Develop Reference

I need to list of all open handles [duplicate]

Is there any way how to enumerate process with given PID in windows, and get list of all his opened handles(locked files, etc.)?
EDIT: I dont care about language. If it is in .NET, I'd be glad, if in WinApi (C), it won't hurt. If in something else, I think I can rewrite it :-)

I did a deep googling and found this article.
This article gave a link to download source code:
I tried method in NtSystemInfoTest.cpp ( downloaded source code ) and it worked superbly.
void ListHandles( DWORD processID, LPCTSTR lpFilter )
The code has following declaimer:
// Written by Zoltan Csizmadia, zoltan_csizmadia#yahoo.com
// For companies(Austin,TX): If you would like to get my resume, send an email.
//
// The source is free, but if you want to use it, mention my name and e-mail address
//
//////////////////////////////////////////////////////////////////////////////////////
//
I hope this helps you.

The command-line 'Handle' tool from Sysinternals does this, if you just want a tool. This won't help you if you're looking for a code solution, though.

Here is an example using ZwQueryProcessInformation from the DDK. The DDK is now known as the "WDK" and is available with MSDN. If you don't have MSDN, apparantly, you can also get it from here.
I haven't tried it, I just googled your question.
#include "ntdll.h"
#include <stdlib.h>
#include <stdio.h>
#include "ntddk.h"
#define DUPLICATE_SAME_ATTRIBUTES 0x00000004
#pragma comment(lib,"ntdll.lib")
BOOL EnablePrivilege(PCSTR name)
{
TOKEN_PRIVILEGES priv = {1, {0, 0, SE_PRIVILEGE_ENABLED}};
LookupPrivilegeValue(0, name, &priv.Privileges[0].Luid);
HANDLE hToken;
OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES, &hToken);
AdjustTokenPrivileges(hToken, FALSE, &priv, sizeof priv, 0, 0);
BOOL rv = GetLastError() == ERROR_SUCCESS;
CloseHandle(hToken);
return rv;
}
int main(int argc, char *argv[])
{
if (argc == 1) return 0;
ULONG pid = strtoul(argv[1], 0, 0);
EnablePrivilege(SE_DEBUG_NAME);
HANDLE hProcess = OpenProcess(PROCESS_DUP_HANDLE, FALSE, pid);
ULONG n = 0x1000;
PULONG p = new ULONG[n];
while (NT::ZwQuerySystemInformation(NT::SystemHandleInformation, p, n * sizeof *p, 0)
== STATUS_INFO_LENGTH_MISMATCH)
delete [] p, p = new ULONG[n *= 2];
NT::PSYSTEM_HANDLE_INFORMATION h = NT::PSYSTEM_HANDLE_INFORMATION(p + 1);
for (ULONG i = 0; i < *p; i++) {
if (h[i].ProcessId == pid) {
HANDLE hObject;
if (NT::ZwDuplicateObject(hProcess, HANDLE(h[i].Handle), NtCurrentProcess(), &hObject,
0, 0, DUPLICATE_SAME_ATTRIBUTES)
!= STATUS_SUCCESS) continue;
NT::OBJECT_BASIC_INFORMATION obi;
NT::ZwQueryObject(hObject, NT::ObjectBasicInformation, &obi, sizeof obi, &n);
printf("%p %04hx %6lx %2x %3lx %3ld %4ld ",
h[i].Object, h[i].Handle, h[i].GrantedAccess,
int(h[i].Flags), obi.Attributes,
obi.HandleCount - 1, obi.PointerCount - 2);
n = obi.TypeInformationLength + 2;
NT::POBJECT_TYPE_INFORMATION oti = NT::POBJECT_TYPE_INFORMATION(new CHAR[n]);
NT::ZwQueryObject(hObject, NT::ObjectTypeInformation, oti, n, &n);
printf("%-14.*ws ", oti[0].Name.Length / 2, oti[0].Name.Buffer);
n = obi.NameInformationLength == 0
? MAX_PATH * sizeof (WCHAR) : obi.NameInformationLength;
NT::POBJECT_NAME_INFORMATION oni = NT::POBJECT_NAME_INFORMATION(new CHAR[n]);
NTSTATUS rv = NT::ZwQueryObject(hObject, NT::ObjectNameInformation, oni, n, &n);
if (NT_SUCCESS(rv))
printf("%.*ws", oni[0].Name.Length / 2, oni[0].Name.Buffer);
printf("\n");
CloseHandle(hObject);
}
}
delete [] p;
CloseHandle(hProcess);
return 0;
}

