env_windows.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  // Windows environment variables.
     6  
     7  package syscall
     8  
     9  import (
    10  	"unsafe"
    11  )
    12  
    13  func Getenv(key string) (value string, found bool) {
    14  	keyp, err := UTF16PtrFromString(key)
    15  	if err != nil {
    16  		return "", false
    17  	}
    18  	n := uint32(100)
    19  	for {
    20  		b := make([]uint16, n)
    21  		n, err = GetEnvironmentVariable(keyp, &b[0], uint32(len(b)))
    22  		if n == 0 && err == ERROR_ENVVAR_NOT_FOUND {
    23  			return "", false
    24  		}
    25  		if n <= uint32(len(b)) {
    26  			return UTF16ToString(b[:n]), true
    27  		}
    28  	}
    29  }
    30  
    31  func Setenv(key, value string) error {
    32  	v, err := UTF16PtrFromString(value)
    33  	if err != nil {
    34  		return err
    35  	}
    36  	keyp, err := UTF16PtrFromString(key)
    37  	if err != nil {
    38  		return err
    39  	}
    40  	e := SetEnvironmentVariable(keyp, v)
    41  	if e != nil {
    42  		return e
    43  	}
    44  	runtimeSetenv(key, value)
    45  	return nil
    46  }
    47  
    48  func Unsetenv(key string) error {
    49  	keyp, err := UTF16PtrFromString(key)
    50  	if err != nil {
    51  		return err
    52  	}
    53  	e := SetEnvironmentVariable(keyp, nil)
    54  	if e != nil {
    55  		return e
    56  	}
    57  	runtimeUnsetenv(key)
    58  	return nil
    59  }
    60  
    61  func Clearenv() {
    62  	for _, s := range Environ() {
    63  		// Environment variables can begin with =
    64  		// so start looking for the separator = at j=1.
    65  		// https://devblogs.microsoft.com/oldnewthing/20100506-00/?p=14133
    66  		for j := 1; j < len(s); j++ {
    67  			if s[j] == '=' {
    68  				Unsetenv(s[0:j])
    69  				break
    70  			}
    71  		}
    72  	}
    73  }
    74  
    75  func Environ() []string {
    76  	envp, e := GetEnvironmentStrings()
    77  	if e != nil {
    78  		return nil
    79  	}
    80  	defer FreeEnvironmentStrings(envp)
    81  
    82  	r := make([]string, 0, 50) // Empty with room to grow.
    83  	const size = unsafe.Sizeof(*envp)
    84  	for *envp != 0 { // environment block ends with empty string
    85  		// find NUL terminator
    86  		end := unsafe.Pointer(envp)
    87  		for *(*uint16)(end) != 0 {
    88  			end = unsafe.Add(end, size)
    89  		}
    90  
    91  		entry := unsafe.Slice(envp, (uintptr(end)-uintptr(unsafe.Pointer(envp)))/size)
    92  		r = append(r, UTF16ToString(entry))
    93  		envp = (*uint16)(unsafe.Add(end, size))
    94  	}
    95  	return r
    96  }
    97
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