Related
What's a correct way to call FormatMessageW in Ruby?
require 'win32api'
FormatMessage = Win32API.new 'kernel32', 'FormatMessageW', 'IPIIPII', 'I'
msg = '\0' * 255
FormatMessage.call 0x00001000 | 0x00000100, nil, 6, 1024, msg, 0, 0
FormatMessage returns not null result but msg contains not readable message. What's wrong?
I believe this is the code you are looking for:
require 'win32api'
FORMAT_MESSAGE_FROM_SYSTEM = 0x1000
FormatMessage = Win32API.new 'kernel32', 'FormatMessageW', 'IPIIPIP', 'I'
msgw = ("\x00" * 256).force_encoding("UTF-16LE")
count = FormatMessage.call FORMAT_MESSAGE_FROM_SYSTEM, nil, 6, 1033, msgw, msgw.size, nil
msgw = msgw[0, count]
msg = msgw.encode("UTF-8")
puts msg
When I run this with Ruby, the output is "The handle is invalid.", which is the correct Windows error message for error code 6.
There were some problems with your original code.
The last argument to FormatMessageW is a pointer, so you should use P instead of I, especially if you want it to work on 64-bit Windows.
In Ruby '\0' is actually a two-byte ASCII string, not a single-byte null character. You can confirm this by running p '\0'.bytes.to_a. It looks like you tried to allocate 255 bytes, but you actually allocated 510 bytes. You should allocate an even number of bytes because wide characters in Windows take 2 bytes.
As #theB pointed out, your first argument to FormatMessageW was wrong, since you specified that FormatMessageW should allocate its own buffer.
You specified language code 1024. I can't find a definition for that. Maybe you meant 1033, which is "English - United States". Specifying 1024 doesn't seem to actually cause problems though.
You should use force_encoding to set the encoding of your string to UTF-16LE, because that is the encoding used for wide strings in Windows (or if it's not exactly the same, at least it is compatible most of the time).
The 6th argument to FormatMessageW should be the number of characters in your buffer (which is the number of bytes divided by 2, by the way). Your code just passed 0 for that argument.
Strings in Ruby can contain any arbitrary bytes, including null characters, but it's not necessarily a good idea to let that happen because things like String#size will return surprising results. FormatMessageW returns the number of characters in the formatted message, so we can use that to trim off the null characters at the end. (Conveniently, FormatMessageW returns 0 if there is an error, so our trimming would result in an empty string.)
You should use String#encode to convert your string from UTF-16LE to UTF-8 because UTF-8 strings are much easier to operate on and print in Ruby.
If you don't care about internationalization and unicode, you could have just used FormatMessageA instead. Here is some code that will work for that:
require 'win32api'
FORMAT_MESSAGE_FROM_SYSTEM = 0x1000
FormatMessage = Win32API.new 'kernel32', 'FormatMessageA', 'IPIIPIP', 'I'
msg = ("\x00" * 256).force_encoding("ASCII-8BIT")
count = FormatMessage.call FORMAT_MESSAGE_FROM_SYSTEM, nil, 6, 1033, msg, msg.size, nil
msg = msg[0, count]
puts msg
P.S. DWORD is an unsigned integer type. I am not sure what the right letter for that is in Ruby's Win32API class; it might be that I represents a signed integer, and should be replaced by something else.
I'm trying to use the (fairly new) GetLogicalProcessorInformationEx function in Windows. The ReturnLength it gives isn't making sense.
The older GetLogicalProcessorInformation gives reasonable results...
ReturnLength = 0;
Result = GetLogicalProcessorInformation(NULL, &ReturnLength);
printf("GLPI (%d): %d %d\n",
Result,
sizeof(SYSTEM_LOGICAL_PROCESSOR_INFORMATION),
ReturnLength);
Here's the output (2-core, 64-bit, Win7 box): GLPI (0): 32 416
In other words, the function will populate the buffer I pass with 416/32=13 SYSTEM_LOGICAL_PROCESSOR_INFORMATION structures.
For GetLogicalProcessorInformationEx, here's my call...
