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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
/*============================================================
**
**
**
**
** Purpose: For reading text from strings
**
**
===========================================================*/
using System;
using System.Runtime.InteropServices;
using System.Diagnostics.Contracts;
using System.Security.Permissions;
using System.Threading.Tasks;
namespace System.IO {
// This class implements a text reader that reads from a string.
//
[Serializable]
[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");
Contract.EndContractBlock();
_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.
//
[Pure]
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"));
Contract.EndContractBlock();
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;
}
#region Task based Async APIs
[ComVisible(false)]
public override Task<String> ReadLineAsync()
{
return Task.FromResult(ReadLine());
}
[ComVisible(false)]
public override Task<String> ReadToEndAsync()
{
return Task.FromResult(ReadToEnd());
}
[ComVisible(false)]
public override Task<int> ReadBlockAsync(char[] buffer, int index, int count)
{
if (buffer==null)
throw new ArgumentNullException("buffer", Environment.GetResourceString("ArgumentNull_Buffer"));
if (index < 0 || count < 0)
throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (buffer.Length - index < count)
throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
Contract.EndContractBlock();
return Task.FromResult(ReadBlock(buffer, index, count));
}
[ComVisible(false)]
public override Task<int> ReadAsync(char[] buffer, int index, int count)
{
if (buffer==null)
throw new ArgumentNullException("buffer", Environment.GetResourceString("ArgumentNull_Buffer"));
if (index < 0 || count < 0)
throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (buffer.Length - index < count)
throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
Contract.EndContractBlock();
return Task.FromResult(Read(buffer, index, count));
}
#endregion
}
}
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