Get Session ID of another process in C++

When I start my application, I try to figure out if there is another process of the application. I also try to figure out if it runs in a different user session.
So far so good, that's what it looks like in C#:
private static bool isThereAnotherInstance() {
string name = Path.GetFileNameWithoutExtension(Application.ExecutablePath);
Process[] pAll = Process.GetProcessesByName(name);
Process pCurrent = Process.GetCurrentProcess();
foreach (Process p in pAll) {
if (p.Id == pCurrent.Id) continue;
if (p.SessionId != pCurrent.SessionId) continue;
return true;
}
return false;
}
But the requirements has changed, I need this piece of code in C++ using plain WinAPI.
Until now, I'm able to find a process that has the same executable path by using CreateToolhelp32Snapshot, OpenProcess, etc.
The missing part is how to get the session id of a process (current and other processes, AND current and other session)
How to do this?

The ProcessIdToSessionId function maps a process ID to a session ID.
You note that this seems to require excessive permissions that aren't needed by .Net.
.Net does get some of its process data from HKEY_PERFORMANCE_DATA in the registry, but this doesn't include the session ID. The session ID is obtained using NtQuerySystemInformation to return an array of SYSTEM_PROCESS_INFORMATION structures. This structure is not well documented, but the session ID immediately follows the handle count (i.e. it is the field currently declared as BYTE Reserved4[4];). Microsoft do not guarantee that this will continue to be true in future versions of Windows.

As mentioned by arx, ProcessIdToSessionId should do the job.
But unfortunately, in my case it tells me ACCESS_DENIED for the processes I'm interested in.
It DOES its job for the current process.
So here's my solution, using NtQuerySystemInformation.
.NETs Process class uses the same function internally .
typedef struct _SYSTEM_PROCESS_INFORMATION_BUG {
//...
}
typedef NTSTATUS (WINAPI *PNtQuerySystemInformation) (
IN SYSTEM_INFORMATION_CLASS SystemInformationClass,
OUT PVOID SystemInformation,
IN ULONG SystemInformationLength,
OUT PULONG ReturnLength OPTIONAL
);
#ifndef NT_ERROR
#define NT_ERROR(Status) ((ULONG)(Status) >> 30 == 3)
#endif
#define PROCESSINFO_BUFFERSIZE (256*1024)
DLL_EXPORT int GetProcessIdFromPath2(char *exePath, int flags) {
char exe[MAX_PATH], *exeName, file[MAX_PATH], *fileName;
DWORD pidCurrent, sessionIdCurrent;
int ret=-1;
strcpy(exe, exePath);
strupr(exe);
exeName=getFileName(exe);
pidCurrent = GetCurrentProcessId();
if (!ProcessIdToSessionId(pidCurrent, &sessionIdCurrent)) sessionIdCurrent=0;
HMODULE hNT = LoadLibrary("Ntdll.dll");
if (hNT) {
PNtQuerySystemInformation pNtQuerySystemInformation = (PNtQuerySystemInformation)GetProcAddress(hNT, "NtQuerySystemInformation");
if (pNtQuerySystemInformation) {
SYSTEM_PROCESS_INFORMATION_BUG* processInfo;
char *buffer = (char*)malloc(PROCESSINFO_BUFFERSIZE);
if (!buffer) {
ret=-3;
}
else {
char *current=buffer;
DWORD len;
int count=0;
NTSTATUS s = pNtQuerySystemInformation(SystemProcessInformation, buffer, PROCESSINFO_BUFFERSIZE, &len);
if (NT_ERROR(s)) {
ret=-2;
}
else {
ret=0;
while(1) {
processInfo = (SYSTEM_PROCESS_INFORMATION_BUG*)current;
if (processInfo->ImageName.Buffer!=NULL){
wcstombs(file, processInfo->ImageName.Buffer, MAX_PATH-1);
strupr(file);
fileName=getFileName(file);
if (strcmp(fileName, exeName)==0) {
if (processInfo->UniqueProcessId!=pidCurrent) {
if (processInfo->SessionId==sessionIdCurrent) {
ret = processInfo->UniqueProcessId;
}
}
}
}
if (processInfo->NextEntryOffset==0) break;
current+=processInfo->NextEntryOffset;
count++;
}
}
free(buffer);
buffer=NULL;
}
}
FreeLibrary(hNT);
}
return ret;
}

