Question

给出C＃/ .NET Core 2.1中的以下代码

class Program
{
    static void Main(string[] args)
    {
        var totalAmountSeconds = 0;

        using (var reader = XmlReader.Create(@"C:\Users\kevin\Desktop\temp\XML.xml"))
        {
            var stopWatch = new Stopwatch();
            var elementCounter = 0;

            stopWatch.Start();

            foreach (var element in XmlReaderUtils.EnumerateAxis(reader, new[] { "Node" }))
            {
                elementCounter += 1;
            }

            stopWatch.Stop();
            totalAmountSeconds += stopWatch.Elapsed.Seconds;

            Console.WriteLine("Total '<Node />' elements: " + elementCounter);
        }

        using (var reader = XmlReader.Create(@"XML.xml"))
        {
            var stopWatch = new Stopwatch();
            var elementCounter = 0;

            stopWatch.Start();

            foreach (var element in XmlReaderUtils.EnumerateAxis(reader, new[] { "ArticleGroup" }))
            {
                elementCounter += 1;
            }

            stopWatch.Stop();
            totalAmountSeconds += stopWatch.Elapsed.Seconds;

            Console.WriteLine("Total '<ArticleGroup />' elements: " + elementCounter);
        }

        Console.WriteLine("Total amount of required seconds: " + totalAmountSeconds);
    }
}

public static class XmlReaderUtils
{
    public static IEnumerable<XElement> EnumerateAxis(XmlReader reader,
        string[] elements)
    {
        reader.MoveToContent();

        while (reader.Read())
        {
            switch (reader.NodeType)
            {
                case XmlNodeType.Element:
                    if (!elements.Contains(reader.Name)) continue;

                    yield return XNode.ReadFrom(reader) as XElement;

                    break;
            }
        }
    }
}

我确实认为GoLang中此代码的确切副本应为以下内容：

package main

import (
    "encoding/xml"
    "fmt"
    "os"
    "time"
)

func main() {
    start := time.Now()

    xmlFile, _ := os.Open("XML.xml")
    defer xmlFile.Close()

    decoder := xml.NewDecoder(xmlFile)

    amountOfElements := 0
    for {
        t, _ := decoder.Token()
        if t == nil {
            break
        }

        // Inspect the type of the token just read.
        switch se := t.(type) {
        case xml.StartElement:
            if se.Name.Local == "Node" {
                amountOfElements++
            }
        }
    }

    fmt.Printf("Total '<Node />' elements: %v\n", amountOfElements)

    xmlFile, _ = os.Open("XML.xml")
    defer xmlFile.Close()

    decoder = xml.NewDecoder(xmlFile)

    amountOfElements = 0
    for {
        t, _ := decoder.Token()
        if t == nil {
            break
        }

        // Inspect the type of the token just read.
        switch se := t.(type) {
        case xml.StartElement:
            if se.Name.Local == "ArticleGroup" {
                amountOfElements++
            }
        }
    }

    fmt.Printf("Total '<ArticleGroup />' elements: %v\n", amountOfElements)

    fmt.Printf("Total elapsed time: %v", time.Since(start))
}

.NET中的代码执行需要1分钟，而在GoLang中则需要2分钟。 .NET版本是使用Release配置构建的，请转到GoLang go build。

我期望GoLang更快，但事实证明它会慢吗？这是正常现象还是我错过了什么？

Answer 1

xml.NewDecoder包含两种从文件读取XML令牌的方法-Token()和RawToken()。

Tocken()包含一些其他有关StartElement和EndElement匹配的检查，并将名称空间前缀转换为它们相应的URL。

如果确实注意到这些功能，请尝试RawToken()。

P.S。在C＃中，您读取2个不同的文件，在GO中，您读取相同的文件两次。难道第二个文件在C＃示例中更小/更简单？

GoLang中的Sax解析-速度慢

1 个答案: