vendor/github.com/hashicorp/terraform/helper/resource/id.go

   1 package resource
   2
   3 import (
   4         "crypto/rand"
   5         "fmt"
   6         "math/big"
   7         "sync"
   8 )
   9
  10 const UniqueIdPrefix = `terraform-`
  11
  12 // idCounter is a randomly seeded monotonic counter for generating ordered
  13 // unique ids.  It uses a big.Int so we can easily increment a long numeric
  14 // string.  The max possible hex value here with 12 random bytes is
  15 // "01000000000000000000000000", so there's no chance of rollover during
  16 // operation.
  17 var idMutex sync.Mutex
  18 var idCounter = big.NewInt(0).SetBytes(randomBytes(12))
  19
  20 // Helper for a resource to generate a unique identifier w/ default prefix
  21 func UniqueId() string {
  22         return PrefixedUniqueId(UniqueIdPrefix)
  23 }
  24
  25 // Helper for a resource to generate a unique identifier w/ given prefix
  26 //
  27 // After the prefix, the ID consists of an incrementing 26 digit value (to match
  28 // previous timestamp output).
  29 func PrefixedUniqueId(prefix string) string {
  30         idMutex.Lock()
  31         defer idMutex.Unlock()
  32         return fmt.Sprintf("%s%026x", prefix, idCounter.Add(idCounter, big.NewInt(1)))
  33 }
  34
  35 func randomBytes(n int) []byte {
  36         b := make([]byte, n)
  37         rand.Read(b)
  38         return b
  39 }