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// Copyright 2009 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.
// Fork, exec, wait, etc.
package syscall
import (
"sync"
"unicode/utf16"
"unsafe"
)
var ForkLock sync.RWMutex
// EscapeArg rewrites command line argument s as prescribed
// in https://msdn.microsoft.com/en-us/library/ms880421.
// This function returns "" (2 double quotes) if s is empty.
// Alternatively, these transformations are done:
// - every back slash (\) is doubled, but only if immediately
// followed by double quote (");
// - every double quote (") is escaped by back slash (\);
// - finally, s is wrapped with double quotes (arg -> "arg"),
// but only if there is space or tab inside s.
func EscapeArg(s string) string {
if len(s) == 0 {
return "\"\""
}
n := len(s)
hasSpace := false
for i := 0; i < len(s); i++ {
switch s[i] {
case '"', '\\':
n++
case ' ', '\t':
hasSpace = true
}
}
if hasSpace {
n += 2
}
if n == len(s) {
return s
}
qs := make([]byte, n)
j := 0
if hasSpace {
qs[j] = '"'
j++
}
slashes := 0
for i := 0; i < len(s); i++ {
switch s[i] {
default:
slashes = 0
qs[j] = s[i]
case '\\':
slashes++
qs[j] = s[i]
case '"':
for ; slashes > 0; slashes-- {
qs[j] = '\\'
j++
}
qs[j] = '\\'
j++
qs[j] = s[i]
}
j++
}
if hasSpace {
for ; slashes > 0; slashes-- {
qs[j] = '\\'
j++
}
qs[j] = '"'
j++
}
return string(qs[:j])
}
// makeCmdLine builds a command line out of args by escaping "special"
// characters and joining the arguments with spaces.
func makeCmdLine(args []string) string {
var s string
for _, v := range args {
if s != "" {
s += " "
}
s += EscapeArg(v)
}
return s
}
// createEnvBlock converts an array of environment strings into
// the representation required by CreateProcess: a sequence of NUL
// terminated strings followed by a nil.
// Last bytes are two UCS-2 NULs, or four NUL bytes.
func createEnvBlock(envv []string) *uint16 {
if len(envv) == 0 {
return &utf16.Encode([]rune("\x00\x00"))[0]
}
length := 0
for _, s := range envv {
length += len(s) + 1
}
length += 1
b := make([]byte, length)
i := 0
for _, s := range envv {
l := len(s)
copy(b[i:i+l], []byte(s))
copy(b[i+l:i+l+1], []byte{0})
i = i + l + 1
}
copy(b[i:i+1], []byte{0})
return &utf16.Encode([]rune(string(b)))[0]
}
func CloseOnExec(fd Handle) {
SetHandleInformation(Handle(fd), HANDLE_FLAG_INHERIT, 0)
}
func SetNonblock(fd Handle, nonblocking bool) (err error) {
return nil
}
// FullPath retrieves the full path of the specified file.
func FullPath(name string) (path string, err error) {
p, err := UTF16PtrFromString(name)
if err != nil {
return "", err
}
n := uint32(100)
for {
buf := make([]uint16, n)
n, err = GetFullPathName(p, uint32(len(buf)), &buf[0], nil)
if err != nil {
return "", err
}
if n <= uint32(len(buf)) {
return UTF16ToString(buf[:n]), nil
}
}
}
func isSlash(c uint8) bool {
return c == '\\' || c == '/'
}
func normalizeDir(dir string) (name string, err error) {
ndir, err := FullPath(dir)
if err != nil {
return "", err
}
if len(ndir) > 2 && isSlash(ndir[0]) && isSlash(ndir[1]) {
// dir cannot have \\server\share\path form
return "", EINVAL
}
return ndir, nil
}
func volToUpper(ch int) int {
if 'a' <= ch && ch <= 'z' {
ch += 'A' - 'a'
}
return ch
}
func joinExeDirAndFName(dir, p string) (name string, err error) {
if len(p) == 0 {
return "", EINVAL
}
if len(p) > 2 && isSlash(p[0]) && isSlash(p[1]) {
// \\server\share\path form
return p, nil
}
if len(p) > 1 && p[1] == ':' {
// has drive letter
if len(p) == 2 {
