github.com/u-root/u-root@v7.0.1-0.20200915234505-ad7babab0a8e+incompatible/cmds/core/init/bgbuild.go (about)

     1  // Copyright 2017 the u-root Authors. All rights reserved
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package main
     6  
     7  import (
     8  	"io/ioutil"
     9  	"log"
    10  	"os"
    11  	"os/exec"
    12  	"runtime"
    13  	"sort"
    14  
    15  	"github.com/u-root/u-root/pkg/cmdline"
    16  )
    17  
    18  // Commands are built approximately in order from smallest to largest length of
    19  // the command name. So, two letter commands like `ls` and `cd` will be built
    20  // before `mknod` and `mount`. Generally, shorter commands are used more often
    21  // (that is why they were made short) and are more likely to be used first,
    22  // thus they should be built first.
    23  type cmdSlice []os.FileInfo
    24  
    25  func (p cmdSlice) Len() int {
    26  	return len(p)
    27  }
    28  
    29  func (p cmdSlice) Less(i, j int) bool {
    30  	return len(p[i].Name()) < len(p[j].Name())
    31  }
    32  
    33  func (p cmdSlice) Swap(i, j int) {
    34  	p[i], p[j] = p[j], p[i]
    35  }
    36  
    37  func worker(cmds chan string) {
    38  	for cmdName := range cmds {
    39  		args := []string{"--onlybuild", "--noforce", "--lowpri", cmdName}
    40  		cmd := exec.Command("installcommand", args...)
    41  		if err := cmd.Start(); err != nil {
    42  			log.Println("Cannot start:", err)
    43  			continue
    44  		}
    45  		if err := cmd.Wait(); err != nil {
    46  			log.Println("installcommand error:", err)
    47  		}
    48  	}
    49  }
    50  
    51  func startBgBuild() {
    52  	cmds := make(chan string)
    53  
    54  	// Start a worker for each CPU.
    55  	for i := 0; i < runtime.NumCPU(); i++ {
    56  		go worker(cmds)
    57  	}
    58  
    59  	// Create a slice of commands and order them by the aformentioned
    60  	// heuristic.
    61  	fis, err := ioutil.ReadDir("/buildbin")
    62  	if err != nil {
    63  		log.Print(err)
    64  		return
    65  	}
    66  	sort.Sort(cmdSlice(fis))
    67  
    68  	// Send the command by name to the workers.
    69  	for _, fi := range fis {
    70  		cmds <- fi.Name()
    71  	}
    72  	close(cmds)
    73  }
    74  
    75  func isBgBuildEnabled() bool {
    76  	return cmdline.ContainsFlag("uroot.bgbuild")
    77  }