'==========================================================
'                    SMS,EMS Decoder
'                      2004-9-24
'1.Description
'   This class decode a SMS or EMS PDU code to a certain
'class. You can use it in your software to read SMSs and 
'EMSs. All of this is done under GSM 03.40. I tested it
'on my SIEMENS M55 and NOKIA 8xxx and it works well.
'2.Useage 
'   If you know what type of PDU code, you can create a 
'new instance of class like DIM s as SMS(myPDUCode)
'When instance is created, you read its public variable 
'to get what you want.
'   When TP_DCS=0, PDU code is coded from 7bit 
'charactor (see GSM 03.38), use shared function 
'Deocde7Bit to decode it.
'   When TP_DCS=8, PDU code is coded from Unicode
'charactor (see GSM 03.38), use shared funtion
'DecodeUnicode to decode it.
'3.Bugs
'   So far in my tests I found none.
'4.When you use it
'   You can freely use it or modify it in your program,
'but when you find bugs or improved it please publish it
'or send one copy to me. Thanks
'5.About me
'   I am writting a program which can list folders and 
'files in SIEMENS M55 mobile phone. It can also read
'and send SMS,EMS. Some documents are hard to find on
'internet, but I keep on my mind to study it and finally
'I found it is full of interests.
'    I like freedom, so'I exchange my ideas with all of 
'the world. It is so happy that you can use my classes!
'   In the end, sorry for my poor english.
'6.Contact me
'   Email:hesicong@mail.sc.cninfo.net
'   QQ:38288890
'   Homepage:http://dream-world.nease.net (Chinese)
'   Thanks for using it!
'                       ----By HESICONG
'
'Revision:
'   2004-10-29:
'       Fix bug in decode "@" charactor.
'       Add functions in "decode 7 bit code to english" region


Imports System.text
Namespace SMS
    Namespace Decoder
        Public MustInherit Class SMSBase
            'Note all of following various with TP_ can be found in GSM 03.40
            Public SCAddressLength As Byte  'Service Center Address length
            Public SCAddressType As Byte    'Service Center Type[See GSM 03.40]
            Public SCAddressValue As String 'Service Center nuber
            Public FirstOctet As Byte       'See GSM 03.40

            Public TP_PID As Byte
            Public TP_DCS As Byte
            Public TP_UDL As Byte
            Public TP_UD As String
            Public Text As String
            Public Type As SMSType
            Public UserData As String

            Public Enum SMSType
                SMS_RECEIVED = 0
                SMS_STATUS_REPORT = 2
                SMS_SUBMIT = 1
                EMS_RECEIVED = 64 'It is "Reserved" on my phone??
                EMS_SUBMIT = 65
            End Enum

            Public MustOverride Sub GetOrignalData(ByVal PDUCode As String)

            'Get a byte from PDU string
            Shared Function GetByte(ByRef PDUCode As String) As Byte
                Dim r As Byte = Val("&H" + Mid(PDUCode, 1, 2))
                PDUCode = Mid(PDUCode, 3)
                Return r
            End Function

            'Get a string of certain length
            Shared Function GetString(ByRef PDUCode As String, ByVal Length As Integer) As String
                Dim r As String = Mid(PDUCode, 1, Length)
                PDUCode = Mid(PDUCode, Length + 1)
                Return r
            End Function

            'Get date from SCTS format
            Shared Function GetDate(ByRef SCTS As String) As Date
                Dim year, month, day, hour, minute, second, timezone As Integer

                year = Val(Swap(GetString(SCTS, 2))) + 2000
                month = Val(Swap(GetString(SCTS, 2)))
                day = Val(Swap(GetString(SCTS, 2)))
                hour = Val(Swap(GetString(SCTS, 2)))
                minute = Val(Swap(GetString(SCTS, 2)))
                second = Val(Swap(GetString(SCTS, 2)))
                timezone = Val(Swap(GetString(SCTS, 2)))

                Dim result As New Date(year, month, day, hour, minute, second)
                Return result
            End Function

            'Swap two bit
            Shared Function Swap(ByRef TwoBitStr As String) As String
                Dim c() As Char = TwoBitStr.ToCharArray
                Dim t As Char
                t = c(0)
                c(0) = c(1)
                c(1) = t
                Return (c(0) + c(1)).ToString
            End Function

            'Get phone address
            Shared Function GetAddress(ByRef Address As String) As String
                Dim tmpChar As Char() = Address.ToCharArray
                Dim i As Integer, result As String
                For i = 0 To tmpChar.GetUpperBound(0) Step 2
                    result += Swap(tmpChar(i) + tmpChar(i + 1))
                Next
                If InStr(result, "F") Then result = Mid(result, 1, result.Length - 1)
                Return result
            End Function

