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// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build windows
package execenv
import (
"internal/syscall/windows"
"syscall"
"unicode/utf16"
"unsafe"
)
// Default will return the default environment
// variables based on the process attributes
// provided.
//
// If the process attributes contain a token, then
// the environment variables will be sourced from
// the defaults for that user token, otherwise they
// will be sourced from syscall.Environ().
func Default(sys *syscall.SysProcAttr) (env []string, err error) {
if sys == nil || sys.Token == 0 {
return syscall.Environ(), nil
}
var block *uint16
err = windows.CreateEnvironmentBlock(&block, sys.Token, false)
if err != nil {
return nil, err
}
defer windows.DestroyEnvironmentBlock(block)
blockp := uintptr(unsafe.Pointer(block))
for {
// find NUL terminator
end := unsafe.Pointer(blockp)
for *(*uint16)(end) != 0 {
end = unsafe.Pointer(uintptr(end) + 2)
}
n := (uintptr(end) - uintptr(unsafe.Pointer(blockp))) / 2
if n == 0 {
// environment block ends with empty string
break
}
entry := (*[(1 << 30) - 1]uint16)(unsafe.Pointer(blockp))[:n:n]
env = append(env, string(utf16.Decode(entry)))
blockp += 2 * (uintptr(len(entry)) + 1)
}
return
}
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