mirror of https://bitbucket.org/ausocean/av.git
144 lines
3.3 KiB
Go
144 lines
3.3 KiB
Go
/*
|
|
NAME
|
|
lex.go
|
|
|
|
AUTHOR
|
|
Trek Hopton <trek@ausocean.org>
|
|
|
|
LICENSE
|
|
This file is Copyright (C) 2019 the Australian Ocean Lab (AusOcean)
|
|
|
|
It is free software: you can redistribute it and/or modify them
|
|
under the terms of the GNU General Public License as published by the
|
|
Free Software Foundation, either version 3 of the License, or (at your
|
|
option) any later version.
|
|
|
|
It is distributed in the hope that it will be useful, but WITHOUT
|
|
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
|
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
|
for more details.
|
|
|
|
You should have received a copy of the GNU General Public License in gpl.txt.
|
|
If not, see [GNU licenses](http://www.gnu.org/licenses).
|
|
*/
|
|
|
|
package codecutil
|
|
|
|
import (
|
|
"fmt"
|
|
"io"
|
|
"time"
|
|
)
|
|
|
|
// ByteLexer is used to lex bytes using a buffer size which is configured upon construction.
|
|
type ByteLexer struct {
|
|
bufSize int
|
|
}
|
|
|
|
// NewByteLexer returns a pointer to a ByteLexer with the given buffer size.
|
|
func NewByteLexer(s int) (*ByteLexer, error) {
|
|
if s <= 0 {
|
|
return nil, fmt.Errorf("invalid buffer size: %v", s)
|
|
}
|
|
return &ByteLexer{bufSize: s}, nil
|
|
}
|
|
|
|
// zeroTicks can be used to create an instant ticker.
|
|
var zeroTicks chan time.Time
|
|
|
|
func init() {
|
|
zeroTicks = make(chan time.Time)
|
|
close(zeroTicks)
|
|
}
|
|
|
|
// Lex reads l.bufSize bytes from src and writes them to dst every d seconds.
|
|
func (l *ByteLexer) Lex(dst io.Writer, src io.Reader, d time.Duration) error {
|
|
if d < 0 {
|
|
return fmt.Errorf("invalid delay: %v", d)
|
|
}
|
|
|
|
var ticker *time.Ticker
|
|
if d == 0 {
|
|
ticker = &time.Ticker{C: zeroTicks}
|
|
} else {
|
|
ticker = time.NewTicker(d)
|
|
defer ticker.Stop()
|
|
}
|
|
|
|
buf := make([]byte, l.bufSize)
|
|
for {
|
|
<-ticker.C
|
|
off, err := src.Read(buf)
|
|
// The only error that will stop the lexer is an EOF.
|
|
if err == io.EOF {
|
|
return err
|
|
} else if err != nil {
|
|
continue
|
|
}
|
|
_, err = dst.Write(buf[:off])
|
|
if err != nil {
|
|
return err
|
|
}
|
|
}
|
|
}
|
|
|
|
// Noop assumes that for writing to src is blocked until the entire previous
|
|
// write to src is read, i.e. src is expected to connected to a pipe-like structure.
|
|
func Noop(dst io.Writer, src io.Reader, d time.Duration) error {
|
|
if d < 0 {
|
|
return fmt.Errorf("invalid delay: %v", d)
|
|
}
|
|
|
|
if d == 0 {
|
|
d = 40 * time.Millisecond
|
|
}
|
|
ticker := time.NewTicker(d)
|
|
defer ticker.Stop()
|
|
|
|
const checkDur = 500 * time.Millisecond
|
|
rateChkTicker := time.NewTicker(checkDur)
|
|
frameCh := make(chan []byte, 1000)
|
|
errCh := make(chan error)
|
|
go func() {
|
|
for {
|
|
toWrite := <-frameCh
|
|
_, err := dst.Write(toWrite)
|
|
if err != nil {
|
|
errCh <- fmt.Errorf("could not write to dst: %w", err)
|
|
}
|
|
|
|
<-ticker.C
|
|
select {
|
|
case <-rateChkTicker.C:
|
|
var adj int
|
|
const equilibrium = 500
|
|
if len(frameCh) > equilibrium {
|
|
adj = -2
|
|
} else if len(frameCh) < equilibrium {
|
|
adj = 2
|
|
}
|
|
d += time.Millisecond * time.Duration(adj)
|
|
ticker.Reset(d)
|
|
default:
|
|
}
|
|
}
|
|
}()
|
|
|
|
const maxFrameSize = 250000 // = 20kB
|
|
buf := make([]byte, maxFrameSize)
|
|
for {
|
|
n, err := src.Read(buf)
|
|
if err != nil {
|
|
return fmt.Errorf("could not read src: %w", err)
|
|
}
|
|
newFrame := make([]byte, n)
|
|
copy(newFrame, buf[:n])
|
|
frameCh <- newFrame
|
|
select {
|
|
case err := <-errCh:
|
|
return fmt.Errorf("error from output routine: %w", err)
|
|
default:
|
|
}
|
|
}
|
|
}
|