class/corlib/System.IO/StringReader.cs

   1 //
   2 // System.IO.StringReader
   3 //
   4 // Author: Marcin Szczepanski (marcins@zipworld.com.au)
   5 //
   6 // Copyright (C) 2004 Novell (http://www.novell.com)
   7 //
   8
   9 //
  10 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
  11 //
  12 // Permission is hereby granted, free of charge, to any person obtaining
  13 // a copy of this software and associated documentation files (the
  14 // "Software"), to deal in the Software without restriction, including
  15 // without limitation the rights to use, copy, modify, merge, publish,
  16 // distribute, sublicense, and/or sell copies of the Software, and to
  17 // permit persons to whom the Software is furnished to do so, subject to
  18 // the following conditions:
  19 //
  20 // The above copyright notice and this permission notice shall be
  21 // included in all copies or substantial portions of the Software.
  22 //
  23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  27 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  28 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  29 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  30 //
  31
  32 using System;
  33 using System.Globalization;
  34 using System.Runtime.InteropServices;
  35
  36 namespace System.IO {
  37         [Serializable]
  38         [ComVisible (true)]
  39         public class StringReader : TextReader {
  40
  41                 string source;
  42                 int nextChar;
  43                 int sourceLength;
  44
  45                 public StringReader( string s ) {
  46
  47                         if (s == null)
  48                                 throw new ArgumentNullException ("s");
  49
  50                         this.source = s;
  51                         nextChar = 0;
  52                         sourceLength = s.Length;
  53                 }
  54
  55                 public override void Close ()
  56                 {
  57                         Dispose (true);
  58                 }
  59
  60                 protected override void Dispose (bool disposing)
  61                 {
  62                         source = null;
  63                         base.Dispose (disposing);
  64                 }
  65
  66                 public override int Peek() {
  67
  68                         CheckObjectDisposedException ();
  69
  70                         if( nextChar >= sourceLength ) {
  71                                 return -1;
  72                         } else {
  73                                 return (int)source[ nextChar ];
  74                         }
  75                 }
  76
  77                 public override int Read() {
  78
  79                         CheckObjectDisposedException ();
  80
  81                         if( nextChar >= sourceLength ) {
  82                                 return -1;
  83                         } else {
  84                                 return (int)source[ nextChar++ ];
  85                         }
  86                 }
  87
  88
  89                 // The method will read up to count characters from the StringReader
  90                 // into the buffer character array starting at position index. Returns
  91                 // the actual number of characters read, or zero if the end of the string
  92                 // has been reached and no characters are read.
  93
  94                 public override int Read ([In, Out] char[] buffer, int index, int count)
  95                 {
  96                         CheckObjectDisposedException ();
  97
  98                         if (buffer == null)
  99                                 throw new ArgumentNullException ("buffer");
 100                         if (buffer.Length - index < count)
 101                                 throw new ArgumentException ();
 102                         if (index < 0 || count < 0)
 103                                 throw new ArgumentOutOfRangeException ();
 104
 105                         int charsToRead;
 106
 107                         // reordered to avoir possible integer overflow
 108                         if (nextChar > sourceLength - count)
 109                                 charsToRead = sourceLength - nextChar;
 110                         else
 111                                 charsToRead = count;
 112
 113                         source.CopyTo (nextChar, buffer, index, charsToRead);
 114
 115                         nextChar += charsToRead;
 116
 117                         return charsToRead;
 118                 }
 119
 120                 public override string ReadLine ()
 121                 {
 122                         // Reads until next \r or \n or \r\n, otherwise return null
 123
 124                         // LAMESPEC:
 125                         // The Beta 2 SDK help says that the ReadLine method
 126                         // returns "The next line from the input stream [...] A
 127                         // line is defined as a sequence of characters followed by
 128                         // a carriage return (\r), a line feed (\n), or a carriage
 129                         // return immediately followed by a line feed (\r\n).
 130                         // [...] The returned value is a null reference if the end
 131                         // of the input stream has been reached."
 132                         //
 133                         // HOWEVER, the MS implementation returns the rest of
 134                         // the string if no \r and/or \n is found in the string
 135
 136                         CheckObjectDisposedException ();
 137
 138                         if (nextChar >= source.Length)
 139                                 return null;
 140
 141                         int nextCR = source.IndexOf ('\r', nextChar);
 142                         int nextLF = source.IndexOf ('\n', nextChar);
 143                         int readTo;
 144                         bool consecutive = false;
 145
 146                         if (nextCR == -1) {
 147                                 if (nextLF == -1)
 148                                         return ReadToEnd ();
 149
 150                                 readTo = nextLF;
 151                         } else if (nextLF == -1) {
 152                                 readTo = nextCR;
 153                         } else {
 154                                 readTo = (nextCR > nextLF) ? nextLF : nextCR;
 155                                 consecutive = (nextCR + 1 == nextLF);
 156                         }
 157
 158                         string nextLine = source.Substring (nextChar, readTo - nextChar);
 159                         nextChar = readTo + ((consecutive) ? 2 : 1);
 160                         return nextLine;
 161                 }
 162
 163                 public override string ReadToEnd() {
 164
 165                         CheckObjectDisposedException ();
 166                         string toEnd = source.Substring( nextChar, sourceLength - nextChar );
 167                         nextChar = sourceLength;
 168                         return toEnd;
 169                 }
 170
 171                 private void CheckObjectDisposedException ()
 172                 {
 173                         if (source == null)
 174                                 throw new ObjectDisposedException ("StringReader",
 175                                         Locale.GetText ("Cannot read from a closed StringReader"));
 176                 }
 177         }
 178 }