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// Copyright (C) 2019-2023 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// go-algorand 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand. If not, see <https://www.gnu.org/licenses/>.
package nodecontrol
import (
"io"
"os"
"strings"
"sync/atomic"
)
// LaggedStdIo is an indirect wrapper around os.Stdin/os.Stdout/os.Stderr that prevents
// direct dependency which could be an issue when a caller panics, leaving the child processes
// alive and blocks for EOF.
type LaggedStdIo struct {
ioClass int
LinePrefix atomic.Value // of datatype string
}
// write responsible for (potentially) splitting the written output into multiple
// lines and adding a prefix for each line.
func (s *LaggedStdIo) write(writer io.Writer, p []byte) (n int, err error) {
linePrefix := s.LinePrefix.Load().(string)
// do we have a line prefix ?
if linePrefix == "" {
// if not, just write it out.
return writer.Write(p)
}
// break the output buffer into multiple lines.
lines := strings.Split(string(p), "\n")
totalBytes := 0
for _, outputLine := range lines {
// avoid outputing empty lines.
if len(outputLine) == 0 {
continue
}
// prepare the line that we want to print
s := linePrefix + " : " + outputLine + "\n"
n, err = writer.Write([]byte(s))
if err != nil {
return totalBytes + n, err
}
totalBytes += n + 1
}
// if we success, output the original len(p), so that the caller won't know
// we've diced and splited the original string.
return len(p), nil
}
// Write implement the io.Writer interface and redirecting the written output
// to the correct pipe.
func (s *LaggedStdIo) Write(p []byte) (n int, err error) {
if s.ioClass == 1 {
return s.write(os.Stdout, p)
}
if s.ioClass == 2 {
return s.write(os.Stderr, p)
}
return 0, nil
}
// Read implmenents the io.Reader interface and redirecting the read request to the
// correct stdin pipe.
func (s *LaggedStdIo) Read(p []byte) (n int, err error) {
if s.ioClass == 0 {
return os.Stdin.Read(p)
}
return 0, nil
}
// SetLinePrefix sets the line prefix that would be used during the write opeearion.
func (s *LaggedStdIo) SetLinePrefix(linePrefix string) {
s.LinePrefix.Store(linePrefix)
}
// NewLaggedStdIo creates a new instance of the LaggedStdIo.
// allowed stdio are limited to os.Stdin, os.Stdout and os.Stderr
func NewLaggedStdIo(stdio interface{}, linePrefix string) *LaggedStdIo {
lio := &LaggedStdIo{}
lio.LinePrefix.Store(linePrefix)
switch stdio {
case os.Stdin:
lio.ioClass = 0
return lio
case os.Stdout:
lio.ioClass = 1
return lio
case os.Stderr:
lio.ioClass = 2
return lio
}
return nil
}
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