[Mono-bugs] [Bug 589236] New: StreamReader class raise IndexOutOfRangeException

bugzilla_noreply at novell.com bugzilla_noreply at novell.com
Wed Mar 17 22:11:14 EDT 2010



           Summary: StreamReader class raise IndexOutOfRangeException
    Classification: Mono
           Product: Mono: Class Libraries
           Version: SVN
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: CORLIB
        AssignedTo: mono-bugs at lists.ximian.com
        ReportedBy: laneser.kuo at gmail.com
         QAContact: mono-bugs at lists.ximian.com
          Found By: ---
           Blocker: ---

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US)
AppleWebKit/533.2 (KHTML, like Gecko) Chrome/5.0.342.5 Safari/533.2

becuase of auto-detecting encoding in StreamReader,
it will change the encoder, but forget to change decoded_buffer size.

bug 411861 and 534137 may be related to the bug because of auto-detect

I suggest change to code inside StreamReader.ReadBuffer()
parse_start = DoChecks (cbEncoded);
if (old != encoding){
    decoder = encoding.GetDecoder ();
        // Change the decoded_buffer after decoder changed.
        // in order to prevent the IndexOutOfRangeException when decode.
    decoded_buffer = new char [encoding.GetMaxCharCount (this.buffer_size) +

Reproducible: Always

Steps to Reproduce:
the following code should reproduce the bug:

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace TestProgram
    class Program
        static void Main(string[] args)
            // to test StreamReader.cs bug in mono
            int testlines = 2048; // all data should larger than stream reader
default buffer size
            string testdata = "test";

            MemoryStream ms = new MemoryStream();
            // write utf8 encoding data.
            using (StreamWriter sw = new StreamWriter(ms, Encoding.UTF8))
                for (int i = 0; i < testlines; i++)

            MemoryStream readms = new MemoryStream(ms.GetBuffer());

            // read from streamreader and let streamreader detect encoding
            using (StreamReader sr = new StreamReader(readms, Encoding.Unicode,
                for (int i = 0; i < testlines; i++)
                    string line = sr.ReadLine();
                    if (line != testdata)
                        Console.WriteLine("read data error : " + line + " , but
should be " + testdata);

            Console.WriteLine("check over");

Actual Results:  
Unhandled Exception: System.IndexOutOfRangeException: Array index is out of
  at System.IO.StreamReader.FindNextEOL () [0x00000]
  at System.IO.StreamReader.ReadLine () [0x00000]
  at ConsoleApplication67.Program.Main (System.String[] args) [0x00000]

Expected Results:  
mono should execute the code without exceptions.

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