从流读取器读取一行而不消耗？

Question

有没有办法提前读取一行来测试下一行是否包含特定的标签数据？

我正在处理具有开始标记但没有结束标记的格式。

我想读一行将它添加到一个结构然后测试下面的行，以确保它不是一个新的“节点”，如果它不是继续添加，如果它关闭该结构并创建一个新的

我能想到的唯一解决方案就是让两个流读取器在同一时间沿着锁定步骤出现，但这看起来很浪费（如果它甚至可以工作）

我需要像peek但peekline这样的东西

Answer 1

问题是潜在的流可能甚至不可寻求。如果您查看流读取器实现，它会使用缓冲区，因此即使流不可搜索，它也可以实现TextReader.Peek（）。

您可以编写一个简单的适配器来读取下一行并在内部缓冲它，如下所示：

 public class PeekableStreamReaderAdapter
    {
        private StreamReader Underlying;
        private Queue<string> BufferedLines;

        public PeekableStreamReaderAdapter(StreamReader underlying)
        {
            Underlying = underlying;
            BufferedLines = new Queue<string>();
        }

        public string PeekLine()
        {
            string line = Underlying.ReadLine();
            if (line == null)
                return null;
            BufferedLines.Enqueue(line);
            return line;
        }


        public string ReadLine()
        {
            if (BufferedLines.Count > 0)
                return BufferedLines.Dequeue();
            return Underlying.ReadLine();
        }
    }

Answer 2

您可以存储访问StreamReader.BaseStream.Position的位置，然后读取下一行的行，进行测试，然后在读取该行之前找到该位置：

            // Peek at the next line
            long peekPos = reader.BaseStream.Position;
            string line = reader.ReadLine();

            if (line.StartsWith("<tag start>"))
            {
                // This is a new tag, so we reset the position
                reader.BaseStream.Seek(pos);    

            }
            else
            {
                // This is part of the same node.
            }

这是很多寻求和重读相同的路线。使用某些逻辑，您可以完全避免这种情况 - 例如，当您看到新标记开始时，关闭现有结构并开始一个新结构 - 这是一个基本算法：

        SomeStructure myStructure = null;
        while (!reader.EndOfStream)
        {
            string currentLine = reader.ReadLine();
            if (currentLine.StartsWith("<tag start>"))
            {
                // Close out existing structure.
                if (myStructure != null)
                {
                    // Close out the existing structure.
                }

                // Create a new structure and add this line.
                myStructure = new Structure();                   
                // Append to myStructure.
            }
            else
            {
                // Add to the existing structure.
                if (myStructure != null)
                {
                    // Append to existing myStructure
                }
                else
                {
                    // This means the first line was not part of a structure.
                    // Either handle this case, or throw an exception.
                }
            }
        }

Answer 3

为什么难度？无论如何，返回下一行。检查它是否是新节点，如果不是，则将其添加到结构中。如果是，则创建一个新结构。

// Not exactly C# but close enough
Collection structs = new Collection();
Struct struct;
while ((line = readline()) != null)) {
    if (IsNode(line)) {
        if (struct != null) structs.add(struct);
        struct = new Struct();
        continue;
    }
    // Whatever processing you need to do
    struct.addLine(line);
}
structs.add(struct); // Add the last one to the collection

// Use your structures here
foreach s in structs {

}

Answer 4

这是我到目前为止所做的事情。我比分线路线更多地使用分流路线。

我敢肯定有一些地方会更加优雅，但现在它似乎正在发挥作用。

请让我知道您的想法

struct INDI
    {
        public string ID;
        public string Name;
        public string Sex;
        public string BirthDay;
        public bool Dead;


    }
    struct FAM
    {
        public string FamID;
        public string type;
        public string IndiID;
    }
    List<INDI> Individuals = new List<INDI>();
    List<FAM> Family = new List<FAM>();
    private void button1_Click(object sender, EventArgs e)
    {
        string path = @"C:\mostrecent.ged";
        ParseGedcom(path);
    }

    private void ParseGedcom(string path)
    {
        //Open path to GED file
        StreamReader SR = new StreamReader(path);

        //Read entire block and then plit on 0 @ for individuals and familys (no other info is needed for this instance)
        string[] Holder = SR.ReadToEnd().Replace("0 @", "\u0646").Split('\u0646');

        //For each new cell in the holder array look for Individuals and familys
        foreach (string Node in Holder)
        {

            //Sub Split the string on the returns to get a true block of info
            string[] SubNode = Node.Replace("\r\n", "\r").Split('\r');
            //If a individual is found
            if (SubNode[0].Contains("INDI"))
            {
                //Create new Structure
                INDI I = new INDI();
                //Add the ID number and remove extra formating
                I.ID = SubNode[0].Replace("@", "").Replace(" INDI", "").Trim();
                //Find the name remove extra formating for last name
                I.Name = SubNode[FindIndexinArray(SubNode, "NAME")].Replace("1 NAME", "").Replace("/", "").Trim(); 
                //Find Sex and remove extra formating
                I.Sex = SubNode[FindIndexinArray(SubNode, "SEX")].Replace("1 SEX ", "").Trim();

                //Deterine if there is a brithday -1 means no
                if (FindIndexinArray(SubNode, "1 BIRT ") != -1)
                {
                    // add birthday to Struct 
                    I.BirthDay = SubNode[FindIndexinArray(SubNode, "1 BIRT ") + 1].Replace("2 DATE ", "").Trim();
                }

                // deterimin if there is a death tag will return -1 if not found
                if (FindIndexinArray(SubNode, "1 DEAT ") != -1)
                {
                    //convert Y or N to true or false ( defaults to False so no need to change unless Y is found.
                    if (SubNode[FindIndexinArray(SubNode, "1 DEAT ")].Replace("1 DEAT ", "").Trim() == "Y")
                    {
                        //set death
                        I.Dead = true;
                    }
                }
                //add the Struct to the list for later use
                Individuals.Add(I);
            }

            // Start Family section
            else if (SubNode[0].Contains("FAM"))
            {
                //grab Fam id from node early on to keep from doing it over and over
                string FamID = SubNode[0].Replace("@ FAM", "");

                // Multiple children can exist for each family so this section had to be a bit more dynaimic

                // Look at each line of node
                foreach (string Line in SubNode)
                {
                    // If node is HUSB
                    if (Line.Contains("1 HUSB "))
                    {

                        FAM F = new FAM();
                        F.FamID = FamID;
                        F.type = "PAR";
                        F.IndiID = Line.Replace("1 HUSB ", "").Replace("@","").Trim();
                        Family.Add(F);
                    }
                        //If node for Wife
                    else if (Line.Contains("1 WIFE "))
                    {
                        FAM F = new FAM();
                        F.FamID = FamID;
                        F.type = "PAR";
                        F.IndiID = Line.Replace("1 WIFE ", "").Replace("@", "").Trim();
                        Family.Add(F);
                    }
                        //if node for multi children
                    else if (Line.Contains("1 CHIL "))
                    {
                        FAM F = new FAM();
                         F.FamID = FamID;
                        F.type = "CHIL";
                        F.IndiID = Line.Replace("1 CHIL ", "").Replace("@", "");
                        Family.Add(F);
                    }
                }
            }
        }
    }

    private int FindIndexinArray(string[] Arr, string search)
    {
        int Val = -1;
        for (int i = 0; i < Arr.Length; i++)
        {
            if (Arr[i].Contains(search))
            {
                Val = i;
            }
        }
        return Val;
    }