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/*
*
* Copyright 2014, Google Inc.
* All rights reserved.
*
* 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 transport
import (
"fmt"
"sync"
"golang.org/x/net/http2"
)
const (
// The default value of flow control window size in HTTP2 spec.
defaultWindowSize = 65535
// The initial window size for flow control.
initialWindowSize = defaultWindowSize // for an RPC
initialConnWindowSize = defaultWindowSize * 16 // for a connection
)
// The following defines various control items which could flow through
// the control buffer of transport. They represent different aspects of
// control tasks, e.g., flow control, settings, streaming resetting, etc.
type windowUpdate struct {
streamID uint32
increment uint32
}
func (*windowUpdate) item() {}
type settings struct {
ack bool
ss []http2.Setting
}
func (*settings) item() {}
type resetStream struct {
streamID uint32
code http2.ErrCode
}
func (*resetStream) item() {}
type flushIO struct {
}
func (*flushIO) item() {}
type ping struct {
ack bool
data [8]byte
}
func (*ping) item() {}
// quotaPool is a pool which accumulates the quota and sends it to acquire()
// when it is available.
type quotaPool struct {
c chan int
mu sync.Mutex
quota int
}
// newQuotaPool creates a quotaPool which has quota q available to consume.
func newQuotaPool(q int) *quotaPool {
qb := "aPool{
c: make(chan int, 1),
}
if q > 0 {
qb.c <- q
} else {
qb.quota = q
}
return qb
}
// add adds n to the available quota and tries to send it on acquire.
func (qb *quotaPool) add(n int) {
qb.mu.Lock()
defer qb.mu.Unlock()
qb.quota += n
if qb.quota <= 0 {
return
}
select {
case qb.c <- qb.quota:
qb.quota = 0
default:
}
}
// cancel cancels the pending quota sent on acquire, if any.
func (qb *quotaPool) cancel() {
qb.mu.Lock()
defer qb.mu.Unlock()
select {
case n := <-qb.c:
qb.quota += n
default:
}
}
// reset cancels the pending quota sent on acquired, incremented by v and sends
// it back on acquire.
func (qb *quotaPool) reset(v int) {
qb.mu.Lock()
defer qb.mu.Unlock()
select {
case n := <-qb.c:
qb.quota += n
default:
}
qb.quota += v
if qb.quota <= 0 {
return
}
select {
case qb.c <- qb.quota:
qb.quota = 0
default:
}
}
// acquire returns the channel on which available quota amounts are sent.
func (qb *quotaPool) acquire() <-chan int {
return qb.c
}
// inFlow deals with inbound flow control
type inFlow struct {
// The inbound flow control limit for pending data.
limit uint32
mu sync.Mutex
// pendingData is the overall data which have been received but not been
// consumed by applications.
pendingData uint32
// The amount of data the application has consumed but grpc has not sent
// window update for them. Used to reduce window update frequency.
pendingUpdate uint32
}
// onData is invoked when some data frame is received. It updates pendingData.
func (f *inFlow) onData(n uint32) error {
f.mu.Lock()
defer f.mu.Unlock()
f.pendingData += n
if f.pendingData+f.pendingUpdate > f.limit {
return fmt.Errorf("received %d-bytes data exceeding the limit %d bytes", f.pendingData+f.pendingUpdate, f.limit)
}
return nil
}
// onRead is invoked when the application reads the data. It returns the window size
// to be sent to the peer.
func (f *inFlow) onRead(n uint32) uint32 {
f.mu.Lock()
defer f.mu.Unlock()
if f.pendingData == 0 {
return 0
}
f.pendingData -= n
f.pendingUpdate += n
if f.pendingUpdate >= f.limit/4 {
wu := f.pendingUpdate
f.pendingUpdate = 0
return wu
}
return 0
}
func (f *inFlow) resetPendingData() uint32 {
f.mu.Lock()
defer f.mu.Unlock()
n := f.pendingData
f.pendingData = 0
return n
}
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