XML file parsing in Go

Question

Below is a piece of code that is responsible for serializing files. ZL_LIST and PERS_LIST are XML file structs, I have not shown them here to save space.

Please check my code.

package parser

import (
    "encoding/xml"
    "fmt"
    "golang.org/x/text/encoding/charmap"
    "io"
    "io/ioutil"
    "os"
    "path/filepath"
    "sync"
)

type Files struct {
   Name          string
   PathZipFile   string
   PathUnzipFile string
}

type nameMap map[string]bool

func (ZL_LIST) Parse(FilesName []*Files) {
    unzipPath, err := filepath.Abs("tmp")

    files, err := ioutil.ReadDir(unzipPath)
    f := make([]*Files, 0)
    for _, file := range files {
        fileZip := new(Files)
        if !file.IsDir() && file.Name()[:1] != "." {
            fileZip.Name = file.Name()
            fileZip.PathUnzipFile = filepath.Join(unzipPath, file.Name())
            f = append(f, fileZip)
        }
    }

    if err != nil {
        fmt.Printf("[ERROR] Error retrieving files %v", err)
    }

    names := make(nameMap, 1)
    var wg sync.WaitGroup
    var countHmLmFiles int = -1
    var countHmFiles int = 0
    var countLmFiles int = 0
    var file *Files
    for countHmLmFiles, file = range f {
        wg.Add(1)
        go func(filename *Files) {
            parseHmLm(filename, &countHmFiles, &countLmFiles, &names)
            wg.Done()
        }(file)
    }
    wg.Wait()

    fmt.Printf("[INFO] Read %d files from them  HM files %d and LM files %d ", countHmLmFiles+1, countHmFiles, countLmFiles)
}

func parseHmLm(filename *Files, countHmFiles *int, countLmFiles *int, names *nameMap) {
    fmt.Println("[INFO] считывается файл ", filename.Name, " с заголовком ", filename.Name[:2])
    xmlFile, err := os.Open(filepath.Join(filename.PathUnzipFile))
    if err != nil {
        fmt.Printf("[ERROR] Cannot open file %e \n", err)
    }

    defer xmlFile.Close()

    switch filename.Name[:2] {
    case "HM":
        (*names)[filename.Name] = true
        (*countHmFiles) += 1
        var hFile ZL_LIST
        decoder := xml.NewDecoder(xmlFile)
        decoder.CharsetReader =  charset
        err := decoder.Decode(&hFile)
        if err != nil {
            fmt.Errorf("[ERROR] Cannot decode file %e", err)
        }
    case "LM":
        (*countLmFiles) += 1
        var lFile PERS_LIST
        decoder := xml.NewDecoder(xmlFile)
        decoder.CharsetReader = charset
        err := decoder.Decode(&lFile)
        if err != nil {
            fmt.Errorf("[ERROR] Cannot decode file %e", err)
        }
    }

}

func charset(charset string, input io.Reader) (io.Reader, error) {
    switch charset {
    case "windows-1251":
        return charmap.Windows1251.NewDecoder().Reader(input), nil
    default:
        return nil, fmt.Errorf("unknown charset: %s", charset)
    }
}

Calling function

package api
    import (
    "net/http"
    "github.com/go-chi/render"
    "../../store/parser"
    "fmt"
    "path/filepath"
)
    func (s *Rest) parse(w http.ResponseWriter, r *http.Request) {
        uploadPath, err := filepath.Abs("./upload/")
        if err != nil {
            fmt.Printf("[ERROR] can not find the specified path %e", err)
        }
        unzipPath, err := filepath.Abs("./tmp")
        if err != nil {
            fmt.Printf("[ERROR] can not find the specified path %e", err)
        }
        p := parser.Files{}
        filesName := p.GetFileName(uploadPath, unzipPath)
            p.UnzipFiles(filesName, unzipPath)
        ...
        ...

Answer 1

Variables

Go has two ways of declaring new variables: a var notation and a short one. It's preferable to use the short one:

wg := sync.WaitGroup{}
countHmLmFiles := -1
countHmFiles := 0
countLmFiles := 0

Also when declaring lots of global variables in the package block you may use block notation:

var (
    a int = 1
    b string = "foo"
)

You can declare variables directly in the for loop:

for countHmLmFiles, file := range f {
    // countHmLmFiles and file will be visible only here
}

This way their scope will be limited to for body.

Maps in Go

You've created a map with make:

names := make(nameMap, 1)

I don't see a point in creating a map for a single element. Also when you don't need the size argument in make you may simply write names := nameMap{}.

No need pass maps with pointer. Maps and slices are already a reference type and may be passed directly by value. It won't issue a full copy.

Error handling

You've missed lots of error checks. Ideally every error must be handled in place. Otherwise use _ to ignore it and make a comment to be specific on this as it looks like a broken code.

The switch lacks the default case. It worth adding it to catch other possible values of filename.Name[:2].

Also don't forget to add terminating \n to fmt.Printf to separate log messages.