c# – 使用TextReader读取字节

2019年8月4日 275次阅读

在过去,我一直在使用BinaryReader读取几个字节,但最近,我收到了这个错误：

An error has occurred: Probable I/O race condition detected while copying memory. The I/O package is not thread safe by default. In multithreaded applications, a stream must be accessed in a thread-safe way, such as a thread-safe wrapper returned by TextReader's or TextWriter's Synchronized methods. This also applies to classes like StreamWriter and StreamReader.    at System.Buffer.InternalBlockCopy(Array src, Int32 srcOffset, Array dst, Int32 dstOffset, Int32 count)
   at System.IO.FileStream.Read(Byte[] array, Int32 offset, Int32 count)
   at System.IO.BinaryReader.FillBuffer(Int32 numBytes)
   at System.IO.BinaryReader.ReadUInt16()

因此,我决定使用TextReader的Synchronized方法,如下所示：

public class SafeReader
{
    private Stream m_Stream;
    private TextReader m_TextReader;
    public SafeReader(Stream stream)
    {
        m_TextReader = TextReader.Synchronized(new StreamReader(m_Stream = stream));
    }
    public Stream BaseStream
    {
        get { return m_Stream; }
    }
    public int ReadInt32()
    {
        // this doesn't even need to do anything (just has to read 4 bytes and it gets disposed of anyway);
        ReadUInt16();
        ReadUInt16();
        return -1;
    }
    public short ReadInt16()
    {
        return (short)(this.ReadUInt16());
    }
    public ushort ReadUInt16()
    {
        return BitConverter.ToUInt16(new byte[] { (byte)(m_TextReader.Read() & 0xFF), (byte)(m_TextReader.Read() & 0xFF) }, 0);
        //return (ushort)(((m_TextReader.Read() & 0xFF)) | ((m_TextReader.Read() & 0xFF) << 8));
    }
}

但是,返回的值(它几乎以专有格式读取图像)是不正确的. “图像”略带蓝色色调,我有一种感觉,这可能是由于TextReader读取文本(并使用编码读取字符而不是仅读取字节值).

有没有“线程安全”的方式,如TextReader的Synchronized()来读取二进制文件？

最佳答案 您应该能够使用BiReader并使用TextReader.只需确保将数组锁定在您访问它的线程上(写入).

Object locker = new Object;

lock (locker) {
    //BinaryReader here
}

从其他线程使用相同的：

lock (locker) {
    //read from array (read is thread-safe though)
}

如果正在进行写操作,则另一个线程将等待对象解锁.

如果您不需要读取块,也可以使用File.ReadAllBytes.

或者使用Textreader的ASCII或UTF8编码.

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