ump3tag.pas

MP3播放器

unit uMP3TAG;

interface

uses SysUtils, Classes;

const
{ 流派索引表 }
  MAXGENRES = 114;
  GENRESTable: array [0..MAXGENRES] 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','AlternRock','Bass','Soul','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 American','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','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');
{ 128字节的ID3v1结构 }
type
    ID3Struct = packed record
    FID:      array [0..2 ] of Char;
    FTitle:   array [0..29] of Char;
    FArtist:  array [0..29] of Char;
    FAlbum:   array [0..29] of Char;
    FYear:    array [0..3 ] of Char;
    FComment: array [0..29] of Char;
    FGenre:   Byte;
  end;
 TID3Tag = class
 private
   FStream: TFileStream;
   Tag, Tag2: ID3Struct;
 public
   Title, Artist, Album, Year, Comment: string;
   Genre: Byte;
   GenreStr: string;// 流派对应字符串
   FileName: string;// 文件名
   function ReadTag: Boolean;   // 读取Tag
   function WriteTag: Boolean;  // 写Tag
   function RemoveTag: Boolean; // 除去Tag
 end;

implementation

function TID3Tag.ReadTag: Boolean;
begin
  Result := False;
  try
    FStream := TFileStream.Create(FileName, fmOpenRead);
    FStream.Seek(-128, soFromEnd);
    FStream.ReadBuffer(Tag, 128); // 读取TAG
    if StrLComp(Tag.FID, 'TAG', 3) = 0 then
    with Tag do
    begin
      Title   := Trim(Copy(FTitle, 1, SizeOf(FTitle)));
      Artist  := Trim(Copy(FArtist, 1, SizeOf(FArtist)));
      Album   := Trim(Copy(FAlbum, 1, SizeOf(FAlbum)));
      Year    := Trim(Copy(FYear, 1, SizeOf(FAlbum)));
      Comment := Trim(Copy(FComment, 1, SizeOf(FComment)));
      Genre   := FGenre;
      if FGenre <= MAXGENRES then
        GenreStr := GENRESTable[FGenre] else GenreStr := 'Unknown';
      Result := True;
    end;
  finally
     Fstream.Free;
  end;
end;

function TID3Tag.WriteTag: Boolean;
  procedure MoveStr(Sour: string; Dest: PChar);
  begin
    if Length(Sour) > 0 then
      Move(Sour[1], Dest^, Length(Sour));
  end;

begin
  Result := False;
  FillChar(Tag, SizeOf(Tag), 32);// 先填充空格
  with Tag do
  begin
    FID := 'TAG';
    FGenre := Genre;
    MoveStr(Title, Ftitle);
    MoveStr(Artist, FArtist);
    MoveStr(Album, FAlbum);
    MoveStr(Year, FYear);
    MoveStr(Comment, FComment);
  end;
  try
    FStream := TFileStream.Create(FileName, fmOpenReadWrite);
    FStream.Seek(-128, soFromEnd);
    FStream.ReadBuffer(Tag2,sizeof(Tag2));
    if StrLComp(Tag.FID, 'TAG', 3) <> 0 then // 判断原来是否有Tag
      FStream.Seek(0, soFromEnd);   // 没有-追加到文件尾 有-覆盖原来的
    FStream.WriteBuffer(Tag, SizeOf(Tag));
    Result := True;
  finally
    FStream.Free;
  end;
end;

function TID3Tag.RemoveTag: Boolean;
begin
  Result := False;
  try
    FStream := TFileStream.Create(FileName, fmOpenReadWrite
    or fmShareExclusive);
    FStream.Seek(-128, soFromEnd);
    FStream.ReadBuffer(Tag,sizeof(Tag));
    if StrLComp(Tag.FID, 'TAG', 3) = 0 then //若有Tag，除去
      FStream.Size := FStream.Size - 128;
    Result := True;
  finally
    FStream.Free;
  end;
end;

end.