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util/sha256x: rename Hash as Block512 (#5351)

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Rename Hash as Block512 to indicate that this is a general-purpose
hash.Hash for any algorithm that operates on 512-bit block sizes.

While we rename the package as hashx in this commit,
a subsequent commit will move the sha256x package to hashx.
This is done separately to avoid confusing git.

Signed-off-by: Joe Tsai <joetsai@digital-static.net>
This commit is contained in:
Joe Tsai 2022-08-16 09:49:48 -07:00 committed by GitHub
parent 44d62b65d0
commit f061d20c9d
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 106 additions and 72 deletions
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11
util/deephash/deephash.go
View File

@ -34,7 +34,7 @@
"time"
"unsafe"
"tailscale.com/util/sha256x"
hashx "tailscale.com/util/sha256x"
)
// There is much overlap between the theory of serialization and hashing.
@ -82,7 +82,7 @@ func newAddressableValue(t reflect.Type) addressableValue {
// hasher is reusable state for hashing a value.
// Get one via hasherPool.
type hasher struct {
sha256x.Hash
hashx.Block512
scratch [scratchSize]byte
visitStack visitStack
}
@ -111,6 +111,13 @@ func initSeed() {
seed = uint64(time.Now().UnixNano())
}
func (h *hasher) Reset() {
if h.Block512.Hash == nil {
h.Block512.Hash = sha256.New()
}
h.Block512.Reset()
}
func (h *hasher) sum() (s Sum) {
h.Sum(s.sum[:0])
return s

8
util/deephash/deephash_test.go
View File

@ -531,7 +531,7 @@ func TestGetTypeHasher(t *testing.T) {
fn := getTypeInfo(va.Type()).hasher()
hb := &hashBuffer{Hash: sha256.New()}
h := new(hasher)
h.Hash.H = hb
h.Block512.Hash = hb
got := fn(h, va)
const ptrSize = 32 << uintptr(^uintptr(0)>>63)
if tt.out32 != "" && ptrSize == 32 {
@ -628,7 +628,7 @@ func TestHashMapAcyclic(t *testing.T) {
v := addressableValue{reflect.ValueOf(&m).Elem()}
hb.Reset()
h := new(hasher)
h.Hash.H = hb
h.Block512.Hash = hb
h.hashMap(v, ti, false)
h.sum()
if got[string(hb.B)] {
@ -648,7 +648,7 @@ type T struct {
x := T{X: [32]byte{1: 1, 31: 31}}
hb := &hashBuffer{Hash: sha256.New()}
h := new(hasher)
h.Hash.H = hb
h.Block512.Hash = hb
h.hashValue(addressableValue{reflect.ValueOf(&x).Elem()}, false)
h.sum()
const want = "\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x1f"
@ -669,7 +669,7 @@ func BenchmarkHashMapAcyclic(b *testing.B) {
ti := getTypeInfo(v.Type())
h := new(hasher)
h.Hash.H = hb
h.Block512.Hash = hb
for i := 0; i < b.N; i++ {
h.Reset()