Code for listing all PID, SID, EXE ("ala" Task Manager, sort of)
Works for me (Windows 7 64b) VS2012 Express
#include <stdio.h>
#include <tchar.h>
#include <Windows.h>
#include <Winternl.h>
#pragma comment( lib, "ntdll.lib" )
typedef LONG KPRIORITY; // Thread priority
typedef struct _SYSTEM_PROCESS_INFORMATION_DETAILD {
ULONG NextEntryOffset;
ULONG NumberOfThreads;
LARGE_INTEGER SpareLi1;
LARGE_INTEGER SpareLi2;
LARGE_INTEGER SpareLi3;
LARGE_INTEGER CreateTime;
LARGE_INTEGER UserTime;
LARGE_INTEGER KernelTime;
UNICODE_STRING ImageName;
KPRIORITY BasePriority;
HANDLE UniqueProcessId;
ULONG InheritedFromUniqueProcessId;
ULONG HandleCount;
BYTE Reserved4[4];
PVOID Reserved5[11];
SIZE_T PeakPagefileUsage;
SIZE_T PrivatePageCount;
LARGE_INTEGER Reserved6[6];
} SYSTEM_PROCESS_INFORMATION_DETAILD, *PSYSTEM_PROCESS_INFORMATION_DETAILD;
int _tmain(int argc, _TCHAR* argv[]) {
SYSTEM_PROCESS_INFORMATION aSPI[ 1024 ];
// could ask for actual needed size size and malloc (with few extra new processes bonus...)
NTSTATUS nts = NtQuerySystemInformation( SystemProcessInformation, aSPI, sizeof( aSPI ), NULL );
if ( NT_ERROR( nts ) ) return -1;
char * pSPI = reinterpret_cast<char*>( &aSPI[ 0 ] );
while ( true ) {
SYSTEM_PROCESS_INFORMATION_DETAILD * pOneSPI = reinterpret_cast<SYSTEM_PROCESS_INFORMATION_DETAILD*>( pSPI );
WCHAR * pwch = pOneSPI->ImageName.Buffer;
if ( pwch == 0 || pOneSPI->ImageName.Length == 0 ) pwch = TEXT( "Unknown" );
_tprintf( TEXT( "PID %d - SID %d EXE %s\n" ), pOneSPI->UniqueProcessId, *reinterpret_cast<LONG*>( &pOneSPI->Reserved4 ), pwch );
if ( pOneSPI->NextEntryOffset ) pSPI += pOneSPI->NextEntryOffset;
else break;
}
return 0;
}
Many thanks to #Oleg for documentation of the SPI structure on SO here

Win api in C#. Get Hi and low word from IntPtr

I am trying to process a WM_MOUSEMOVE message in C#.
What is the proper way to get an X and Y coordinate from lParam which is a type of IntPtr?

Try:
(note that this was the initial version, read below for the final version)
IntPtr xy = value;
int x = unchecked((short)xy);
int y = unchecked((short)((uint)xy >> 16));
The unchecked normally isn't necessary (because the "default" c# projects are unchecked)
Consider that these are the definitions of the used macros:
#define LOWORD(l) ((WORD)(((DWORD_PTR)(l)) & 0xffff))
#define HIWORD(l) ((WORD)((((DWORD_PTR)(l)) >> 16) & 0xffff))
#define GET_X_LPARAM(lp) ((int)(short)LOWORD(lp))
#define GET_Y_LPARAM(lp) ((int)(short)HIWORD(lp))
Where WORD == ushort, DWORD == uint. I'm cutting some ushort->short conversions.
Addendum:
one and half year later, and having experienced the "vagaries" of 64 bits .NET, I concur with Celess (but note that 99% of the Windows messages are still 32 bits for reasons of compatibility, so I don't think the problem isn't really big now. It's more for the future and because if you want to do something, you should do it correctly.)
The only thing I would make different is this:
IntPtr xy = value;
int x = unchecked((short)(long)xy);
int y = unchecked((short)((long)xy >> 16));
instead of doing the check "is the IntPtr 4 or 8 bytes long", I take the worst case (8 bytes long) and cast xy to a long. With a little luck the double cast (to long and then to short/to uint) will be optimized by the compiler (in the end, the explicit conversion to int of IntPtr is a red herring... If you use it you are putting yourself at risk in the future. You should always use the long conversion and then use it directly/re-cast it to what you need, showing to the future programmers that you knew what you were doing.
A test example: http://ideone.com/a4oGW2 (sadly only 32 bits, but if you have a 64 bits machine you can test the same code)

