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117 lines
2.3 KiB
Go
117 lines
2.3 KiB
Go
package stream
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import (
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"github.com/yangjiechina/avformat/utils"
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)
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// MemoryPool 从解复用阶段，拼凑成完整的AVPacket开始(写)，到GOP缓存结束(释放)，整个过程都使用池中内存
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// 类似环形缓冲区, 区别在于，写入的内存块是连续的、整块内存.
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type MemoryPool interface {
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// Mark 标记一块写的内存地址
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//使用流程 Mark->Write/Allocate....->Fetch/Reset
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Mark()
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Write(data []byte)
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Allocate(size int) []byte
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Fetch() []byte
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// Reset 清空此次Write的标记，本次缓存的数据无效
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Reset()
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// FreeHead 从头部释放指定大小内存
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FreeHead(size int)
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// FreeTail 从尾部释放指定大小内存
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FreeTail(size int)
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}
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func NewMemoryPool(capacity int) MemoryPool {
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pool := &memoryPool{
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data: make([]byte, capacity),
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capacity: capacity,
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}
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return pool
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}
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type memoryPool struct {
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data []byte
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ptrStart uintptr
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ptrEnd uintptr
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//剩余的可用内存空间不足以为此次write
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capacity int
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head int
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tail int
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//保存开始索引
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mark int
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}
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// 根据head和tail计算出可用的内存地址
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func (m *memoryPool) allocate(size int) []byte {
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if m.capacity-m.tail < size {
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//使用从头释放的内存
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if m.tail-m.mark+size <= m.head {
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copy(m.data, m.data[m.mark:m.tail])
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m.capacity = m.mark
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m.tail = m.tail - m.mark
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m.mark = 0
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} else {
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//扩容
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capacity := (cap(m.data) + m.tail - m.mark + size) * 3 / 2
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bytes := make([]byte, capacity)
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//不对之前的内存进行复制, 已经被AVPacket引用, 自行GC
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copy(bytes, m.data[m.mark:m.tail])
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m.data = bytes
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m.capacity = capacity
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m.tail = m.tail - m.mark
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m.mark = 0
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m.head = 0
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}
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}
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bytes := m.data[m.tail:]
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m.tail += size
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return bytes
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}
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func (m *memoryPool) Mark() {
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m.mark = m.tail
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}
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func (m *memoryPool) Write(data []byte) {
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allocate := m.allocate(len(data))
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copy(allocate, data)
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}
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func (m *memoryPool) Allocate(size int) []byte {
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return m.allocate(size)
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}
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func (m *memoryPool) Fetch() []byte {
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return m.data[m.mark:m.tail]
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}
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func (m *memoryPool) Reset() {
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m.tail = m.mark
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}
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func (m *memoryPool) FreeHead(size int) {
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m.head += size
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if m.head == m.tail {
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m.head = 0
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m.tail = 0
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} else if m.head >= m.capacity {
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m.head = 0
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}
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}
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func (m *memoryPool) FreeTail(size int) {
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m.tail -= size
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utils.Assert(m.tail >= 0)
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}
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