260 lines
6.2 KiB
Go
260 lines
6.2 KiB
Go
/*
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*
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* Copyright 2014, Google Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following disclaimer
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* in the documentation and/or other materials provided with the
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* distribution.
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* * Neither the name of Google Inc. nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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package transport
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import (
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"fmt"
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"sync"
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"golang.org/x/net/http2"
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)
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const (
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// The default value of flow control window size in HTTP2 spec.
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defaultWindowSize = 65535
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// The initial window size for flow control.
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initialWindowSize = defaultWindowSize // for an RPC
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initialConnWindowSize = defaultWindowSize * 16 // for a connection
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)
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// The following defines various control items which could flow through
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// the control buffer of transport. They represent different aspects of
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// control tasks, e.g., flow control, settings, streaming resetting, etc.
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type windowUpdate struct {
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streamID uint32
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increment uint32
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}
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func (windowUpdate) isItem() bool {
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return true
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}
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type settings struct {
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ack bool
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ss []http2.Setting
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}
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func (settings) isItem() bool {
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return true
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}
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type resetStream struct {
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streamID uint32
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code http2.ErrCode
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}
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func (resetStream) isItem() bool {
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return true
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}
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type flushIO struct {
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}
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func (flushIO) isItem() bool {
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return true
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}
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type ping struct {
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ack bool
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data [8]byte
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}
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func (ping) isItem() bool {
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return true
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}
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// quotaPool is a pool which accumulates the quota and sends it to acquire()
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// when it is available.
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type quotaPool struct {
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c chan int
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mu sync.Mutex
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quota int
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}
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// newQuotaPool creates a quotaPool which has quota q available to consume.
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func newQuotaPool(q int) *quotaPool {
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qb := "aPool{
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c: make(chan int, 1),
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}
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if q > 0 {
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qb.c <- q
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} else {
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qb.quota = q
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}
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return qb
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}
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// add adds n to the available quota and tries to send it on acquire.
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func (qb *quotaPool) add(n int) {
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qb.mu.Lock()
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defer qb.mu.Unlock()
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qb.quota += n
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if qb.quota <= 0 {
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return
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}
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select {
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case qb.c <- qb.quota:
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qb.quota = 0
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default:
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}
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}
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// cancel cancels the pending quota sent on acquire, if any.
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func (qb *quotaPool) cancel() {
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qb.mu.Lock()
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defer qb.mu.Unlock()
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select {
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case n := <-qb.c:
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qb.quota += n
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default:
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}
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}
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// reset cancels the pending quota sent on acquired, incremented by v and sends
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// it back on acquire.
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func (qb *quotaPool) reset(v int) {
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qb.mu.Lock()
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defer qb.mu.Unlock()
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select {
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case n := <-qb.c:
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qb.quota += n
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default:
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}
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qb.quota += v
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if qb.quota <= 0 {
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return
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}
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select {
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case qb.c <- qb.quota:
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qb.quota = 0
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default:
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}
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}
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// acquire returns the channel on which available quota amounts are sent.
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func (qb *quotaPool) acquire() <-chan int {
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return qb.c
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}
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// inFlow deals with inbound flow control
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type inFlow struct {
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// The inbound flow control limit for pending data.
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limit uint32
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// conn points to the shared connection-level inFlow that is shared
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// by all streams on that conn. It is nil for the inFlow on the conn
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// directly.
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conn *inFlow
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mu sync.Mutex
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// pendingData is the overall data which have been received but not been
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// consumed by applications.
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pendingData uint32
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// The amount of data the application has consumed but grpc has not sent
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// window update for them. Used to reduce window update frequency.
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pendingUpdate uint32
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}
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// onData is invoked when some data frame is received. It increments not only its
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// own pendingData but also that of the associated connection-level flow.
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func (f *inFlow) onData(n uint32) error {
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if n == 0 {
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return nil
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}
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f.mu.Lock()
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defer f.mu.Unlock()
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if f.pendingData+f.pendingUpdate+n > f.limit {
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return fmt.Errorf("recieved %d-bytes data exceeding the limit %d bytes", f.pendingData+f.pendingUpdate+n, f.limit)
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}
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if f.conn != nil {
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if err := f.conn.onData(n); err != nil {
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return ConnectionErrorf("%v", err)
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}
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}
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f.pendingData += n
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return nil
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}
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// connOnRead updates the connection level states when the application consumes data.
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func (f *inFlow) connOnRead(n uint32) uint32 {
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if n == 0 || f.conn != nil {
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return 0
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}
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f.mu.Lock()
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defer f.mu.Unlock()
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f.pendingData -= n
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f.pendingUpdate += n
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if f.pendingUpdate >= f.limit/4 {
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ret := f.pendingUpdate
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f.pendingUpdate = 0
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return ret
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}
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return 0
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}
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// onRead is invoked when the application reads the data. It returns the window updates
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// for both stream and connection level.
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func (f *inFlow) onRead(n uint32) (swu, cwu uint32) {
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if n == 0 {
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return
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}
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f.mu.Lock()
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defer f.mu.Unlock()
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if f.pendingData == 0 {
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// pendingData has been adjusted by restoreConn.
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return
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}
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f.pendingData -= n
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f.pendingUpdate += n
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if f.pendingUpdate >= f.limit/4 {
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swu = f.pendingUpdate
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f.pendingUpdate = 0
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}
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cwu = f.conn.connOnRead(n)
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return
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}
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// restoreConn is invoked when a stream is terminated. It removes its stake in
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// the connection-level flow and resets its own state.
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func (f *inFlow) restoreConn() uint32 {
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if f.conn == nil {
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return 0
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}
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f.mu.Lock()
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defer f.mu.Unlock()
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n := f.pendingData
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f.pendingData = 0
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f.pendingUpdate = 0
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return f.conn.connOnRead(n)
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}
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