Correct for both 32 and 64-bit:
Point GetPoint(IntPtr _xy)
{
uint xy = unchecked(IntPtr.Size == 8 ? (uint)_xy.ToInt64() : (uint)_xy.ToInt32());
int x = unchecked((short)xy);
int y = unchecked((short)(xy >> 16));
return new Point(x, y);
}
- or -
int GetIntUnchecked(IntPtr value)
{
return IntPtr.Size == 8 ? unchecked((int)value.ToInt64()) : value.ToInt32();
}
int Low16(IntPtr value)
{
return unchecked((short)GetIntUnchecked(value));
}
int High16(IntPtr value)
{
return unchecked((short)(((uint)GetIntUnchecked(value)) >> 16));
}
These also work:
int Low16(IntPtr value)
{
return unchecked((short)(uint)value); // classic unchecked cast to uint
}
int High16(IntPtr value)
{
return unchecked((short)((uint)value >> 16));
}
- or -
int Low16(IntPtr value)
{
return unchecked((short)(long)value); // presumption about internals
} // is what framework lib uses
int High16(IntPtr value)
{
return unchecked((short)((long)value >> 16));
}
Going the other way
public static IntPtr GetLParam(Point point)
{
return (IntPtr)((point.Y << 16) | (point.X & 0xffff));
} // mask ~= unchecked((int)(short)x)
- or -
public static IntPtr MakeLParam(int low, int high)
{
return (IntPtr)((high << 16) | (low & 0xffff));
} // (IntPtr)x is same as 'new IntPtr(x)'
The accepted answer is good translation of the C definition. If were dealing with just the raw 'void*' directly, then would be mostly ok. However when using 'IntPtr' in a .Net 64-bit execution environment, 'unchecked' will not stop conversion overflow exceptions from being thrown from inside IntPtr. The unchecked block does not affect conversions that happen inside IntPtr funcitons and operators. Currently the accepted answer states that use of 'unchecked' is not necesary. However the use of 'unchecked' is absolutely necessary, as would always be the case in casting to negative values from a larger type.
On 64-bit, from the accepted answer:
var xy = new IntPtr(0x0FFFFFFFFFFFFFFF);
int x = unchecked((short)xy); // <-- throws
int y = unchecked((short)((uint)xy >> 16)); // gets lucky, 'uint' implicit 'long'
y = unchecked((short)((int)xy >> 16)); // <-- throws
xy = new IntPtr(0x00000000FFFF0000); // 0, -1
x = unchecked((short)xy); // <-- throws
y = unchecked((short)((uint)xy >> 16)); // still lucky
y = (short)((uint)xy >> 16); // <-- throws (short), no longer lucky
On 64-bit, using extrapolated version of DmitryG's:
var ptr = new IntPtr(0x0FFFFFFFFFFFFFFF);
var xy = IntPtr.Size == 8 ? (int)ptr.ToInt64() : ptr.ToInt32(); // <-- throws (int)
int x = unchecked((short)xy); // fine, if gets this far
int y = unchecked((short)((uint)xy >> 16)); // fine, if gets this far
y = unchecked((short)(xy >> 16)); // also fine, if gets this far
ptr = new IntPtr(0x00000000FFFF0000); // 0, -1
xy = IntPtr.Size == 8 ? (int)ptr.ToInt64() : ptr.ToInt32(); // <-- throws (int)
On performance
return IntPtr.Size == 8 ? unchecked((int)value.ToInt64()) : value.ToInt32();
The IntPtr.Size property returns a constant as compile time literal that is capable if being inlined across assemblies. Thus is possible for the JIT to have nearly all of this optimized out. Could also do:
