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package stream
import (
"fmt"
"io"
"time"
)
type Direction uint8
const (
Upstream Direction = iota
Downstream
NumDirections
)
// Stores a slice of bytes with its receive timestmap
type StreamChunk struct {
Data []byte
Timestamp time.Time
}
// Implements the io.WriteCloser interface for a chan []byte
type ChanWriter struct {
output chan<- *StreamChunk
}
func NewChanWriter(output chan<- *StreamChunk) *ChanWriter {
return &ChanWriter{output}
}
// Write `buf` as a StreamChunk to the channel. The full buffer is always written, and error
// will always be nil. Calling `Write()` after closing the channel will panic.
func (c *ChanWriter) Write(buf []byte) (int, error) {
packet := &StreamChunk{make([]byte, len(buf)), time.Now()}
copy(packet.Data, buf) // Make a copy before sending it to the channel
c.output <- packet
return len(buf), nil
}
// Close the output channel
func (c *ChanWriter) Close() error {
close(c.output)
return nil
}
// Implements the io.Reader interface for a chan []byte
type ChanReader struct {
input <-chan *StreamChunk
interrupt <-chan struct{}
buffer []byte
}
var ErrInterrupted = fmt.Errorf("read interrupted by channel")
func NewChanReader(input <-chan *StreamChunk) *ChanReader {
return &ChanReader{input, make(chan struct{}), []byte{}}
}
// Specify a channel that can interrupt a read if it is blocking.
func (c *ChanReader) SetInterrupt(interrupt <-chan struct{}) {
c.interrupt = interrupt
}
// Read from the channel into `out`. This will block until data is available,
// and can be interrupted with a channel using `SetInterrupt()`. If the read
// was interrupted, `ErrInterrupted` will be returned.
func (c *ChanReader) Read(out []byte) (int, error) {
if c.buffer == nil {
return 0, io.EOF
}
n := copy(out, c.buffer)
c.buffer = c.buffer[n:]
if len(out) <= len(c.buffer) {
return n, nil
} else if n > 0 {
// We have some data to return, so make the channel read optional
select {
case p := <-c.input:
if p == nil { // Stream was closed
c.buffer = nil
if n > 0 {
return n, nil
}
return 0, io.EOF
}
n2 := copy(out[n:], p.Data)
c.buffer = p.Data[n2:]
return n + n2, nil
default:
return n, nil
}
}
var p *StreamChunk
select {
case p = <-c.input:
case <-c.interrupt:
c.buffer = c.buffer[:0]
return n, ErrInterrupted
}
if p == nil { // Stream was closed
c.buffer = nil
return 0, io.EOF
}
n2 := copy(out[n:], p.Data)
c.buffer = p.Data[n2:]
return n + n2, nil
}
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