C# と VB.NET の質問掲示板

■クラス別に構造体を定義した例
�@1つのサイズの大きい固定文字列が定義されている構造体(A1)から複数の構造体(B1,B2,B3…Bn)にコピーする手法
�A複数の構造体(B1,B2,B3…Bn)から1つのサイズの大きい固定文字列が定義されている構造体(A1)にコピーする手法
※複数の構造体には、複数の固定文字列が定義されています。

Public Class ClassA
    Inherits Class1
    Public MAXLENGTH As Integer = 17

    Public Sub New()
        MyBase.New(2, 3, 5, 7)
    End Sub

    Public Property aaaa() As String
        Get
            Return MyBase.Value(0)
        End Get
        Set(ByVal value As String)
            MyBase.Value(0) = value
        End Set
    End Property

    Public Property bbbb() As String
        Get
            Return MyBase.Value(1)
        End Get
        Set(ByVal value As String)
            MyBase.Value(1) = value
        End Set
    End Property

    Public Property cccc() As String
        Get
            Return MyBase.Value(2)
        End Get
        Set(ByVal value As String)
            MyBase.Value(2) = value
        End Set
    End Property

    Public Property dddd() As String
        Get
            Return MyBase.Value(3)
        End Get
        Set(ByVal value As String)
            MyBase.Value(3) = value
        End Set
    End Property

End Class

Public Class ClassB
    Inherits Class1

    Public Sub New()
        MyBase.New(100)
    End Sub

    Public Property strB() As String
        Get
            Return MyBase.Value(0)
        End Get
        Set(ByVal value As String)
            MyBase.Value(0) = value
        End Set
    End Property

End Class

Public Class ClassC
    Inherits Class1
    Public MAXLENGTH As Integer = 5

    Public Sub New()
        MyBase.New(2, 3)
    End Sub

    Public Property aaaa() As String
        Get
            Return MyBase.Value(0)
        End Get
        Set(ByVal value As String)
            MyBase.Value(0) = value
        End Set
    End Property

    Public Property bbbb() As String
        Get
            Return MyBase.Value(1)
        End Get
        Set(ByVal value As String)
            MyBase.Value(1) = value
        End Set
    End Property

End Class

Public Class ClassD
    Inherits Class1
    Public MAXLENGTH As Integer = 2

    Public Sub New()
        MyBase.New(2)
    End Sub

    Public Property aaaa() As String
        Get
            Return MyBase.Value(0)
        End Get
        Set(ByVal value As String)
            MyBase.Value(0) = value
        End Set
    End Property

End Class

Public Class Class1
    Private _InnerValue As String
    Private _FieldStarts() As Integer
    Private _FieldLengths() As Integer

    Public Sub New(ByVal ParamArray FieldLengthS() As Integer)
        Dim TotalSize As Integer = 0
        Dim FieldLength As Integer
        Dim Pos As Integer = 0
        Dim Idx As Integer = 0

        _FieldStarts = New Integer(FieldLengthS.Length) {}
        _FieldStarts(Idx) = Pos
        For Each FieldLength In FieldLengthS
            TotalSize += FieldLength
            Idx += 1
            Pos += FieldLength
            _FieldStarts(Idx) = Pos
        Next
        _FieldLengths = FieldLengthS
        _InnerValue = New String(" "c, TotalSize)
    End Sub

    Protected Property InnerValue(ByVal start As Integer) As String
        Get
            Return _InnerValue
        End Get
        Set(ByVal value As String)
            Dim NewValueLength = value.Length
            Dim MyValueLength = _InnerValue.Length
            Select Case NewValueLength
                Case Is < MyValueLength
                    If Trim(_InnerValue) <> "" Then
                        _InnerValue = _InnerValue.Substring(0, start) & value & New String(" "c, MyValueLength - (Trim(_InnerValue).Length + NewValueLength))
                    Else
                        _InnerValue = value & New String(" "c, MyValueLength - NewValueLength)
                    End If
                Case MyValueLength
                    _InnerValue = value
                Case Else
                    If Trim(_InnerValue) <> "" Then
                        _InnerValue = Trim(_InnerValue) & value.Substring(start, MyValueLength)
                    Else
                        _InnerValue = value.Substring(start, MyValueLength)
                    End If
            End Select
        End Set
    End Property

