Better DLL detection, synchronous command execution

 * Added a libversion() function to the DLL which is used by the Vim
   script to verify that the DLL exists & can be loaded and that there
   isn't a version mismatch between the Vim script and the DLL.

 * Added the option of waiting for the external command to finish
   by removing execute() from the DLL and adding execute_synchronous()
   as well as execute_asynchronous(). The Vim script still contains the
   single function xolox#shell#execute() however it used to take
   printf()-style variable arguments and now always requires two
   arguments: the command to execute and whether to wait for the command
   to finish, where 1 = yes and 0 = no.

 * Because the Vim script already contained code to build command-lines
   but that functionality was removed from the xolox#shell#execute()
   function I've decided to make the function used to build
   command-lines public. This way there's no loss in functionality, only
   ease of use.

autoload.vim

@@ -1,6 +1,6 @@
 " Vim autoload plug-in
 " Maintainer: Peter Odding <peter@peterodding.com>
-" Last Change: June 13, 2010
+" Last Change: June 14, 2010
 " URL: http://peterodding.com/code/vim/shell
 
 " This Vim script enables tighter integration between Vim and its environment
@@ -52,16 +52,17 @@ function! xolox#shell#openurl(url) " {{{1
   throw printf(s:enoimpl, s:script, 'openurl', s:contact)
 endfunction
 
-function! xolox#shell#execute(cmd, ...) " {{{1
-  let cmd = s:make_cmdline(a:cmd, a:000)
+function! xolox#shell#execute(command, synchronous) " {{{1
   if s:is_windows() && s:has_dll()
-    let error = s:library_call('execute', cmd)
+    let fn = 'execute_' . (a:synchronous ? '' : 'a') . 'synchronous'
+    let error = s:library_call(fn, a:command)
     if error != ''
-      let msg = '%s: execute(%s) failed! (error: %s)'
-      throw printf(msg, s:script, strtrans(cmd), strtrans(error))
+      let msg = '%s: %s(%s) failed! (error: %s)'
+      throw printf(msg, s:script, fn, strtrans(a:command), strtrans(error))
     endif
   else
-    if has('unix')
+    let cmd = a:command
+    if has('unix') && !a:synchronous
       let cmd = '(' . cmd . ') &'
     endif
     let output = system(cmd)
@@ -109,6 +110,16 @@ function! xolox#shell#fullscreen() " {{{1
   return 0
 endfunction
 
+function! xolox#shell#buildcmd(cmd, args) " {{{1
+  if a:args == []
+    return a:cmd
+  else
+    let args = map(copy(a:args), 'shellescape(v:val)')
+    call insert(args, a:cmd, 0)
+    return call('printf', args)
+  endif
+endfunction
+
 " Supporting functions. {{{1
 
 function! s:is_windows() " {{{2
@@ -119,28 +130,37 @@ if s:is_windows()
 
   let s:library = expand('<sfile>:p:h') . '\shell.dll'
 
-  function! s:has_dll() " {{{2
-    return filereadable(s:library)
-  endfunction
-
   function! s:library_call(fn, arg) " {{{2
     return libcall(s:library, a:fn, a:arg)
   endfunction
 
-endif
+  function! s:find_dll_version() " {{{2
+    try
+      return s:library_call('libversion', '')
+    catch
+      let msg = "%s: Failed to load %s DLL!"
+      let lib = fnamemodify(s:library, ':~')
+      echohl warningmsg
+      echomsg printf(msg, s:script, lib)
+      echohl none
+    endtry
+    return '?'
+  endfunction
 
-function! s:make_cmdline(cmd, args) " {{{2
-  if a:args == []
-    return a:cmd
-  else
-    let args = map(copy(a:args), 'shellescape(v:val)')
-    call insert(args, a:cmd, 0)
-    return call('printf', args)
-  endif
-endfunction
+  function! s:has_dll() " {{{2
+    " Check that the DLL is available using libversion() before calling any of
+    " the other functions. This is only done the first time this plug-in needs
+    " to call the DLL and also makes sure the right version is loaded.
+    if !exists('s:library_version')
+      let s:library_version = s:find_dll_version()
+    endif
+    return s:library_version == '0.2'
+  endfunction
+
+endif
 
 function! s:execute(cmd, args) " {{{2
-  let cmd = s:make_cmdline(a:cmd, a:args)
+  let cmd = xolox#shell#buildcmd(a:cmd, a:args)
   let output = system(cmd)
   call s:handle_error(cmd, output)
   return output

