Scott Baker | 2d89798 | 2019-09-24 11:50:08 -0700 | [diff] [blame^] | 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 | } |