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messenger.go
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/
messenger.go
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package pipes
import (
"encoding/binary"
"io"
"os"
"sync"
)
// Messenger intermediates communication (message exchange) via pipes
type Messenger struct {
reader *os.File
writer *os.File
writerMutex sync.Mutex
}
// NewMessenger creates a new messenger
func NewMessenger(reader *os.File, writer *os.File) *Messenger {
return &Messenger{
reader: reader,
writer: writer,
}
}
// SendMessage sends a message over the pipe
func (messenger *Messenger) SendMessage(message []byte) (int, error) {
messenger.writerMutex.Lock()
defer messenger.writerMutex.Unlock()
length := len(message)
err := messenger.sendMessageLength(length)
if err != nil {
return 0, err
}
_, err = messenger.writer.Write(message)
if err != nil {
return 0, err
}
return length, nil
}
func (messenger *Messenger) sendMessageLength(length int) error {
buffer := make([]byte, sizeOfUint32)
binary.LittleEndian.PutUint32(buffer, uint32(length))
_, err := messenger.writer.Write(buffer)
return err
}
// ReadMessage reads a message from the pipe
// Reading messages is normally performed from a single go-routine, no mutex required
func (messenger *Messenger) ReadMessage() ([]byte, error) {
length, err := messenger.readMessageLength()
if err != nil {
return nil, err
}
return messenger.readMessagePayload(length)
}
func (messenger *Messenger) readMessageLength() (int, error) {
buffer := make([]byte, sizeOfUint32)
_, err := io.ReadFull(messenger.reader, buffer)
if err != nil {
return 0, err
}
length := binary.LittleEndian.Uint32(buffer)
return int(length), nil
}
func (messenger *Messenger) readMessagePayload(length int) ([]byte, error) {
buffer := make([]byte, length)
_, err := io.ReadFull(messenger.reader, buffer)
if err != nil {
return nil, err
}
return buffer, nil
}