Question

我是编码的新手。我试图从文件中一次读取几个字符，我的代码如下所示。但是，当文件少于请求的字符时，它会将\ 0返回到数组中，\ 0表示什么。请帮我理解。

using (StreamReader sr = new StreamReader(m_segmentFile.TempFileName))
using (StreamWriter sw = new StreamWriter(m_segmentFile.DisplayFile))
{
    while ( sr.Peek() >= 0 || m_segmentFile.ParserStatus == ParserStatus.Stopped)
    {
        buffer = new char[m_segmentFile.FieldWidth];
        sr.Read(buffer, 0, buffer.Length);
        block = new string(buffer);
        if (block[0] != '%')
        {
            noerrors = m_segmentFile.CheckBlockValidity(block) && noerrors;
            int percentComplete = (int)Math.Round((double)(offset * 100) / sr.BaseStream.Length);
            if (percentComplete > m_percentParsed && percentComplete <= 100)
            {
                m_percentParsed = (int)percentComplete;
                m_segmentFile.PercentParsed = m_percentParsed;
            }
            block = (m_segmentFile.FieldWidth * index).ToString() + ":" +block;
            sw.WriteLine(block);
            index++;
            m_parserStatus = ParserStatus.Parsing;
        }
        else
        {
            sw.WriteLine(block);
            //sr.BaseStream.Seek();
        }
    }

Answer 1

值0表示文件结束。

来自StreamReader.Read Method (Char[], Int32, Int32)文档：

返回值
  类型：System.Int32
  已读取的字符数，如果在流的末尾没有读取数据，则为0。该数字将小于或等于count参数，具体取决于数据是否在流中可用。

从文件中读取字符的更正确方法是仅使用String Constructor (Char[], Int32, Int32)从文件中读取的字符。这应该会从您的字符串中删除额外的0字符，并且还会阻止您从以前的读取中重新读取buffer中的字符。

int readLength = sr.Read(buffer, 0, buffer.Length);
block = new string(buffer, 0, readLength);

更好的选择可能是使用StringReader来换行StreamReader。

Answer 2

\ 0是字符串终止控制字符它表示字符串的结尾 - 或者在您的情况下 - 表示文件的结尾。

Answer 3

因为看起来你正在解析固定宽度的文件结构，所以你很可能会遇到段对齐问题。如果每次需要保持读数，每个块的长度应为m_segmentFile.FieldWidth，直到填满缓冲区为止。

using (StreamReader sr = new StreamReader(m_segmentFile.TempFileName))
using (StreamWriter sw = new StreamWriter(m_segmentFile.DisplayFile))
{
    //I bet money you meant to use && with != stopped not || with == stopped.
    while ( sr.Peek() >= 0 && m_segmentFile.ParserStatus != ParserStatus.Stopped)
    {
        buffer = new char[m_segmentFile.FieldWidth];
        int offset = 0;

        //Keeps reading till the buffer is totally full;
        while(offset < m_segmentFile.FieldWidth && sr.Peek() >= 0 && m_segmentFile.ParserStatus != ParserStatus.Stopped)
        {
            offset += sr.Read(buffer, offset, buffer.Length - offset);
        }


        //Reads in to the offset we got to, in case we ended early due to the stream ending or being signaled to stop.
        block = new string(buffer, 0, offset);
        if (block[0] != '%')
        {
            noerrors = m_segmentFile.CheckBlockValidity(block) && noerrors;
            int percentComplete = (int)Math.Round((double)(offset * 100) / sr.BaseStream.Length);
            if (percentComplete > m_percentParsed && percentComplete <= 100)
            {
                m_percentParsed = (int)percentComplete;
                m_segmentFile.PercentParsed = m_percentParsed;
            }
            block = (m_segmentFile.FieldWidth * index).ToString() + ":" +block;
            sw.WriteLine(block);
            index++;
            m_parserStatus = ParserStatus.Parsing;
        }
        else
        {
            sw.WriteLine(block);
            //sr.BaseStream.Seek();
        }
    }

StreamReader.Read返回\ 0

3 个答案: