56 lines
1.1 KiB
Go
56 lines
1.1 KiB
Go
package models
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import (
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"encoding/binary"
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"fmt"
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"hash"
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"hash/fnv"
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"math"
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"unsafe"
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)
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// fingerprint is a wrapper for hash.Hash64 that adds utility methods to simplify hash calculation of structs
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type fingerprint struct {
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h hash.Hash64
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}
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// creates a fingerprint that is backed by 64bit FNV-1a hash
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func newFingerprint() fingerprint {
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return fingerprint{h: fnv.New64a()}
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}
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func (f fingerprint) String() string {
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return fmt.Sprintf("%016x", f.h.Sum64())
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}
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func (f fingerprint) writeBytes(b []byte) {
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_, _ = f.h.Write(b)
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// add a byte sequence that cannot happen in UTF-8 strings.
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_, _ = f.h.Write([]byte{255})
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}
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func (f fingerprint) writeString(s string) {
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if len(s) == 0 {
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f.writeBytes(nil)
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return
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}
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// #nosec G103
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// avoid allocation when converting string to byte slice
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f.writeBytes(unsafe.Slice(unsafe.StringData(s), len(s)))
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}
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func (f fingerprint) writeFloat64(num float64) {
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bits := math.Float64bits(num)
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bytes := make([]byte, 8)
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binary.LittleEndian.PutUint64(bytes, bits)
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f.writeBytes(bytes)
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}
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func (f fingerprint) writeBool(b bool) {
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if b {
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f.writeBytes([]byte{1})
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} else {
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f.writeBytes([]byte{0})
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}
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}
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