id3v2.pas

Lossless Audio 缩解压 window

end;

{ --------------------------------------------------------------------------- }

function ExtractGenre(const GenreString: string): string;
begin
  { Extract genre from string }
  Result := Trim(GenreString);
  if Pos(')', Result) > 0 then Delete(Result, 1, LastDelimiter(')', Result));
end;

{ --------------------------------------------------------------------------- }

function ExtractComment(const CommentString: string): string;
var
  Comment: string;
begin
  { Extract comment from string }
  Comment := CommentString;
  Delete(Comment, 1, 4);
  Delete(Comment, 1, Pos(#0, Comment));
  Result := Trim(Comment);
end;

{ --------------------------------------------------------------------------- }

function ExtractLink(const LinkString: string): string;
var
  Link: string;
begin
  { Extract URL link from string }
  Link := LinkString;
  Delete(Link, 1, 1);
  Delete(Link, 1, Pos(#0, Link));
  Result := Trim(Link);
end;

{ --------------------------------------------------------------------------- }

procedure BuildHeader(var Tag: TagInfo);
var
  Iterator, TagSize: Integer;
begin
  { Build tag header }
  Tag.ID := ID3V2_ID;
  Tag.Version := TAG_VERSION_2_3;
  Tag.Revision := 0;
  Tag.Flags := 0;
  TagSize := 0;
  for Iterator := 1 to ID3V2_FRAME_COUNT do
    if Tag.Frame[Iterator] <> '' then
      Inc(TagSize, Length(Tag.Frame[Iterator]) + 11);
  { Convert tag size }
  Tag.Size[1] := TagSize div $200000;
  Tag.Size[2] := TagSize div $4000;
  Tag.Size[3] := TagSize div $80;
  Tag.Size[4] := TagSize mod $80;
end;

{ --------------------------------------------------------------------------- }

function RebuildFile(const FileName: string; TagData: TStream): Boolean;
var
  Tag: TagInfo;
  Source, Destination: TFileStream;
  BufferName: string;
begin
  { Rebuild file with old file data and new tag data (optional) }
  Result := false;
  if (not FileExists(FileName)) or (FileSetAttr(FileName, 0) <> 0) then exit;
  if not ReadHeader(FileName, Tag) then exit;
  if (TagData = nil) and (Tag.ID <> ID3V2_ID) then exit;
  try
    { Create file streams }
    BufferName := FileName + '~';
    Source := TFileStream.Create(FileName, fmOpenRead or fmShareExclusive);
    Destination := TFileStream.Create(BufferName, fmCreate);
    { Copy data blocks }
    if Tag.ID = ID3V2_ID then Source.Seek(GetTagSize(Tag), soFromBeginning);
    if TagData <> nil then Destination.CopyFrom(TagData, 0);
    Destination.CopyFrom(Source, Source.Size - Source.Position);
    { Free resources }
    Source.Free;
    Destination.Free;
    { Replace old file and delete temporary file }
    if (DeleteFile(FileName)) and (RenameFile(BufferName, FileName)) then
      Result := true
    else
      raise Exception.Create('');
  except
    { Access error }
    if FileExists(BufferName) then DeleteFile(BufferName);
  end;
end;

{ --------------------------------------------------------------------------- }

function SaveTag(const FileName: string; Tag: TagInfo): Boolean;
var
  TagData: TStringStream;
  Iterator, FrameSize: Integer;
begin
  { Build and write tag header and frames to stream }
  TagData := TStringStream.Create('');
  BuildHeader(Tag);
  TagData.Write(Tag, 10);
  for Iterator := 1 to ID3V2_FRAME_COUNT do
    if Tag.Frame[Iterator] <> '' then
    begin
      TagData.WriteString(ID3V2_FRAME_NEW[Iterator]);
      FrameSize := Swap32(Length(Tag.Frame[Iterator]) + 1);
      TagData.Write(FrameSize, SizeOf(FrameSize));
      TagData.WriteString(#0#0#0 + Tag.Frame[Iterator]);
    end;
  { Rebuild file with new tag data }
  Result := RebuildFile(FileName, TagData);
  TagData.Free;
end;

