一个简明的编译器

答案：一个简明的编译器

 

多次看到有人提起文本表达式的计算问题，就动手整理以前的代码并加上注释。

写一个简单的编译器并不是很复杂的，当中要用到些反射的知识。自已觉得，反射的使用在NET中真是无处不在，使用反射没什么效率不效率的问题，毕竟现在的电脑配置并不是很低。适当使用反射，或者通过使用反射本身，会使自己加深对NET的理解。以后会写些运用反射增加代码灵活性的小”文章”供初学者参考。


如果只是计算表达式的值的,当然用不了那么多的代码.这样写法,只是使它通用性强些.
 

以下的我直接贴代码了,不再说些什么(可以说如何如何臭,只是不许骂人)。

 

Imports System.Reflection

Imports System.CodeDom

Imports System.CodeDom.Compiler

Public Class SourceComp

 

    '//编译器接口

    Private m_Compiler As ICodeCompiler

    '//编译器参数

    Private m_CompilerParameters As CompilerParameters

    '//引用的程序集

    Private m_RefAssemblies As String() = {"System.dll", "System.Data.dll"}

    '//源代码

    Private m_Source As String = ""

    '//记录是否是默认的源代码

    Private m_Is_Default As Boolean = True

    '//记录编译状态

    Private m_Compiled As Boolean = False

    '//编译生成的程序集

    Private m_Assembly As System.Reflection.Assembly

    '//默认源代码生成的实例

    Private m_tmpClass As Object

    '//默认源代码生成的实例函数

    Private m_MethodInfo As System.Reflection.MethodInfo

    '//默认源代码函数的表达式参数

    Private m_Expression As String

    '//返回程序集

    Public ReadOnly Property cpAssembly() As System.Reflection.Assembly

        Get

            Return Me.m_Assembly

        End Get

    End Property

    Sub New()

        '//获取VB编译器实例

        Me.m_Compiler = New VBCodeProvider().CreateCompiler

        '//初始编译器参数

        Me.m_CompilerParameters = New CompilerParameters

        With Me.m_CompilerParameters

            .GenerateExecutable = False '//False值指定编译为类集,True编译为可执行程序

            .GenerateInMemory = False '//只在内存中生成程序集，不输出到磁盘

            '//添加默认的程序集

            Me.Add_CompilerParameters()

        End With

    End Sub

 

    '//添加要引用的程序集

    Private Sub Add_CompilerParameters()

        Me.m_CompilerParameters.ReferencedAssemblies.AddRange(Me.m_RefAssemblies)

    End Sub

    '//添加指定的引用程序集

    Public Sub Add_CompilerParameters(ByVal RefAssemblies As String())

        Me.m_RefAssemblies = RefAssemblies

        Me.m_CompilerParameters.ReferencedAssemblies.Clear() '//清除原有的程序集，重复引用编译会产生异常

        Me.Add_CompilerParameters()

    End Sub

 

    '//生成默认的源代码

    '//类名：tmpClass

    '//函数名：GetExpressionValue ,参数:Expression ,参数类型:字符串

    '//主要功能：返回表达式Expression的值 ,返回值类型:Object

    Private Sub BuildDefaultSource()

        Dim mCodeBuilder As CodeBuilder = New CodeBuilder

        With mCodeBuilder

            .AppendCode("Imports System")

            .AppendCode("Imports System.Data")

            .AppendCode("Imports System.Math")

            .AppendCode("Imports Microsoft.VisualBasic")

            .AppendCode()

            .AppendCode("Public Class tmpClass")

            .AppendCode("   Public Function GetExpressionValue() As Object")

            .AppendCode("       Dim Result As Object")

            .AppendCode("       Result={0}") '这里传入表达式

            .AppendCode("       Return Result")

            .AppendCode("   End Function")

            .AppendCode("End Class")

        End With

        Me.m_Source = mCodeBuilder.ToString

    End Sub

    '//指定源代码

    Public Sub SetSource(ByVal Source As String)

        Me.m_Source = Source

        Me.m_Compiled = False

        Me.m_Is_Default = False

    End Sub

    '//从指定文件中读取源代码

    Public Sub GetSourceFormFile(ByVal SourceFileName As String)

        Dim mCodeBuilder As CodeBuilder = New CodeBuilder

        mCodeBuilder.AppendFromFile(SourceFileName)

        Me.m_Source = mCodeBuilder.ToString

        Me.m_Compiled = False

        Me.m_Is_Default = False

    End Sub

 

 

    '//编译

    Public Sub Complile()

        If Me.m_Source = "" Then

            Me.BuildDefaultSource()

        End If

        If Me.m_Is_Default Then

            '传入参数

            Me.m_Source = String.Format(Me.m_Source, Me.m_Expression)

        End If

 

        Dim mCompResult As CompilerResults = Me.m_Compiler.CompileAssemblyFromSource(Me.m_CompilerParameters, Me.m_Source)

        '//错误提示

        If (mCompResult.Errors.HasErrors) Then

            Dim ErrorMessage As String

            ErrorMessage = "编译错误:" & vbCrLf

            Dim Err As CompilerError

            For Each Err In mCompResult.Errors

                ErrorMessage = ErrorMessage & Err.ErrorText & vbCrLf

            Next

            Throw New Exception("编译错误: " + ErrorMessage)

        End If

        Me.m_Assembly = mCompResult.CompiledAssembly

        Me.m_Compiled = True

    End Sub

 

 

    '//如果是默认源代码，此函数取表达式的值；

    '//如果自定义源代码，请参考本函数视实际自己写

    Public Function GetExpressionValue(ByVal Expression As String) As Object

        If Not Me.m_Is_Default Then

            MsgBox("所用的代码不是默认代码，此函数无效")

            Return Nothing

        End If

 

        '如果还没有编译则编译

        If Not Me.m_Compiled Then
            '//传入参数表达式作为代码


            Me.m_Expression = Expression

            Complile()

            '//生成实例，注意类名区分大小写

            Me.m_tmpClass = Me.m_Assembly.CreateInstance("tmpClass")

            '//取函数，注意大小写

            m_MethodInfo = Me.m_tmpClass.GetType().GetMethod("GetExpressionValue")

        End If

            '//计算结果

        Dim Result As Object = m_MethodInfo.Invoke(m_tmpClass, Nothing)


        '表达式不同时要重新编译
        Me.m_Compiled = False

        Return Result

    End Function

 

End Class

 

 

'//格式生成或读取代码的类

Public Class CodeBuilder

    Private _StringBuilder As System.Text.StringBuilder

    '//格式，{0}为空格数,{1}代码字串，最后加回车换行

    Private Const CodeFormat As String = "{0}{1}" & ControlChars.CrLf

    Sub New()

        _StringBuilder = New System.Text.StringBuilder

    End Sub

    Public Overloads Sub AppendCode()

        _StringBuilder.AppendFormat(CodeFormat, Space(0), Space(0))

    End Sub

    Public Overloads Sub AppendCode(ByVal CodeString As String)

        _StringBuilder.AppendFormat(CodeFormat, Space(0), CodeString)

    End Sub

    Public Overloads Sub AppendCode(ByVal CodeFloor As Integer, ByVal CodeString As String)

        _StringBuilder.AppendFormat(CodeFormat, Space(CodeFloor * 4), CodeString)

    End Sub

    '//直接从已有vb文件中读取代码

    Public Sub AppendFromFile(ByVal FileName As 

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