ReturnLength = 0;
Result = GetLogicalProcessorInformationEx(RelationProcessorCore,
NULL, &ReturnLength);
printf("GLPIX (%d): %d %d %d\n",
Result,
sizeof(PROCESSOR_RELATIONSHIP),
sizeof(SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX),
ReturnLength);
Here's the output (2-core, 64-bit, Win7 box): GLPIX (0): 40 80 96
The Microsoft docs (http://msdn.microsoft.com/en-us/library/windows/desktop/dd405488(v=vs.85).aspx) indicate that the function will return either PROCESSOR_RELATIONSHIP or SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX structures, depending on the value of the first argument. ReturnLength suggests it isn't going to return either, though - 96 isn't divisible by sizeof(PROCESSOR_RELATIONSHIP) or sizeof(SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX).
I also tried RelationAll for the first argument, and that gave a ReturnLength of 768 - also not a multiple or 40 or 80.
Can anyone shed any light?
You'll need to trust what the function returns you. Necessarily so, the structures in the union have an unpredictable size. Particularly this member of PROCESSOR_RELATIONSHIP:
GROUP_AFFINITY GroupMask[ANYSIZE_ARRAY];
The ANYSIZE_ARRAY macro is the hint, that says that the size of the GroupMask array is variable and depends on the value of the GroupCount member. Using sizeof on the structure never gives you the correct size, it will be too low. Be sure to use the returned size to allocate the storage for the struct, like this:
SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX* buf =
(SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX*)malloc(ReturnLength);
This pattern is otherwise common in C and the winapi.
I am a new member and joined this site after referring to it loads of times when i was stuck with some programming problems. I am trying to code a media player (Win32 SDK VC++ 6.0) for my college project and I am stuck. I have searched on various forums and msdn and finally landed on the function GetShortPathName which enables me to play through folders and files which have a whitespace in their names. I will paste the code here so it will be much more clearer as to what i am trying to do.
case IDM_FILE_OPEN :
ZeroMemory(&ofn, sizeof(ofn));
ofn.lStructSize = sizeof(ofn);
ofn.hwndOwner = hwnd;
ofn.lpstrFilter = "Media Files (All Supported Types)\0*.avi;*.mpg;*.mpeg;*.asf;*.wmv;*.mp2;*.mp3\0"
"Movie File (*.avi;*.mpg;*.mpeg)\0*.avi;*.mpg;*.mpeg\0"
"Windows Media File (*.asf;*.wmv)\0*.asf;*.wmv\0"
"Audio File (*.mp2;*.mp3)\0*.mp2;*.mp3\0"
"All Files(*.*)\0*.*\0";
ofn.lpstrFile = szFileName;
ofn.nMaxFile = MAX_PATH;
ofn.Flags = OFN_EXPLORER | OFN_FILEMUSTEXIST | OFN_HIDEREADONLY | OFN_ALLOWMULTISELECT | OFN_CREATEPROMPT;
ofn.lpstrDefExt = "mp3";
if(GetOpenFileName(&ofn))
{
length = GetShortPathName(szFileName, NULL, 0);
buffer = (TCHAR *) malloc (sizeof(length));
length = GetShortPathName(szFileName, buffer, length);
for(i = 0 ; i < MAX_PATH ; i++)
{
if(buffer[i] == '\\')
buffer[i] = '/';
}
SendMessage(hList,LB_ADDSTRING,0,(LPARAM)buffer);
mciSendString("open buffer alias myFile", NULL, 0, NULL);
mciSendString("play buffer", NULL, 0, NULL);
}
return 0;
using the GetShortPathName function i get the path as : D:/Mp3z/DEEPBL~1/03SLEE~1.mp3
Putting this path directly in Play button case
mciSendString("open D:/Mp3jh/DEEPBL~1/03SLEE~1.mp3 alias myFile", NULL, 0, NULL);
mciSendString("play myFile", NULL, 0, NULL);
the file opens and plays fine. But as soon as i try to open and play it through the open file dialog box, nothing happens. Any input appreciated.
It looks like the problem is that you're passing the name of the buffer variable to the mciSendString function as a string, rather than passing the contents of the buffer.
