package stream

const (
	ReceiveBufferUdpBlockCount = 200

	ReceiveBufferTCPBlockCount = 100
)

// ReceiveBuffer 收流缓冲区. 网络收流->解析流->封装流->发送流是同步的,从解析到发送可能耗时,从而影响读取网络流. 使用收流缓冲区,可有效降低出现此问题的概率.
// 从网络IO读取数据->送给解复用器, 此过程需做到无内存拷贝
// rtmp和1078推流直接使用ReceiveBuffer
// 国标推流,UDP收流都要经过jitter buffer处理, 还是需要拷贝一次, 没必要使用ReceiveBuffer. TCP全都使用ReceiveBuffer, 区别在于多端口模式, 第一包传给source, 单端口模式先解析出ssrc, 找到source. 后续再传给source.
type ReceiveBuffer struct {
	blockSize  int //单个缓存块大小
	blockCount int //缓存块数据流. 应当和Source的数据输入管道容量保持一致.
	data       []byte
	index      int
}

func (r *ReceiveBuffer) GetBlock() []byte {
	bytes := r.data[r.index*r.blockSize:]
	r.index = r.index + 1%r.blockCount
	return bytes[:r.blockSize]
}

func NewReceiveBuffer(blockSize, blockCount int) *ReceiveBuffer {
	return &ReceiveBuffer{blockSize: blockSize, blockCount: blockCount, data: make([]byte, blockSize*blockCount), index: 0}
}

func NewUDPReceiveBuffer() *ReceiveBuffer {
	return NewReceiveBuffer(1500, ReceiveBufferUdpBlockCount)
}

func NewTCPReceiveBuffer() *ReceiveBuffer {
	return NewReceiveBuffer(4096*20, ReceiveBufferTCPBlockCount)
}