56 lines
1.2 KiB
Go
56 lines
1.2 KiB
Go
package ksuid
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import (
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cryptoRand "crypto/rand"
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"encoding/binary"
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"io"
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"math/rand"
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)
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// FastRander is an io.Reader that uses math/rand and is optimized for
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// generating 16 bytes KSUID payloads. It is intended to be used as a
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// performance improvements for programs that have no need for
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// cryptographically secure KSUIDs and are generating a lot of them.
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var FastRander = newRBG()
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func newRBG() io.Reader {
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r, err := newRandomBitsGenerator()
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if err != nil {
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panic(err)
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}
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return r
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}
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func newRandomBitsGenerator() (r io.Reader, err error) {
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var seed int64
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if seed, err = readCryptoRandomSeed(); err != nil {
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return
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}
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r = &randSourceReader{source: rand.NewSource(seed).(rand.Source64)}
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return
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}
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func readCryptoRandomSeed() (seed int64, err error) {
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var b [8]byte
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if _, err = io.ReadFull(cryptoRand.Reader, b[:]); err != nil {
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return
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}
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seed = int64(binary.LittleEndian.Uint64(b[:]))
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return
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}
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type randSourceReader struct {
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source rand.Source64
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}
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func (r *randSourceReader) Read(b []byte) (int, error) {
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// optimized for generating 16 bytes payloads
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binary.LittleEndian.PutUint64(b[:8], r.source.Uint64())
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binary.LittleEndian.PutUint64(b[8:], r.source.Uint64())
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return 16, nil
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}
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