pwd_plan9.go

     1  // Copyright 2015 The Go 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  // The working directory in Plan 9 is effectively per P, so different
     6  // goroutines and even the same goroutine as it's rescheduled on
     7  // different Ps can see different working directories.
     8  //
     9  // Instead, track a Go process-wide intent of the current working directory,
    10  // and switch to it at important points.
    11  
    12  package syscall
    13  
    14  import "sync"
    15  
    16  var (
    17  	wdmu  sync.Mutex // guards following
    18  	wdSet bool
    19  	wdStr string
    20  )
    21  
    22  func Fixwd() {
    23  	wdmu.Lock()
    24  	defer wdmu.Unlock()
    25  	fixwdLocked()
    26  }
    27  
    28  func fixwdLocked() {
    29  	if !wdSet {
    30  		return
    31  	}
    32  	// always call chdir when getwd returns an error
    33  	wd, _ := getwd()
    34  	if wd == wdStr {
    35  		return
    36  	}
    37  	if err := chdir(wdStr); err != nil {
    38  		return
    39  	}
    40  }
    41  
    42  func fixwd(paths ...string) {
    43  	for _, path := range paths {
    44  		if path != "" && path[0] != '/' && path[0] != '#' {
    45  			Fixwd()
    46  			return
    47  		}
    48  	}
    49  }
    50  
    51  // goroutine-specific getwd
    52  func getwd() (wd string, err error) {
    53  	fd, err := open(".", O_RDONLY)
    54  	if err != nil {
    55  		return "", err
    56  	}
    57  	defer Close(fd)
    58  	return Fd2path(fd)
    59  }
    60  
    61  func Getwd() (wd string, err error) {
    62  	wdmu.Lock()
    63  	defer wdmu.Unlock()
    64  
    65  	if wdSet {
    66  		return wdStr, nil
    67  	}
    68  	wd, err = getwd()
    69  	if err != nil {
    70  		return
    71  	}
    72  	wdSet = true
    73  	wdStr = wd
    74  	return wd, nil
    75  }
    76  
    77  func Chdir(path string) error {
    78  	fixwd(path)
    79  	wdmu.Lock()
    80  	defer wdmu.Unlock()
    81  
    82  	if err := chdir(path); err != nil {
    83  		return err
    84  	}
    85  
    86  	wd, err := getwd()
    87  	if err != nil {
    88  		return err
    89  	}
    90  	wdSet = true
    91  	wdStr = wd
    92  	return nil
    93  }
    94
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