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@@ -44,7 +44,7 @@ func NewV7FromReader(r io.Reader) (UUID, error) {
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// makeV7 fill 48 bits time (uuid[0] - uuid[5]), set version b0111 (uuid[6])
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// uuid[8] already has the right version number (Variant is 10)
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-// see function NewV7 and NewV7FromReader
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+// see function NewV7 and NewV7FromReader
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func makeV7(uuid []byte) {
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/*
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0 1 2 3
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@@ -52,7 +52,7 @@ func makeV7(uuid []byte) {
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| unix_ts_ms |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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- | unix_ts_ms | ver | rand_a |
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+ | unix_ts_ms | ver | rand_a (12 bit seq) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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|var| rand_b |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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@@ -61,7 +61,7 @@ func makeV7(uuid []byte) {
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*/
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_ = uuid[15] // bounds check
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- t := timeNow().UnixMilli()
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+ t, s := getV7Time()
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uuid[0] = byte(t >> 40)
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uuid[1] = byte(t >> 32)
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@@ -70,6 +70,35 @@ func makeV7(uuid []byte) {
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uuid[4] = byte(t >> 8)
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uuid[5] = byte(t)
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- uuid[6] = 0x70 | (uuid[6] & 0x0F)
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- // uuid[8] has already has right version
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+ uuid[6] = 0x70 | (0x0F & byte(s>>8))
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+ uuid[7] = byte(s)
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+}
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+
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+// lastV7time is the last time we returned stored as:
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+//
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+// 52 bits of time in milliseconds since epoch
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+// 12 bits of (fractional nanoseconds) >> 8
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+var lastV7time int64
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+
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+const nanoPerMilli = 1000000
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+
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+// getV7Time returns the time in milliseconds and nanoseconds / 256.
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+// The returned (milli << 12 + seq) is guarenteed to be greater than
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+// (milli << 12 + seq) returned by any previous call to getV7Time.
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+func getV7Time() (milli, seq int64) {
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+ timeMu.Lock()
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+ defer timeMu.Unlock()
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+
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+ nano := timeNow().UnixNano()
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+ milli = nano / nanoPerMilli
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+ // Sequence number is between 0 and 3906 (nanoPerMilli>>8)
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+ seq = (nano - milli*nanoPerMilli) >> 8
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+ now := milli<<12 + seq
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+ if now <= lastV7time {
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+ now = lastV7time + 1
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+ milli = now >> 12
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+ seq = now & 0xfff
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+ }
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+ lastV7time = now
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+ return milli, seq
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}
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