54 lines
1.5 KiB
Go
54 lines
1.5 KiB
Go
package resource
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import (
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"crypto/rand"
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"encoding/base32"
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"fmt"
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"strings"
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"time"
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)
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const UniqueIdPrefix = `terraform-`
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// Helper for a resource to generate a unique identifier w/ default prefix
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func UniqueId() string {
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return PrefixedUniqueId(UniqueIdPrefix)
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}
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// Helper for a resource to generate a unique identifier w/ given prefix
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//
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// After the prefix, the ID consists of a timestamp and 12 random base32
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// characters. The timestamp means that multiple IDs created with the same
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// prefix will sort in the order of their creation.
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func PrefixedUniqueId(prefix string) string {
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// Be precise to the level nanoseconds, but remove the dot before the
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// nanosecond. We assume that the randomCharacters call takes at least a
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// nanosecond, so that multiple calls to this function from the same goroutine
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// will have distinct ordered timestamps.
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timestamp := strings.Replace(
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time.Now().UTC().Format("20060102150405.000000000"),
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".",
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"", 1)
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// This uses 3 characters, so that the length of the unique ID is the same as
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// it was before we added the timestamp prefix, which happened to be 23
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// characters.
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return fmt.Sprintf("%s%s%s", prefix, timestamp, randomCharacters(3))
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}
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func randomCharacters(n int) string {
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// Base32 has 5 bits of information per character.
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b := randomBytes(n * 8 / 5)
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chars := strings.ToLower(
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strings.Replace(
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base32.StdEncoding.EncodeToString(b),
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"=", "", -1))
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// Trim extra characters.
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return chars[:n]
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}
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func randomBytes(n int) []byte {
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b := make([]byte, n)
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rand.Read(b)
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return b
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}
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