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

   1 //
   2 // System.IO.StringReader
   3 //
   4 // Author: Marcin Szczepanski (marcins@zipworld.com.au)
   5 //
   6
   7
   8 using System;
   9
  10 namespace System.IO {
  11         [Serializable]
  12         public class StringReader : TextReader {
  13
  14                 private string source;
  15                 private char[] sourceChars;
  16
  17                 private int nextChar;
  18                 private int sourceLength;
  19
  20                 public StringReader( string s ) {
  21                         this.source = s;
  22                         nextChar = 0;
  23                         sourceLength = s.Length;
  24                         sourceChars = s.ToCharArray();
  25                 }
  26
  27                 public override void Close() {
  28                         Dispose( true );
  29                 }
  30
  31                 protected override void Dispose (bool disposing)
  32                 {
  33                         sourceChars = null;
  34                         base.Dispose (disposing);
  35                 }
  36
  37                 public override int Peek() {
  38                         if( nextChar >= sourceLength ) {
  39                                 return -1;
  40                         } else {
  41                                 return (int)source[ nextChar ];
  42                         }
  43                 }
  44
  45                 public override int Read() {
  46                         if( nextChar >= sourceLength ) {
  47                                 return -1;
  48                         } else {
  49                                 return (int)source[ nextChar++ ];
  50                         }
  51                 }
  52
  53
  54                 // The method will read up to count characters from the StringReader
  55                 // into the buffer character array starting at position index. Returns
  56                 // the actual number of characters read, or zero if the end of the string
  57                 // has been reached and no characters are read.
  58
  59                 public override int Read( char[] buffer, int index, int count ) {
  60
  61                         if( buffer == null ) {
  62                                 throw new ArgumentNullException();
  63                         } else if( buffer.Length - index < count ) {
  64                                 throw new ArgumentException();
  65                         } else if( index < 0 || count < 0 ) {
  66                                 throw new ArgumentOutOfRangeException();
  67                         }
  68
  69                         int charsToRead;
  70
  71                         if( nextChar + count > sourceLength ) {
  72                                 charsToRead = sourceLength - nextChar;
  73                         } else {
  74                                 charsToRead = count;
  75                         }
  76
  77                         Array.Copy(sourceChars, nextChar, buffer, index, charsToRead );
  78
  79                         nextChar += count;
  80
  81                         return charsToRead;
  82                 }
  83
  84                 public override string ReadLine() {
  85                         // Reads until next \r or \n or \r\n, otherwise return null
  86
  87                         // LAMESPEC:
  88                         // The Beta 2 SDK help says that the ReadLine method returns
  89                         // "The next line from the input stream [...] A line is defined as a sequence of
  90                         // characters followed by a carriage return (\r), a line feed (\n), or a carriage
  91                         // return immediately followed by a line feed (\r\n). [...]
  92                         // The returned value is a null reference if the end of the input stream has been reached."
  93                         //
  94                         // HOWEVER, the MS implementation returns the rest of the string if no \r and/or \n is found
  95                         // in the string
  96
  97                         if (nextChar >= source.Length)
  98                                 return null;
  99
 100                         int nextCR = source.IndexOf( '\r', nextChar );
 101                         int nextLF = source.IndexOf( '\n', nextChar );
 102
 103                         if( nextCR == -1 && nextLF == -1 ) {
 104                                 return ReadToEnd();
 105                         }
 106
 107                         int readTo;
 108
 109                         if( nextCR == -1 ) {
 110                                 readTo = nextLF;
 111                         } else {
 112                                 readTo = nextCR;
 113                         }
 114
 115                         string nextLine = source.Substring( nextChar, readTo - nextChar );
 116
 117                         if( nextLF == nextCR + 1 ) {
 118                                 nextChar = readTo + 2;
 119                         } else {
 120                                 nextChar = readTo + 1;
 121                         }
 122
 123                         return nextLine;
 124                 }
 125
 126                 public override string ReadToEnd() {
 127                         string toEnd = source.Substring( nextChar, sourceLength - nextChar );
 128                         nextChar = sourceLength;
 129                         return toEnd;
 130                 }
 131
 132         }
 133 }