map_reference_test.go

// Copyright (c) 2009 The Go Authors. All rights resered.
// Modified <Yusuke Kato (kpango)>

// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:

//    * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//    * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
package gache_test

import (
	"sync"
	"sync/atomic"
)

type mapInterface interface {
	Load(any) (any, bool)
	Store(key, value any)
	LoadOrStore(key, value any) (actual any, loaded bool)
	LoadAndDelete(key any) (value any, loaded bool)
	Delete(any)
	Swap(key, value any) (previous any, loaded bool)
	CompareAndSwap(key, old, new any) (swapped bool)
	CompareAndDelete(key, old any) (deleted bool)
	Range(func(key, value any) (shouldContinue bool))
}

var (
	_ mapInterface = &RWMutexMap{}
	_ mapInterface = &DeepCopyMap{}
)

// RWMutexMap is an implementation of mapInterface using a sync.RWMutex.
type RWMutexMap struct {
	mu    sync.RWMutex
	dirty map[any]any
}

func (m *RWMutexMap) Load(key any) (value any, ok bool) {
	m.mu.RLock()
	value, ok = m.dirty[key]
	m.mu.RUnlock()
	return
}

func (m *RWMutexMap) Store(key, value any) {
	m.mu.Lock()
	if m.dirty == nil {
		m.dirty = make(map[any]any)
	}
	m.dirty[key] = value
	m.mu.Unlock()
}

func (m *RWMutexMap) LoadOrStore(key, value any) (actual any, loaded bool) {
	m.mu.Lock()
	actual, loaded = m.dirty[key]
	if !loaded {
		actual = value
		if m.dirty == nil {
			m.dirty = make(map[any]any)
		}
		m.dirty[key] = value
	}
	m.mu.Unlock()
	return actual, loaded
}

func (m *RWMutexMap) Swap(key, value any) (previous any, loaded bool) {
	m.mu.Lock()
	if m.dirty == nil {
		m.dirty = make(map[any]any)
	}

	previous, loaded = m.dirty[key]
	m.dirty[key] = value
	m.mu.Unlock()
	return
}

func (m *RWMutexMap) LoadAndDelete(key any) (value any, loaded bool) {
	m.mu.Lock()
	value, loaded = m.dirty[key]
	if !loaded {
		m.mu.Unlock()
		return nil, false
	}
	delete(m.dirty, key)
	m.mu.Unlock()
	return value, loaded
}

func (m *RWMutexMap) Delete(key any) {
	m.mu.Lock()
	delete(m.dirty, key)
	m.mu.Unlock()
}

func (m *RWMutexMap) CompareAndSwap(key, old, new any) (swapped bool) {
	m.mu.Lock()
	defer m.mu.Unlock()
	if m.dirty == nil {
		return false
	}

	value, loaded := m.dirty[key]
	if loaded && value == old {
		m.dirty[key] = new
		return true
	}
	return false
}

func (m *RWMutexMap) CompareAndDelete(key, old any) (deleted bool) {
	m.mu.Lock()
	defer m.mu.Unlock()
	if m.dirty == nil {
		return false
	}

	value, loaded := m.dirty[key]
	if loaded && value == old {
		delete(m.dirty, key)
		return true
	}
	return false
}

func (m *RWMutexMap) Range(f func(key, value any) (shouldContinue bool)) {
	m.mu.RLock()
	keys := make([]any, 0, len(m.dirty))
	for k := range m.dirty {
		keys = append(keys, k)
	}
	m.mu.RUnlock()

	for _, k := range keys {
		v, ok := m.Load(k)
		if !ok {
			continue
		}
		if !f(k, v) {
			break
		}
	}
}

// DeepCopyMap is an implementation of mapInterface using a Mutex and
// atomic.Value.  It makes deep copies of the map on every write to avoid
// acquiring the Mutex in Load.
type DeepCopyMap struct {
	mu    sync.Mutex
	clean atomic.Value
}

func (m *DeepCopyMap) Load(key any) (value any, ok bool) {
	clean, _ := m.clean.Load().(map[any]any)
	value, ok = clean[key]
	return value, ok
}

func (m *DeepCopyMap) Store(key, value any) {
	m.mu.Lock()
	dirty := m.dirty()
	dirty[key] = value
	m.clean.Store(dirty)
	m.mu.Unlock()
}

func (m *DeepCopyMap) LoadOrStore(key, value any) (actual any, loaded bool) {
	clean, _ := m.clean.Load().(map[any]any)
	actual, loaded = clean[key]
	if loaded {
		return actual, loaded
	}

	m.mu.Lock()
	// Reload clean in case it changed while we were waiting on m.mu.
	clean, _ = m.clean.Load().(map[any]any)
	actual, loaded = clean[key]
	if !loaded {
		dirty := m.dirty()
		dirty[key] = value
		actual = value
		m.clean.Store(dirty)
	}
	m.mu.Unlock()
	return actual, loaded
}

func (m *DeepCopyMap) Swap(key, value any) (previous any, loaded bool) {
	m.mu.Lock()
	dirty := m.dirty()
	previous, loaded = dirty[key]
	dirty[key] = value
	m.clean.Store(dirty)
	m.mu.Unlock()
	return
}

func (m *DeepCopyMap) LoadAndDelete(key any) (value any, loaded bool) {
	m.mu.Lock()
	dirty := m.dirty()
	value, loaded = dirty[key]
	delete(dirty, key)
	m.clean.Store(dirty)
	m.mu.Unlock()
	return
}

func (m *DeepCopyMap) Delete(key any) {
	m.mu.Lock()
	dirty := m.dirty()
	delete(dirty, key)
	m.clean.Store(dirty)
	m.mu.Unlock()
}

func (m *DeepCopyMap) CompareAndSwap(key, old, new any) (swapped bool) {
	clean, _ := m.clean.Load().(map[any]any)
	if previous, ok := clean[key]; !ok || previous != old {
		return false
	}

	m.mu.Lock()
	defer m.mu.Unlock()
	dirty := m.dirty()
	value, loaded := dirty[key]
	if loaded && value == old {
		dirty[key] = new
		m.clean.Store(dirty)
		return true
	}
	return false
}

func (m *DeepCopyMap) CompareAndDelete(key, old any) (deleted bool) {
	clean, _ := m.clean.Load().(map[any]any)
	if previous, ok := clean[key]; !ok || previous != old {
		return false
	}

	m.mu.Lock()
	defer m.mu.Unlock()

	dirty := m.dirty()
	value, loaded := dirty[key]
	if loaded && value == old {
		delete(dirty, key)
		m.clean.Store(dirty)
		return true
	}
	return false
}

func (m *DeepCopyMap) Range(f func(key, value any) (shouldContinue bool)) {
	clean, _ := m.clean.Load().(map[any]any)
	for k, v := range clean {
		if !f(k, v) {
			break
		}
	}
}

func (m *DeepCopyMap) dirty() map[any]any {
	clean, _ := m.clean.Load().(map[any]any)
	dirty := make(map[any]any, len(clean)+1)
	for k, v := range clean {
		dirty[k] = v
	}
	return dirty
}