libgo/go/runtime/env_posix.go

   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 //go:build aix || darwin || dragonfly || freebsd || hurd || (js && wasm) || linux || netbsd || openbsd || solaris || windows || plan9
   6
   7 package runtime
   8
   9 func 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.
  24 func 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
  38 func lowerASCII(c byte) byte {
  39         if 'A' <= c && c <= 'Z' {
  40                 return c + ('a' - 'A')
  41         }
  42         return c
  43 }