Click here to Skip to main content
Click here to Skip to main content
Add your own
alternative version
Go to top

A Macro Preprocessor in C#

, 6 Apr 2005
This library supplies the same macro substitution facilities as the C/C++ preprocessor.
prepro_src.zip
using System;
using System.IO;
using System.Collections;
using System.Text.RegularExpressions;

public class MacroEntry {
    public const string Custom = "##";
    public string   Subst;
    public string[] Parms;
}

public class MacroSubstitutor {
    Hashtable macroTable = new Hashtable();    
   
    public void AddMacro(string name, string subst, string[] parms) {
        MacroEntry me = new MacroEntry();
        string pstr = "";
        if (parms != null)
            pstr = string.Join(",",parms);
        me.Subst = subst;
        me.Parms = parms;
        macroTable[name] = me;
    }
    
    public MacroEntry Lookup(string s) {
        return (MacroEntry)macroTable[s];
    }
    
    static Regex iden = new Regex(@"[a-zA-Z_]\w*");            
    
    public string ReplaceParms(MacroEntry me, string[] actual_parms) {
        Match m;
        int istart = 0;
        string subst = me.Subst;
        while ((m = iden.Match(subst,istart)) != Match.Empty) {
            int idx = Array.IndexOf(me.Parms,m.Value);
            int len = m.Length;
            if (idx != -1) {
                string actual = actual_parms[idx];
                // A _single_ # before a token  means the 'stringizing' operator
                if (m.Index > 0 && subst[m.Index-1] == '#') {
                    // whereas ## means 'token-pasting'!  #s will be removed later!
                    if (! (m.Index > 1 && subst[m.Index-2] == '#'))
                        actual = '\"' + actual + '\"';                
                }
                subst = iden.Replace(subst,actual,1,istart);                
                len = actual.Length;
            }
            istart = m.Index + len;
        }
        subst = subst.Replace("#","");
        return subst;
    }
    
    public string Substitute(string str) {
        Match m;
        int istart = 0;
        while ((m = iden.Match(str,istart)) != Match.Empty) {
            MacroEntry me = (MacroEntry)macroTable[m.Value];
            if (me != null) {
                string subst = me.Subst;
                if (subst == MacroEntry.Custom)
                    subst = CustomReplacement(m.Value);
                if (me.Parms != null) {
                    int i = m.Index + m.Length;  // points to char just beyond match
                    while (i < str.Length && str[i] != '(')
                        i++;
                    i++; // just past '('
                    int parenDepth = 1;
                    string [] actuals = new string[me.Parms.Length];
                    int idx = 0, isi = i;
                    while (parenDepth > 0) {
                        if (parenDepth == 1 && (str[i] == ',' || str[i] == ')')) {
                            actuals[idx] = str.Substring(isi,i - isi);
                            idx++;
                            isi = i+1;  // past ',' or ')'
                        }
                        if (str[i] == '(') parenDepth++;  else 
                        if (str[i] == ')') parenDepth--; 
                        i++;
                    }                    
                    subst = ReplaceParms(me,actuals);
                    istart = m.Index;
                    str = str.Remove(istart,i - istart);
                    str = str.Insert(istart,subst);
                    
                } else {                    
                    //Console.WriteLine("{0} {1} {2}",str,subst,istart);
                    //Console.In.ReadLine();
                    
                    str = iden.Replace(str,subst,1,istart);
                }
            } else
            istart = m.Index + m.Length;
        }
        return str;
    }
    
    static Regex define =  new Regex(@"#def (\w+)($|\s+|\(.+\)\s+)(.+)");    
    
    public string ProcessLine(string line) {
        Match m = define.Match(line);
        if (m != Match.Empty) {
            string [] parms = null;
            string sym = m.Groups[1].ToString();
            string subst = m.Groups[3].ToString();
            string arg = m.Groups[2].ToString();
            if (arg != "") {
                arg = arg.ToString();
                if (arg[0] == '(') {
                    arg = arg.TrimEnd(null);
                    arg = arg.Substring(1,arg.Length-2);
                    parms = arg.Split(new char[]{','});
                }
            }
            AddMacro(sym,subst,parms);
            return "";
        } else
            return Substitute(line);       
    }
    
    public virtual string CustomReplacement(string s) {
        return "";
    }
}


By viewing downloads associated with this article you agree to the Terms of Service and the article's licence.

If a file you wish to view isn't highlighted, and is a text file (not binary), please let us know and we'll add colourisation support for it.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

Share

About the Author

Steve Donovan
Web Developer
South Africa South Africa
Steve is the author of 'C++ By Example'
(Que 2002) and developer of the UnderC interactive C++ interpreter.

| Advertise | Privacy | Mobile
Web03 | 2.8.140916.1 | Last Updated 7 Apr 2005
Article Copyright 2005 by Steve Donovan
Everything else Copyright © CodeProject, 1999-2014
Terms of Service
Layout: fixed | fluid