You need to concatenate the arguments you want to pass (open and alias myFile) with the contents of buffer.
The code can also be much simplified by replacing malloc with an automatic array. You don't need to malloc it because you don't need it outside of the block scope. (And you shouldn't be using malloc in C++ code anyway; use new[] instead.)
Here's a modified snippet of the code shown in your question:
(Warning: changes made using only my eyes as a compiler! Handle with care.)
if(GetOpenFileName(&ofn))
{
// Get the short path name, and place it in the buffer array.
// We know that a short path won't be any longer than MAX_PATH, so we can
// simply allocate a statically-sized array without futzing with new[].
//
// Note: In production code, you should probably check the return value
// of the GetShortPathName function to make sure it succeeded.
TCHAR buffer[MAX_PATH];
GetShortPathName(szFileName, buffer, MAX_PATH);
// Add the short path name to your ListBox control.
//
// Note: In C++ code, you should probably use C++-style casts like
// reinterpret_cast, rather than C-style casts!
SendMessage(hList, LB_ADDSTRING, 0, reinterpret_cast<LPARAM>(buffer));
// Build the argument string to pass to the mciSendString function.
//
// Note: In production code, you probably want to use the more secure
// alternatives to the string concatenation functions.
// See the documentation for more details.
// And, as before, you should probably check return values for error codes.
TCHAR arguments[MAX_PATH * 2]; // this will definitely be large enough
lstrcat(arguments, TEXT("open"));
lstrcat(arguments, buffer);
lstrcat(arguments, TEXT("alias myFile"));
// Or, better yet, use a string formatting function, like StringCbPrintf:
// StringCbPrintf(arguments, MAX_PATH * 2, TEXT("open %s alias myFile"),
// buffer);
// Call the mciSendString function with the argument string we just built.
mciSendString(arguments, NULL, 0, NULL);
mciSendString("play myFile", NULL, 0, NULL);
}
Do note that, as the above code shows, working with C-style strings (character arrays) is a real pain in the ass. C++ provides a better alternative, in the form of the std::string class. You should strongly consider using that instead. To call Windows API functions, you'll still need a C-style string, but you can get one of those by using the c_str method of the std::string class.
The GetModuleFileName() takes a buffer and size of buffer as input; however its return value can only tell us how many characters is has copied, and if the size is not enough (ERROR_INSUFFICIENT_BUFFER).
How do I determine the real required buffer size to hold entire file name for GetModuleFileName()?
Most people use MAX_PATH but I remember the path can exceed that (260 by default definition)...
(The trick of using zero as size of buffer does not work for this API - I've already tried before)
The usual recipe is to call it setting the size to zero and it is guaranteed to fail and provide the size needed to allocate sufficient buffer. Allocate a buffer (don't forget room for nul-termination) and call it a second time.
In a lot of cases MAX_PATH is sufficient because many of the file systems restrict the total length of a path name. However, it is possible to construct legal and useful file names that exceed MAX_PATH, so it is probably good advice to query for the required buffer.
Don't forget to eventually return the buffer from the allocator that provided it.
Edit: Francis points out in a comment that the usual recipe doesn't work for GetModuleFileName(). Unfortunately, Francis is absolutely right on that point, and my only excuse is that I didn't go look it up to verify before providing a "usual" solution.
I don't know what the author of that API was thinking, except that it is possible that when it was introduced, MAX_PATH really was the largest possible path, making the correct recipe easy. Simply do all file name manipulation in a buffer of length no less than MAX_PATH characters.
Oh, yeah, don't forget that path names since 1995 or so allow Unicode characters. Because Unicode takes more room, any path name can be preceeded by \\?\ to explicitly request that the MAX_PATH restriction on its byte length be dropped for that name. This complicates the question.
MSDN has this to say about path length in the article titled File Names, Paths, and Namespaces:
Maximum Path Length
In the Windows API (with some
exceptions discussed in the following
paragraphs), the maximum length for a
path is MAX_PATH, which is defined as
260 characters. A local path is
structured in the following order:
drive letter, colon, backslash,
components separated by backslashes,
and a terminating null character. For
example, the maximum path on drive D
is "D:\<some 256 character path
string><NUL>" where "<NUL>" represents
the invisible terminating null
character for the current system
codepage. (The characters < > are used
here for visual clarity and cannot be
part of a valid path string.)
