journald.go/journal-basetypes.go at master · lemenkov/journald.go · GitHub

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// SPDX-License-Identifier: Apache-2.0
// Copyright 2014 Peter Lemenkov <lemenkov@gmail.com>

package journal

// SDID128 represents a 128-bit systemd identifier (file_id, machine_id, boot_id, seqnum_id).
type SDID128 [16]byte

// JenkinsHash computes the Jenkins lookup3 hashlittle2 hash used by journal files
// without the KEYED_HASH incompatible flag.
// Returns (uint64(pc) << 32) | uint64(pb) per the journal file format spec.
func JenkinsHash(data []byte) uint64 {
	pc, pb := jenkinsHashlittle2(data, 0, 0)
	return uint64(pc)<<32 | uint64(pb)
}

func rot32(x, k uint32) uint32 {
	return (x << k) | (x >> (32 - k))
}

func jenkinsMix(a, b, c uint32) (uint32, uint32, uint32) {
	a -= c
	a ^= rot32(c, 4)
	c += b
	b -= a
	b ^= rot32(a, 6)
	a += c
	c -= b
	c ^= rot32(b, 8)
	b += a
	a -= c
	a ^= rot32(c, 16)
	c += b
	b -= a
	b ^= rot32(a, 19)
	a += c
	c -= b
	c ^= rot32(b, 4)
	b += a
	return a, b, c
}

func jenkinsFinal(a, b, c uint32) (uint32, uint32, uint32) {
	c ^= b
	c -= rot32(b, 14)
	a ^= c
	a -= rot32(c, 11)
	b ^= a
	b -= rot32(a, 25)
	c ^= b
	c -= rot32(b, 16)
	a ^= c
	a -= rot32(c, 4)
	b ^= a
	b -= rot32(a, 14)
	c ^= b
	c -= rot32(b, 24)
	return a, b, c
}

// jenkinsHashlittle2 is a Go translation of Bob Jenkins' hashlittle2() from lookup3.c.
func jenkinsHashlittle2(data []byte, initPC, initPB uint32) (uint32, uint32) {
	length := len(data)
	a := uint32(0xdeadbeef) + uint32(length) + initPC
	b := a
	c := a + initPB

	i := 0
	for length > 12 {
		a += uint32(data[i]) | uint32(data[i+1])<<8 | uint32(data[i+2])<<16 | uint32(data[i+3])<<24
		b += uint32(data[i+4]) | uint32(data[i+5])<<8 | uint32(data[i+6])<<16 | uint32(data[i+7])<<24
		c += uint32(data[i+8]) | uint32(data[i+9])<<8 | uint32(data[i+10])<<16 | uint32(data[i+11])<<24
		a, b, c = jenkinsMix(a, b, c)
		i += 12
		length -= 12
	}

	k := data[i:]
	switch length {
	case 12:
		c += uint32(k[11]) << 24
		fallthrough
	case 11:
		c += uint32(k[10]) << 16
		fallthrough
	case 10:
		c += uint32(k[9]) << 8
		fallthrough
	case 9:
		c += uint32(k[8])
		fallthrough
	case 8:
		b += uint32(k[7]) << 24
		fallthrough
	case 7:
		b += uint32(k[6]) << 16
		fallthrough
	case 6:
		b += uint32(k[5]) << 8
		fallthrough
	case 5:
		b += uint32(k[4])
		fallthrough
	case 4:
		a += uint32(k[3]) << 24
		fallthrough
	case 3:
		a += uint32(k[2]) << 16
		fallthrough
	case 2:
		a += uint32(k[1]) << 8
		fallthrough
	case 1:
		a += uint32(k[0])
		a, b, c = jenkinsFinal(a, b, c)
	}

	return c, b
}