return unchecked((int)value.ToInt64());
- or -
return unchecked((int)(long)value);
- or -
return unchecked((uint)value); // traditional
and all 3 of these will always call the equivalient of IntPtr.ToInt64(). ToInt64(), and 'operator long', are also capable of being inlined, but less likely to be. Is much more code in 32-bit version than the Size constant. I would submit that the solution at the top is maybe more symantically correct. Its also important to be aware of sign-extension artifacts, which would fill all 64-bits reguardless on something like (long)int_val, though i've pretty much glossed over that here, however may additionally affect inlining on 32-bit.
Useage
if (Low16(wParam) == NativeMethods.WM_CREATE)) { }
var x = Low16(lParam);
var point = GetPoint(lParam);
A 'safe' IntPtr mockup shown below for future traverlers.
Run this without setting the WIN32 define on 32-bit to get a solid simulation of the 64-bit IntPtr behavour.
public struct IntPtrMock
{
#if WIN32
int m_value;
#else
long m_value;
#endif
int IntPtr_ToInt32() {
#if WIN32
return (int)m_value;
#else
long l = m_value;
return checked((int)l);
#endif
}
public static explicit operator int(IntPtrMock value) { //(short) resolves here
#if WIN32
return (int)value.m_value;
#else
long l = value.m_value;
return checked((int)l); // throws here if any high 32 bits
#endif // check forces sign stay signed
}
public static explicit operator long(IntPtrMock value) { //(uint) resolves here
#if WIN32
return (long)(int)value.m_value;
#else
return (long)value.m_value;
#endif
}
public int ToInt32() {
#if WIN32
return (int)value.m_value;
#else
long l = m_value;
return checked((int)l); // throws here if any high 32 bits
#endif // check forces sign stay signed
}
public long ToInt64() {
#if WIN32
return (long)(int)m_value;
#else
return (long)m_value;
#endif
}
public IntPtrMock(long value) {
#if WIN32
m_value = checked((int)value);
#else
m_value = value;
#endif
}
}
public static IntPtr MAKELPARAM(int low, int high)
{
return (IntPtr)((high << 16) | (low & 0xffff));
}
public Main()
{
var xy = new IntPtrMock(0x0FFFFFFFFFFFFFFF); // simulate 64-bit, overflow smaller
int x = unchecked((short)xy); // <-- throws
int y = unchecked((short)((uint)xy >> 16)); // got lucky, 'uint' implicit 'long'
y = unchecked((short)((int)xy >> 16)); // <-- throws
int xy2 = IntPtr.Size == 8 ? (int)xy.ToInt64() : xy.ToInt32(); // <-- throws
int xy3 = unchecked(IntPtr.Size == 8 ? (int)xy.ToInt64() : xy.ToInt32()); //ok
// proper 32-bit lParam, overflow signed
var xy4 = new IntPtrMock(0x00000000FFFFFFFF); // x = -1, y = -1
int x2 = unchecked((short)xy4); // <-- throws
int xy5 = IntPtr.Size == 8 ? (int)xy4.ToInt64() : xy4.ToInt32(); // <-- throws
var xy6 = new IntPtrMock(0x00000000FFFF0000); // x = 0, y = -1
int x3 = unchecked((short)xy6); // <-- throws
int xy7 = IntPtr.Size == 8 ? (int)xy6.ToInt64() : xy6.ToInt32(); // <-- throws
var xy8 = MAKELPARAM(-1, -1); // WinForms macro
int x4 = unchecked((short)xy8); // <-- throws
int xy9 = IntPtr.Size == 8 ? (int)xy8.ToInt64() : xy8.ToInt32(); // <-- throws
}

