/
hash.go
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/
hash.go
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// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to You under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package exec
import (
"encoding/binary"
"fmt"
"hash"
"hash/maphash"
"math"
"reflect"
"github.com/apache/beam/sdks/v2/go/pkg/beam/core/graph/coder"
"github.com/apache/beam/sdks/v2/go/pkg/beam/core/typex"
"github.com/apache/beam/sdks/v2/go/pkg/beam/core/util/reflectx"
)
// Infrastructure for hashing values for lifted combines.
type elementHasher interface {
Hash(element interface{}, w typex.Window) (uint64, error)
}
func makeElementHasher(c *coder.Coder, wc *coder.WindowCoder) elementHasher {
hasher := &maphash.Hash{}
we := MakeWindowEncoder(wc)
switch c.Kind {
case coder.Bytes:
return &bytesHasher{hash: hasher, we: we}
case coder.VarInt:
return newNumberHasher(hasher, we)
case coder.String:
return &stringHasher{hash: hasher, we: we}
case coder.Row:
enc := MakeElementEncoder(c)
return &rowHasher{
hash: hasher,
coder: enc,
we: we,
}
case coder.Custom:
// Shortcut for primitives where we know we can do better.
switch c.Custom.Type {
case reflectx.Int, reflectx.Int8, reflectx.Int16, reflectx.Int32, reflectx.Int64,
reflectx.Uint, reflectx.Uint8, reflectx.Uint16, reflectx.Uint32, reflectx.Uint64,
reflectx.Float32, reflectx.Float64:
return newNumberHasher(hasher, we)
}
// TODO(lostluck): 2019.02.07 - consider supporting encoders that
// take in a io.Writer instead.
return &customEncodedHasher{
hash: hasher,
t: c.Custom.Type,
coder: makeEncoder(c.Custom.Enc.Fn),
we: we,
}
default:
panic(fmt.Sprintf("Unexpected coder for hashing: %v", c))
}
}
type bytesHasher struct {
hash hash.Hash64
we WindowEncoder
}
func (h *bytesHasher) Hash(element interface{}, w typex.Window) (uint64, error) {
h.hash.Reset()
h.hash.Write(element.([]byte))
h.we.EncodeSingle(w, h.hash)
return h.hash.Sum64(), nil
}
type stringHasher struct {
hash hash.Hash64
we WindowEncoder
}
func (h *stringHasher) Hash(element interface{}, w typex.Window) (uint64, error) {
h.hash.Reset()
s := element.(string)
var b [64]byte
l := len(s)
i := 0
for len(s)-i > 64 {
n := i + 64
copy(b[:], s[i:n])
h.hash.Write(b[:])
i = n
}
n := l - i
copy(b[:], s[i:])
h.hash.Write(b[:n])
h.we.EncodeSingle(w, h.hash)
return h.hash.Sum64(), nil
}
type numberHasher struct {
hash hash.Hash64
we WindowEncoder
cache []byte
}
func newNumberHasher(hash hash.Hash64, we WindowEncoder) *numberHasher {
return &numberHasher{
hash: hash,
we: we,
// Pre allocate slice to avoid re-allocations.
cache: make([]byte, 8),
}
}
func (h *numberHasher) Hash(element interface{}, w typex.Window) (uint64, error) {
h.hash.Reset()
var val uint64
switch n := element.(type) {
case int:
val = uint64(n)
case int8:
val = uint64(n)
case int16:
val = uint64(n)
case int32:
val = uint64(n)
case int64:
val = uint64(n)
case uint:
val = uint64(n)
case uint8:
val = uint64(n)
case uint16:
val = uint64(n)
case uint32:
val = uint64(n)
case uint64:
val = n
case float64:
val = math.Float64bits(n)
case float32:
val = uint64(math.Float64bits(float64(n)))
default:
panic(fmt.Sprintf("received unknown value type: want a number:, got %T", n))
}
binary.LittleEndian.PutUint64(h.cache, val)
h.hash.Write(h.cache)
h.we.EncodeSingle(w, h.hash)
return h.hash.Sum64(), nil
}
type rowHasher struct {
hash hash.Hash64
coder ElementEncoder
we WindowEncoder
fv FullValue
}
func (h *rowHasher) Hash(element interface{}, w typex.Window) (uint64, error) {
h.hash.Reset()
h.fv.Elm = element
if err := h.coder.Encode(&h.fv, h.hash); err != nil {
return 0, err
}
h.fv.Elm = nil
h.we.EncodeSingle(w, h.hash)
return h.hash.Sum64(), nil
}
type customEncodedHasher struct {
hash hash.Hash64
t reflect.Type
coder Encoder
we WindowEncoder
}
func (h *customEncodedHasher) Hash(element interface{}, w typex.Window) (uint64, error) {
h.hash.Reset()
b, err := h.coder.Encode(h.t, element)
if err != nil {
return 0, err
}
h.hash.Write(b)
h.we.EncodeSingle(w, h.hash)
return h.hash.Sum64(), nil
}