dsn

We often work with configuration strings like pq database connection:

user=mylogin password=mypass database=mydb host=127.0.0.1 port=5432 sslmode=true

The simplest way to parse them in Golang is regular expressions:

package main

import (
  "fmt"
  "regexp"
)

var rex = regexp.MustCompile("(\\w+)=(\\w+)")

func main() {
  conn := `user=mylogin password=mypass database=mydb
           host=127.0.0.1 port=5432 sslmode=true`

  data := rex.FindAllStringSubmatch(conn, -1)

  res := make(map[string]string)
  for _, kv := range data {
    k := kv[1]
    v := kv[2]
    res[k] = v
  }

  fmt.Println(res)
}

But if the value can contain a space character, then you need to add escaping support in a regular expression. And so on, each additional action makes processing harder. But there is an easier way (wmentor/dsn).

Install package:

go get github.com/wmentor/dsn

Usage:

package main

import (
  "fmt"

  "github.com/wmentor/dsn"
)

func main() {

  str := `user=mylogin passwd=mypass database=mydb
          port=5432 sslmode=true`

  ds, err := dsn.New(str)
  if err != nil {
    panic("invalid string")
  }

  // print user=mylogin
  fmt.Printf( "user=%s\n", ds.GetString("user","unknown") )

  // print passwd=mypass
  fmt.Printf( "passwd=%s\n", ds.GetString("passwd","nopass") )

  // host is not exists, print host=127.0.0.1
  fmt.Printf( "host=%s\n", ds.GetString("host","127.0.0.1") )

  // get int value and print port=5432
  fmt.Printf( "port=%d\n", ds.GetInt("port", 4321) )

  // print sslmode=true
  fmt.Printf( "sslmode=%t\n", ds.GetBool("sslmode", false) )

  // print keepalive=false
  fmt.Printf( "keepalive=%t\n", ds.GetBool("keepalive", false) )
}

dns.New returns object dsn.DSN or an error. All get methods (GetString,GetBool,GetInt,GetInt64,GetFloat) take 2 arguments - key name and default value. The default value is used when the key is missing or contains a invalid value.

Moreover, dsn support escape some characters in key name and value (\s,\t,\r,\n,=,\,",'). See example below:

package main

import (
  "fmt"

  "github.com/wmentor/dsn"
)

func main() {

  str := `message=Hello,\sWorld! calc=1+1\=2`

  ds, err := dsn.New(str)
  if err != nil {
    panic("invalid string")
  }

  // print message=Hello, World!
  fmt.Printf( "message=%s\n", ds.GetString("message","") )

  // print calc=1+2=2
  fmt.Printf( "calc=%s\n", ds.GetString("calc","") )
}

Object dsn.DSN support set methods (SetString,SetBool,SetInt,SetInt64,SetFloat). They take 2 arguments - key name and value:

ds.SetString("host", "192.168.1.1")

Stringer interface implemention makes simple convert dsn.DSN to string:

str := ds.String()
// or
fmt.Println(ds)