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99 lines
2.5 KiB
Go
99 lines
2.5 KiB
Go
// Package stringid provides helper functions for dealing with string identifiers
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package stringid // import "github.com/docker/docker/pkg/stringid"
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import (
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cryptorand "crypto/rand"
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"encoding/hex"
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"fmt"
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"io"
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"math"
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"math/big"
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"math/rand"
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"regexp"
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"strconv"
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"strings"
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"time"
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)
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const shortLen = 12
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var (
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validShortID = regexp.MustCompile("^[a-f0-9]{12}$")
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validHex = regexp.MustCompile(`^[a-f0-9]{64}$`)
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)
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// IsShortID determines if an arbitrary string *looks like* a short ID.
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func IsShortID(id string) bool {
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return validShortID.MatchString(id)
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}
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// TruncateID returns a shorthand version of a string identifier for convenience.
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// A collision with other shorthands is very unlikely, but possible.
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// In case of a collision a lookup with TruncIndex.Get() will fail, and the caller
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// will need to use a longer prefix, or the full-length Id.
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func TruncateID(id string) string {
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if i := strings.IndexRune(id, ':'); i >= 0 {
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id = id[i+1:]
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}
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if len(id) > shortLen {
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id = id[:shortLen]
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}
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return id
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}
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func generateID(r io.Reader) string {
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b := make([]byte, 32)
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for {
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if _, err := io.ReadFull(r, b); err != nil {
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panic(err) // This shouldn't happen
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}
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id := hex.EncodeToString(b)
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// if we try to parse the truncated for as an int and we don't have
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// an error then the value is all numeric and causes issues when
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// used as a hostname. ref #3869
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if _, err := strconv.ParseInt(TruncateID(id), 10, 64); err == nil {
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continue
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}
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return id
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}
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}
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// GenerateRandomID returns a unique id.
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func GenerateRandomID() string {
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return generateID(cryptorand.Reader)
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}
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// GenerateNonCryptoID generates unique id without using cryptographically
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// secure sources of random.
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// It helps you to save entropy.
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func GenerateNonCryptoID() string {
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return generateID(readerFunc(rand.Read))
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}
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// ValidateID checks whether an ID string is a valid image ID.
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func ValidateID(id string) error {
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if ok := validHex.MatchString(id); !ok {
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return fmt.Errorf("image ID %q is invalid", id)
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}
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return nil
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}
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func init() {
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// safely set the seed globally so we generate random ids. Tries to use a
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// crypto seed before falling back to time.
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var seed int64
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if cryptoseed, err := cryptorand.Int(cryptorand.Reader, big.NewInt(math.MaxInt64)); err != nil {
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// This should not happen, but worst-case fallback to time-based seed.
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seed = time.Now().UnixNano()
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} else {
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seed = cryptoseed.Int64()
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}
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rand.Seed(seed)
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}
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type readerFunc func(p []byte) (int, error)
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func (fn readerFunc) Read(p []byte) (int, error) {
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return fn(p)
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}
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