forked from apache/beam
/
iterable.go
122 lines (114 loc) · 3.66 KB
/
iterable.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
// 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 coder
import (
"io"
"reflect"
"github.com/apache/beam/sdks/go/pkg/beam/internal/errors"
)
// TODO(lostluck): 2020.06.29 export these for use for others?
// iterableEncoder reflectively encodes a slice or array type using
// the beam fixed length iterable encoding.
func iterableEncoder(rt reflect.Type, encode func(reflect.Value, io.Writer) error) func(reflect.Value, io.Writer) error {
return func(rv reflect.Value, w io.Writer) error {
size := rv.Len()
if err := EncodeInt32((int32)(size), w); err != nil {
return err
}
for i := 0; i < size; i++ {
if err := encode(rv.Index(i), w); err != nil {
return err
}
}
return nil
}
}
// iterableDecoderForSlice can decode from both the fixed sized and
// multi-chunk variants of the beam iterable protocol.
// Returns an error for other protocols (such as state backed).
func iterableDecoderForSlice(rt reflect.Type, decodeToElem func(reflect.Value, io.Reader) error) func(reflect.Value, io.Reader) error {
return func(ret reflect.Value, r io.Reader) error {
// (1) Read count prefixed encoded data
size, err := DecodeInt32(r)
if err != nil {
return err
}
n := int(size)
switch {
case n >= 0:
rv := reflect.MakeSlice(rt, n, n)
if err := decodeToIterable(rv, r, decodeToElem); err != nil {
return err
}
ret.Set(rv)
return nil
case n == -1:
chunk, err := DecodeVarInt(r)
if err != nil {
return err
}
rv := reflect.MakeSlice(rt, 0, int(chunk))
for chunk != 0 {
rvi := reflect.MakeSlice(rt, int(chunk), int(chunk))
if err := decodeToIterable(rvi, r, decodeToElem); err != nil {
return err
}
rv = reflect.AppendSlice(rv, rvi)
chunk, err = DecodeVarInt(r)
if err != nil {
return err
}
}
ret.Set(rv)
return nil
default:
return errors.Errorf("unable to decode slice iterable with size: %d", n)
}
}
}
// iterableDecoderForArray can decode from only the fixed sized and
// multi-chunk variant of the beam iterable protocol.
// Returns an error for other protocols (such as state backed).
func iterableDecoderForArray(rt reflect.Type, decodeToElem func(reflect.Value, io.Reader) error) func(reflect.Value, io.Reader) error {
return func(ret reflect.Value, r io.Reader) error {
// (1) Read count prefixed encoded data
size, err := DecodeInt32(r)
if err != nil {
return err
}
n := int(size)
if rt.Len() != n {
return errors.Errorf("len mismatch decoding a %v: want %d got %d", rt, rt.Len(), n)
}
switch {
case n >= 0:
if err := decodeToIterable(ret, r, decodeToElem); err != nil {
return err
}
return nil
default:
return errors.Errorf("unable to decode array iterable with size: %d", n)
}
}
}
func decodeToIterable(rv reflect.Value, r io.Reader, decodeTo func(reflect.Value, io.Reader) error) error {
for i := 0; i < rv.Len(); i++ {
err := decodeTo(rv.Index(i), r)
if err != nil {
return err
}
}
return nil
}