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
7package syscall
8
9import (
10	"unicode/utf16"
11	"unsafe"
12)
13
14func 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
32func 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
48func Unsetenv(key string) error {
49	keyp, err := UTF16PtrFromString(key)
50	if err != nil {
51		return err
52	}
53	return SetEnvironmentVariable(keyp, nil)
54}
55
56func 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
70func 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