Note File I/O functions in the
Windows API convert "/" to "\" as part
of converting the name to an NT-style
name, except when using the "\\?\"
prefix as detailed in the following
sections.
The Windows API has many functions
that also have Unicode versions to
permit an extended-length path for a
maximum total path length of 32,767
characters. This type of path is
composed of components separated by
backslashes, each up to the value
returned in the
lpMaximumComponentLength parameter of
the GetVolumeInformation function. To
specify an extended-length path, use
the "\\?\" prefix. For example,
"\\?\D:\<very long path>". (The
characters < > are used here for
visual clarity and cannot be part of a
valid path string.)
Note The maximum path of 32,767
characters is approximate, because the
"\\?\" prefix may be expanded to a
longer string by the system at run
time, and this expansion applies to
the total length.
The "\\?\" prefix can also be used
with paths constructed according to
the universal naming convention (UNC).
To specify such a path using UNC, use
the "\\?\UNC\" prefix. For example,
"\\?\UNC\server\share", where "server"
is the name of the machine and "share"
is the name of the shared folder.
These prefixes are not used as part of
the path itself. They indicate that
the path should be passed to the
system with minimal modification,
which means that you cannot use
forward slashes to represent path
separators, or a period to represent
the current directory. Also, you
cannot use the "\\?\" prefix with a
relative path, therefore relative
paths are limited to MAX_PATH
characters as previously stated for
paths not using the "\\?\" prefix.
When using an API to create a
directory, the specified path cannot
be so long that you cannot append an
8.3 file name (that is, the directory name cannot exceed MAX_PATH minus 12).
The shell and the file system have
different requirements. It is possible
to create a path with the Windows API
that the shell user interface might
not be able to handle.
So an easy answer would be to allocate a buffer of size MAX_PATH, retrieve the name and check for errors. If it fit, you are done. Otherwise, if it begins with "\\?\", get a buffer of size 64KB or so (the phrase "maximum path of 32,767 characters is approximate" above is a tad troubling here so I'm leaving some details for further study) and try again.
Overflowing MAX_PATH but not beginning with "\\?\" appears to be a "can't happen" case. Again, what to do then is a detail you'll have to deal with.
There may also be some confusion over what the path length limit is for a network name which begins "\\Server\Share\", not to mention names from the kernel object name space which begin with "\\.\". The above article does not say, and I'm not certain about whether this API could return such a path.
Implement some reasonable strategy for growing the buffer like start with MAX_PATH, then make each successive size 1,5 times (or 2 times for less iterations) bigger then the previous one. Iterate until the function succeeds.
Using
extern char* _pgmptr
might work.
From the documentation of GetModuleFileName:
The global variable _pgmptr is automatically initialized to the full path of the executable file, and can be used to retrieve the full path name of an executable file.
But if I read about _pgmptr:
When a program is not run from the command line, _pgmptr might be initialized to the program name (the file's base name without the file name extension) or to a file name, relative path, or full path.
Anyone who knows how _pgmptr is initialized? If SO had support for follow-up questions I would posted this question as a follow up.
While the API is proof of bad design, the solution is actually very simple. Simple, yet sad it has to be this way, for it's somewhat of a performance hog as it might require multiple memory allocations. Here is some keypoints to the solution:
You can't really rely on the return value between different Windows-versions as it can have different semantics on different Windows-versions (XP for example).
If the supplied buffer is too small to hold the string, the return value is the amount of characters including the 0-terminator.
If the supplied buffer is large enough to hold the string, the return value is the amount of characters excluding the 0-terminator.
This means that if the returned value exactly equals the buffer size, you still don't know whether it succeeded or not. There might be more data. Or not. In the end you can only be certain of success if the buffer length is actually greater than required. Sadly...
