mcs/ilasm/scanner/StringHelper.cs

   1 // StringHelper.cs
   2 // Author: Sergey Chaban (serge@wildwestsoftware.com)
   3
   4 using System;
   5 using System.Text;
   6
   7 namespace Mono.ILASM {
   8
   9         /// <summary>
  10         /// </summary>
  11         internal class StringHelper : StringHelperBase {
  12
  13                 private static readonly string startIdChars = "#$@_";
  14                 private static readonly string idChars = "_$@?`";
  15
  16                 /// <summary>
  17                 /// </summary>
  18                 /// <param name="host"></param>
  19                 public StringHelper (ILTokenizer host) : base (host)
  20                 {
  21                 }
  22
  23
  24                 /// <summary>
  25                 /// </summary>
  26                 /// <returns></returns>
  27                 public override bool Start (char ch)
  28                 {
  29                         mode = Token.UNKNOWN;
  30
  31                         if (Char.IsLetter (ch) || startIdChars.IndexOf (ch) != -1) {
  32                                 mode = Token.ID;
  33                         } else if (ch == '\'') {
  34                                 mode = Token.SQSTRING;
  35                         } else if (ch == '"') {
  36                                 mode = Token.QSTRING;
  37                         }
  38
  39                         return (mode != Token.UNKNOWN);
  40                 }
  41
  42
  43                 private static bool IsIdChar (int c)
  44                 {
  45                         char ch = (char) c;
  46                         return (Char.IsLetterOrDigit(ch) || idChars.IndexOf (ch) != -1);
  47                 }
  48
  49                 /// <summary>
  50                 /// </summary>
  51                 /// <returns></returns>
  52                 public override string Build ()
  53                 {
  54                         if (mode == Token.UNKNOWN) return String.Empty;
  55                         int ch = 0;
  56
  57                         ILReader reader = host.Reader;
  58
  59                         StringBuilder idsb = new StringBuilder ();
  60                         if (mode == Token.SQSTRING || mode == Token.QSTRING) {
  61                                 int term = (mode == Token.SQSTRING) ? '\'' : '"';
  62                                 reader.Read (); // skip quote
  63                                 for (ch = reader.Read (); ch != -1; ch = reader.Read ()) {
  64                                         if (ch == term) {
  65                                                 break;
  66                                         }
  67
  68                                         if (ch == '\\') {
  69                                                 ch = reader.Read ();
  70
  71                                                 /*
  72                                                  * Long string can be broken across multiple lines
  73                                                  * by using '\' as the last char in line.
  74                                                  * Any white space chars between '\' and the first
  75                                                  * char on the next line are ignored.
  76                                                  */
  77                                                 if (ch == '\n') {
  78                                                         reader.SkipWhitespace ();
  79                                                         continue;
  80                                                 }
  81
  82                                                 int escaped = Escape (reader, ch);
  83                                                 if (escaped == -1) {
  84                                                         reader.Unread (ch);
  85                                                         ch = '\\';
  86                                                 } else {
  87                                                         ch = escaped;
  88                                                 }
  89                                         }
  90
  91                                         idsb.Append((char)ch);
  92                                 }
  93                         } else { // ID
  94                                 while ((ch = reader.Read ()) != -1) {
  95                                         if (IsIdChar (ch)) {
  96                                                 idsb.Append ((char) ch);
  97                                         } else {
  98                                                 reader.Unread (ch);
  99                                                 break;
 100                                         }
 101                                 }
 102                         }
 103                         return idsb.ToString ();
 104                 }
 105
 106
 107
 108
 109                 /// <summary>
 110                 /// </summary>
 111                 /// <param name="ch"></param>
 112                 /// <returns></returns>
 113                 public static int Escape (ILReader reader, int ch)
 114                 {
 115                         int res = -1;
 116
 117                         if (ch >= '0' && ch <='7') {
 118                                 StringBuilder octal = new StringBuilder ();
 119                                 octal.Append ((char)ch);
 120                                 int possibleOctalChar = reader.Peek ();
 121                                 if (possibleOctalChar >= '0' && possibleOctalChar <='7') {
 122                                         octal.Append ((char)reader.Read ());
 123                                         possibleOctalChar = reader.Peek ();
 124                                         if (possibleOctalChar >= '0' && possibleOctalChar <='7')
 125                                                 octal.Append ((char)reader.Read ());
 126                                 }
 127                                 res = Convert.ToInt32(octal.ToString (), 8);
 128                         } else {
 129                                 int id = "abfnrtv\"'\\".IndexOf ((char)ch);
 130                                 if (id != -1) {
 131                                         res = "\a\b\f\n\r\t\v\"'\\" [id];
 132                                 }
 133                         }
 134
 135                         return res;
 136                 }
 137
 138         }
 139
 140
 141 }
 142