/* Auxiliary functions for the creation of subprocesses.  Native Woe32 API.
   Copyright (C) 2003, 2006-2008 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2003.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* Get declarations of the Win32 API functions.  */
#define WIN32_LEAN_AND_MEAN
#include <windows.h>

/* Get _get_osfhandle() and _open_osfhandle().  */
#include <io.h>

#include <stdbool.h>
#include <string.h>
#include <errno.h>

#include "xalloc.h"

/* Duplicates a file handle, making the copy uninheritable.  */
static int
dup_noinherit (int fd)
{
  HANDLE curr_process = GetCurrentProcess ();
  HANDLE old_handle = (HANDLE) _get_osfhandle (fd);
  HANDLE new_handle;
  int nfd;

  if (!DuplicateHandle (curr_process,		    /* SourceProcessHandle */
			old_handle,		    /* SourceHandle */
			curr_process,		    /* TargetProcessHandle */
			(PHANDLE) &new_handle,	    /* TargetHandle */
			(DWORD) 0,		    /* DesiredAccess */
			FALSE,			    /* InheritHandle */
			DUPLICATE_SAME_ACCESS))	    /* Options */
    error (EXIT_FAILURE, 0, _("DuplicateHandle failed with error code 0x%08x"),
	   GetLastError ());

  nfd = _open_osfhandle ((long) new_handle, O_BINARY);
  if (nfd < 0)
    error (EXIT_FAILURE, errno, _("_open_osfhandle failed"));

  return nfd;
}

/* Prepares an argument vector before calling spawn().
   Note that spawn() does not by itself call the command interpreter
     (getenv ("COMSPEC") != NULL ? getenv ("COMSPEC") :
      ({ OSVERSIONINFO v; v.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
         GetVersionEx(&v);
         v.dwPlatformId == VER_PLATFORM_WIN32_NT;
      }) ? "cmd.exe" : "command.com").
   Instead it simply concatenates the arguments, separated by ' ', and calls
   CreateProcess().  We must quote the arguments since Win32 CreateProcess()
   interprets characters like ' ', '\t', '\\', '"' (but not '<' and '>') in a
   special way:
   - Space and tab are interpreted as delimiters. They are not treated as
     delimiters if they are surrounded by double quotes: "...".
   - Unescaped double quotes are removed from the input. Their only effect is
     that within double quotes, space and tab are treated like normal
     characters.
   - Backslashes not followed by double quotes are not special.
   - But 2*n+1 backslashes followed by a double quote become
     n backslashes followed by a double quote (n >= 0):
       \" -> "
       \\\" -> \"
       \\\\\" -> \\"
 */
#define SHELL_SPECIAL_CHARS "\"\\ \001\002\003\004\005\006\007\010\011\012\013\014\015\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037"
#define SHELL_SPACE_CHARS " \001\002\003\004\005\006\007\010\011\012\013\014\015\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037"
static char **
prepare_spawn (char **argv)
{
  size_t argc;
  char **new_argv;
  size_t i;

  /* Count number of arguments.  */
  for (argc = 0; argv[argc] != NULL; argc++)
    ;

  /* Allocate new argument vector.  */
  new_argv = XNMALLOC (1 + argc + 1, char *);

  /* Add an element upfront that can be used when argv[0] turns out to be a
     script, not a program.
     On Unix, this would be "/bin/sh". On native Windows, "sh" is actually
     "sh.exe".  We have to omit the directory part and rely on the search in
     PATH, because the mingw "mount points" are not visible inside Win32
     CreateProcess().  */
  *new_argv++ = "sh.exe";

  /* Put quoted arguments into the new argument vector.  */
  for (i = 0; i < argc; i++)
    {
      const char *string = argv[i];

      if (string[0] == '\0')
	new_argv[i] = xstrdup ("\"\"");
      else if (strpbrk (string, SHELL_SPECIAL_CHARS) != NULL)
	{
	  bool quote_around = (strpbrk (string, SHELL_SPACE_CHARS) != NULL);
	  size_t length;
	  unsigned int backslashes;
	  const char *s;
	  char *quoted_string;
	  char *p;

	  length = 0;
	  backslashes = 0;
	  if (quote_around)
	    length++;
	  for (s = string; *s != '\0'; s++)
	    {
	      char c = *s;
	      if (c == '"')
		length += backslashes + 1;
	      length++;
	      if (c == '\\')
		backslashes++;
	      else
		backslashes = 0;
	    }
	  if (quote_around)
	    length += backslashes + 1;

	  quoted_string = (char *) xmalloc (length + 1);

	  p = quoted_string;
	  backslashes = 0;
	  if (quote_around)
	    *p++ = '"';
	  for (s = string; *s != '\0'; s++)
	    {
	      char c = *s;
	      if (c == '"')
		{
		  unsigned int j;
		  for (j = backslashes + 1; j > 0; j--)
		    *p++ = '\\';
		}
	      *p++ = c;
	      if (c == '\\')
		backslashes++;
	      else
		backslashes = 0;
	    }
	  if (quote_around)
	    {
	      unsigned int j;
	      for (j = backslashes; j > 0; j--)
		*p++ = '\\';
	      *p++ = '"';
	    }
	  *p = '\0';

	  new_argv[i] = quoted_string;
	}
      else
	new_argv[i] = (char *) string;
    }
  new_argv[argc] = NULL;

  return new_argv;
}