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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Fork, exec, wait, etc.
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package windows
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import (
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	errorspkg "errors"
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	"unsafe"
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)
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// EscapeArg rewrites command line argument s as prescribed
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// in http://msdn.microsoft.com/en-us/library/ms880421.
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// This function returns "" (2 double quotes) if s is empty.
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// Alternatively, these transformations are done:
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//   - every back slash (\) is doubled, but only if immediately
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//     followed by double quote (");
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//   - every double quote (") is escaped by back slash (\);
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//   - finally, s is wrapped with double quotes (arg -> "arg"),
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//     but only if there is space or tab inside s.
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func EscapeArg(s string) string {
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	if len(s) == 0 {
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		return `""`
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	}
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	n := len(s)
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	hasSpace := false
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	for i := 0; i < len(s); i++ {
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		switch s[i] {
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		case '"', '\\':
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			n++
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		case ' ', '\t':
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			hasSpace = true
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		}
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	}
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	if hasSpace {
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		n += 2 // Reserve space for quotes.
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	}
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	if n == len(s) {
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		return s
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	}
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	qs := make([]byte, n)
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	j := 0
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	if hasSpace {
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		qs[j] = '"'
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		j++
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	}
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	slashes := 0
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	for i := 0; i < len(s); i++ {
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		switch s[i] {
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		default:
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			slashes = 0
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			qs[j] = s[i]
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		case '\\':
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			slashes++
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			qs[j] = s[i]
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		case '"':
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			for ; slashes > 0; slashes-- {
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				qs[j] = '\\'
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				j++
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			}
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			qs[j] = '\\'
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			j++
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			qs[j] = s[i]
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		}
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		j++
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	}
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	if hasSpace {
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		for ; slashes > 0; slashes-- {
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			qs[j] = '\\'
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			j++
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		}
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		qs[j] = '"'
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		j++
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	}
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	return string(qs[:j])
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}
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// ComposeCommandLine escapes and joins the given arguments suitable for use as a Windows command line,
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// in CreateProcess's CommandLine argument, CreateService/ChangeServiceConfig's BinaryPathName argument,
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// or any program that uses CommandLineToArgv.
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func ComposeCommandLine(args []string) string {
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	if len(args) == 0 {
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		return ""
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	}
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	// Per https://learn.microsoft.com/en-us/windows/win32/api/shellapi/nf-shellapi-commandlinetoargvw:
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	// “This function accepts command lines that contain a program name; the
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	// program name can be enclosed in quotation marks or not.”
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	//
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	// Unfortunately, it provides no means of escaping interior quotation marks
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	// within that program name, and we have no way to report them here.
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	prog := args[0]
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	mustQuote := len(prog) == 0
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	for i := 0; i < len(prog); i++ {
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		c := prog[i]
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		if c <= ' ' || (c == '"' && i == 0) {
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			// Force quotes for not only the ASCII space and tab as described in the
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			// MSDN article, but also ASCII control characters.
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			// The documentation for CommandLineToArgvW doesn't say what happens when
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			// the first argument is not a valid program name, but it empirically
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			// seems to drop unquoted control characters.
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			mustQuote = true
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			break
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		}
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	}
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	var commandLine []byte
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	if mustQuote {
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		commandLine = make([]byte, 0, len(prog)+2)
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		commandLine = append(commandLine, '"')
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		for i := 0; i < len(prog); i++ {
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			c := prog[i]
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			if c == '"' {
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				// This quote would interfere with our surrounding quotes.
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				// We have no way to report an error, so just strip out
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				// the offending character instead.
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				continue
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			}
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			commandLine = append(commandLine, c)
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		}
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		commandLine = append(commandLine, '"')
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	} else {
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		if len(args) == 1 {
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			// args[0] is a valid command line representing itself.
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			// No need to allocate a new slice or string for it.
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			return prog
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		}
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		commandLine = []byte(prog)
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	}
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	for _, arg := range args[1:] {
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		commandLine = append(commandLine, ' ')
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		// TODO(bcmills): since we're already appending to a slice, it would be nice
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		// to avoid the intermediate allocations of EscapeArg.
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		// Perhaps we can factor out an appendEscapedArg function.
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		commandLine = append(commandLine, EscapeArg(arg)...)
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	}
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	return string(commandLine)
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}
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// DecomposeCommandLine breaks apart its argument command line into unescaped parts using CommandLineToArgv,
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// as gathered from GetCommandLine, QUERY_SERVICE_CONFIG's BinaryPathName argument, or elsewhere that
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// command lines are passed around.