{ ********************** Private functions & procedures ********************* }

procedure TID3v2.FSetTitle(const NewTitle: string);
begin
  { Set song title }
  FTitle := Trim(NewTitle);
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.FSetArtist(const NewArtist: string);
begin
  { Set artist name }
  FArtist := Trim(NewArtist);
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.FSetAlbum(const NewAlbum: string);
begin
  { Set album title }
  FAlbum := Trim(NewAlbum);
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.FSetTrack(const NewTrack: Byte);
begin
  { Set track number }
  FTrack := NewTrack;
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.FSetYear(const NewYear: string);
begin
  { Set release year }
  FYear := Trim(NewYear);
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.FSetGenre(const NewGenre: string);
begin
  { Set genre name }
  FGenre := Trim(NewGenre);
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.FSetComment(const NewComment: string);
begin
  { Set comment }
  FComment := Trim(NewComment);
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.FSetComposer(const NewComposer: string);
begin
  { Set composer name }
  FComposer := Trim(NewComposer);
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.FSetEncoder(const NewEncoder: string);
begin
  { Set encoder name }
  FEncoder := Trim(NewEncoder);
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.FSetCopyright(const NewCopyright: string);
begin
  { Set copyright information }
  FCopyright := Trim(NewCopyright);
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.FSetLanguage(const NewLanguage: string);
begin
  { Set language }
  FLanguage := Trim(NewLanguage);
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.FSetLink(const NewLink: string);
begin
  { Set URL link }
  FLink := Trim(NewLink);
end;

{ ********************** Public functions & procedures ********************** }

constructor TID3v2.Create;
begin
  { Create object }
  inherited;
  ResetData;
end;

{ --------------------------------------------------------------------------- }

procedure TID3v2.ResetData;
begin
  { Reset all variables }
  FExists := false;
  FVersionID := 0;
  FSize := 0;
  FTitle := '';
  FArtist := '';
  FAlbum := '';
  FTrack := 0;
  FYear := '';
  FGenre := '';
  FComment := '';
  FComposer := '';
  FEncoder := '';
  FCopyright := '';
  FLanguage := '';
  FLink := '';
end;

{ --------------------------------------------------------------------------- }

function TID3v2.ReadFromFile(const FileName: string): Boolean;
var
  Tag: TagInfo;
begin
  { Reset data and load header from file to variable }
  ResetData;
  Result := ReadHeader(FileName, Tag);
  { Process data if loaded and header valid }
  if (Result) and (Tag.ID = ID3V2_ID) then
  begin
    FExists := true;
    { Fill properties with header data }
    FVersionID := Tag.Version;
    FSize := GetTagSize(Tag);
    { Get information from frames if version supported }
    if (FVersionID in [TAG_VERSION_2_2..TAG_VERSION_2_4]) and (FSize > 0) then
    begin
      if FVersionID > TAG_VERSION_2_2 then ReadFramesNew(FileName, Tag)
      else ReadFramesOld(FileName, Tag);
      FTitle := GetContent(Tag.Frame[1], Tag.Frame[15]);
      FArtist := GetContent(Tag.Frame[2], Tag.Frame[14]);
      FAlbum := GetContent(Tag.Frame[3], Tag.Frame[16]);
      FTrack := ExtractTrack(Tag.Frame[4]);
      FYear := ExtractYear(Tag.Frame[5], Tag.Frame[13]);
      FGenre := ExtractGenre(Tag.Frame[6]);
      FComment := ExtractComment(Tag.Frame[7]);
      FComposer := Trim(Tag.Frame[8]);
      FEncoder := Trim(Tag.Frame[9]);
      FCopyright := Trim(Tag.Frame[10]);
      FLanguage := Trim(Tag.Frame[11]);
      FLink := ExtractLink(Tag.Frame[12]);
    end;
  end;
end;

{ --------------------------------------------------------------------------- }

function TID3v2.SaveToFile(const FileName: string): Boolean;
var
  Tag: TagInfo;
begin
  { Prepare tag data and save to file }
  FillChar(Tag, SizeOf(Tag), 0);
  Tag.Frame[1] := FTitle;
  Tag.Frame[2] := FArtist;
  Tag.Frame[3] := FAlbum;
  if FTrack > 0 then Tag.Frame[4] := IntToStr(FTrack);
  Tag.Frame[5] := FYear;
  Tag.Frame[6] := FGenre;
  if FComment <> '' then Tag.Frame[7] := 'eng' + #0 + FComment;
  Tag.Frame[8] := FComposer;
  Tag.Frame[9] := FEncoder;
  Tag.Frame[10] := FCopyright;
  Tag.Frame[11] := FLanguage;
  if FLink <> '' then Tag.Frame[12] := #0 + FLink;
  Result := SaveTag(FileName, Tag);
end;

{ --------------------------------------------------------------------------- }

function TID3v2.RemoveFromFile(const FileName: string): Boolean;
begin
  { Remove tag from file }
  Result := RebuildFile(FileName, nil);
end;

end.