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// Package stringid provides helper functions for dealing with string identifiers
package stringid // import "github.com/docker/docker/pkg/stringid"
import (
"crypto/rand"
"encoding/hex"
"errors"
"regexp"
"strconv"
"strings"
)
const (
shortLen = 12
fullLen = 64
)
var (
validShortID = regexp.MustCompile("^[a-f0-9]{12}$")
validHex = regexp.MustCompile(`^[a-f0-9]{64}$`)
)
// IsShortID determines if id has the correct format and length for a short ID.
// It checks the IDs length and if it consists of valid characters for IDs (a-f0-9).
func IsShortID(id string) bool {
if len(id) != shortLen {
return false
}
return validShortID.MatchString(id)
}
// TruncateID returns a shorthand version of a string identifier for convenience.
// A collision with other shorthands is very unlikely, but possible.
// In case of a collision a lookup with TruncIndex.Get() will fail, and the caller
// will need to use a longer prefix, or the full-length Id.
func TruncateID(id string) string {
if i := strings.IndexRune(id, ':'); i >= 0 {
id = id[i+1:]
}
if len(id) > shortLen {
id = id[:shortLen]
}
return id
}
// GenerateRandomID returns a unique id.
func GenerateRandomID() string {
b := make([]byte, 32)
for {
if _, err := rand.Read(b); err != nil {
panic(err) // This shouldn't happen
}
id := hex.EncodeToString(b)
// if we try to parse the truncated for as an int and we don't have
// an error then the value is all numeric and causes issues when
// used as a hostname. ref #3869
if _, err := strconv.ParseInt(TruncateID(id), 10, 64); err == nil {
continue
}
return id
}
}
// ValidateID checks whether an ID string is a valid, full-length image ID.
func ValidateID(id string) error {
if len(id) != fullLen {
return errors.New("image ID '" + id + "' is invalid")
}
if !validHex.MatchString(id) {
return errors.New("image ID '" + id + "' is invalid")
}
return nil
}
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