source: trunk/ab5.0/ablib/src/Classes/System/IO/StreamReader.ab@ 605

'Classes/System/IO/StreamReader.ab

Namespace System
Namespace IO

/*
@brief ストリームから読み取りを行うTextReaderの実装。
@date 2008/02/25
@auther Egtra
*/
Class StreamReader
    Inherits TextReader
Public
    /*
    @date 2008/02/25
    @auther Egtra
    */
    Sub StreamReader(path As String)
        init(New FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read))
    End Sub

    /*
    @date 2008/02/25
    @auther Egtra
    */
    Sub StreamReader(stream As Stream)
        init(stream)
    End Sub

    /*
    @date 2008/02/25
    @auther Egtra
    */
    Override Function Peek() As Long
        If cur = last Then
            last = s.Read(buf As *Byte, 0, size)
            cur = 0
            If last = 0 Then
                Peek = -1
                Exit Function
            End If
        End If
        Peek = buf[cur]
    End Function

    /*
    @date 2008/02/25
    @auther Egtra
    */
    Override Function Read() As Long
        Read = Peek()
        If Read <> -1 Then
            cur++
        End If
    End Function

    /*
    @date 2008/02/26
    @auther Egtra
    */
    Override Function ReadToEnd() As String
        Dim sb = New Text.StringBuilder(65536)
        sb.Append(buf, cur, last - cur)
        Do
            Dim read = Read(buf, 0, size)
            sb.Append(buf, 0, read)
            If read < size Then
                ReadToEnd = sb.ToString
                Exit Function
            End If
        Loop
    End Function

Protected
    /*
    @date 2008/02/25
    @auther Egtra
    */
    Override Sub Dispose(disposing As Boolean)
        If disposing Then
            If Not ActiveBasic.IsNothing(s) Then
                s.Dispose(True)
            End If
        End If
        s = Nothing
        size = 0
        cur = 0
        last = 0
    End Sub

    /*
    @date 2008/02/25
    @auther Egtra
    */
    Override Function ReadImpl(buffer As *Char, index As Long, count As Long) As Long
        Dim n = last - cur
        If count <= n Then
            ReadImpl = ReadFromBuffer(buffer, index, count)
            Exit Function
        End If
        Dim p = VarPtr(buffer[index])
        ReadImpl = ReadFromBuffer(p, 0, n)
        If ReadImpl = count Then 'バッファの中身で足りた場合
            Exit Function
        End If
        p = VarPtr(p[n])
        count -= n
        If count > size Then
            n = (count \ size) * size 'sizeの倍数分だけは直接bufferへ読み込ませる
            Dim read = s.Read(p As *Byte, 0, n)
            If read = 0 Then 'EOF
                Exit Function
            End If
            p = VarPtr(p[n])
            ReadImpl += n
            count -= n
        End If
        last = s.Read(buffer As *Byte, 0, size)
        cur = 0
        If last = 0 Then 'EOF
            Exit Function
        End If
        ReadImpl += ReadFromBuffer(p, 0, Math.Min(last, count))
    End Function

Private
    /*
    @date 2008/02/25
    @auther Egtra
    */
    Sub init(str As Stream)
        s = str
        size = 4096
        last = 0
        cur = 0
        buf = GC_malloc(size)
    End Sub

    /**
    @brief バッファの中身から読み取る。
    @date 2008/02/25
    @auther Egtra
    文字数が足りなくても、元のストリームまで読みには行かない。
    */
    Function ReadFromBuffer(p As *Char, index As Long, count As Long) As Long
        memcpy(VarPtr(p[index]), VarPtr(buf[cur]), count * SizeOf (Char))
        cur += count
        ReadFromBuffer = count
    End Function

    s As Stream
    size As Long
    cur As Long
    last As Long '中身の終わり
    buf As *SByte '暫定
End Class

End Namespace
End Namespace