Usualy, for low-level mouse processing I have used the following helper (it also considers that IntPtr size depends on x86/x64):
//...
Point point = WinAPIHelper.GetPoint(msg.LParam);
//...
static class WinAPIHelper {
public static Point GetPoint(IntPtr lParam) {
return new Point(GetInt(lParam));
}
public static MouseButtons GetButtons(IntPtr wParam) {
MouseButtons buttons = MouseButtons.None;
int btns = GetInt(wParam);
if((btns & MK_LBUTTON) != 0) buttons |= MouseButtons.Left;
if((btns & MK_RBUTTON) != 0) buttons |= MouseButtons.Right;
return buttons;
}
static int GetInt(IntPtr ptr) {
return IntPtr.Size == 8 ? unchecked((int)ptr.ToInt64()) : ptr.ToInt32();
}
const int MK_LBUTTON = 1;
const int MK_RBUTTON = 2;
}

C++ Equivalent of C# Yield?

public void Consumer()
{
foreach(int i in Integers())
{
Console.WriteLine(i.ToString());
}
}
public IEnumerable<int> Integers()
{
yield return 1;
yield return 2;
yield return 4;
yield return 8;
yield return 16;
yield return 16777216;
}
Is there a way with template trick (or other) to get the same syntax in c++?

Take a look at boost::Coroutine. It does what you want.
http://www.crystalclearsoftware.com/soc/coroutine/index.html#coroutine.intro
Example from tutorial
http://www.crystalclearsoftware.com/soc/coroutine/coroutine/tutorial.html
int range_generator(generator_type::self& self, int min, int max)
{
while(min < max)
self.yield(min++);
self.exit();
}

You can always code this by hand. Truthfully, yield really seems like sugar coating to me (and co-routines too).
What a coroutine is, really ? Some state bundled up together with:
one function to create it (isn't it a constructor ?)
one function to move to the next state (isn't it operator++, traditionally ?)
In C++, it's called an InputIterator, and can be arbitrarily fat.
So, it's true that the syntax won't be as pretty, but this should do, just with the Standard Library:
static std::array<int, 6> const Array = {{1, 2, 4, 8, 16, 16777216}};
class Integers: public std::iterator<std::input_iterator_tag,
int, ptrdiff_t, int const*, int>
{
public:
Integers(): _index(0) {}
operator bool() const { return _index < Array.size(); }
Integers& operator++() { assert(*this); ++_index; return *this; }
Integers operator++(int) { Integers tmp = *this; ++*this; return tmp; }
int operator*() const { assert(*this); return Array[_index]; }
int const* operator->() const { assert(*this); return &Array[_index]; }
private:
size_t _index;
}; // class Integers
And obviously, since you decide exactly what state is stored, you decide if all is pre-computed or if part (or whole of it) is lazily computed, and possibly cached, and possibly multi-threaded, and ... you got the idea :)

In C++14, you can mimic yield this way:
auto&& function = []() {
int i = 0;
return [=]() mutable {
int arr[] = { 1, 2, 4, 8, 16, 16777216};
if (i < 6)
return arr[i++];
return 0;
};
}();
A live example is available at http://ideone.com/SQZ1qZ

Coroutines are in the standard library since C++20 and uses co_yield instead of yield.
See also: What are coroutines in C++20?
There are some example usages in the first link: (the second one is probably what you're looking for)
uses the co_await operator to suspend execution until resumed
task<> tcp_echo_server() {
char data[1024];
while (true) {
size_t n = co_await socket.async_read_some(buffer(data));
co_await async_write(socket, buffer(data, n));
}
}
uses the keyword co_yield to suspend execution returning a value
generator<int> iota(int n = 0) {
while (true)
co_yield n++;
}
uses the keyword co_return to complete execution returning a value
lazy<int> f() {
co_return 7;
}

Here is ASM "roll your own" version : http://www.flipcode.com/archives/Yield_in_C.shtml
#include <stdio.h
#include <conio.h
#include <iostream.h
//
// marks a location in the program for resume
// does not return control, exits function from inside macro
//
// yield( x, ret )
// x : the 'name' of the yield, cannot be ambiguous in the
// function namespace
// ret : the return value for when yield() exits the function;
// must match function return type (leave blank for no return type)
#define yield(x,ret) \
{ \
/* store the resume location */ \
__asm { \
mov _myStaticMkr,offset label_##x \
} \
\
/* return the supplied value */ \
return ret; \
} \
/* our offset in the function */ \
label_##x:
//
// resumes function from the stored offset, or
// continues without notice if there's not one
// stored
//
// resume()
// <void
#define resume() \
/* our stored offset */ \
static _myStaticMkr=0; \
\
/* test for no offset */ \
if( _myStaticMkr ) \
{ \
/* resume from offset */ \
__asm \
{ \
jmp _myStaticMkr \
} \
}
// example demonstrating a function with an int return type
// using the yield() and resume() macros
//
// myFunc()
// <void
int myFunc()
{
resume();
cout << "1\n";
yield(1,1);
cout << "2\n";
yield(2,1);
cout << "3\n";
yield(3,1);
cout << "4\n";
return 0;
}
// main function
//
// main()
// <void
void main( void )
{
cout << "Yield in C++\n";
cout << "Chris Pergrossi\n\n";
myFunc();
do
{
cout << "main()\n";
cout.flush();
} while( myFunc() );
cout.flush();
getch();
}
/*
// example demonstrating a function with no return type
// using the yield() and resume() macros
//
// myFunc()
// <void
void myFunc()
{
resume();
cout << "1\n";
yield(1);
cout << "2\n";
yield(2);
cout << "3\n";
yield(3);
cout << "4\n";
return;
}
// main function
//
// main()
// <void
void main( void )
{
cout << "Yield in C++\n";
cout << "Chris Pergrossi\n\n";
myFunc();
for( int k = 0; k < 4; k ++ )
{
cout << "main()\n";
cout.flush();
myFunc();
}
cout.flush();
getch();
}
*/

