comp_lzsslazy.bas

包含几十个加密解密类和压缩解压缩类,DES,LZW,Huffman

Attribute VB_Name = "Comp_LZSSLazy"

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Option Explicit

'This is a 1 run method but we have to keep the whole contents
'in memory until some variables are saved wich are needed bij the decompressor
'This is the same as the normal LZSS method only this one has Lazy matching implemeted

Private Type LZSSStream
    Data() As Byte
    Position As Long
    BitPos As Byte
    Buffer As Byte
End Type
Private Stream(3) As LZSSStream   '0=controlstream   1=distenceStream  2=lengthstream   3=literalstream
Private HistPos As Long
Private MaxHistory As Long
Private History As String

Public Sub Compress_LZSSLazy(ByteArray() As Byte)
    Dim SearchStr As String
    Dim X As Long
    Dim Y As Long
    Dim InPos As Long
    Dim NewFileLen As Long
    Dim DistPos As Long
    Dim NewPos As Long
    Call init_LZSS
    MaxHistory = CLng(1024) * DictionarySize
'The first 4 bytes are literal data
    Call AddBitsToStream(Stream(3), DictionarySize, 8)
    For X = 0 To 3
        Call AddBitsToStream(Stream(3), CLng(ByteArray(X)), 8)
        History = History & Chr(ByteArray(X))
    Next
    InPos = 4
    Do While InPos <= UBound(ByteArray)
        If SearchStr = "" Then
            For X = 1 To 2
                If InPos <= UBound(ByteArray) Then
                    SearchStr = SearchStr & Chr(ByteArray(InPos))
                    InPos = InPos + 1
                End If
            Next
        End If
        If InPos <= UBound(ByteArray) Then
            If InStr(History, SearchStr & Chr(ByteArray(InPos))) <> 0 Then
                If Len(SearchStr) = 258 Then
                    NewPos = InStr(History, SearchStr)
                    Do
                        DistPos = NewPos
                        NewPos = InStr(DistPos + 1, History, SearchStr)
                    Loop While NewPos <> 0
                    Call AddBitsToStream(Stream(0), 1, 1)
                    Call AddBitsToStream(Stream(2), 255, 8)
                    Call AddBitsToStream(Stream(1), ((Len(History) - DistPos) And &HFF00) / &H100, 8)
                    Call AddBitsToStream(Stream(1), (Len(History) - DistPos) And &HFF, 8)
                    Call AddToHistory(SearchStr)
                End If
                SearchStr = SearchStr & Chr(ByteArray(InPos))
                InPos = InPos + 1
            Else
                If Len(SearchStr) < 3 Then
                    Call AddBitsToStream(Stream(0), 0, 1)
                    Call AddBitsToStream(Stream(3), ASC(Left(SearchStr, 1)), 8)
                    Call AddToHistory(Left(SearchStr, 1))
                    SearchStr = Mid(SearchStr, 2)
                Else
                    If Check_For_Better_Match(ByteArray, SearchStr, InPos) = False Then
                        NewPos = InStr(History, SearchStr)
                        Do
                            DistPos = NewPos
                            NewPos = InStr(DistPos + 1, History, SearchStr)
                        Loop While NewPos <> 0
                        Call AddBitsToStream(Stream(0), 1, 1)
                        Call AddBitsToStream(Stream(2), Len(SearchStr) - 3, 8)
                        Call AddBitsToStream(Stream(1), ((Len(History) - DistPos) And &HFF00) / &H100, 8)
                        Call AddBitsToStream(Stream(1), (Len(History) - DistPos) And &HFF, 8)
                        Call AddToHistory(SearchStr)
                    End If
                End If
            End If
        End If
    Loop
'check if we have had all the data
    If SearchStr <> "" Then
        If Len(SearchStr) < 3 Then
            For X = 1 To Len(SearchStr)
                Call AddBitsToStream(Stream(0), 0, 1)
                Call AddBitsToStream(Stream(3), ASC(Mid(SearchStr, X, 1)), 8)
            Next
        Else
            NewPos = InStr(History, SearchStr)
            Do
                DistPos = NewPos
                NewPos = InStr(DistPos + 1, History, SearchStr)
            Loop While NewPos <> 0
            Call AddBitsToStream(Stream(0), 1, 1)
            Call AddBitsToStream(Stream(2), Len(SearchStr) - 3, 8)
            Call AddBitsToStream(Stream(1), ((Len(History) - DistPos) And &HFF00) / &H100, 8)
            Call AddBitsToStream(Stream(1), (Len(History) - DistPos) And &HFF, 8)
        End If
    End If
'send EOF code
    Call AddBitsToStream(Stream(0), 1, 1)
    Call AddBitsToStream(Stream(1), 0, 8)
    Call AddBitsToStream(Stream(1), 0, 8)
'store the last leftover bits
    For X = 0 To 3
        Do While Stream(X).BitPos > 0
            Call AddBitsToStream(Stream(X), 0, 1)
        Loop
    Next
'redim to the correct bounderies
    NewFileLen = 0
    For X = 0 To 3
        If Stream(X).Position > 0 Then
            ReDim Preserve Stream(X).Data(Stream(X).Position - 1)
            NewFileLen = NewFileLen + Stream(X).Position
        Else
            ReDim Stream(X).Data(0)
            NewFileLen = NewFileLen + 1
        End If
    Next
    
