Source file src/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	// +build aix darwin dragonfly freebsd js,wasm 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 env {
    17			if len(s) > len(key) && s[len(key)] == '=' && envKeyEqual(s[:len(key)], key) {
    18				return s[len(key)+1:]
    19			}
    20		}
    21		return ""
    22	}
    23	
    24	// envKeyEqual reports whether a == b, with ASCII-only case insensitivity
    25	// on Windows. The two strings must have the same length.
    26	func envKeyEqual(a, b string) bool {
    27		if GOOS == "windows" { // case insensitive
    28			for i := 0; i < len(a); i++ {
    29				ca, cb := a[i], b[i]
    30				if ca == cb || lowerASCII(ca) == lowerASCII(cb) {
    31					continue
    32				}
    33				return false
    34			}
    35			return true
    36		}
    37		return a == b
    38	}
    39	
    40	func lowerASCII(c byte) byte {
    41		if 'A' <= c && c <= 'Z' {
    42			return c + ('a' - 'A')
    43		}
    44		return c
    45	}
    46	
    47	var _cgo_setenv unsafe.Pointer   // pointer to C function
    48	var _cgo_unsetenv unsafe.Pointer // pointer to C function
    49	
    50	// Update the C environment if cgo is loaded.
    51	// Called from syscall.Setenv.
    52	//go:linkname syscall_setenv_c syscall.setenv_c
    53	func syscall_setenv_c(k string, v string) {
    54		if _cgo_setenv == nil {
    55			return
    56		}
    57		arg := [2]unsafe.Pointer{cstring(k), cstring(v)}
    58		asmcgocall(_cgo_setenv, unsafe.Pointer(&arg))
    59	}
    60	
    61	// Update the C environment if cgo is loaded.
    62	// Called from syscall.unsetenv.
    63	//go:linkname syscall_unsetenv_c syscall.unsetenv_c
    64	func syscall_unsetenv_c(k string) {
    65		if _cgo_unsetenv == nil {
    66			return
    67		}
    68		arg := [1]unsafe.Pointer{cstring(k)}
    69		asmcgocall(_cgo_unsetenv, unsafe.Pointer(&arg))
    70	}
    71	
    72	func cstring(s string) unsafe.Pointer {
    73		p := make([]byte, len(s)+1)
    74		copy(p, s)
    75		return unsafe.Pointer(&p[0])
    76	}
    77	

View as plain text