    Public Property Value(ByVal Index As Integer) As String
        Get
            Dim FieldStart As Integer = _FieldStarts(Index)
            Dim FieldLength As Integer = _FieldLengths(Index)

            Return _InnerValue.Substring(FieldStart, FieldLength)
        End Get
        Set(ByVal value As String)
            Dim FieldStart As Integer = _FieldStarts(Index)
            Dim FieldLength As Integer = _FieldLengths(Index)

            Dim NewValue As New System.Text.StringBuilder
            '設定する部分の前
            If FieldStart > 1 Then
                NewValue.Append(_InnerValue.Substring(0, FieldStart))
            End If
            '設定する文字列
            Select Case value.Length
                Case Is < FieldLength
                    NewValue.Append(value.PadRight(FieldLength, " "c))
                Case FieldLength
                    NewValue.Append(value)
                Case Else
                    NewValue.Append(value.Substring(0, FieldLength))
            End Select
            '設定する部分の後ろ
            If _InnerValue.Length > FieldStart + FieldLength + 1 Then
                NewValue.Append(_InnerValue.Substring(FieldStart + FieldLength))
            End If
            _InnerValue = NewValue.ToString
        End Set
    End Property

    Public Sub Copy(ByVal Dest As Class1, Optional ByVal start As Integer = 0)
        Dest.InnerValue(start) = Me.InnerValue(start)
    End Sub

End Class


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim clsA As New ClassA
        Dim clsB As New ClassB
        Dim clsC As New ClassC
        Dim clsD As New ClassD

        '各構造体の内容をメインとなる構造体にコピー
        clsA.aaaa = "1"
        clsA.bbbb = "a1"
        clsA.cccc = "a123"
        clsA.dddd = "ああいう"
        clsC.aaaa = "2"
        clsC.bbbb = "c2"
        clsD.aaaa = "3"
        clsA.Copy(clsB)
        clsC.Copy(clsB, clsA.MAXLENGTH)
        clsD.Copy(clsB, clsA.MAXLENGTH + clsC.MAXLENGTH)

        'メインとなる構造体の内容を各構造体にコピー
        clsA = New ClassA
        clsC = New ClassC
        clsD = New ClassD
        clsB.Copy(clsA, 0)
        clsB.Copy(clsC, clsA.MAXLENGTH)
        clsB.Copy(clsD, clsA.MAXLENGTH + clsC.MAXLENGTH)

    End Sub

開始位置のパラメータを追加した別建てのメソッドを作成しました。
以下のような感じでしょうか。

＃前述の話題ですが、Midだから+1ですよね。substringでしたら0スタートなので+1の心配はしなくてよいということをすっかり失念してました。


        Dim a5 As AAA = StructureFromText(Of AAA)(strW)
        Dim b5 As BBB = StructureFromText(Of BBB)(strW, Len(a5))


    '指定された文字列を、VBFixedString 属性の付いたフィールドに順次格納した値を返します。
    Public Function StructureFromText(Of T As Structure)(ByVal str As String, ByVal intStart As Integer) As T
        'RuntimeHelpers.GetObjectValue 対策の為、ValueType で受ける
        Dim newValue As ValueType = StructureFromText
        Dim pos As Integer = 1
        For Each f As FieldInfo In newValue.GetType().GetFields()
            Dim attributes() As Object = f.GetCustomAttributes(GetType(VBFixedStringAttribute), False)
            If attributes.Length <> 0 Then
                Dim attr As VBFixedStringAttribute = DirectCast(attributes(0), VBFixedStringAttribute)
                Dim value As String = Strings.Mid(str & StrDup(attr.Length, " "c), intStart + pos, attr.Length)
                f.SetValue(newValue, value)
                pos += attr.Length
            End If
        Next
        Return DirectCast(newValue, T)
    End Function