一个优化后的压缩算法（上）

2022-07-15 80酷酷网 80kuku.com

　　算法|压缩|优化

这是一个在CSDN论坛中讨论过的压缩算法代码。

与WinRAR以最快方式压缩ZIP比较，
255M的文件
Level=0时用时24.98秒大小95.1M
Level=255时用时30.24秒大小91.6M

WinRAR最快压缩ZIP 用时 25.2秒大小58.6M
标准RAR压缩，我看了一下，实在太慢，也就没试了，估计要几分钟才会有结果。

从速度看，基本持平了，这个算法虽然最大压缩能力有限，但感觉设计得很巧妙，每次都基于动态表，使软件可以做得很小巧，资源占用也很少。非常值得收藏！

'测试窗体中的代码
Option Explicit
Private WithEvents ObjZip As ClassZip
Private BgTime As Single
Private Sub Command1_Click()
    BgTime = Timer
    Command1.Enabled = False
    Command2.Enabled = False
    With ObjZip
    .InputFileName = Text1.Text
    .OutputFileName = Text2.Text
    .IsCompress = True
    .CompressLevel = Val(Text4.Text)
    .BeginProcss
    End With
    Label1.Caption = Round(Timer - BgTime, 2) & "秒"
    Command1.Enabled = True
    Command2.Enabled = True
End Sub
Private Sub Command2_Click()
    BgTime = Timer
    Command1.Enabled = False
    Command2.Enabled = False
    With ObjZip
    .InputFileName = Text2.Text
    .OutputFileName = Text3.Text
    .IsCompress = False
    .BeginProcss
    End With
    Label1 = Round(Timer - BgTime, 2) & "秒"
    Command1.Enabled = True
    Command2.Enabled = True
End Sub
Private Sub Command3_Click()
    ObjZip.CancelProcss = True
End Sub

Private Sub Form_Load()
    Set ObjZip = New ClassZip
    Command1.Caption = "压缩"
    Command2.Caption = "解压"
    Command3.Caption = "中断"
End Sub

Private Sub Form_Unload(Cancel As Integer)
Set ObjZip = Nothing
End Sub

Private Sub ObjZip_FileProgress(sngPercentage As Single)
Label1 = Int(sngPercentage * 100) & "%"
End Sub

Private Sub ObjZip_ProcssError(ErrorDescription As String)
MsgBox ErrorDescription
End Sub

'ClassZip类中的声明与属性、方法、事件

Option Explicit
Public Event FileProgress(sngPercentage As Single)
Public Event ProcssError(ErrorDescription As String)
Private Type FileHeader
    HeaderTag As String * 3
    HeaderSize As Integer
    Flag As Byte
    FileLength As Long
    Version As Integer
End Type
Private mintCompressLevel As Long
Private m_bEnableProcss As Boolean
Private m_bCompress As Boolean
Private m_strInputFileName As String
Private m_strOutputFileName As String
Private Const mcintWindowSize As Integer = &H1000
Private Const mcintMaxMatchLen As Integer = 18
Private Const mcintMinMatchLen As Integer = 3
Private Const mcintNull As Long = &H1000
Private Const mcstrSignature As String = "FMZ"
Private Declare Sub CopyMemory Lib "Kernel32" Alias "RtlMoveMemory" (pDest As Any, pSource As Any, ByVal dwLength As Long)
Public Sub BeginProcss()
    If m_bCompress Then
        Compress
    Else
        Decompress
    End If
End Sub
Private Function LastError(ErrNo As Integer) As String
    Select Case ErrNo
        Case 1
            LastError = "待压缩文件未设置或不存在"
        Case 2
            LastError = "待压缩文件长度太小"
        Case 3
            LastError = "待压缩文件已经过压缩"
        Case 4
            LastError = "待解压文件未设置或不存在"
        Case 5
            LastError = "待解压文件格式不对或为本软件不能认别的高版本软件所压缩"
        Case 254
            LastError = "用户取消了操作"
        Case 255
            LastError = "未知错误"
    End Select
End Function
Public Property Get CompressLevel() As Integer
    CompressLevel = mintCompressLevel \ 16
End Property
Public Property Let CompressLevel(ByVal intValue As Integer)
    mintCompressLevel = intValue * 16
    If mintCompressLevel < 0 Then mintCompressLevel = 0
End Property

Public Property Get IsCompress() As Boolean
IsCompress = m_bCompress
End Property
Public Property Let IsCompress(ByVal bValue As Boolean)
m_bCompress = bValue
End Property

Public Property Let CancelProcss(ByVal bValue As Boolean)
m_bEnableProcss = Not bValue
End Property

Public Property Get InputFileName() As String
InputFileName = m_strInputFileName
End Property

Public Property Get OutputFileName() As String
    OutputFileName = m_strOutputFileName
End Property
Public Property Let OutputFileName(ByVal strValue As String)
    m_strOutputFileName = strValue
End Property
Public Property Let InputFileName(ByVal strValue As String)
    m_strInputFileName = strValue
End Property
Private Sub Class_Terminate()
    m_bEnableProcss = False
End Sub