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//
// assembly: System
// namespace: System.Text.RegularExpressions
// file: replace.cs
//
// author: Dan Lewis (dlewis@gmx.co.uk)
// (c) 2002
using System;
using System.Text;
using System.Collections;
using Parser = System.Text.RegularExpressions.Syntax.Parser;
namespace System.Text.RegularExpressions {
class ReplacementEvaluator {
public static string Evaluate (string replacement, Match match) {
ReplacementEvaluator ev = new ReplacementEvaluator (match.Regex, replacement);
return ev.Evaluate (match);
}
public ReplacementEvaluator (Regex regex, string replacement) {
this.regex = regex;
terms = new ArrayList ();
Compile (replacement);
}
public string Evaluate (Match match) {
StringBuilder result = new StringBuilder ();
foreach (Term term in terms)
result.Append (term.GetResult (match));
return result.ToString ();
}
// private
private void Compile (string replacement) {
replacement = Parser.Unescape (replacement);
string literal = "";
int ptr = 0;
char c;
Term term = null;
while (ptr < replacement.Length) {
c = replacement[ptr ++];
if (c == '$') {
if (replacement[ptr] == '$') {
++ ptr;
break;
}
term = CompileTerm (replacement, ref ptr);
}
if (term != null) {
term.Literal = literal;
terms.Add (term);
term = null;
literal = "";
}
else
literal += c;
}
if (term == null && literal.Length > 0) {
terms.Add (new Term (literal));
}
}
private Term CompileTerm (string str, ref int ptr) {
char c = str[ptr];
if (Char.IsDigit (c)) { // numbered group
int n = Parser.ParseDecimal (str, ref ptr);
if (n < 0 || n > regex.GroupCount)
throw new ArgumentException ("Bad group number.");
return new Term (TermOp.Match, n);
}
++ ptr;
switch (c) {
case '{': { // named group
string name = Parser.ParseName (str, ref ptr);
if (str[ptr ++] != '}' || name == null)
throw new ArgumentException ("Bad group name.");
int n = regex.GroupNumberFromName (name);
if (n < 0)
throw new ArgumentException ("Bad group name.");
return new Term (TermOp.Match, n);
}
case '&': // entire match
return new Term (TermOp.Match, 0);
case '`': // text before match
return new Term (TermOp.PreMatch, 0);
case '\'': // text after match
return new Term (TermOp.PostMatch, 0);
case '+': // last group
return new Term (TermOp.Match, regex.GroupCount - 1);
case '_': // entire text
return new Term (TermOp.All, 0);
default:
throw new ArgumentException ("Bad replacement pattern.");
}
}
private Regex regex;
private ArrayList terms;
private enum TermOp {
None, // no action
Match, // input within group
PreMatch, // input before group
PostMatch, // input after group
All // entire input
}
private class Term {
public Term (TermOp op, int arg) {
this.op = op;
this.arg = arg;
this.literal = "";
}
public Term (string literal) {
this.op = TermOp.None;
this.arg = 0;
this.literal = literal;
}
public string Literal {
set { literal = value; }
}
public string GetResult (Match match) {
Group group = match.Groups[arg];
switch (op) {
case TermOp.None:
return literal;
case TermOp.Match:
return literal + group.Value;
case TermOp.PreMatch:
return literal + group.Text.Substring (0, group.Index);
case TermOp.PostMatch:
return literal + group.Text.Substring (group.Index + group.Length);
case TermOp.All:
return literal + group.Text;
}
return "";
}
public TermOp op; // term type
public int arg; // group argument
public string literal; // literal to prepend
public override string ToString () {
return op.ToString () + "(" + arg + ") " + literal;
}
}
}
}
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