package syscall
-import "errors"
+import (
+ "errors"
+ "sync"
+)
-func Getenv(key string) (value string, found bool) {
- if len(key) == 0 {
- return "", false
+var (
+ // envOnce guards initialization by copyenv, which populates env.
+ envOnce sync.Once
+
+ // envLock guards env.
+ envLock sync.RWMutex
+
+ // env maps from an environment variable to its value.
+ env map[string]string
+)
+
+func readenv(key string) (string, error) {
+ fd, err := Open("/env/"+key, O_RDONLY)
+ if err != nil {
+ return "", err
}
- f, e := Open("/env/"+key, O_RDONLY)
- if e != nil {
- return "", false
+ defer Close(fd)
+ l, _ := Seek(fd, 0, 2)
+ Seek(fd, 0, 0)
+ buf := make([]byte, l)
+ n, err := Read(fd, buf)
+ if err != nil {
+ return "", err
}
- defer Close(f)
+ if n > 0 && buf[n-1] == 0 {
+ buf = buf[:n-1]
+ }
+ return string(buf), nil
+}
- l, _ := Seek(f, 0, 2)
- Seek(f, 0, 0)
- buf := make([]byte, l)
- n, e := Read(f, buf)
- if e != nil {
+func writeenv(key, value string) error {
+ fd, err := Create("/env/"+key, O_RDWR, 0666)
+ if err != nil {
+ return err
+ }
+ defer Close(fd)
+ _, err = Write(fd, []byte(value))
+ return err
+}
+
+func copyenv() {
+ env = make(map[string]string)
+ fd, err := Open("/env", O_RDONLY)
+ if err != nil {
+ return
+ }
+ defer Close(fd)
+ files, err := readdirnames(fd)
+ if err != nil {
+ return
+ }
+ for _, key := range files {
+ v, err := readenv(key)
+ if err != nil {
+ continue
+ }
+ env[key] = v
+ }
+}
+
+func Getenv(key string) (value string, found bool) {
+ envOnce.Do(copyenv)
+ if len(key) == 0 {
return "", false
}
- if n > 0 && buf[n-1] == 0 {
- buf = buf[:n-1]
+ envLock.RLock()
+ defer envLock.RUnlock()
+
+ v, ok := env[key]
+ if !ok {
+ return "", false
}
- return string(buf), true
+ return v, true
}
func Setenv(key, value string) error {
+ envOnce.Do(copyenv)
if len(key) == 0 {
- return errors.New("bad arg in system call")
+ return errors.New("zero length key")
}
- f, e := Create("/env/"+key, O_RDWR, 0666)
- if e != nil {
- return e
- }
- defer Close(f)
+ envLock.Lock()
+ defer envLock.Unlock()
- _, e = Write(f, []byte(value))
+ err := writeenv(key, value)
+ if err != nil {
+ return err
+ }
+ env[key] = value
return nil
}
func Clearenv() {
+ envOnce.Do(copyenv) // prevent copyenv in Getenv/Setenv
+
+ envLock.Lock()
+ defer envLock.Unlock()
+
+ env = make(map[string]string)
RawSyscall(SYS_RFORK, RFCENVG, 0, 0)
}
func Environ() []string {
- env := make([]string, 0, 100)
-
- f, e := Open("/env", O_RDONLY)
- if e != nil {
- panic(e)
- }
- defer Close(f)
-
- names, e := readdirnames(f)
- if e != nil {
- panic(e)
- }
-
- for _, k := range names {
- if v, ok := Getenv(k); ok {
- env = append(env, k+"="+v)
- }
+ envOnce.Do(copyenv)
+ envLock.RLock()
+ defer envLock.RUnlock()
+ a := make([]string, len(env))
+ i := 0
+ for k, v := range env {
+ a[i] = k + "=" + v
+ i++
}
- return env[0:len(env)]
+ return a
}