mcs/class/corlib/System.IO/StringReader.cs

   1 //
   2 // System.IO.StringReader
   3 //
   4 // Authors:
   5 //   Marcin Szczepanski (marcins@zipworld.com.au)
   6 //   Marek Safar (marek.safar@gmail.com)
   7 //
   8 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
   9 // Copyright 2011 Xamarin Inc.
  10 //
  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 #if NET_4_5
  36 using System.Threading.Tasks;
  37 #endif
  38
  39 namespace System.IO {
  40         [Serializable]
  41         [ComVisible (true)]
  42         public class StringReader : TextReader {
  43
  44                 string source;
  45                 int nextChar;
  46                 int sourceLength;
  47                 static char[] cr_lf;
  48
  49                 public StringReader (string s)
  50                 {
  51                         if (s == null)
  52                                 throw new ArgumentNullException ("s");
  53
  54                         this.source = s;
  55                         nextChar = 0;
  56                         sourceLength = s.Length;
  57                 }
  58
  59                 public override void Close ()
  60                 {
  61                         Dispose (true);
  62                 }
  63
  64                 protected override void Dispose (bool disposing)
  65                 {
  66                         source = null;
  67                         base.Dispose (disposing);
  68                 }
  69
  70                 public override int Peek ()
  71                 {
  72                         if (source == null)
  73                                 ObjectDisposedException ();
  74
  75                         if (nextChar >= sourceLength)
  76                                 return -1;
  77                         return (int)source [nextChar];
  78                 }
  79
  80                 public override int Read ()
  81                 {
  82                         if (source == null)
  83                                 ObjectDisposedException ();
  84
  85                         if (nextChar >= sourceLength)
  86                                 return -1;
  87                         return (int)source [nextChar++];
  88                 }
  89
  90                 // The method will read up to count characters from the StringReader
  91                 // into the buffer character array starting at position index. Returns
  92                 // the actual number of characters read, or zero if the end of the string
  93                 // has been reached and no characters are read.
  94
  95                 public override int Read ([In, Out] char[] buffer, int index, int count)
  96                 {
  97                         if (source == null)
  98                                 ObjectDisposedException ();
  99
 100                         if (buffer == null)
 101                                 throw new ArgumentNullException ("buffer");
 102                         if (buffer.Length - index < count)
 103                                 throw new ArgumentException ();
 104                         if (index < 0 || count < 0)
 105                                 throw new ArgumentOutOfRangeException ();
 106
 107                         int charsToRead;
 108
 109                         // reordered to avoir possible integer overflow
 110                         if (nextChar > sourceLength - count)
 111                                 charsToRead = sourceLength - nextChar;
 112                         else
 113                                 charsToRead = count;
 114
 115                         source.CopyTo (nextChar, buffer, index, charsToRead);
 116
 117                         nextChar += charsToRead;
 118
 119                         return charsToRead;
 120                 }
 121
 122                 public override string ReadLine ()
 123                 {
 124                         // Reads until next \r or \n or \r\n, otherwise return null
 125
 126                         if (source == null)
 127                                 ObjectDisposedException ();
 128
 129                         if (nextChar >= source.Length)
 130                                 return null;
 131
 132                         if (cr_lf == null)
 133                                 cr_lf = new char [] { '\n', '\r' };
 134
 135                         int readto = source.IndexOfAny (cr_lf, nextChar);
 136
 137                         if (readto == -1)
 138                                 return ReadToEnd ();
 139
 140                         bool consecutive = source[readto] == '\r'
 141                                 && readto + 1 < source.Length
 142                                 && source[readto + 1] == '\n';
 143
 144                         string nextLine = source.Substring (nextChar, readto - nextChar);
 145                         nextChar = readto + ((consecutive) ? 2 : 1);
 146                         return nextLine;
 147                 }
 148
 149                 public override string ReadToEnd ()
 150                 {
 151                         if (source == null)
 152                                 ObjectDisposedException ();
 153                         string toEnd = source.Substring (nextChar, sourceLength - nextChar);
 154                         nextChar = sourceLength;
 155                         return toEnd;
 156                 }
 157
 158 #if NET_4_5
 159                 //
 160                 // All async methods return finished task with a result as it's faster
 161                 // than setting up async call
 162                 //
 163                 public override Task<int> ReadAsync (char[] buffer, int index, int count)
 164                 {
 165                         return Task.FromResult (Read (buffer, index, count));
 166                 }
 167
 168                 public override Task<int> ReadBlockAsync (char[] buffer, int index, int count)
 169                 {
 170                         return Task.FromResult (ReadBlock (buffer, index, count));
 171                 }
 172
 173                 public override Task<string> ReadLineAsync ()
 174                 {
 175                         return Task.FromResult (ReadLine ());
 176                 }
 177
 178                 public override Task<string> ReadToEndAsync ()
 179                 {
 180                         return Task.FromResult (ReadToEnd ());
 181                 }
 182 #endif
 183
 184                 static void ObjectDisposedException ()
 185                 {
 186                         throw new ObjectDisposedException ("StringReader",
 187                                                            Locale.GetText ("Cannot read from a closed StringReader"));
 188                 }
 189         }
 190 }