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cfg_mem.go
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/
cfg_mem.go
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// Copyright (c) 2014 Couchbase, Inc.
// Licensed 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 main
import (
"fmt"
"sync"
)
// A local-only, memory-only implementation of Cfg interface, useful
// for development and testing.
type CfgMem struct {
m sync.Mutex
CASNext uint64
Entries map[string]*CfgMemEntry
}
type CfgMemEntry struct {
CAS uint64
Val []byte
}
func NewCfgMem() *CfgMem {
return &CfgMem{
CASNext: 1,
Entries: make(map[string]*CfgMemEntry),
}
}
func (c *CfgMem) Get(key string, cas uint64) (
[]byte, uint64, error) {
c.m.Lock()
defer c.m.Unlock()
entry, exists := c.Entries[key]
if !exists {
return nil, 0, nil
}
if cas != 0 && cas != entry.CAS {
return nil, 0, &CfgCASError{}
}
val := make([]byte, len(entry.Val))
copy(val, entry.Val)
return val, entry.CAS, nil
}
func (c *CfgMem) Set(key string, val []byte, cas uint64) (
uint64, error) {
c.m.Lock()
defer c.m.Unlock()
prevEntry, exists := c.Entries[key]
if cas == 0 {
if exists {
return 0, fmt.Errorf("error: entry already exists, key: %s", key)
}
} else { // cas != 0
if !exists || cas != prevEntry.CAS {
return 0, &CfgCASError{}
}
}
nextEntry := &CfgMemEntry{
CAS: c.CASNext,
Val: make([]byte, len(val)),
}
copy(nextEntry.Val, val)
c.Entries[key] = nextEntry
c.CASNext += 1
return nextEntry.CAS, nil
}
func (c *CfgMem) Del(key string, cas uint64) error {
c.m.Lock()
defer c.m.Unlock()
if cas != 0 {
entry, exists := c.Entries[key]
if !exists || cas != entry.CAS {
return &CfgCASError{}
}
}
delete(c.Entries, key)
return nil
}