github.com/reiver/go@v0.0.0-20150109200633-1d0c7792f172/src/runtime/env_posix.go (about)

     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 getenv(s *byte) *byte {
    12  	val := gogetenv(gostringnocopy(s))
    13  	if val == "" {
    14  		return nil
    15  	}
    16  	// Strings found in environment are NUL-terminated.
    17  	return &bytes(val)[0]
    18  }
    19  
    20  func gogetenv(key string) string {
    21  	env := environ()
    22  	if env == nil {
    23  		throw("getenv before env init")
    24  	}
    25  	for _, s := range environ() {
    26  		if len(s) > len(key) && s[len(key)] == '=' && s[:len(key)] == key {
    27  			return s[len(key)+1:]
    28  		}
    29  	}
    30  	return ""
    31  }
    32  
    33  var _cgo_setenv unsafe.Pointer   // pointer to C function
    34  var _cgo_unsetenv unsafe.Pointer // pointer to C function
    35  
    36  // Update the C environment if cgo is loaded.
    37  // Called from syscall.Setenv.
    38  //go:linkname syscall_setenv_c syscall.setenv_c
    39  func syscall_setenv_c(k string, v string) {
    40  	if _cgo_setenv == nil {
    41  		return
    42  	}
    43  	arg := [2]unsafe.Pointer{cstring(k), cstring(v)}
    44  	asmcgocall(unsafe.Pointer(_cgo_setenv), unsafe.Pointer(&arg))
    45  }
    46  
    47  // Update the C environment if cgo is loaded.
    48  // Called from syscall.unsetenv.
    49  //go:linkname syscall_unsetenv_c syscall.unsetenv_c
    50  func syscall_unsetenv_c(k string) {
    51  	if _cgo_unsetenv == nil {
    52  		return
    53  	}
    54  	arg := [1]unsafe.Pointer{cstring(k)}
    55  	asmcgocall(unsafe.Pointer(_cgo_unsetenv), unsafe.Pointer(&arg))
    56  }
    57  
    58  func cstring(s string) unsafe.Pointer {
    59  	p := make([]byte, len(s)+1)
    60  	sp := (*_string)(unsafe.Pointer(&s))
    61  	memmove(unsafe.Pointer(&p[0]), unsafe.Pointer(sp.str), uintptr(len(s)))
    62  	return unsafe.Pointer(&p[0])
    63  }