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 darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows 6 7 package runtime 8 9 import "unsafe" 10 11 func gogetenv(key string) string { 12 env := environ() 13 if env == nil { 14 throw("getenv before env init") 15 } 16 for _, s := range environ() { 17 if len(s) > len(key) && s[len(key)] == '=' && s[:len(key)] == key { 18 return s[len(key)+1:] 19 } 20 } 21 return "" 22 } 23 24 var _cgo_setenv unsafe.Pointer // pointer to C function 25 var _cgo_unsetenv unsafe.Pointer // pointer to C function 26 27 // Update the C environment if cgo is loaded. 28 // Called from syscall.Setenv. 29 //go:linkname syscall_setenv_c syscall.setenv_c 30 func syscall_setenv_c(k string, v string) { 31 if _cgo_setenv == nil { 32 return 33 } 34 arg := [2]unsafe.Pointer{cstring(k), cstring(v)} 35 asmcgocall(unsafe.Pointer(_cgo_setenv), unsafe.Pointer(&arg)) 36 } 37 38 // Update the C environment if cgo is loaded. 39 // Called from syscall.unsetenv. 40 //go:linkname syscall_unsetenv_c syscall.unsetenv_c 41 func syscall_unsetenv_c(k string) { 42 if _cgo_unsetenv == nil { 43 return 44 } 45 arg := [1]unsafe.Pointer{cstring(k)} 46 asmcgocall(unsafe.Pointer(_cgo_unsetenv), unsafe.Pointer(&arg)) 47 } 48 49 func cstring(s string) unsafe.Pointer { 50 p := make([]byte, len(s)+1) 51 sp := (*_string)(unsafe.Pointer(&s)) 52 memmove(unsafe.Pointer(&p[0]), unsafe.Pointer(sp.str), uintptr(len(s))) 53 return unsafe.Pointer(&p[0]) 54 } 55
