82 lines
2 KiB
Go
82 lines
2 KiB
Go
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// Copyright 2015 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package segmentmap
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import (
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"hash/crc32"
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"github.com/juju/errors"
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)
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// SegmentMap is used for handle a big map slice by slice.
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// It's not thread safe.
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type SegmentMap struct {
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size int64
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maps []map[string]interface{}
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crcTable *crc32.Table
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}
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// NewSegmentMap create a new SegmentMap.
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func NewSegmentMap(size int64) (*SegmentMap, error) {
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if size <= 0 {
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return nil, errors.Errorf("Invalid size: %d", size)
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}
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sm := &SegmentMap{
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maps: make([]map[string]interface{}, size),
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size: size,
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}
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for i := int64(0); i < size; i++ {
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sm.maps[i] = make(map[string]interface{})
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}
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sm.crcTable = crc32.MakeTable(crc32.Castagnoli)
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return sm, nil
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}
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// Get is the same as map[k].
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func (sm *SegmentMap) Get(key []byte) (interface{}, bool) {
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idx := int64(crc32.Checksum(key, sm.crcTable)) % sm.size
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val, ok := sm.maps[idx][string(key)]
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return val, ok
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}
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// GetSegment gets the map specific by index.
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func (sm *SegmentMap) GetSegment(index int64) (map[string]interface{}, error) {
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if index >= sm.size || index < 0 {
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return nil, errors.Errorf("index out of bound: %d", index)
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}
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return sm.maps[index], nil
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}
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// Set if key not exists, returns whether already exists.
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func (sm *SegmentMap) Set(key []byte, value interface{}, force bool) bool {
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idx := int64(crc32.Checksum(key, sm.crcTable)) % sm.size
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k := string(key)
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_, exist := sm.maps[idx][k]
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if exist && !force {
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return exist
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}
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sm.maps[idx][k] = value
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return exist
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}
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// SegmentCount returns how many inner segments.
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func (sm *SegmentMap) SegmentCount() int64 {
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return sm.size
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}
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