So, the solution is to start off with a small buffer. We then call GetModuleFileName passing the exact buffer length (in TCHARs) and comparing the return result with it. If the return result is less than our buffer length, it succeeded. If the return result is greater than or equal to our buffer length, we have to try again with a larger buffer. Rinse and repeat until done. When done we make a string copy (strdup/wcsdup/tcsdup) of the buffer, clean up, and return the string copy. This string will have the right allocation size rather than the likely overhead from our temporary buffer. Note that the caller is responsible for freeing the returned string (strdup/wcsdup/tcsdup mallocs memory).
See below for an implementation and usage code example. I have been using this code for over a decade now, including in enterprise document management software where there can be a lot of quite long paths. The code can ofcourse be optimized in various ways, for example by first loading the returned string into a local buffer (TCHAR buf[256]). If that buffer is too small you can then start the dynamic allocation loop. Other optimizations are possible but that's beyond the scope here.
Implementation and usage example:
/* Ensure Win32 API Unicode setting is in sync with CRT Unicode setting */
#if defined(_UNICODE) && !defined(UNICODE)
# define UNICODE
#elif defined(UNICODE) && !defined(_UNICODE)
# define _UNICODE
#endif
#include <stdio.h> /* not needed for our function, just for printf */
#include <tchar.h>
#include <windows.h>
LPCTSTR GetMainModulePath(void)
{
TCHAR* buf = NULL;
DWORD bufLen = 256;
DWORD retLen;
while (32768 >= bufLen)
{
if (!(buf = (TCHAR*)malloc(sizeof(TCHAR) * (size_t)bufLen))
{
/* Insufficient memory */
return NULL;
}
if (!(retLen = GetModuleFileName(NULL, buf, bufLen)))
{
/* GetModuleFileName failed */
free(buf);
return NULL;
}
else if (bufLen > retLen)
{
/* Success */
LPCTSTR result = _tcsdup(buf); /* Caller should free returned pointer */
free(buf);
return result;
}
free(buf);
bufLen <<= 1;
}
/* Path too long */
return NULL;
}
int main(int argc, char* argv[])
{
LPCTSTR path;
if (!(path = GetMainModulePath()))
{
/* Insufficient memory or path too long */
return 0;
}
_tprintf("%s\n", path);
free(path); /* GetMainModulePath malloced memory using _tcsdup */
return 0;
}
Having said all that, I like to point out you need to be very aware of various other caveats with GetModuleFileName(Ex). There are varying issues between 32/64-bit/WOW64. Also the output is not necessarily a full, long path, but could very well be a short-filename or be subject to path aliasing. I expect when you use such a function that the goal is to provide the caller with a useable, reliable full, long path, therefor I suggest to indeed ensure to return a useable, reliable, full, long absolute path, in such a way that it is portable between various Windows-versions and architectures (again 32/64-bit/WOW64). How to do that efficiently is beyond the scope here.
While this is one of the worst Win32 APIs in existance, I wish you alot of coding joy nonetheless.
My example is a concrete implementation of the "if at first you don't succeed, double the length of the buffer" approach. It retrieves the path of the executable that is running, using a string (actually a wstring, since I want to be able to handle Unicode) as the buffer. To determine when it has successfully retrieved the full path, it checks the value returned from GetModuleFileNameW against the value returned by wstring::length(), then uses that value to resize the final string in order to strip the extra null characters. If it fails, it returns an empty string.
inline std::wstring getPathToExecutableW()
{
static const size_t INITIAL_BUFFER_SIZE = MAX_PATH;
static const size_t MAX_ITERATIONS = 7;
std::wstring ret;
DWORD bufferSize = INITIAL_BUFFER_SIZE;
for (size_t iterations = 0; iterations < MAX_ITERATIONS; ++iterations)
{
ret.resize(bufferSize);
DWORD charsReturned = GetModuleFileNameW(NULL, &ret[0], bufferSize);
if (charsReturned < ret.length())
{
ret.resize(charsReturned);
return ret;
}
else
{
bufferSize *= 2;
}
}
return L"";
}
Here is a another solution with std::wstring:
DWORD getCurrentProcessBinaryFile(std::wstring& outPath)
{
// #see https://msdn.microsoft.com/en-us/magazine/mt238407.aspx
DWORD dwError = 0;
DWORD dwResult = 0;
DWORD dwSize = MAX_PATH;
SetLastError(0);
while (dwSize <= 32768) {
outPath.resize(dwSize);
dwResult = GetModuleFileName(0, &outPath[0], dwSize);
dwError = GetLastError();
/* if function has failed there is nothing we can do */
if (0 == dwResult) {
return dwError;
}
/* check if buffer was too small and string was truncated */
if (ERROR_INSUFFICIENT_BUFFER == dwError) {
dwSize *= 2;
dwError = 0;
continue;
}
/* finally we received the result string */
outPath.resize(dwResult);
return 0;
}
return ERROR_BUFFER_OVERFLOW;
}
Windows cannot handle properly paths longer than 260 characters, so just use MAX_PATH.
