88 lines
2.4 KiB
Go
88 lines
2.4 KiB
Go
package rand
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import (
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"encoding/hex"
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"io"
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)
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const dash byte = '-'
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// UUIDIdempotencyToken provides a utility to get idempotency tokens in the
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// UUID format.
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type UUIDIdempotencyToken struct {
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uuid *UUID
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}
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// NewUUIDIdempotencyToken returns a idempotency token provider returning
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// tokens in the UUID random format using the reader provided.
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func NewUUIDIdempotencyToken(r io.Reader) *UUIDIdempotencyToken {
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return &UUIDIdempotencyToken{uuid: NewUUID(r)}
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}
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// GetIdempotencyToken returns a random UUID value for Idempotency token.
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func (u UUIDIdempotencyToken) GetIdempotencyToken() (string, error) {
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return u.uuid.GetUUID()
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}
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// UUID provides computing random UUID version 4 values from a random source
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// reader.
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type UUID struct {
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randSrc io.Reader
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}
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// NewUUID returns an initialized UUID value that can be used to retrieve
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// random UUID version 4 values.
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func NewUUID(r io.Reader) *UUID {
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return &UUID{randSrc: r}
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}
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// GetUUID returns a random UUID version 4 string representation sourced from the random reader the
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// UUID was created with. Returns an error if unable to compute the UUID.
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func (r *UUID) GetUUID() (string, error) {
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var b [16]byte
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if _, err := io.ReadFull(r.randSrc, b[:]); err != nil {
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return "", err
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}
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r.makeUUIDv4(b[:])
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return format(b), nil
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}
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// GetBytes returns a byte slice containing a random UUID version 4 sourced from the random reader the
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// UUID was created with. Returns an error if unable to compute the UUID.
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func (r *UUID) GetBytes() (u []byte, err error) {
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u = make([]byte, 16)
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if _, err = io.ReadFull(r.randSrc, u); err != nil {
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return u, err
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}
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r.makeUUIDv4(u)
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return u, nil
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}
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func (r *UUID) makeUUIDv4(u []byte) {
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// 13th character is "4"
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u[6] = (u[6] & 0x0f) | 0x40 // Version 4
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// 17th character is "8", "9", "a", or "b"
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u[8] = (u[8] & 0x3f) | 0x80 // Variant most significant bits are 10x where x can be either 1 or 0
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}
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// Format returns the canonical text representation of a UUID.
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// This implementation is optimized to not use fmt.
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// Example: 82e42f16-b6cc-4d5b-95f5-d403c4befd3d
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func format(u [16]byte) string {
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// https://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_.28random.29
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var scratch [36]byte
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hex.Encode(scratch[:8], u[0:4])
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scratch[8] = dash
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hex.Encode(scratch[9:13], u[4:6])
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scratch[13] = dash
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hex.Encode(scratch[14:18], u[6:8])
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scratch[18] = dash
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hex.Encode(scratch[19:23], u[8:10])
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scratch[23] = dash
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hex.Encode(scratch[24:], u[10:])
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return string(scratch[:])
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}
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