Darwinism/Google.Protobuf/Stream/LimitedInputStream.vb

#Region "Microsoft.VisualBasic::eeea47d5ebf98bf06d4ed5ef36bc7c84, Google.Protobuf\Stream\LimitedInputStream.vb"

    ' Author:
    ' 
    '       asuka (amethyst.asuka@gcmodeller.org)
    '       xie (genetics@smrucc.org)
    '       xieguigang (xie.guigang@live.com)
    ' 
    ' Copyright (c) 2018 GPL3 Licensed
    ' 
    ' 
    ' GNU GENERAL PUBLIC LICENSE (GPL3)
    ' 
    ' 
    ' This program is free software: you can redistribute it and/or modify
    ' it under the terms of the GNU General Public License as published by
    ' the Free Software Foundation, either version 3 of the License, or
    ' (at your option) any later version.
    ' 
    ' This program is distributed in the hope that it will be useful,
    ' but WITHOUT ANY WARRANTY; without even the implied warranty of
    ' MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ' GNU General Public License for more details.
    ' 
    ' You should have received a copy of the GNU General Public License
    ' along with this program. If not, see <http://www.gnu.org/licenses/>.



    ' /********************************************************************************/

    ' Summaries:

    '     Class LimitedInputStream
    ' 
    '         Properties: CanRead, CanSeek, CanWrite, Length, Position
    ' 
    '         Constructor: (+1 Overloads) Sub New
    ' 
    '         Function: Read, Seek
    ' 
    '         Sub: Flush, SetLength, Write
    ' 
    ' 
    ' /********************************************************************************/

#End Region

#Region "Copyright notice and license"
' Protocol Buffers - Google's data interchange format
' Copyright 2015 Google Inc.  All rights reserved.
' https://developers.google.com/protocol-buffers/
'
' Redistribution and use in source and binary forms, with or without
' modification, are permitted provided that the following conditions are
' met:
'
'     * Redistributions of source code must retain the above copyright
' notice, this list of conditions and the following disclaimer.
'     * Redistributions in binary form must reproduce the above
' copyright notice, this list of conditions and the following disclaimer
' in the documentation and/or other materials provided with the
' distribution.
'     * Neither the name of Google Inc. nor the names of its
' contributors may be used to endorse or promote products derived from
' this software without specific prior written permission.
'
' THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
' "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
' LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
' A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
' OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
' SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
' LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
' DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
' THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
' (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
' OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#End Region

Imports System
Imports System.IO

Namespace Google.Protobuf
    ''' <summary>
    ''' Stream implementation which proxies another stream, only allowing a certain amount
    ''' of data to be read. Note that this is only used to read delimited streams, so it
    ''' doesn't attempt to implement everything.
    ''' </summary>
    Friend NotInheritable Class LimitedInputStream
        Inherits Stream

        Private ReadOnly proxied As Stream
        Private bytesLeft As Integer

        Friend Sub New(proxied As Stream, size As Integer)
            Me.proxied = proxied
            bytesLeft = size
        End Sub

        Public Overrides ReadOnly Property CanRead As Boolean
            Get
                Return True
            End Get
        End Property

        Public Overrides ReadOnly Property CanSeek As Boolean
            Get
                Return False
            End Get
        End Property

        Public Overrides ReadOnly Property CanWrite As Boolean
            Get
                Return False
            End Get
        End Property

        Public Overrides Sub Flush()
        End Sub

        Public Overrides ReadOnly Property Length As Long
            Get
                Throw New NotSupportedException()
            End Get
        End Property

        Public Overrides Property Position As Long
            Get
                Throw New NotSupportedException()
            End Get
            Set(value As Long)
                Throw New NotSupportedException()
            End Set
        End Property

        Public Overrides Function Read(buffer As Byte(), offset As Integer, count As Integer) As Integer
            If bytesLeft > 0 Then
                Dim bytesRead = proxied.Read(buffer, offset, Math.Min(bytesLeft, count))
                bytesLeft -= bytesRead
                Return bytesRead
            End If

            Return 0
        End Function

        Public Overrides Function Seek(offset As Long, origin As SeekOrigin) As Long
            Throw New NotSupportedException()
        End Function

        Public Overrides Sub SetLength(value As Long)
            Throw New NotSupportedException()
        End Sub

        Public Overrides Sub Write(buffer As Byte(), offset As Integer, count As Integer)
            Throw New NotSupportedException()
        End Sub
    End Class
End Namespace