You cannot run a program having path longer than MAX_PATH.
My approach to this is to use argv, assuming you only want to get the filename of the running program. When you try to get the filename from a different module, the only secure way to do this without any other tricks is described already, an implementation can be found here.
// assume argv is there and a char** array
int nAllocCharCount = 1024;
int nBufSize = argv[0][0] ? strlen((char *) argv[0]) : nAllocCharCount;
TCHAR * pszCompleteFilePath = new TCHAR[nBufSize+1];
nBufSize = GetModuleFileName(NULL, (TCHAR*)pszCompleteFilePath, nBufSize);
if (!argv[0][0])
{
// resize memory until enough is available
while (GetLastError() == ERROR_INSUFFICIENT_BUFFER)
{
delete[] pszCompleteFilePath;
nBufSize += nAllocCharCount;
pszCompleteFilePath = new TCHAR[nBufSize+1];
nBufSize = GetModuleFileName(NULL, (TCHAR*)pszCompleteFilePath, nBufSize);
}
TCHAR * pTmp = pszCompleteFilePath;
pszCompleteFilePath = new TCHAR[nBufSize+1];
memcpy_s((void*)pszCompleteFilePath, nBufSize*sizeof(TCHAR), pTmp, nBufSize*sizeof(TCHAR));
delete[] pTmp;
pTmp = NULL;
}
pszCompleteFilePath[nBufSize] = '\0';
// do work here
// variable 'pszCompleteFilePath' contains always the complete path now
// cleanup
delete[] pszCompleteFilePath;
pszCompleteFilePath = NULL;
I had no case where argv didn't contain the file path (Win32 and Win32-console application), yet. But just in case there is a fallback to a solution that has been described above. Seems a bit ugly to me, but still gets the job done.
i have a function like this:
BOOL WINAPI MyFunction(HDC hdc, LPCWSTR text, UINT cbCount){
char AnsiBuffer[255];
int written = WideCharToMultiByte(CP_ACP, 0, text, cbCount, AnsiBuffer , 0, NULL, NULL);
if(written > -1) AnsiBuffer[written] = '\0';
if(written>0){
ofstream myfile;
myfile.open ("C:\\example.txt", ios::app);
myfile.write(AnsiBuffer, sizeof(AnsiBuffer));
myfile.write("\n", 1);
myfile.close();
}
....
When i display the input LPCWSTR text with MessageBoxW(), the text shows up fine. When i try to convert it to multibyte, the return value looks normal (ex: 22, 45, etc), but the result is strings of gibberish (ex ÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌ). Suggestions?
I see two problems;
1) You are passing '0' to WideCharToMultiByte for the size of the multibyte buffer. If you read the documents this results in the function returning the NUMBER of bytes needed but performing no actual conversion. (This is to allow you to subsequently allocate a buffer of the correct size and recall the function).
2) in file.write sizeof(AnsiBuffer) will result in 255 bytes being written regardless of what is in the buffer. sizeof is a compile-time calculation that returns the size of a variable. You should replace this with the 'written' variable that represents the length of the string.
You need to pass the length of the buffer to the API, instead of passing 0. When you pass 0, the function returns the required length of the buffer, but doesn't write to it. You're seeing the results of the uninitialized array.
Here's the right call, with the 255 in the right place:
int written = WideCharToMultiByte(CP_ACP, 0, text, cbCount, AnsiBuffer , 255, NULL, NULL);