env_windows.go

Documentation: syscall

     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  	"unicode/utf16"
    11  	"unsafe"
    12  )
    13  
    14  func Getenv(key string) (value string, found bool) {
    15  	keyp, err := UTF16PtrFromString(key)
    16  	if err != nil {
    17  		return "", false
    18  	}
    19  	n := uint32(100)
    20  	for {
    21  		b := make([]uint16, n)
    22  		n, err = GetEnvironmentVariable(keyp, &b[0], uint32(len(b)))
    23  		if n == 0 && err == ERROR_ENVVAR_NOT_FOUND {
    24  			return "", false
    25  		}
    26  		if n <= uint32(len(b)) {
    27  			return string(utf16.Decode(b[:n])), true
    28  		}
    29  	}
    30  }
    31  
    32  func Setenv(key, value string) error {
    33  	v, err := UTF16PtrFromString(value)
    34  	if err != nil {
    35  		return err
    36  	}
    37  	keyp, err := UTF16PtrFromString(key)
    38  	if err != nil {
    39  		return err
    40  	}
    41  	e := SetEnvironmentVariable(keyp, v)
    42  	if e != nil {
    43  		return e
    44  	}
    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  	return SetEnvironmentVariable(keyp, nil)
    54  }
    55  
    56  func Clearenv() {
    57  	for _, s := range Environ() {
    58  		// Environment variables can begin with =
    59  		// so start looking for the separator = at j=1.
    60  		// https://blogs.msdn.com/b/oldnewthing/archive/2010/05/06/10008132.aspx
    61  		for j := 1; j < len(s); j++ {
    62  			if s[j] == '=' {
    63  				Unsetenv(s[0:j])
    64  				break
    65  			}
    66  		}
    67  	}
    68  }
    69  
    70  func Environ() []string {
    71  	s, e := GetEnvironmentStrings()
    72  	if e != nil {
    73  		return nil
    74  	}
    75  	defer FreeEnvironmentStrings(s)
    76  	r := make([]string, 0, 50) // Empty with room to grow.
    77  	for from, i, p := 0, 0, (*[1 << 24]uint16)(unsafe.Pointer(s)); true; i++ {
    78  		if p[i] == 0 {
    79  			// empty string marks the end
    80  			if i <= from {
    81  				break
    82  			}
    83  			r = append(r, string(utf16.Decode(p[from:i])))
    84  			from = i + 1
    85  		}
    86  	}
    87  	return r
    88  }
    89
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