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// DecomposeCommandLine returns an error if commandLine contains NUL.
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func DecomposeCommandLine(commandLine string) ([]string, error) {
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	if len(commandLine) == 0 {
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		return []string{}, nil
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	}
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	utf16CommandLine, err := UTF16FromString(commandLine)
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	if err != nil {
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		return nil, errorspkg.New("string with NUL passed to DecomposeCommandLine")
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	}
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	var argc int32
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	argv, err := commandLineToArgv(&utf16CommandLine[0], &argc)
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	if err != nil {
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		return nil, err
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	}
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	defer LocalFree(Handle(unsafe.Pointer(argv)))
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	var args []string
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	for _, p := range unsafe.Slice(argv, argc) {
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		args = append(args, UTF16PtrToString(p))
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	}
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	return args, nil
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}
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// CommandLineToArgv parses a Unicode command line string and sets
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// argc to the number of parsed arguments.
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//
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// The returned memory should be freed using a single call to LocalFree.
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//
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// Note that although the return type of CommandLineToArgv indicates 8192
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// entries of up to 8192 characters each, the actual count of parsed arguments
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// may exceed 8192, and the documentation for CommandLineToArgvW does not mention
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// any bound on the lengths of the individual argument strings.
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// (See https://go.dev/issue/63236.)
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func CommandLineToArgv(cmd *uint16, argc *int32) (argv *[8192]*[8192]uint16, err error) {
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	argp, err := commandLineToArgv(cmd, argc)
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	argv = (*[8192]*[8192]uint16)(unsafe.Pointer(argp))
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	return argv, err
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}
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func CloseOnExec(fd Handle) {
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	SetHandleInformation(Handle(fd), HANDLE_FLAG_INHERIT, 0)
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}
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// FullPath retrieves the full path of the specified file.
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func FullPath(name string) (path string, err error) {
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	p, err := UTF16PtrFromString(name)
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	if err != nil {
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		return "", err
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	}
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	n := uint32(100)
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	for {
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		buf := make([]uint16, n)
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		n, err = GetFullPathName(p, uint32(len(buf)), &buf[0], nil)
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		if err != nil {
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			return "", err
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		}
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		if n <= uint32(len(buf)) {
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			return UTF16ToString(buf[:n]), nil
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		}
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	}
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}
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// NewProcThreadAttributeList allocates a new ProcThreadAttributeListContainer, with the requested maximum number of attributes.
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func NewProcThreadAttributeList(maxAttrCount uint32) (*ProcThreadAttributeListContainer, error) {
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	var size uintptr
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	err := initializeProcThreadAttributeList(nil, maxAttrCount, 0, &size)
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	if err != ERROR_INSUFFICIENT_BUFFER {
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		if err == nil {
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			return nil, errorspkg.New("unable to query buffer size from InitializeProcThreadAttributeList")
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		}
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		return nil, err
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	}
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	alloc, err := LocalAlloc(LMEM_FIXED, uint32(size))
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	if err != nil {
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		return nil, err
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	}
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	// size is guaranteed to be ≥1 by InitializeProcThreadAttributeList.
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	al := &ProcThreadAttributeListContainer{data: (*ProcThreadAttributeList)(unsafe.Pointer(alloc))}
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	err = initializeProcThreadAttributeList(al.data, maxAttrCount, 0, &size)
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	if err != nil {
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		return nil, err
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	}
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	return al, err
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}
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// Update modifies the ProcThreadAttributeList using UpdateProcThreadAttribute.
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func (al *ProcThreadAttributeListContainer) Update(attribute uintptr, value unsafe.Pointer, size uintptr) error {
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	al.pointers = append(al.pointers, value)
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	return updateProcThreadAttribute(al.data, 0, attribute, value, size, nil, nil)
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}
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// Delete frees ProcThreadAttributeList's resources.
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func (al *ProcThreadAttributeListContainer) Delete() {
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	deleteProcThreadAttributeList(al.data)
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	LocalFree(Handle(unsafe.Pointer(al.data)))
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	al.data = nil
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	al.pointers = nil
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}
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// List returns the actual ProcThreadAttributeList to be passed to StartupInfoEx.
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func (al *ProcThreadAttributeListContainer) List() *ProcThreadAttributeList {
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	return al.data
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}
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