            Shared Function GetSMSType(ByVal PDUCode As String) As SMSBase.SMSType
                'Get first october
                Dim FirstOctet As Byte
                Dim L As Integer = SMSBase.GetByte(PDUCode)
                SMSBase.GetByte(PDUCode)
                SMSBase.GetString(PDUCode, (L - 1) * 2)
                FirstOctet = SMSBase.GetByte(PDUCode)
                '[Chinese]取得特征碼
                '[Chinese]取得基本碼 最后兩個bit + 是否有header作為標記
                'Get base code. Use last 2 bit and whether there's a header as remark
                Dim t1 As Integer = FirstOctet And 3 '00000011
                Dim t2 As Integer = FirstOctet And 64 '01000000
                '[Chinese]特別處理
                If t1 = 3 And t2 = 64 Then Return SMSBase.SMSType.EMS_SUBMIT
                Return t1 + t2
            End Function

            'Deoce a unicode string
            Shared Function DecodeUnicode(ByVal strUnicode As String) As String
                Dim Code As String
                Dim i, j As Integer
                Dim c() As String       'temp
                ReDim c(strUnicode.Length / 4)     '2 Byte a Unicode char

                For j = 0 To strUnicode.Length \ 4 - 1
                    Dim d() As Char = strUnicode.ToCharArray(j * 4, 4)
                    c(j) = "&H" & CType(d, String)
                    c(j) = ChrW(Val(c(j)))
                    Code += c(j)
                Next
                Return Code
            End Function

#Region "'Deocde 7Bit to english"
            '2004-10-29:Region added
            'Fixed decode "@" charactor
            'I use a new method, it is easily to understand but look much longer than before.
            Shared Function InvertHexString(ByVal HexString As String) As String
                'For example:
                '123456
                '===>
                '563412
                Dim Result As New StringBuilder
                Dim i As Integer
                For i = HexString.Length - 2 To 0 Step -2
                    Result.Append(HexString.Substring(i, 2))
                Next
                Return Result.ToString
            End Function

            Shared Function ByteToBinary(ByVal Dec As Byte) As String
                Dim Result As String
                Dim Temp As Byte = Dec
                Do
                    Result = (Temp Mod 2) & Result
                    If Temp = 1 Or Temp = 0 Then Exit Do
                    Temp = Temp \ 2
                Loop
                Result = Result.PadLeft(8, "0")
                Return Result
            End Function

            Shared Function BinaryToInt(ByVal Binary As String) As Integer
                Dim Result As Integer
                Dim i As Integer
                For i = 0 To Binary.Length - 1
                    Result = Result + Val(Binary.Substring(Binary.Length - i - 1, 1)) * 2 ^ i
                Next
                Return Result
            End Function

            Shared Function Decode7Bit(ByVal str7BitCode As String, ByVal charCount As Integer) As String
                Dim Inv7BitCode As String = InvertHexString(str7BitCode)
                Dim Binary As String
                Dim Result As String
                Dim i As Integer
                For i = 0 To Inv7BitCode.Length - 1 Step 2
                    Binary += ByteToBinary(Val("&H" & Inv7BitCode.Substring(i, 2)))
                Next
                Dim Temp As Integer
                For i = 1 To charCount
                    Temp = BinaryToInt(Binary.Substring(Binary.Length - i * 7, 7))
                    'There is a problem:
                    '"@" charactor is decoded to binary "0000000", but its Ascii Code is 64!!
                    'Don't know what to do with it,maybe it is a bug!
                    If Temp = 0 Then Temp = 64
                    Result = Result + ChrW(Temp)
                Next
                Return (Result)
            End Function
#End Region
        End Class

        Public Class SMS_RECEIVED
            Inherits SMSBase
            Public SrcAddressLength As Byte
            Public SrcAddressType As Byte
            Public SrcAddressValue As String
            Public TP_SCTS As Date

            Sub New(ByVal PDUCode As String)
                Type = SMSBase.SMSType.SMS_RECEIVED
                GetOrignalData(PDUCode)
            End Sub
            Public Overrides Sub GetOrignalData(ByVal PDUCode As String)
                SCAddressLength = GetByte(PDUCode)
                SCAddressType = GetByte(PDUCode)
                SCAddressValue = GetAddress((GetString(PDUCode, (SCAddressLength - 1) * 2)))
                FirstOctet = GetByte(PDUCode)

                SrcAddressLength = GetByte(PDUCode)
                SrcAddressType = GetByte(PDUCode)
                SrcAddressLength += SrcAddressLength Mod 2
                SrcAddressValue = GetAddress((GetString(PDUCode, SrcAddressLength)))


                TP_PID = GetByte(PDUCode)
                TP_DCS = GetByte(PDUCode)
                TP_SCTS = GetDate(GetString(PDUCode, 14))
                TP_UDL = GetByte(PDUCode)
                TP_UD = GetString(PDUCode, TP_UDL * 2)
            End Sub
        End Class

        Public Class SMS_SUBMIT
            Inherits SMSBase
            Public TP_MR As Byte
            Public DesAddressLength As Byte
            Public DesAddressType As Byte
            Public DesAddressValue As String