mirror of
https://github.com/hajimehoshi/ebiten.git
synced 2024-09-20 05:12:18 +02:00
135 lines
3.1 KiB
Go
135 lines
3.1 KiB
Go
// Copyright 2023 The Ebitengine Authors
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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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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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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 graphics
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import (
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"runtime"
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"sync"
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)
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// ManagedBytes is a managed byte slice.
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// The internal byte alice are managed in a pool.
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// ManagedBytes is useful when its lifetime is explicit, as the underlying byte slice can be reused for another ManagedBytes later.
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// This can reduce allocations and GCs.
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type ManagedBytes struct {
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bytes []byte
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pool *bytesPool
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}
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// Len returns the length of the slice.
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func (m *ManagedBytes) Len() int {
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return len(m.bytes)
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}
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// Read reads the byte slice's content to dst.
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func (m *ManagedBytes) Read(dst []byte, from, to int) {
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copy(dst, m.bytes[from:to])
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}
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// Clone creates a new ManagedBytes with the same content.
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func (m *ManagedBytes) Clone() *ManagedBytes {
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return NewManagedBytes(len(m.bytes), func(bs []byte) {
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copy(bs, m.bytes)
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})
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}
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// GetAndRelease returns the raw byte slice and a finalizer.
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// A finalizer should be called when you can ensure that the slice is no longer used,
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// e.g. when a graphics command using this slice is sent and executed.
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//
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// After GetAndRelease is called, the underlying byte slice is no longer available.
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func (m *ManagedBytes) GetAndRelease() ([]byte, func()) {
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bs := m.bytes
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m.bytes = nil
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return bs, func() {
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m.pool.put(bs)
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runtime.SetFinalizer(m, nil)
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}
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}
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// NewManagedBytes returns a managed byte slice initialized by the given constructor f.
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//
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// The byte slice is not zero-cleared at the constructor.
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func NewManagedBytes(size int, f func([]byte)) *ManagedBytes {
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bs := theBytesPool.get(size)
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f(bs.bytes)
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return bs
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}
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type bytesPool struct {
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pool [][]byte
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m sync.Mutex
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}
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var theBytesPool bytesPool
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func (b *bytesPool) get(size int) *ManagedBytes {
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bs := b.getFromCache(size)
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if bs == nil {
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bs = make([]byte, size)
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}
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m := &ManagedBytes{
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bytes: bs,
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pool: b,
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}
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runtime.SetFinalizer(m, func(m *ManagedBytes) {
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b.put(m.bytes)
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})
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return m
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}
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func (b *bytesPool) getFromCache(size int) []byte {
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b.m.Lock()
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defer b.m.Unlock()
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for i, bs := range b.pool {
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if cap(bs) < size {
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continue
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}
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copy(b.pool[i:], b.pool[i+1:])
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b.pool[len(b.pool)-1] = nil
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b.pool = b.pool[:len(b.pool)-1]
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return bs[:size]
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}
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return nil
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}
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func (b *bytesPool) put(bs []byte) {
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if len(bs) == 0 {
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return
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}
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b.m.Lock()
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defer b.m.Unlock()
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b.pool = append(b.pool, bs)
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// GC the pool. The size limitation is arbitrary.
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for len(b.pool) >= 32 || b.totalSize() >= 1024*1024*1024 {
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b.pool = b.pool[1:]
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}
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}
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func (b *bytesPool) totalSize() int {
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var s int
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for _, bs := range b.pool {
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s += len(bs)
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}
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return s
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}
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