libgo/go/syscall/env_unix.go

   1 // Copyright 2010 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 // +build darwin dragonfly freebsd linux netbsd openbsd
   6
   7 // Unix environment variables.
   8
   9 package syscall
  10
  11 import "sync"
  12
  13 var (
  14         // envOnce guards initialization by copyenv, which populates env.
  15         envOnce sync.Once
  16
  17         // envLock guards env and envs.
  18         envLock sync.RWMutex
  19
  20         // env maps from an environment variable to its first occurrence in envs.
  21         env map[string]int
  22
  23         // envs is provided by the runtime. elements are expected to be
  24         // of the form "key=value".
  25         Envs []string
  26 )
  27
  28 // setenv_c is provided by the runtime, but is a no-op if cgo isn't
  29 // loaded.
  30 func setenv_c(k, v string)
  31
  32 func copyenv() {
  33         env = make(map[string]int)
  34         for i, s := range Envs {
  35                 for j := 0; j < len(s); j++ {
  36                         if s[j] == '=' {
  37                                 key := s[:j]
  38                                 if _, ok := env[key]; !ok {
  39                                         env[key] = i
  40                                 }
  41                                 break
  42                         }
  43                 }
  44         }
  45 }
  46
  47 func Getenv(key string) (value string, found bool) {
  48         envOnce.Do(copyenv)
  49         if len(key) == 0 {
  50                 return "", false
  51         }
  52
  53         envLock.RLock()
  54         defer envLock.RUnlock()
  55
  56         i, ok := env[key]
  57         if !ok {
  58                 return "", false
  59         }
  60         s := Envs[i]
  61         for i := 0; i < len(s); i++ {
  62                 if s[i] == '=' {
  63                         return s[i+1:], true
  64                 }
  65         }
  66         return "", false
  67 }
  68
  69 func Setenv(key, value string) error {
  70         envOnce.Do(copyenv)
  71         if len(key) == 0 {
  72                 return EINVAL
  73         }
  74         for i := 0; i < len(key); i++ {
  75                 if key[i] == '=' || key[i] == 0 {
  76                         return EINVAL
  77                 }
  78         }
  79         for i := 0; i < len(value); i++ {
  80                 if value[i] == 0 {
  81                         return EINVAL
  82                 }
  83         }
  84
  85         envLock.Lock()
  86         defer envLock.Unlock()
  87
  88         i, ok := env[key]
  89         kv := key + "=" + value
  90         if ok {
  91                 Envs[i] = kv
  92         } else {
  93                 i = len(Envs)
  94                 Envs = append(Envs, kv)
  95         }
  96         env[key] = i
  97         setenv_c(key, value)
  98         return nil
  99 }
 100
 101 func Clearenv() {
 102         envOnce.Do(copyenv) // prevent copyenv in Getenv/Setenv
 103
 104         envLock.Lock()
 105         defer envLock.Unlock()
 106
 107         env = make(map[string]int)
 108         Envs = []string{}
 109         // TODO(bradfitz): pass through to C
 110 }
 111
 112 func Environ() []string {
 113         envOnce.Do(copyenv)
 114         envLock.RLock()
 115         defer envLock.RUnlock()
 116         a := make([]string, len(Envs))
 117         copy(a, Envs)
 118         return a
 119 }