136
util/sha256x/sha256.go
View File

@ -2,51 +2,76 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package sha256x is like crypto/sha256 with extra methods.
// It exports a concrete Hash type
// rather than only returning an interface implementation.
package sha256x
// Package hashx provides a concrete implementation of [hash.Hash]
// that operates on a particular block size.
package hashx
import (
"crypto/sha256"
"encoding/binary"
"fmt"
"hash"
"unsafe"
)
var _ hash.Hash = (*Hash)(nil)
var _ hash.Hash = (*Block512)(nil)
// Hash is a hash.Hash for SHA-256,
// but has efficient methods for hashing fixed-width integers.
type Hash struct {
// The optimization is to maintain our own block and
// only call h.Write with entire blocks.
// This avoids double-copying of buffers within sha256.digest itself.
// However, it does mean that sha256.digest.x goes unused,
// which is a waste of 64B.
// Block512 wraps a [hash.Hash] for functions that operate on 512-bit block sizes.
// It has efficient methods for hashing fixed-width integers.
//
// A hashing algorithm that operates on 512-bit block sizes should be used.
// The hash still operates correctly even with misaligned block sizes,
// but operates less efficiently.
//
// Example algorithms with 512-bit block sizes include:
// - MD4 (https://golang.org/x/crypto/md4)
// - MD5 (https://golang.org/pkg/crypto/md5)
// - BLAKE2s (https://golang.org/x/crypto/blake2s)
// - BLAKE3
// - RIPEMD (https://golang.org/x/crypto/ripemd160)
// - SHA-0
// - SHA-1 (https://golang.org/pkg/crypto/sha1)
// - SHA-2 (https://golang.org/pkg/crypto/sha256)
// - Whirlpool
//
// See https://en.wikipedia.org/wiki/Comparison_of_cryptographic_hash_functions#Parameters
// for a list of hash functions and their block sizes.
//
// Block512 assumes that [hash.Hash.Write] never fails and
// never allows the provided buffer to escape.
type Block512 struct {
hash.Hash
// H is the underlying hash.Hash.
// The hash.Hash.BlockSize must be equal to sha256.BlockSize.
// It is exported only for testing purposes.
H hash.Hash // usually a *sha256.digest
x [sha256.BlockSize]byte // equivalent to sha256.digest.x
nx int // equivalent to sha256.digest.nx
x [512 / 8]byte
nx int
}
func New() *Hash {
return &Hash{H: sha256.New()}
// New512 constructs a new Block512 that wraps h.
//
// It reports an error if the block sizes do not match.
// Misaligned block sizes perform poorly, but execute correctly.
// The error may be ignored if performance is not a concern.
func New512(h hash.Hash) (*Block512, error) {
b := &Block512{Hash: h}
if len(b.x)%h.BlockSize() != 0 {
return b, fmt.Errorf("hashx.Block512: inefficient use of hash.Hash with %d-bit block size", 8*h.BlockSize())
}
return b, nil
}
func (h *Hash) Write(b []byte) (int, error) {
// Write hashes the contents of b.
func (h *Block512) Write(b []byte) (int, error) {
h.HashBytes(b)
return len(b), nil
}
func (h *Hash) Sum(b []byte) []byte {
// Sum appends the current hash to b and returns the resulting slice.
//
// It flushes any partially completed blocks to the underlying [hash.Hash],
// which may cause future operations to be misaligned and less efficient
// until [Block512.Reset] is called.
func (h *Block512) Sum(b []byte) []byte {
if h.nx > 0 {
// This causes block mis-alignment. Future operations will be correct,
// but are less efficient until Reset is called.
h.H.Write(h.x[:h.nx])
h.Hash.Write(h.x[:h.nx])
h.nx = 0
}
@ -54,27 +79,19 @@ func (h *Hash) Sum(b []byte) []byte {
// escape analysis cannot prove anything past an interface method call.
// Assuming h already escapes, we call Sum with h.x first,
// and then copy the result to b.
sum := h.H.Sum(h.x[:0])
sum := h.Hash.Sum(h.x[:0])
return append(b, sum...)
}
func (h *Hash) Reset() {
if h.H == nil {
h.H = sha256.New()
}
h.H.Reset()
// Reset resets Block512 to its initial state.
// It recursively resets the underlying [hash.Hash].
func (h *Block512) Reset() {
h.Hash.Reset()
h.nx = 0
}
func (h *Hash) Size() int {
return h.H.Size()
}
func (h *Hash) BlockSize() int {
return h.H.BlockSize()
}
func (h *Hash) HashUint8(n uint8) {
// HashUint8 hashes n as a 1-byte integer.
func (h *Block512) HashUint8(n uint8) {
// NOTE: This method is carefully written to be inlineable.
if h.nx <= len(h.x)-1 {
h.x[h.nx] = n
@ -85,9 +102,10 @@ func (h *Hash) HashUint8(n uint8) {
}
//go:noinline
func (h *Hash) hashUint8Slow(n uint8) { h.hashUint(uint64(n), 1) }
func (h *Block512) hashUint8Slow(n uint8) { h.hashUint(uint64(n), 1) }
func (h *Hash) HashUint16(n uint16) {
// HashUint16 hashes n as a 2-byte little-endian integer.
func (h *Block512) HashUint16(n uint16) {
// NOTE: This method is carefully written to be inlineable.
if h.nx <= len(h.x)-2 {
binary.LittleEndian.PutUint16(h.x[h.nx:], n)
@ -98,9 +116,10 @@ func (h *Hash) HashUint16(n uint16) {
}
//go:noinline
func (h *Hash) hashUint16Slow(n uint16) { h.hashUint(uint64(n), 2) }
func (h *Block512) hashUint16Slow(n uint16) { h.hashUint(uint64(n), 2) }
func (h *Hash) HashUint32(n uint32) {
// HashUint32 hashes n as a 4-byte little-endian integer.
func (h *Block512) HashUint32(n uint32) {
// NOTE: This method is carefully written to be inlineable.
if h.nx <= len(h.x)-4 {
binary.LittleEndian.PutUint32(h.x[h.nx:], n)
@ -111,9 +130,10 @@ func (h *Hash) HashUint32(n uint32) {
}
//go:noinline
func (h *Hash) hashUint32Slow(n uint32) { h.hashUint(uint64(n), 4) }
func (h *Block512) hashUint32Slow(n uint32) { h.hashUint(uint64(n), 4) }
func (h *Hash) HashUint64(n uint64) {
// HashUint64 hashes n as a 8-byte little-endian integer.
func (h *Block512) HashUint64(n uint64) {
// NOTE: This method is carefully written to be inlineable.
if h.nx <= len(h.x)-8 {
binary.LittleEndian.PutUint64(h.x[h.nx:], n)
@ -124,12 +144,12 @@ func (h *Hash) HashUint64(n uint64) {
}
//go:noinline
func (h *Hash) hashUint64Slow(n uint64) { h.hashUint(uint64(n), 8) }
func (h *Block512) hashUint64Slow(n uint64) { h.hashUint(uint64(n), 8) }
func (h *Hash) hashUint(n uint64, i int) {
func (h *Block512) hashUint(n uint64, i int) {
for ; i > 0; i-- {
if h.nx == len(h.x) {
h.H.Write(h.x[:])
h.Hash.Write(h.x[:])
h.nx = 0
}
h.x[h.nx] = byte(n)
@ -138,20 +158,22 @@ func (h *Hash) hashUint(n uint64, i int) {
}
}
func (h *Hash) HashBytes(b []byte) {
// HashBytes hashes the contents of b.
// It does not explicitly hash the length separately.
func (h *Block512) HashBytes(b []byte) {
// Nearly identical to sha256.digest.Write.
if h.nx > 0 {
n := copy(h.x[h.nx:], b)
h.nx += n
if h.nx == len(h.x) {
h.H.Write(h.x[:])
h.Hash.Write(h.x[:])
h.nx = 0
}
b = b[n:]
}
if len(b) >= len(h.x) {
n := len(b) &^ (len(h.x) - 1) // n is a multiple of len(h.x)
h.H.Write(b[:n])
h.Hash.Write(b[:n])
b = b[n:]
}
if len(b) > 0 {
@ -159,7 +181,11 @@ func (h *Hash) HashBytes(b []byte) {
}
}
func (h *Hash) HashString(s string) {
// HashString hashes the contents of s.
// It does not explicitly hash the length separately.
func (h *Block512) HashString(s string) {
// TODO: Avoid unsafe when standard hashers implement io.StringWriter.
// See https://go.dev/issue/38776.
type stringHeader struct {
p unsafe.Pointer
n int

