vendor/golang.org/x/net/http2/flow.go

   1 // Copyright 2014 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Flow control
   6
   7 package http2
   8
   9 // flow is the flow control window's size.
  10 type flow struct {
  11         // n is the number of DATA bytes we're allowed to send.
  12         // A flow is kept both on a conn and a per-stream.
  13         n int32
  14
  15         // conn points to the shared connection-level flow that is
  16         // shared by all streams on that conn. It is nil for the flow
  17         // that's on the conn directly.
  18         conn *flow
  19 }
  20
  21 func (f *flow) setConnFlow(cf *flow) { f.conn = cf }
  22
  23 func (f *flow) available() int32 {
  24         n := f.n
  25         if f.conn != nil && f.conn.n < n {
  26                 n = f.conn.n
  27         }
  28         return n
  29 }
  30
  31 func (f *flow) take(n int32) {
  32         if n > f.available() {
  33                 panic("internal error: took too much")
  34         }
  35         f.n -= n
  36         if f.conn != nil {
  37                 f.conn.n -= n
  38         }
  39 }
  40
  41 // add adds n bytes (positive or negative) to the flow control window.
  42 // It returns false if the sum would exceed 2^31-1.
  43 func (f *flow) add(n int32) bool {
  44         sum := f.n + n
  45         if (sum > n) == (f.n > 0) {
  46                 f.n = sum
  47                 return true
  48         }
  49         return false
  50 }