diff options
Diffstat (limited to 'dependencies/pkg/mod/github.com/google/uuid@v1.6.0/version7.go')
-rw-r--r-- | dependencies/pkg/mod/github.com/google/uuid@v1.6.0/version7.go | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/dependencies/pkg/mod/github.com/google/uuid@v1.6.0/version7.go b/dependencies/pkg/mod/github.com/google/uuid@v1.6.0/version7.go new file mode 100644 index 0000000..3167b64 --- /dev/null +++ b/dependencies/pkg/mod/github.com/google/uuid@v1.6.0/version7.go @@ -0,0 +1,104 @@ +// Copyright 2023 Google Inc. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package uuid + +import ( + "io" +) + +// UUID version 7 features a time-ordered value field derived from the widely +// implemented and well known Unix Epoch timestamp source, +// the number of milliseconds seconds since midnight 1 Jan 1970 UTC, leap seconds excluded. +// As well as improved entropy characteristics over versions 1 or 6. +// +// see https://datatracker.ietf.org/doc/html/draft-peabody-dispatch-new-uuid-format-03#name-uuid-version-7 +// +// Implementations SHOULD utilize UUID version 7 over UUID version 1 and 6 if possible. +// +// NewV7 returns a Version 7 UUID based on the current time(Unix Epoch). +// Uses the randomness pool if it was enabled with EnableRandPool. +// On error, NewV7 returns Nil and an error +func NewV7() (UUID, error) { + uuid, err := NewRandom() + if err != nil { + return uuid, err + } + makeV7(uuid[:]) + return uuid, nil +} + +// NewV7FromReader returns a Version 7 UUID based on the current time(Unix Epoch). +// it use NewRandomFromReader fill random bits. +// On error, NewV7FromReader returns Nil and an error. +func NewV7FromReader(r io.Reader) (UUID, error) { + uuid, err := NewRandomFromReader(r) + if err != nil { + return uuid, err + } + + makeV7(uuid[:]) + return uuid, nil +} + +// makeV7 fill 48 bits time (uuid[0] - uuid[5]), set version b0111 (uuid[6]) +// uuid[8] already has the right version number (Variant is 10) +// see function NewV7 and NewV7FromReader +func makeV7(uuid []byte) { + /* + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | unix_ts_ms | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | unix_ts_ms | ver | rand_a (12 bit seq) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |var| rand_b | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | rand_b | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + */ + _ = uuid[15] // bounds check + + t, s := getV7Time() + + uuid[0] = byte(t >> 40) + uuid[1] = byte(t >> 32) + uuid[2] = byte(t >> 24) + uuid[3] = byte(t >> 16) + uuid[4] = byte(t >> 8) + uuid[5] = byte(t) + + uuid[6] = 0x70 | (0x0F & byte(s>>8)) + uuid[7] = byte(s) +} + +// lastV7time is the last time we returned stored as: +// +// 52 bits of time in milliseconds since epoch +// 12 bits of (fractional nanoseconds) >> 8 +var lastV7time int64 + +const nanoPerMilli = 1000000 + +// getV7Time returns the time in milliseconds and nanoseconds / 256. +// The returned (milli << 12 + seq) is guarenteed to be greater than +// (milli << 12 + seq) returned by any previous call to getV7Time. +func getV7Time() (milli, seq int64) { + timeMu.Lock() + defer timeMu.Unlock() + + nano := timeNow().UnixNano() + milli = nano / nanoPerMilli + // Sequence number is between 0 and 3906 (nanoPerMilli>>8) + seq = (nano - milli*nanoPerMilli) >> 8 + now := milli<<12 + seq + if now <= lastV7time { + now = lastV7time + 1 + milli = now >> 12 + seq = now & 0xfff + } + lastV7time = now + return milli, seq +} |