/*!
@file	Classes/System/Text/UTF8Encoding.ab
@brief	UTF8Encodingクラスとそれに関係するクラスなどの宣言・定義
*/

Namespace System
Namespace Text

Namespace Detail

Class UTF8Encoder
	Inherits Encoder
Protected
	Override Sub EncodeImpl(src As *WCHAR, size As SIZE_T, s As IO.Stream, last As Boolean)
		Dim i As Long
		For i = 0 To ELM(size)
			If buffer <> 0 Then
				If _System_IsLowSurrogate(src[i]) Then
					'UTF-16列からUnicodeコードポイントを復元
					Dim c = (((buffer And &h3FF) As DWord << 10) Or (src[i] And &h3FF)) + &h10000
					'4バイト変換
					s.WriteByte(((c >> 18) Or &hf0) As Byte)
					s.WriteByte(((c >> 12) And &h3F Or &h80) As Byte)
					s.WriteByte(((c >> 6) And &h3F Or &h80) As Byte)
					s.WriteByte((c And &h3F Or &h80) As Byte)
				Else
					writeReplacementChar(s)
				End If
				buffer = 0
			ElseIf src[i] < &h80 Then
				'1バイト変換
				s.WriteByte(src[i] As Byte)
			ElseIf src[i] < &h800 Then
				'2バイト変換
				s.WriteByte(((src[i] >> 6) Or &hC0) As Byte)
				s.WriteByte((src[i] And &h3F Or &h80) As Byte)
			ElseIf _System_IsHighSurrogate(src[i]) Then
				'バッファに貯め込む
				buffer = src[i]
			ElseIf _System_IsLowSurrogate(src[i]) Then
				writeReplacementChar(s)
			Else
				'3バイト変換
				s.WriteByte(((src[i] >> 12) Or &hE0) As Byte)
				s.WriteByte(((src[i] >> 6) And &h3F Or &h80) As Byte)
				s.WriteByte((src[i] And &h3F Or &h80) As Byte)
			End If
		Next
	End Sub

Private
	' U+FFFD Replacement CharacterのUTF-8表現、EF BF BDを書き込む。
	Sub writeReplacementChar(s As IO.Stream)
		Dim rc[2] = [&hef, &hbf, &hbd] As Byte
		s.Write(rc, 0, Len(rc))
	End Sub

	buffer As WCHAR
End Class

Class UTF8Decoder
	Inherits Decoder
Protected
	Override Function DecodeImpl(dst As Collections.Generic.List<WCHAR>, s As IO.Stream) As Boolean
		Dim i As Long
		For i = 0 To DefalultDecodingBufferSize - 1 'ELM
			Dim b = s.ReadByte()
			If b = -1 Then
				DecodeImpl = False
				Exit Function
			ElseIf state = 0 Then
				If b <= &h80 Then
					'1バイト変換
					dst.Add(b As WCHAR)
				ElseIf b < &hC0 Then
					'先頭バイトがなく、いきなりマルチバイトの2バイト目以降
					dst.Add(&hFFFD As WCHAR)
				ElseIf b < &hD0 Then
					'2バイト文字の始まり
					last = 2
					buffer = b And &h3F
					state++
				ElseIf b < &hF0 Then
					'3バイト文字の始まり
					last = 3
					buffer = b And &h1F
					state++
				ElseIf b < &hF8 Then
					'4バイト文字の始まり
					last = 4
					buffer = b And &h0F
					state++
				Else
					'現在のUTF-8は4バイトを超える表現を認めていない。
					dst.Add(&hFFFD As WCHAR)
				End If
			Else
				If &h80 <= b And b < &hC0 Then
					'マルチバイト文字の2バイト目以降
					buffer <<= 6
					buffer Or= b And &h3F
					state++
					If state = last Then '最終バイトに到達
						If state = 2 And buffer >= &h80 Then
							dst.Add(buffer As WCHAR)
						ElseIf state = 3 And buffer >= &h800 And buffer < &hD800 And &hE0000 >= buffer Then
							dst.Add(buffer As WCHAR)
						ElseIf state = 4 And buffer <= &h10FFFF Then
							buffer -= &h10000
							dst.Add((&hD800 Or (buffer >> 10)) As WCHAR)
							dst.Add((&hDC00 Or (buffer And &h3FF)) As WCHAR)
						Else
							'最短形式でないもの、または4バイト形式で10FFFFを超えるコードポイントのもの
							dst.Add(&hfffd As WCHAR)
						End If
						state = 0
					End If
				Else
					'マルチバイト文字の途中なのに、それ以外のバイトが現れた場合
					dst.Add(&hFFFD As WCHAR)
					state = 0
				End If
			End If
		Next
		DecodeImpl = True
	End Function

Private
	buffer As DWord
	state As Long
	last As Long
End Class

End Namespace 'Detail


/*!
@brief UTF-8用のEncoding
@date 2007/12/21
@auther Egtra
*/
Class UTF8Encoding
	Inherits Encoding
Public
	Override Function Clone() As Object
		Clone = New UTF8Encoding
	End Function

	Override Function GetDecoder() As Decoder
		GetDecoder = New Detail.UTF8Decoder
	End Function

	Override Function GetEncoder() As Encoder
		GetEncoder = New Detail.UTF8Encoder
	End Function

	Override Function GetMaxByteCount(charCount As Long) As Long
		GetMaxByteCount = charCount * 3
		'全てがUTF-8で3バイトになる文字の場合が最大。

		'なお、UTF-8で4バイトになる列は、UTF-16だとサロゲートペアで表現するので、
		'1単位あたりでは2バイトしか食わないことになり、最大ではない。
	End Function

	Override Function GetMaxCharCount(byteCount As Long) As Long
		'全てU+7F以下の文字だけだった場合
		GetMaxCharCount = byteCount
	End Function

	Override Function GetPreamble() As *Byte
		Return bom
	End Function

	Override Function GetPreambleLength() As Long
		Return Len(bom)
	End Function
/*
	Override Function BodyName() As String
		Return "utf-8"
	End Function

	Override Function HeaderName() As String
		Return "utf-8"
	End Function

	Override Function EncodingName() As String
		Return "UTF-8"
	End Function

	Override Function WebName() As String
		Return "utf-8"
	End Function

	Override Function IsSingleByte() As Boolean
		Return False
	End Function
*/

Private
	Static bom[2] = [&hEF, &hBB, &hBF] As Byte
End Class

End Namespace 'Text
End Namespace 'System