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process.go
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process.go
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package main
import (
"io"
"os"
"os/exec"
)
func startCommandPipeline(proc *exec.Cmd, input <-chan Packet, inputDemand chan<- Packet, outputDemand <-chan Packet) <-chan Packet {
cmdInput, err := proc.StdinPipe()
fatalIf(err)
cmdOutput, err := proc.StdoutPipe()
fatalIf(err)
cmdError, err := proc.StderrPipe()
fatalIf(err)
execErr := proc.Start()
fatalIf(execErr)
go writeToCommandStdin(cmdInput, input, inputDemand)
go printStderr(cmdError)
output := make(chan Packet)
go readCommandStdout(cmdOutput, outputDemand, output)
return output
}
func writeToCommandStdin(cmdInput io.WriteCloser, input <-chan Packet, inputDemand chan<- Packet) {
var packet Packet
var ok bool
defer func() {
cmdInput.Close()
// close(inputDemand)
}()
for {
inputDemand <- Packet{SendInput, make([]byte, 0)}
select {
case packet, ok = <-input:
if !ok {
return
}
}
switch packet.tag {
case CloseInput:
return
case Input:
// blocking
_, writeErr := cmdInput.Write(packet.data)
if writeErr != nil {
switch writeErr.(type) {
// ignore broken pipe or closed pipe errors
case *os.PathError:
return
default:
fatal(writeErr)
}
}
}
}
}
func readCommandStdout(cmdOutput io.ReadCloser, outputDemand <-chan Packet, output chan<- Packet) {
var buf [BufferSize]byte
defer func() {
output <- Packet{OutputEOF, make([]byte, 0)}
cmdOutput.Close()
close(output)
}()
for {
select {
case _, ok := <-outputDemand:
if !ok {
return
}
}
// blocking
bytesRead, readErr := cmdOutput.Read(buf[:])
if bytesRead > 0 {
output <- Packet{Output, buf[:bytesRead]}
} else if readErr == io.EOF || bytesRead == 0 {
return
} else {
fatal(readErr)
}
}
}
func printStderr(cmdError io.ReadCloser) {
var buf [BufferSize]byte
defer func() {
cmdError.Close()
}()
for {
bytesRead, readErr := cmdError.Read(buf[:])
if bytesRead > 0 {
logger.Printf(string(buf[:bytesRead]))
} else if readErr == io.EOF || bytesRead == 0 {
return
} else {
fatal(readErr)
}
}
}