/
null.go
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/
null.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 array
import (
"bytes"
"fmt"
"reflect"
"strings"
"sync/atomic"
"github.com/apache/arrow/go/v16/arrow"
"github.com/apache/arrow/go/v16/arrow/internal/debug"
"github.com/apache/arrow/go/v16/arrow/memory"
"github.com/apache/arrow/go/v16/internal/json"
)
// Null represents an immutable, degenerate array with no physical storage.
type Null struct {
array
}
// NewNull returns a new Null array value of size n.
func NewNull(n int) *Null {
a := &Null{}
a.refCount = 1
data := NewData(
arrow.Null, n,
[]*memory.Buffer{nil},
nil,
n,
0,
)
a.setData(data)
data.Release()
return a
}
// NewNullData returns a new Null array value, from data.
func NewNullData(data arrow.ArrayData) *Null {
a := &Null{}
a.refCount = 1
a.setData(data.(*Data))
return a
}
func (a *Null) ValueStr(int) string { return NullValueStr }
func (a *Null) Value(int) interface{} { return nil }
func (a *Null) String() string {
o := new(strings.Builder)
o.WriteString("[")
for i := 0; i < a.Len(); i++ {
if i > 0 {
o.WriteString(" ")
}
o.WriteString(NullValueStr)
}
o.WriteString("]")
return o.String()
}
func (a *Null) setData(data *Data) {
a.array.setData(data)
a.array.nullBitmapBytes = nil
a.array.data.nulls = a.array.data.length
}
func (a *Null) GetOneForMarshal(i int) interface{} {
return nil
}
func (a *Null) MarshalJSON() ([]byte, error) {
return json.Marshal(make([]interface{}, a.Len()))
}
type NullBuilder struct {
builder
}
// NewNullBuilder returns a builder, using the provided memory allocator.
func NewNullBuilder(mem memory.Allocator) *NullBuilder {
return &NullBuilder{builder: builder{refCount: 1, mem: mem}}
}
func (b *NullBuilder) Type() arrow.DataType { return arrow.Null }
// Release decreases the reference count by 1.
// When the reference count goes to zero, the memory is freed.
func (b *NullBuilder) Release() {
debug.Assert(atomic.LoadInt64(&b.refCount) > 0, "too many releases")
if atomic.AddInt64(&b.refCount, -1) == 0 {
if b.nullBitmap != nil {
b.nullBitmap.Release()
b.nullBitmap = nil
}
}
}
func (b *NullBuilder) AppendNull() {
b.builder.length++
b.builder.nulls++
}
func (b *NullBuilder) AppendNulls(n int) {
for i := 0; i < n; i++ {
b.AppendNull()
}
}
func (b *NullBuilder) AppendValueFromString(s string) error {
if s == NullValueStr {
b.AppendNull()
return nil
}
return fmt.Errorf("cannot convert %q to null", s)
}
func (b *NullBuilder) AppendEmptyValue() { b.AppendNull() }
func (b *NullBuilder) AppendEmptyValues(n int) { b.AppendNulls(n) }
func (*NullBuilder) Reserve(size int) {}
func (*NullBuilder) Resize(size int) {}
func (*NullBuilder) init(cap int) {}
func (*NullBuilder) resize(newBits int, init func(int)) {}
// NewArray creates a Null array from the memory buffers used by the builder and resets the NullBuilder
// so it can be used to build a new array.
func (b *NullBuilder) NewArray() arrow.Array {
return b.NewNullArray()
}
// NewNullArray creates a Null array from the memory buffers used by the builder and resets the NullBuilder
// so it can be used to build a new array.
func (b *NullBuilder) NewNullArray() (a *Null) {
data := b.newData()
a = NewNullData(data)
data.Release()
return
}
func (b *NullBuilder) newData() (data *Data) {
data = NewData(
arrow.Null, b.length,
[]*memory.Buffer{nil},
nil,
b.nulls,
0,
)
b.reset()
return
}
func (b *NullBuilder) UnmarshalOne(dec *json.Decoder) error {
t, err := dec.Token()
if err != nil {
return err
}
switch t.(type) {
case nil:
b.AppendNull()
default:
return &json.UnmarshalTypeError{
Value: fmt.Sprint(t),
Type: reflect.TypeOf(nil),
Offset: dec.InputOffset(),
}
}
return nil
}
func (b *NullBuilder) Unmarshal(dec *json.Decoder) error {
for dec.More() {
if err := b.UnmarshalOne(dec); err != nil {
return err
}
}
return nil
}
func (b *NullBuilder) UnmarshalJSON(data []byte) error {
dec := json.NewDecoder(bytes.NewReader(data))
t, err := dec.Token()
if err != nil {
return err
}
if delim, ok := t.(json.Delim); !ok || delim != '[' {
return fmt.Errorf("null builder must unpack from json array, found %s", delim)
}
return b.Unmarshal(dec)
}
var (
_ arrow.Array = (*Null)(nil)
_ Builder = (*NullBuilder)(nil)
)