sandbox: move params setup functions

Signed-off-by: Ophestra <cat@gensokyo.uk>

helper/proc/fd.go

@@ -1,48 +0,0 @@
-package proc
-
-import (
-	"encoding/gob"
-	"errors"
-	"os"
-	"strconv"
-)
-
-var (
-	ErrNotSet  = errors.New("environment variable not set")
-	ErrInvalid = errors.New("bad file descriptor")
-)
-
-// Setup appends the read end of a pipe for payload transmission and returns its fd.
-func Setup(extraFiles *[]*os.File) (int, *gob.Encoder, error) {
-	if r, w, err := os.Pipe(); err != nil {
-		return -1, nil, err
-	} else {
-		fd := 3 + len(*extraFiles)
-		*extraFiles = append(*extraFiles, r)
-		return fd, gob.NewEncoder(w), nil
-	}
-}
-
-// Receive retrieves payload pipe fd from the environment,
-// receives its payload and returns the Close method of the pipe.
-func Receive(key string, e any, v **os.File) (func() error, error) {
-	var setup *os.File
-
-	if s, ok := os.LookupEnv(key); !ok {
-		return nil, ErrNotSet
-	} else {
-		if fd, err := strconv.Atoi(s); err != nil {
-			return nil, err
-		} else {
-			setup = os.NewFile(uintptr(fd), "setup")
-			if setup == nil {
-				return nil, ErrInvalid
-			}
-			if v != nil {
-				*v = setup
-			}
-		}
-	}
-
-	return setup.Close, gob.NewDecoder(setup).Decode(e)
-}