'and copy the to the outarray
    ReDim ByteArray(NewFileLen + 5)
    ByteArray(0) = Int(UBound(Stream(0).Data) / &H10000) And &HFF
    ByteArray(1) = Int(UBound(Stream(0).Data) / &H100) And &HFF
    ByteArray(2) = UBound(Stream(0).Data) And &HFF
    ByteArray(3) = Int(UBound(Stream(2).Data) / &H10000) And &HFF
    ByteArray(4) = Int(UBound(Stream(2).Data) / &H100) And &HFF
    ByteArray(5) = UBound(Stream(2).Data) And &HFF
    InPos = 6
    For X = 0 To 3
        For Y = 0 To UBound(Stream(X).Data)
            ByteArray(InPos) = Stream(X).Data(Y)
            InPos = InPos + 1
        Next
    Next
End Sub

Public Sub DeCompress_LZSSLazy(ByteArray() As Byte)
    Dim X As Long
    Dim InPos As Long
    Dim Temp As Long
    Dim ContPos As Long
    Dim ContBit As Byte
    Dim DistPos As Long
    Dim LengthPos As Long
    Dim LitPos As Long
    Dim Data As Integer
    Dim Distance As Long
    Dim Length As Integer
    Dim CopyPos As Long
    Dim AddText As String
    Call init_LZSS
    ReDim Stream(0).Data(500)
    Stream(0).BitPos = 0
    Stream(0).Buffer = 0
    Stream(0).Position = 0
    HistPos = 1
    ContPos = 6
    ContBit = 0
    Temp = CLng(ByteArray(0)) * 256 + ByteArray(1)
    Temp = CLng(Temp) * 256 + ByteArray(2)
    DistPos = ContPos + Temp + 1
    Temp = CLng(ByteArray(3)) * 256 + ByteArray(4)
    Temp = CLng(Temp) * 256 + ByteArray(5)
    LengthPos = Temp + Temp + DistPos + 2 + 2
    LitPos = LengthPos + Temp + 1
    MaxHistory = CLng(1024) * ByteArray(LitPos)
    LitPos = LitPos + 1
    For X = 0 To 3
        Call AddBitsToStream(Stream(0), CLng(ByteArray(LitPos + X)), 8)
        History = History & Chr(ByteArray(LitPos + X))
    Next
    LitPos = LitPos + 4
    Do
        If ReadBitsFromArray(ByteArray, ContPos, ContBit, 1) = 0 Then
'read literal data
            Data = ReadBitsFromArray(ByteArray, LitPos, 0, 8)
            Call AddBitsToStream(Stream(0), Data, 8)
            AddText = Chr(Data)
        Else
            Distance = ReadBitsFromArray(ByteArray, DistPos, 0, 8)
            Distance = CLng(Distance) * 256 + ReadBitsFromArray(ByteArray, DistPos, 0, 8)
            If Distance = 0 Then
                Exit Do
            End If
            Length = ReadBitsFromArray(ByteArray, LengthPos, 0, 8) + 3
            CopyPos = Len(History) - Distance
            AddText = Mid(History, CopyPos, Length)
            For X = 1 To Length
                Call AddBitsToStream(Stream(0), ASC(Mid(AddText, X, 1)), 8)