23
util/sha256x/sha256_test.go
View File

@ -2,7 +2,7 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package sha256x
package hashx
import (
"crypto/sha256"
@ -12,6 +12,7 @@
"testing"
qt "github.com/frankban/quicktest"
"tailscale.com/util/must"
)
// naiveHash is an obviously correct implementation of Hash.
@ -74,7 +75,7 @@ func hashSuite(h hasher) {
func Test(t *testing.T) {
c := qt.New(t)
h1 := New()
h1 := must.Get(New512(sha256.New()))
h2 := newNaive()
hashSuite(h1)
hashSuite(h2)
@ -84,44 +85,44 @@ func Test(t *testing.T) {
func TestAllocations(t *testing.T) {
c := qt.New(t)
c.Run("Sum", func(c *qt.C) {
h := New()
h := must.Get(New512(sha256.New()))
c.Assert(testing.AllocsPerRun(100, func() {
var a [sha256.Size]byte
h.Sum(a[:0])
}), qt.Equals, 0.0)
})
c.Run("HashUint8", func(c *qt.C) {
h := New()
h := must.Get(New512(sha256.New()))
c.Assert(testing.AllocsPerRun(100, func() {
h.HashUint8(0x01)
}), qt.Equals, 0.0)
})
c.Run("HashUint16", func(c *qt.C) {
h := New()
h := must.Get(New512(sha256.New()))
c.Assert(testing.AllocsPerRun(100, func() {
h.HashUint16(0x0123)
}), qt.Equals, 0.0)
})
c.Run("HashUint32", func(c *qt.C) {
h := New()
h := must.Get(New512(sha256.New()))
c.Assert(testing.AllocsPerRun(100, func() {
h.HashUint32(0x01234567)
}), qt.Equals, 0.0)
})
c.Run("HashUint64", func(c *qt.C) {
h := New()
h := must.Get(New512(sha256.New()))
c.Assert(testing.AllocsPerRun(100, func() {
h.HashUint64(0x0123456789abcdef)
}), qt.Equals, 0.0)
})
c.Run("HashBytes", func(c *qt.C) {
h := New()
h := must.Get(New512(sha256.New()))
c.Assert(testing.AllocsPerRun(100, func() {
h.HashBytes(bytes)
}), qt.Equals, 0.0)
})
c.Run("HashString", func(c *qt.C) {
h := New()
h := must.Get(New512(sha256.New()))
c.Assert(testing.AllocsPerRun(100, func() {
h.HashString("abcdefghijklmnopqrstuvwxyz")
}), qt.Equals, 0.0)
@ -158,7 +159,7 @@ func Fuzz(f *testing.F) {
r1 := rand.New(rand.NewSource(seed))
r2 := rand.New(rand.NewSource(seed))
h1 := New()
h1 := must.Get(New512(sha256.New()))
h2 := newNaive()
execute(h1, r1)
@ -185,7 +186,7 @@ func Benchmark(b *testing.B) {
var sum [sha256.Size]byte
b.Run("Hash", func(b *testing.B) {
b.ReportAllocs()
h := New()
h := must.Get(New512(sha256.New()))
for i := 0; i < b.N; i++ {
h.Reset()
hashSuite(h)