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Make the broadcaster write messages to the observers in the same units they were written to the broadcaster

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This means the writing to a WriteFlusher will flush in the same places
as it would if the broadcaster wasn't sitting in front of it.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
This commit is contained in:
Aaron Lehmann 2015-08-28 10:09:00 -07:00
parent b8c40573a4
commit 6fb5c112d5
1 changed files with 16 additions and 10 deletions
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26
progressreader/broadcaster.go
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@ -1,7 +1,6 @@
package progressreader
import (
"bytes"
"errors"
"io"
"sync"
@ -19,8 +18,10 @@ type Broadcaster struct {
// new data available.
cond *sync.Cond
// history is a buffer of the progress output so far, so a new observer
// can catch up.
history bytes.Buffer
// can catch up. The history is stored as a slice of separate byte
// slices, so that if the writer is a WriteFlusher, the flushes will
// happen in the right places.
history [][]byte
// wg is a WaitGroup used to wait for all writes to finish on Close
wg sync.WaitGroup
// isClosed is set to true when Close is called to avoid closing c
@ -58,19 +59,20 @@ func (broadcaster *Broadcaster) receiveWrites(observer io.Writer) {
// The condition variable wait is at the end of this loop, so that the
// first iteration will write the history so far.
for {
newData := broadcaster.history.Bytes()[n:]
newData := broadcaster.history[n:]
// Make a copy of newData so we can release the lock
sendData := make([]byte, len(newData), len(newData))
sendData := make([][]byte, len(newData), len(newData))
copy(sendData, newData)
broadcaster.Unlock()
if len(sendData) > 0 {
written, err := observer.Write(sendData)
for len(sendData) > 0 {
_, err := observer.Write(sendData[0])
if err != nil {
broadcaster.wg.Done()
return
}
n += written
n++
sendData = sendData[1:]
}
broadcaster.Lock()
@ -82,7 +84,7 @@ func (broadcaster *Broadcaster) receiveWrites(observer io.Writer) {
return
}
if broadcaster.history.Len() == n {
if len(broadcaster.history) == n {
broadcaster.cond.Wait()
}
@ -101,7 +103,11 @@ func (broadcaster *Broadcaster) Write(p []byte) (n int, err error) {
return 0, errors.New("attempted write to closed progressreader Broadcaster")
}
broadcaster.history.Write(p)
// Add message in p to the history slice
newEntry := make([]byte, len(p), len(p))
copy(newEntry, p)
broadcaster.history = append(broadcaster.history, newEntry)
broadcaster.cond.Broadcast()
return len(p), nil