1// Copyright 2012 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 aix darwin dragonfly freebsd hurd js,wasm linux netbsd openbsd solaris windows
6
7package runtime
8
9func gogetenv(key string) string {
10	env := environ()
11	if env == nil {
12		throw("getenv before env init")
13	}
14	for _, s := range env {
15		if len(s) > len(key) && s[len(key)] == '=' && envKeyEqual(s[:len(key)], key) {
16			return s[len(key)+1:]
17		}
18	}
19	return ""
20}
21
22// envKeyEqual reports whether a == b, with ASCII-only case insensitivity
23// on Windows. The two strings must have the same length.
24func envKeyEqual(a, b string) bool {
25	if GOOS == "windows" { // case insensitive
26		for i := 0; i < len(a); i++ {
27			ca, cb := a[i], b[i]
28			if ca == cb || lowerASCII(ca) == lowerASCII(cb) {
29				continue
30			}
31			return false
32		}
33		return true
34	}
35	return a == b
36}
37
38func lowerASCII(c byte) byte {
39	if 'A' <= c && c <= 'Z' {
40		return c + ('a' - 'A')
41	}
42	return c
43}
44