無外部控件製作多媒體播放器（四）

音樂文件列表也是個不容忽視的問題，自己定個格式當然可以，但好在大家熟悉的M3U格式並不複雜，MediaPlayer或WinAmp都支持它，通用性也好，比起wpl要簡易得多，所以我就來介紹一下M3U格式文件的製作與讀寫

M3U是文本文件，以#EXTM3U開頭，每個音樂條目佔1-2行，當存在擴展信息時，首行採用#EXTINF:開頭，第二行纔是文件名；當沒有擴展信息時，只是簡單的一行，就是文件名；文件名可包含路徑，也可不包含，不包含時音樂文件應該是與M3U文件在同一目錄下。

整個格式就這麼簡單，下面是讀取函數，與保存函數，讀取時返回的是一個M3U集合，每個集合項目爲一首音樂信息的字符串，想獲取這個串的具體內容， 可用GetM3UInfo函數返回MusicInfo結構。

保存函數不太完善，需傳入一個M3U集合，因使用集合傳遞M3U字串信息，每個條目只能添加刪除，不能直接修改。若有興趣，可採取類封裝MusicInfo結構，並提供修改功能。

Private Function LoadM3UFile(strFileName As String) As Collection
    Dim a() As String, s1 As String, s As String, i As Long, FileLine() As String
    Dim blnAddOK As Boolean, strFilePath As String, colTemp As Collection, LineNum As Long
    On Error GoTo fail
    Set colTemp = New Collection
    If Dir(strFileName) = vbNullString Then GoTo fail
    strFilePath = Left$(strFileName, InStrRev(strFileName, "/"))
    Open strFileName For Binary As #1
        s = Input(LOF(1), 1)
    Close
    If s = vbNullString Then GoTo fail
    i = InStr(1, s, "#EXTM3U", vbTextCompare)
    If i = 0 Then GoTo fail
    If i > 1 Then s = Mid$(s, i)
    s = Trim$(Replace$(s, vbCrLf & vbCrLf, vbCrLf))
    FileLine = Split(s, vbCrLf)
        Do While LineNum <= UBound(FileLine)
            s = Trim$(FileLine(LineNum))
            If s <> vbNullString Then
                blnAddOK = False
                If UCase$(Left$(s, 8)) <> "#EXTINF:" Then
                    If InStr(1, s, ":/") = 0 Then
                        s = strFilePath & s
                        If Dir(s, vbNormal Or vbHidden Or vbReadOnly Or vbSystem Or vbArchive) <> vbNullString Then blnAddOK = True
                    Else
                        If Dir(s, vbNormal Or vbHidden Or vbReadOnly Or vbSystem Or vbArchive) <> vbNullString Then
                            blnAddOK = True
                        Else
                            s = strFilePath & Mid$(s, InStrRev(s, "/") + 1)
                            If Dir(s, vbNormal Or vbHidden Or vbReadOnly Or vbSystem Or vbArchive) <> vbNullString Then blnAddOK = True
                        End If
                    End If
                    If blnAddOK Then
                        If GetMCIType(s) > 0 Then
                            colTemp.Add s, s
                        End If
                    End If
                Else
                    s = Mid$(s, 9)
                    LineNum = LineNum + 1
                    s1 = Trim$(FileLine(LineNum))
                    If s1 <> vbNullString Then
                        If InStr(1, s1, ":/") = 0 Then
                            s1 = strFilePath & s1
                            If Dir(s1, vbNormal Or vbHidden Or vbReadOnly Or vbSystem Or vbArchive) <> vbNullString Then blnAddOK = True
                        Else
                            If Dir(s1, vbNormal Or vbHidden Or vbReadOnly Or vbSystem Or vbArchive) <> vbNullString Then
                                blnAddOK = True
                            Else
                                s1 = strFilePath & Mid$(s1, InStrRev(s1, "/") + 1)
                                If Dir(s1, vbNormal Or vbHidden Or vbReadOnly Or vbSystem Or vbArchive) <> vbNullString Then blnAddOK = True
                            End If
                        End If
                        If blnAddOK Then
                            If GetMCIType(s1) > 0 Then
                                colTemp.Add s & vbCrLf & s1, s1
                            End If
                        End If
                    End If
                End If
            End If
            LineNum = LineNum + 1
        Loop
fail:
    Set LoadM3UFile = colTemp
End Function
Private Function SaveM3U(strFileName As String, colM3UList As Collection) As Boolean
    Dim FreeNo As Long, i As Long, a() As String
    On Error GoTo fail
    If colM3UListe.Count > 0 Then
        FreeNo = FreeFile
        Open strFileName For Output As #FreeNo
        Print #FreeNo, "#EXTM3U"
        For i = 1 To colM3UListe.Count
        a = Split(colM3UListe(i), vbCrLf)
        If UBound(a) > 0 Then
            Print #FreeNo, "#EXTINF:" & colM3UListe(i)
        Else
            Print #FreeNo, colM3UListe(i)
        End If
        Next
        Close #FreeNo
        SaveM3U = True
    End If
fail:
End Function
Private Function GetM3UInfo(M3UItem As String) As MusicInfo
    Dim a() As String, b() As String, tmpinfo As MusicInfo
    Dim i As Long, j As Long, k As Long, s As String
    If Trim(M3UItem) = vbNullString Then Exit Function
    a = Split(M3UItem, vbCrLf)
    If UBound(a) > 0 Then
        j = InStr(1, a(0), ",")
        k = InStr(1, a(0), "-")
        If j > 0 And k > 0 Then
            b = Split(a(0), ",")
            If Val(b(0)) > 0 Then tmpinfo.length = Val(b(0))
            b = Split(Trim$(b(1)), "-")
            If b(0) <> vbNullString Then tmpinfo.Artist = Trim$(b(0))
            If b(1) <> vbNullString Then
                tmpinfo.Title = Trim$(b(1))
            Else
                s = Trim$(a(1))
                i = InStrRev(s, "/")
                If i > 0 Then
                    tmpinfo.Title = Mid$(s, i + 1)
                Else
                    tmpinfo.Title = s
                End If
            End If
        End If
        tmpinfo.FileName = a(1)
    Else
        tmpinfo.FileName = a(0)
    End If
    GetM3UInfo = tmpinfo
End Function

Private Sub Command1_Click()
    Dim tmp As Collection, tmpinfo As MusicInfo, s As String
    Set tmp = LoadM3UFile(Text1.Text)
    If tmp.Count > 0 Then
        tmpinfo = GetM3UInfo(tmp(tmp.Count))
        s = "文件：" & tmpinfo.FileName
        s = s & vbCrLf & "歌名：" & tmpinfo.Title
        s = s & vbCrLf & "歌手：" & tmpinfo.Artist
        s = s & vbCrLf & "曲長：" & tmpinfo.length & "秒"
        MsgBox s
    End If
End Sub

這是一個與上篇相聯繫的代碼，對於一些沒定義的函數，可在前面的文章中找到
http://blog.csdn.net/homezj/archive/2005/04/15/349005.aspx