dll/shell.c

@@ -1,9 +1,10 @@
 /* This is a dynamic link library for Vim on Windows that makes the following
  * features available to Vim:
  *
- *	- Open the user's preferred web browser with a given URL;
- *	- Execute external programs *without* showing a command prompt;
- *	- Toggle Vim's full-screen state using a bit of Windows API magic.
+ *  - Open the user's preferred web browser with a given URL;
+ *  - Execute external commands *without* showing a command prompt,
+ *    optionally waiting for the command to finish;
+ *  - Toggle Vim's full-screen state using a bit of Windows API magic.
  * 
  * If you want to compile this library yourself you need to have the Microsoft
  * Windows SDK installed, you can find a download link on the following web
@@ -14,14 +15,14 @@
  *
  * Open the Windows SDK command prompt and run the following command:
  *
- *		 CL /LD shell.c shell32.lib user32.lib
+ *     CL /LD shell.c shell32.lib user32.lib
  *
  * This should create the dynamic link library "shell.dll" which you can call
  * from Vim using for example :call libcall('c:/shell.dll', 'fullscreen', 1).
  *
  * Happy vimming!
  *
- *	- Peter Odding <peter@peterodding.com>
+ *  - Peter Odding <peter@peterodding.com>
  */
 
 #define _WIN32_WINNT 0x0500 /* GetConsoleWindow() */
@@ -35,7 +36,7 @@ static char buffer[1024 * 10];
 #undef MessageBox
 #define MessageBox(message) MessageBoxA(NULL, message, "Vim Library", 0)
 
-static char *GetError(void)
+static char *GetError(void) /* {{{1 */
 {
 	int i;
 
@@ -49,42 +50,67 @@ static char *GetError(void)
 	return buffer;
 }
 
-static char *Success(char *result)
+static char *Success(char *result) /* {{{1 */
 {
 	/* printf("OK\n"); */
 	return result;
 }
 
-static char *Failure(char *result)
+static char *Failure(char *result) /* {{{1 */
 {
 	/* if (result && strlen(result)) MessageBox(result); */
 	return result;
 }
 
-__declspec(dllexport)
-char *execute(char *command)
+static char *execute(char *command, int wait) /* {{{1 */
 {
 	STARTUPINFO si;
 	PROCESS_INFORMATION pi;
 	ZeroMemory(&si, sizeof(si));
 	ZeroMemory(&pi, sizeof(pi));
 	si.cb = sizeof(si);
 	if (CreateProcess(0, command, 0, 0, 0, CREATE_NO_WINDOW, 0, 0, &si, &pi)) {
+		if (wait) {
+			WaitForSingleObject(pi.hProcess, INFINITE);
+			/* long exit_code; */
+			/* TODO: GetExitCodeProcess( pi.hProcess, &exit_code); */
+			CloseHandle(pi.hProcess);
+			CloseHandle(pi.hThread);
+		}
 		return Success(NULL);
 	} else {
 		return Failure(GetError());
 	}
 }
 
 __declspec(dllexport)
-char *openurl(char *path)
+char *execute_synchronous(char *command) /* {{{1 */
+{
+	return execute(command, 1);
+}
+
+__declspec(dllexport)
+char *execute_asynchronous(char *command) /* {{{1 */
+{
+	return execute(command, 0);
+}
+
+__declspec(dllexport)
+char *libversion(char *ignored) /* {{{1 */
+{
+	(void)ignored;
+	return Success("0.2");
+}
+
+__declspec(dllexport)
+char *openurl(char *path) /* {{{1 */
 {
 	ShellExecute(NULL, "open", path, NULL, NULL, SW_SHOWNORMAL);
 	return Success(NULL);
 }
 
 __declspec(dllexport)
-char *fullscreen(long enable)
+char *fullscreen(long enable) /* {{{1 */
 {
 	HWND window;
 	LONG styles;
@@ -98,7 +124,7 @@ char *fullscreen(long enable)
 		return Failure("Could not query window styles!");
 
 	if (enable) styles ^= WS_CAPTION | WS_THICKFRAME;
-	else				styles |= WS_CAPTION | WS_THICKFRAME;
+	else        styles |= WS_CAPTION | WS_THICKFRAME;
 
 	if (!SetWindowLong(window, GWL_STYLE, styles))
 		return Failure("Could not apply window styles!");
@@ -122,13 +148,13 @@ char *fullscreen(long enable)
 	return Success(NULL);
 }
 
-/* TODO: The quest to embedding a command prompt in Vim :)
- * This doesn't quite work and I'm afraid it never will.
- */
-
 __declspec(dllexport)
-char *console(char *command)
+char *console(char *command) /* {{{1 */
 {
+	/* TODO: The quest to embedding a command prompt in Vim :)
+	 * This doesn't quite work and I'm afraid it never will.
+	 */
+
 	HWND gvim, console;
 	LONG styles;