{ *************************************************************************** }
{                                                                             }
{ Audio Tools Library (Freeware)                                              }
{ Class TID3v1 - for manipulating with ID3v1 tags                             }
{                                                                             }
{ Copyright (c) 2001,2002 by Jurgen Faul                                      }
{ E-mail: jfaul@gmx.de                                                        }
{ http://jfaul.de/atl                                                         }
{                                                                             }
{ Version 1.0 (25 July 2001)                                                  }
{   - Reading & writing support for ID3v1.x tags                              }
{   - Tag info: title, artist, album, track, year, genre, comment             }
{                                                                             }
{ *************************************************************************** }

unit ID3v1;

interface

uses
  Classes, SysUtils;

const
  MAX_MUSIC_GENRES = 148;                       { Max. number of music genres }
  DEFAULT_GENRE = 255;                              { Index for default genre }

  { Used with VersionID property }
  TAG_VERSION_1_0 = 1;                                { Index for ID3v1.0 tag }
  TAG_VERSION_1_1 = 2;                                { Index for ID3v1.1 tag }

var
  MusicGenre: array [0..MAX_MUSIC_GENRES - 1] of string;        { Genre names }

type
  { Used in TID3v1 class }
  String04 = string[4];                          { String with max. 4 symbols }
  String30 = string[30];                        { String with max. 30 symbols }

  { Class TID3v1 }
  TID3v1 = class(TObject)
    private
      { Private declarations }
      FExists: Boolean;
      FVersionID: Byte;
      FTitle: String30;
      FArtist: String30;
      FAlbum: String30;
      FYear: String04;
      FComment: String30;
      FTrack: Byte;
      FGenreID: Byte;
      procedure FSetTitle(const NewTitle: String30);
      procedure FSetArtist(const NewArtist: String30);
      procedure FSetAlbum(const NewAlbum: String30);
      procedure FSetYear(const NewYear: String04);
      procedure FSetComment(const NewComment: String30);
      procedure FSetTrack(const NewTrack: Byte);
      procedure FSetGenreID(const NewGenreID: Byte);
      function FGetGenre: string;
    public
      { Public declarations }
      constructor Create;                                     { Create object }
      procedure ResetData;                                   { Reset all data }
      function ReadFromFile(const FileName: string): Boolean;      { Load tag }
      function RemoveFromFile(const FileName: string): Boolean;  { Delete tag }
      function SaveToFile(const FileName: string): Boolean;        { Save tag }
      property Exists: Boolean read FExists;              { True if tag found }
      property VersionID: Byte read FVersionID;                { Version code }
      property Title: String30 read FTitle write FSetTitle;      { Song title }
      property Artist: String30 read FArtist write FSetArtist;  { Artist name }
      property Album: String30 read FAlbum write FSetAlbum;      { Album name }
      property Year: String04 read FYear write FSetYear;               { Year }
      property Comment: String30 read FComment write FSetComment;   { Comment }
      property Track: Byte read FTrack write FSetTrack;        { Track number }
      property GenreID: Byte read FGenreID write FSetGenreID;    { Genre code }
      property Genre: string read FGetGenre;                     { Genre name }
  end;

implementation

type
  { Real structure of ID3v1 tag }
  TagRecord = record
    Header: array [1..3] of Char;                { Tag header - must be "TAG" }
    Title: array [1..30] of Char;                                { Title data }
    Artist: array [1..30] of Char;                              { Artist data }
    Album: array [1..30] of Char;                                { Album data }
    Year: array [1..4] of Char;                                   { Year data }
    Comment: array [1..30] of Char;                            { Comment data }
    Genre: Byte;                                                 { Genre data }
  end;

{ ********************* Auxiliary functions & procedures ******************** }

function ReadTag(const FileName: string; var TagData: TagRecord): Boolean;
var
  SourceFile: file;
begin
  try
    Result := true;
    { Set read-access and open file }
    AssignFile(SourceFile, FileName);
    FileMode := 0;
    Reset(SourceFile, 1);
    { Read tag }
    Seek(SourceFile, FileSize(SourceFile) - 128);
    BlockRead(SourceFile, TagData, 128);
    CloseFile(SourceFile);
  except
    { Error }
    Result := false;
  end;
end;

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

function RemoveTag(const FileName: string): Boolean;
var
  SourceFile: file;
begin
  try
    Result := true;
    { Allow write-access and open file }
    FileSetAttr(FileName, 0);
    AssignFile(SourceFile, FileName);
    FileMode := 2;
    Reset(SourceFile, 1);
    { Delete tag }
    Seek(SourceFile, FileSize(SourceFile) - 128);
    Truncate(SourceFile);
    CloseFile(SourceFile);
  except
    { Error }
    Result := false;
  end;
end;

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

function SaveTag(const FileName: string; TagData: TagRecord): Boolean;
var
  SourceFile: file;
begin
  try
    Result := true;
    { Allow write-access and open file }
    FileSetAttr(FileName, 0);
    AssignFile(SourceFile, FileName);
    FileMode := 2;
    Reset(SourceFile, 1);
    { Write tag }
    Seek(SourceFile, FileSize(SourceFile));
    BlockWrite(SourceFile, TagData, SizeOf(TagData));
    CloseFile(SourceFile);
  except
    { Error }
    Result := false;
  end;
end;

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

function GetTagVersion(const TagData: TagRecord): Byte;
begin
  Result := TAG_VERSION_1_0;
  { Terms for ID3v1.1 }
  if ((TagData.Comment[29] = #0) and (TagData.Comment[30] <> #0)) or
    ((TagData.Comment[29] = #32) and (TagData.Comment[30] <> #32)) then
    Result := TAG_VERSION_1_1;
end;

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

procedure TID3v1.FSetTitle(const NewTitle: String30);
begin
  FTitle := TrimRight(NewTitle);
end;

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

procedure TID3v1.FSetArtist(const NewArtist: String30);
begin
  FArtist := TrimRight(NewArtist);
end;

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

procedure TID3v1.FSetAlbum(const NewAlbum: String30);
begin
  FAlbum := TrimRight(NewAlbum);
end;

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

procedure TID3v1.FSetYear(const NewYear: String04);
begin
  FYear := TrimRight(NewYear);
end;

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

procedure TID3v1.FSetComment(const NewComment: String30);
begin
  FComment := TrimRight(NewComment);
end;

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

procedure TID3v1.FSetTrack(const NewTrack: Byte);
begin
  FTrack := NewTrack;
end;

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

procedure TID3v1.FSetGenreID(const NewGenreID: Byte);
begin
  FGenreID := NewGenreID;
end;

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

function TID3v1.FGetGenre: string;
begin
  Result := '';
  { Return an empty string if the current GenreID is not valid }
  if FGenreID in [0..MAX_MUSIC_GENRES - 1] then Result := MusicGenre[FGenreID];
end;

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

constructor TID3v1.Create;
begin
  inherited;
  ResetData;
end;

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