在大文件中搜索和替换正则表达式而不会出现OutOfMemoryException

Question

我创建了一个小代码,用于搜索正则表达式字符串并将其替换为其他字符串,然后创建一个包含所做更改的新输出文件.代码似乎适用于较小的文件,但对于100 MB或更大的文件,我给出了System.OutOfMemoryException错误.

这是我的代码:

string foldername = Path.Combine(
    Environment.GetFolderPath(Environment.SpecialFolder.Desktop),
    String.Format("FIXED_{0}.tmx",
        Path.GetFileNameWithoutExtension(textBox1.Text)));

string text = File.ReadAllText(textBox1.Text);
text = Regex.Replace(text, @"<seg\b[^>]*>", "<seg>", RegexOptions.Multiline);
text = Regex.Replace(text, @"<seg>
                    </tuv>", "<seg></seg></tuv>", RegexOptions.Multiline);

File.WriteAllText(foldername, text);

Visual Studio突出了该string text = File.ReadAllText(textBox1.Text);部分.我认为也许使用File.ReadAllLines可以更好地工作,但我无法使其与正则表达式一起工作.

有人可以帮我这个吗？我是C#的新手,可能我的代码不是最好的.

Answer 1

我担心你必须自己实施更换.以下是使用状态机来代替示例代码<seg\b[^>*]>用<seg>.唯一的问题是,如果文件结束<seg attr="",则只会<seg写入输出.

enum TruncateSegState
{
    Idle,
    TagStart,
    TagStartS,
    TagStartSE,
    TagStartSEG,
    TagSEG
}

static void TruncateSeg(StreamReader input, StreamWriter output)
{
    TruncateSegState state = TruncateSegState.Idle;
    while (!input.EndOfStream)
    {
        char ch = (char)input.Read();
        switch (state)
        {
            case TruncateSegState.Idle:
                if (ch == '<')
                    state = TruncateSegState.TagStart;
                output.Write(ch);
                break;
            case TruncateSegState.TagStart:
                if (ch == 's')
                    state = TruncateSegState.TagStartS;
                else
                    state = TruncateSegState.Idle;
                output.Write(ch);
                break;
            case TruncateSegState.TagStartS:
                if (ch == 'e')
                    state = TruncateSegState.TagStartSE;
                else
                    state = TruncateSegState.Idle;
                output.Write(ch);
                break;
            case TruncateSegState.TagStartSE:
                if (ch == 'g')
                    state = TruncateSegState.TagStartSEG;
                else
                    state = TruncateSegState.Idle;
                output.Write(ch);
                break;
            case TruncateSegState.TagStartSEG:
                if (char.IsWhiteSpace(ch))
                    state = TruncateSegState.TagSEG;
                else
                {
                    state = TruncateSegState.Idle;
                    output.Write(ch);
                }
                break;
            case TruncateSegState.TagSEG:
                if (ch == '>')
                {
                    state = TruncateSegState.Idle;
                    output.Write(ch);
                }
                break;
        }
    }
}

用法:

using (StreamReader reader = new StreamReader("input.txt"))
using (StreamWriter writer = new StreamWriter("temp.txt"))
    TruncateSeg(reader, writer);

生成后temp.txt,将其用作下一个方法的输入,这会添加缺少的</seg>标记.

enum ReplaceSegTuvState
{
    Idle,
    InsideSEG
}

static void ReplaceSegTuv(StreamReader input, StreamWriter output)
{
    ReplaceSegTuvState state = ReplaceSegTuvState.Idle;
    StringBuilder segBuffer = new StringBuilder();
    while (!input.EndOfStream)
    {
        char ch = (char)input.Read();
        switch (state)
        {
            case ReplaceSegTuvState.Idle:
                if (ch == '<')
                {
                    char[] buffer = new char[4];
                    int bufferActualLength = input.ReadBlock(buffer, 0, buffer.Length);
                    output.Write('<');
                    output.Write(buffer, 0, bufferActualLength);
                    if (bufferActualLength == buffer.Length && "seg>".SequenceEqual(buffer))
                    {
                        segBuffer.Clear();
                        state = ReplaceSegTuvState.InsideSEG;
                    }
                }
                else
                    output.Write(ch);
                break;
            case ReplaceSegTuvState.InsideSEG:
                if (ch == '<')
                {
                    char[] buffer = new char[5];
                    int bufferActualLength = input.ReadBlock(buffer, 0, buffer.Length);
                    if (bufferActualLength == buffer.Length && "/tuv>".SequenceEqual(buffer))
                    {
                        output.Write("</seg>");
                        output.Write("</tuv>");
                        state = ReplaceSegTuvState.Idle;
                    }
                    else
                    {
                        output.Write(segBuffer.ToString());
                        output.Write('<');
                        output.Write(buffer, 0, bufferActualLength);
                        state = ReplaceSegTuvState.Idle;
                    }
                }
                else if (!char.IsWhiteSpace(ch))
                {
                    output.Write(segBuffer.ToString());
                    output.Write(ch);
                    state = ReplaceSegTuvState.Idle;
                }
                else
                    segBuffer.Append(ch);
                break;
        }
    }
}

用法:

using (StreamReader reader = new StreamReader("temp.txt"))
using (StreamWriter writer = new StreamWriter("output.txt"))
    ReplaceSegTuv(reader, writer);