StringReader.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / IO / StringReader.cs / 1 / StringReader.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
/*============================================================
** 
** Class:  StringReader 
**
** Purpose: For reading text from strings 
**
**
===========================================================*/
 
using System;
using System.Runtime.InteropServices; 
 
namespace System.IO {
    // This class implements a text reader that reads from a string. 
    //
 	 [Serializable()]
[System.Runtime.InteropServices.ComVisible(true)]
    public class StringReader : TextReader 
    {
        private String _s; 
        private int _pos; 
        private int _length;
 
        public StringReader(String s) {
            if (s == null)
                throw new ArgumentNullException("s");
            _s = s; 
            _length = s == null? 0: s.Length;
        } 
 
        // Closes this StringReader. Following a call to this method, the String
        // Reader will throw an ObjectDisposedException. 
        public override void Close() {
            Dispose(true);
        }
 
        protected override void Dispose(bool disposing) {
            _s = null; 
            _pos = 0; 
            _length = 0;
            base.Dispose(disposing); 
        }

        // Returns the next available character without actually reading it from
        // the underlying string. The current position of the StringReader is not 
        // changed by this operation. The returned value is -1 if no further
        // characters are available. 
        // 
        public override int Peek() {
            if (_s == null) 
                __Error.ReaderClosed();
            if (_pos == _length) return -1;
            return _s[_pos];
        } 

        // Reads the next character from the underlying string. The returned value 
        // is -1 if no further characters are available. 
        //
        public override int Read() { 
            if (_s == null)
                __Error.ReaderClosed();
            if (_pos == _length) return -1;
            return _s[_pos++]; 
        }
 
        // Reads a block of characters. This method will read up to count 
        // characters from this StringReader into the buffer character
        // array starting at position index. Returns the actual number of 
        // characters read, or zero if the end of the string is reached.
        //
        public override int Read([In, Out] char[] buffer, int index, int count) {
    		if (buffer==null) 
    			throw new ArgumentNullException("buffer", Environment.GetResourceString("ArgumentNull_Buffer"));
    		if (index < 0) 
    			throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
    		if (count < 0)
    			throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
            if (buffer.Length - index < count)
                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
            if (_s == null)
                __Error.ReaderClosed(); 

    		int n = _length - _pos; 
            if (n > 0) { 
                if (n > count) n = count;
                _s.CopyTo(_pos, buffer, index, n); 
                _pos += n;
            }
            return n;
        } 

        public override String ReadToEnd() 
        { 
            if (_s == null)
                __Error.ReaderClosed(); 
            String s;
            if (_pos==0)
                s = _s;
            else 
                s = _s.Substring(_pos, _length - _pos);
            _pos = _length; 
            return s; 
        }
 
        // Reads a line. A line is defined as a sequence of characters followed by
        // a carriage return ('\r'), a line feed ('\n'), or a carriage return
        // immediately followed by a line feed. The resulting string does not
        // contain the terminating carriage return and/or line feed. The returned 
        // value is null if the end of the underlying string has been reached.
        // 
        public override String ReadLine() { 
            if (_s == null)
                __Error.ReaderClosed(); 
            int i = _pos;
            while (i < _length) {
                char ch = _s[i];
                if (ch == '\r' || ch == '\n') { 
                    String result = _s.Substring(_pos, i - _pos);
                    _pos = i + 1; 
                    if (ch == '\r' && _pos < _length && _s[_pos] == '\n') _pos++; 
                    return result;
                } 
                i++;
            }
            if (i > _pos) {
                String result = _s.Substring(_pos, i - _pos); 
                _pos = i;
                return result; 
            } 
            return null;
        } 
    }
}

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