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      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