'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

Public
	/*
	@brief 基になるストリームを取得する
	@date 2008/09/02
	@auther NoWest
	*/
	Function BaseStream () As Stream
		Return s
	End Function

	/*
	@date 2008/02/25
	@auther Egtra
	*/
	Override Function Peek() As Long
		If charSize = charCur Then
			fillCharBuf()
			If charSize = charCur Then
				Peek = -1
				Exit Function
			End If
		End If
		Peek = charBuf[charCur]
	End Function

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

	/*
	@date 2008/02/25
	@auther Egtra
	*/
	Override Function ReadImpl(buffer As *WCHAR, count As Long) As Long
		Dim n = charSize - charCur '現在のバッファに溜まっている文字数
		If count <= n And charEof <> False Then
			ReadImpl = readFromBuffer(buffer, count)
			Exit Function
		End If
		ReadImpl = readFromBuffer(buffer, n)
		If ReadImpl = count Then 'バッファの中身で足りた場合
			Exit Function
		End If
		fillCharBuf()
		ReadImpl += ReadImpl(VarPtr(buffer[n]), count - n)
	End Function

Private
	/*
	@date 2008/02/25
	@auther Egtra
	*/
	Sub init(str As Stream)
		s = str
		'暫定。正式版ではUTF-8を標準とする。
		encoding = New Text.Detail.WindowsCodePageEncoding(CP_ACP)
		decoder = encoding.GetDecoder()
		charCapacity = 4096
		byteCapacity = 4096
		charBuf = GC_malloc(charCapacity * SizeOf(WCHAR))
		byteBuf = GC_malloc(byteCapacity)
		charCur = 0
		byteCur = 0
		charSize = 0
		byteSize = 0
		charEof = False
		byteEof = False
	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 *WCHAR, count As Long) As Long
		memcpy(p, VarPtr(charBuf[charCur]), count * SizeOf (WCHAR))
		charCur += count
		readFromBuffer = count
	End Function

	/*!
	@brief byteBufを基にcharBufを埋める。charBufが空になったときに用いる。
	@date 2008/11/08
	@auther Egtra
	*/
	Sub fillCharBuf()
		charCur = 0
		charSize = 0
		If charEof = False Then
			If byteCur = byteSize Then
				byteSize = s.Read(byteBuf, 0, byteCapacity)
				byteCur = 0
				If byteSize = 0 Then
					byteEof = True
				End If
			End If
			Dim charUsed As Long
			Dim byteUsed As Long
			Dim completed As Boolean
			decoder.Convert(VarPtr(byteBuf[byteCur]), byteSize - byteCur,
				VarPtr(charBuf[charSize]), charCapacity - charSize,
				byteEof, charUsed, byteUsed, completed)
			charEof = byteEof And completed And byteCur = byteSize
			byteCur += byteUsed
			charSize += charUsed
		End If
	End Sub

	s As Stream
	encoding As Text.Encoding
	decoder As Text.Decoder
	charBuf As *WCHAR
	byteBuf As *Byte
	charCur As Long '読み取っていないデータの開始位置
	byteCur As Long
	charSize As Long 'Bufの内、有効なデータの数
	byteSize As Long
	charCapacity As Long '確保済み容量 = GC_mallocしたときの引数の値
	byteCapacity As Long
	charEof As Boolean 'Trueのとき、次にcur = sizeになるまでしかデータがことを示す
	byteEof As Boolean
	'常に0 <= cur <= size <= capacity
End Class

End Namespace
End Namespace