51 lines
1.0 KiB
Go
51 lines
1.0 KiB
Go
package hash
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import (
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"unsafe"
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)
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// Bytes hashes the given byte slice.
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func Bytes(in []byte) uint64 {
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return add(0, in)
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}
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func add(x uint64, in []byte) uint64 {
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var i int
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// Cache lines on modern processors are 64 bytes long.
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// A single uint64 consumes 8 bytes.
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// That means we should read 8 uint64 at a time.
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for ; i < len(in)-63; i += 64 {
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words := (*[8]uint64)(unsafe.Pointer(&in[i]))
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x = mix(x, words[0])
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x = mix(x, words[1])
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x = mix(x, words[2])
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x = mix(x, words[3])
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x = mix(x, words[4])
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x = mix(x, words[5])
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x = mix(x, words[6])
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x = mix(x, words[7])
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}
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// While we have at least 8 bytes left, convert them to uint64.
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for ; i < len(in)-7; i += 8 {
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word := *(*uint64)(unsafe.Pointer(&in[i]))
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x = mix(x, word)
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}
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// Hash the remaining bytes.
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for ; i < len(in); i++ {
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x = mix(x, uint64(in[i]))
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}
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// This helps to avoid clashes between different lengths
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// of all-zero bytes by making the data length significant.
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x = mix(x, uint64(len(in)))
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return x
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}
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func mix(x uint64, b uint64) uint64 {
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return (x + b) * 0xD0003
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}
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