return "", EINVAL
}
if isSlash(p[2]) {
return p, nil
} else {
d, err := normalizeDir(dir)
if err != nil {
return "", err
}
if volToUpper(int(p[0])) == volToUpper(int(d[0])) {
return FullPath(d + "\\" + p[2:])
} else {
return FullPath(p)
}
}
} else {
// no drive letter
d, err := normalizeDir(dir)
if err != nil {
return "", err
}
if isSlash(p[0]) {
return FullPath(d[:2] + p)
} else {
return FullPath(d + "\\" + p)
}
}
}
type ProcAttr struct {
Dir string
Env []string
Files []uintptr
Sys *SysProcAttr
}
type SysProcAttr struct {
HideWindow bool
CmdLine string // used if non-empty, else the windows command line is built by escaping the arguments passed to StartProcess
CreationFlags uint32
Token Token // if set, runs new process in the security context represented by the token
}
var zeroProcAttr ProcAttr
var zeroSysProcAttr SysProcAttr
func StartProcess(argv0 string, argv []string, attr *ProcAttr) (pid int, handle uintptr, err error) {
if len(argv0) == 0 {
return 0, 0, EWINDOWS
}
if attr == nil {
attr = &zeroProcAttr
}
sys := attr.Sys
if sys == nil {
sys = &zeroSysProcAttr
}
if len(attr.Files) > 3 {
return 0, 0, EWINDOWS
}
if len(attr.Files) < 3 {
return 0, 0, EINVAL
}
if len(attr.Dir) != 0 {
// StartProcess assumes that argv0 is relative to attr.Dir,
// because it implies Chdir(attr.Dir) before executing argv0.
// Windows CreateProcess assumes the opposite: it looks for
// argv0 relative to the current directory, and, only once the new
// process is started, it does Chdir(attr.Dir). We are adjusting
// for that difference here by making argv0 absolute.
var err error
argv0, err = joinExeDirAndFName(attr.Dir, argv0)
if err != nil {
return 0, 0, err
}
}
argv0p, err := UTF16PtrFromString(argv0)
if err != nil {
return 0, 0, err
}
var cmdline string
// Windows CreateProcess takes the command line as a single string:
// use attr.CmdLine if set, else build the command line by escaping
// and joining each argument with spaces
if sys.CmdLine != "" {
cmdline = sys.CmdLine
} else {
cmdline = makeCmdLine(argv)
}
var argvp *uint16
if len(cmdline) != 0 {
argvp, err = UTF16PtrFromString(cmdline)
if err != nil {
return 0, 0, err
}
}
var dirp *uint16
if len(attr.Dir) != 0 {
dirp, err = UTF16PtrFromString(attr.Dir)
if err != nil {
return 0, 0, err
}
}
// Acquire the fork lock so that no other threads
// create new fds that are not yet close-on-exec
// before we fork.
ForkLock.Lock()
defer ForkLock.Unlock()
p, _ := GetCurrentProcess()
fd := make([]Handle, len(attr.Files))
for i := range attr.Files {
if attr.Files[i] > 0 {
err := DuplicateHandle(p, Handle(attr.Files[i]), p, &fd[i], 0, true, DUPLICATE_SAME_ACCESS)
if err != nil {
return 0, 0, err
}
defer CloseHandle(Handle(fd[i]))
}
}
si := new(StartupInfo)
si.Cb = uint32(unsafe.Sizeof(*si))
si.Flags = STARTF_USESTDHANDLES
if sys.HideWindow {
si.Flags |= STARTF_USESHOWWINDOW
si.ShowWindow = SW_HIDE
}
si.StdInput = fd[0]
si.StdOutput = fd[1]
si.StdErr = fd[2]
pi := new(ProcessInformation)
flags := sys.CreationFlags | CREATE_UNICODE_ENVIRONMENT
if sys.Token != 0 {
err = CreateProcessAsUser(sys.Token, argv0p, argvp, nil, nil, true, flags, createEnvBlock(attr.Env), dirp, si, pi)
} else {
err = CreateProcess(argv0p, argvp, nil, nil, true, flags, createEnvBlock(attr.Env), dirp, si, pi)
}
if err != nil {
return 0, 0, err
}
defer CloseHandle(Handle(pi.Thread))
return int(pi.ProcessId), uintptr(pi.Process), nil
}
func Exec(argv0 string, argv []string, envv []string) (err error) {
return EWINDOWS
}