album := Copy(Buffer, 64, 30);  
      Year := Copy(Buffer, 94, 4);  
      Comment := Copy(Buffer, 98, 30);  
      Genre := Ord(Buffer[128]);  
    end;  
  finally  
    FS.Free;  
  end;  
end;

procedure TfrmMain.Button1Click(Sender: TObject);  
begin  
  if OpenDialog1.Execute then  
  begin  
    with readID3Tag(OpenDialog1.FileName) do  
    begin  
      LlbID.Caption := 'ID: ' + ID;  
      LlbTitel.Caption := 'Titel: ' + Titel;  
      LlbArtist.Caption := 'Artist: ' + Artist;  
      LlbAlbum.Caption := 'Album: ' + Album;  
      LlbYear.Caption := 'Year: ' + Year;  
      LlbComment.Caption := 'Comment: ' + Comment;  
      if (Genre >= 0) and (Genre <=146) then  
       LlbGenre.Caption := 'Genre: ' + Genres[Genre]  
      else  
       LlbGenre.Caption := 'N/A';  
    end;  
  end;  
end;

вверх

Q: Работа с TGA файлами

const 
  FERRORMSG2 = 'Sorry, Unsupported Compressed(RLE) File Format'; 
  FERRORMSG3 = 'Sorry, Unsupported More Than 256 Colours File Format';

type 
  TArrBuff = array[1..512] of Byte; 
  TPalette_Cell = record 
    b2, g2, r2: byte; 
  end; 
  TPal = array[0..255] of TPalette_Cell; 
  TPPal = ^TPal; 
  TTGA_Header = record // Targa(TGA) HEADER // 
    IDLength, ColorMap, ImageType: byte; 
    ClrMapSpes: array[1..5] of byte; 
    XAwal, YAwal, Width, Height: SmallInt; 
    BpPixel, ImageDescription: byte; 
  end;

var 
  pal: TPPal; 
  pFile: file; 
  buffer: TArrBuff; 
  FTgaHeader: TTGA_Header;

procedure THPTGA.ReadImageData2Bitmap; 
var 
  i, j, idx: integer; 
begin 
  Seek(pFile, sizeof(FtgaHeader) + FtgaHeader.IDLength + 768); 
  for i := FtgaHeader.Height - 1 downto FtgaHeader.YAwal do 
  begin 
    BlockRead(pFile, buffer, FtgaHeader.Width); 
    for j := FtgaHeader.XAwal to FtgaHeader.Width - 1 do 
    begin 
      idx := j - FtgaHeader.XAwal + 1; 
      SetPixel(Bitmap.Canvas.Handle, j, i, rgb(pal^[buffer[idx]].r2, 
        pal^[buffer[idx]].g2, pal^[buffer[idx]].b2)); 
    end; 
  end; 
end;

procedure THPTGA.LoadFromFile(const FileName: string); 
begin 
  AssignFile(pFile, FileName); 
{$I-}Reset(pFile, 1); 
{$I+} 
  if (IOResult = 0) then 
  begin 
    try 
      BlockRead(pFile, FtgaHeader, SizeOf(FtgaHeader)); 
      // checking unsupported features here 
      if (FtgaHeader.ImageType > 3) then 
      begin 
        MessageBox(Application.Handle, FERRORMSG2, 'TGA Viewer Error', MB_ICONHAND); 
        exit; 
      end; 
      if (FtgaHeader.BpPixel > 8) then 
      begin 
        MessageBox(Application.Handle, FERRORMSG3, 'TGA Viewer Error', MB_ICONHAND); 
        exit; 
      end; 
      GetMem(pal, 768); 
      try 
        Bitmap.Width := FtgaHeader.Width; 
        Bitmap.Height := FtgaHeader.Height; 
        // if use Color-Map and Uncompressed then read it 
        if (FtgaHeader.ImageType = 1) then 
          BlockRead(pFile, pal^, 768); 
        ReadImageData2Bitmap; 
      finally 
        FreeMem(pal); 
      end; 
    finally 
      CloseFile(pFile); 
    end; 
  end 
  else 
    MessageBox(Application.Handle, 'Error Opening File', 'TGA Viewer Error', 
      MB_ICONHAND); 
end;

вверх

При составлении использовались материалы:

популярный форум программистов forum.vingrad.ru
Delphi Knowledge Base baltsoft.com
swissdelphicenter.ch

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