qurl/qurl/qurl.go

package qurl

import (
	"fmt"
	"strings"
	"time"
	"net/url"
)

type QURL struct {
	ID      uint64
	URL     string
	Created time.Time
	IP      []byte
	Browser string
}

func (q *QURL) CheckValid() error {
	if q == nil {
		return fmt.Errorf("QURL is nil")
	}

	if q.URL == "" {
		return fmt.Errorf("URL may not be empty")
	}

	u, err := url.Parse(q.URL)
	if err != nil {
		return err
	}

	if !u.IsAbs() {
		return fmt.Errorf("Relative URLs are not allowed")
	}

	return nil
}

const alpha = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
const alphalen = uint64(len(alpha))

func ToString(v uint64) string {
	var r strings.Builder
	var i uint64
	for i = v; i >= alphalen; i = (i / alphalen) - 1 {
		r.WriteByte(alpha[i%alphalen])
	}
	r.WriteByte(alpha[i])
	return r.String()
}

func FromString(s string) (uint64, error) {
	var r uint64
	vlen := uint64(len(s))

	for i := uint64(0); i < vlen; i++ {
		x := strings.IndexByte(alpha, s[i])
		if x == -1 {
			return 0, fmt.Errorf("Invalid character [%s]", s[i])
		}

		if i == 0 {
			r += uint64(x)
		} else {
			r += (uint64(x+1) * pow(alphalen, i))
		}
	}
	return r, nil
}

func pow(a, b uint64) uint64 {
	p := uint64(1)
	for b > 0 {
		if b&1 != 0 {
			p *= a
		}
		b >>= 1
		a *= a
	}
	return p
}