一個簡明的編譯器 - 中國WEB開發者網絡 (http://www.webasp.net) -- 技術教程 (http://www.webasp.net/article/) --- 一個簡明的編譯器 (http://www.webasp.net/article/15/14651.htm)

-- 作者：未知 -- 發佈日期： 2004-11-08

一個簡明的編譯器 多次看到有人提起文本表達式的計算問題，就動手整理以前的代碼並加上註釋。 寫一個簡單的編譯器並不是很複雜的，當中要用到些反射的知識。自已覺得，反射的使用在NET中真是無處不在，使用反射沒什麼效率不效率的問題，畢竟現在的電腦配置並不是很低。適當使用反射，或者通過使用反射本身，會使自己加深對NET的理解。以後會寫些運用反射增加代碼靈活性的小」文章」供初學者參考。 如果只是計算表達式的值的,當然用不了那麼多的代碼.這樣寫法,只是使它通用性強些. 以下的我直接貼代碼了,不再說些什麼(可以說如何如何臭,只是不許罵人)。 Imports System.Reflection Imports System.CodeDom Imports System.CodeDom.Compiler Public Class SourceComp '//編譯器接口 Private m_Compiler As ICodeCompiler '//編譯器參數 Private m_CompilerParameters As CompilerParameters '//引用的程序集 Private m_RefAssemblies As String() = {"System.dll", "System.Data.dll"} '//源代碼 Private m_Source As String = "" '//記錄是否是默認的源代碼 Private m_Is_Default As Boolean = True '//記錄編譯狀態 Private m_Compiled As Boolean = False '//編譯生成的程序集 Private m_Assembly As System.Reflection.Assembly '//默認源代碼生成的實例 Private m_tmpClass As Object '//默認源代碼生成的實例函數 Private m_MethodInfo As System.Reflection.MethodInfo '//默認源代碼函數的表達式參數 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() '//獲取VB編譯器實例 Me.m_Compiler = New VBCodeProvider().CreateCompiler '//初始編譯器參數 Me.m_CompilerParameters = New CompilerParameters With Me.m_CompilerParameters .GenerateExecutable = False '//False值指定編譯為類集,True編譯為可執行程序 .GenerateInMemory = False '//只在內存中生成程序集，不輸出到磁盤 '//添加默認的程序集 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，重複引用編譯會產生異常 Me.Add_CompilerParameters() End Sub '//生成默認的源代碼 '//類名：tmpClass '//函數名：GetExpressionValue ,參數:Expression ,參數類型:字符串 '//主要功能：返回表達式Expression的值 ,返回值類型: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}") '這裡傳入表達式 .AppendCode(" Return Result") .AppendCode(" End Function") .AppendCode("End Class") End With Me.m_Source = mCodeBuilder.ToString End Sub '//指定源代碼 Public Sub SetSource(ByVal Source As String) Me.m_Source = Source Me.m_Compiled = False Me.m_Is_Default = False End Sub '//從指定文件中讀取源代碼 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 '//編譯 Public Sub Complile() If Me.m_Source = "" Then Me.BuildDefaultSource() End If If Me.m_Is_Default Then '傳入參數 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) '//錯誤提示 If (mCompResult.Errors.HasErrors) Then Dim ErrorMessage As String ErrorMessage = "編譯錯誤:" & vbCrLf Dim Err As CompilerError For Each Err In mCompResult.Errors ErrorMessage = ErrorMessage & Err.ErrorText & vbCrLf Next Throw New Exception("編譯錯誤: " + ErrorMessage) End If Me.m_Assembly = mCompResult.CompiledAssembly Me.m_Compiled = True End Sub '//如果是默認源代碼，此函數取表達式的值； '//如果自定義源代碼，請參考本函數視實際自己寫 Public Function GetExpressionValue(ByVal Expression As String) As Object If Not Me.m_Is_Default Then MsgBox("所用的代碼不是默認代碼，此函數無效") Return Nothing End If '如果還沒有編譯則編譯 If Not Me.m_Compiled Then '//傳入參數表達式作為代碼 Me.m_Expression = Expression Complile() '//生成實例，注意類名區分大小寫 Me.m_tmpClass = Me.m_Assembly.CreateInstance("tmpClass") '//取函數，注意大小寫 m_MethodInfo = Me.m_tmpClass.GetType().GetMethod("GetExpressionValue") End If '//計算結果 Dim Result As Object = m_MethodInfo.Invoke(m_tmpClass, Nothing) '表達式不同時要重新編譯 Me.m_Compiled = False Return Result End Function End Class '//格式生成或讀取代碼的類 Public Class CodeBuilder Private _StringBuilder As System.Text.StringBuilder '//格式，{0}為空格數,{1}代碼字串，最後加回車換行 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 '//直接從已有vb文件中讀取代碼 Public Sub AppendFromFile(ByVal FileName As String) If Not System.IO.File.Exists(FileName) Then MsgBox(FileName & "不存在.") Exit Sub End If Dim tmpStr As String Dim fs As System.IO.FileStream fs = New System.IO.FileStream(FileName, IO.FileMode.Open, IO.FileAccess.Read, IO.FileShare.Read) Dim Reader As New System.IO.StreamReader(fs, System.Text.Encoding.Default) tmpStr = Reader.ReadToEnd Reader.Close() fs.Close() _StringBuilder.Append(tmpStr) End Sub '//返回代碼串 Public Overrides Function ToString() As String Return _StringBuilder.ToString End Function '//清除原有代碼 Public Sub Clear() If _StringBuilder.Length > 0 Then _StringBuilder.Remove(0, _StringBuilder.Length - 1) End Sub End Class 'CodeBuilder '測試 Dim MyComp As SourceComp Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click '如果不重新生成實例，則因重新編譯時輸出同名的臨時程序集，會出錯 MyComp = New SourceComp Console.WriteLine(MyComp.GetExpressionValue("Math.Round(Math.SQRT(123 * 456), 2) ").ToString) '結果236.83 MyComp = New SourceComp Console.WriteLine(MyComp.GetExpressionValue("123 * 456 > 12 * 6987").ToString) '結果False End Sub

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