If all what you need is just foreach-like stuff, then following syntax is available in C++:
#define GENERATOR(name) \
struct name \
{ \
template<typename F> \
void operator()(F yield) \
/**/
#define _ };
template<typename Gen>
struct Adaptor
{
Gen f;
template<typename C>
void operator*(C cont)
{
f(cont);
}
};
template<typename Gen>
Adaptor<Gen> make_adaptor(Gen gen)
{
return {gen};
}
#define FOREACH(arg, gen) make_adaptor(gen) * [&](arg)
#include <iostream>
using namespace std;
GENERATOR(integers)
{
yield(1);
yield(2);
yield(4);
yield(8);
yield(16777216);
}_
int main()
{
FOREACH(int i, integers())
{
cout << i << endl;
};
}
Live Demo
If you need a little bit of coroutine "power", then you can try stackless coroutines.
Or if you need full power - then go with stackful coroutines. There is Boost.Coroutine library which implements stackful coroutines for different platforms.

An try to implement yield in c++ coroutine

If you write static unsigned int checkpoint = 0;, make all your variables static, switch (checkpoint), set each case: goto to some label, above each return set checkpoint to unique value, and below define label, and at the end of the function set checkpoint to zero, and all static variables to their default value, and at last return the end value of the function. If you do all this then the function becomes enumerable and iterative. The two lines you add above and below each return line, makes the return command to behave like yield return. goto allows you to continue and resume where you left off, and static integer variable, like checkpoint, help you to remember where you stopped, from where to continue/resume and where to go. You test it's values with switch case statements. Making all other variables static, is to save their value to the next call, so in the next call, their value won't be reset!
Here for example:
#define PowerEnd INT_MIN
int Power(int number, int exponent)
{
static unsigned int checkpoint = 0;
static int result = 1, i = 0;
switch (checkpoint)
{
case 1: goto _1;
}
for (i = 0; i < exponent; i++)
{
result *= number;
checkpoint = 1;
return result;
_1:;
}
checkpoint = 0;
result = 1;
i = 0;
return PowerEnd;
}
void main()
{
while (true)
{
int result = Power(2, 8);
if (result == PowerEnd)
break;
cout << result << endl;
}
//to print only the first 4 results (if there are at least 4 results) then
for (int i = 0; i < 4; i++)
{
int result = Power(2, 8);
if (result == PowerEnd)
break;
cout << result << endl;
}
}
The above program produces the following output:
2
4
8
16
32
64
128
256
2
4
8
16

Something similar is proposed for C++17 and there is already an experimental implementation in Visual C++ 2015. Here's a good overview talk from Gor Nishanov, one of the main authors of the proposal.

#include <setjmp.h>
class superclass
{
public:
jmp_buf jbuf;
public:
virtual int enumerate(void) { return -1; }
};
class subclass: public superclass
{
public:
int enumerate()
{
static int i;
static bool b = false;
if(b)
longjmp(jbuf, 1);
for(b = true, i = 0; i < 5; (i)++)
{
printf("\ndoing stuff: i = %d\n", i);
if(setjmp(jbuf) != 1)
return i;
}
return -1;
}
};
To use the code...
int iret;
subclass *sc;
sc = new subclass();
while((iret = sc->enumerate()) != -1)
{
printf("\nsc->enumerate() returned: %d\n", iret);
}
Just got this working; it seems quite simple now, although I had a few false starts with it :)

You can of course always write your own iterators and return from them whatever you desire, but why would you want to? In the given example, why not simply put your values into a container like vector and iterate over that?

Problem porting PHP crypt() function to C#

Im working on porting some old ALP user accounts to a new ASP.Net solution, and I would like for the users to be able to use their old passwords.
However, in order for that to work, I need to be able to compare the old hashes to a newly calculated one, based on a newly typed password.
I searched around, and found this as the implementation of crypt() called by PHP:
char *
crypt_md5(const char *pw, const char *salt)
{
MD5_CTX ctx,ctx1;
unsigned long l;
int sl, pl;
u_int i;
u_char final[MD5_SIZE];
static const char *sp, *ep;
static char passwd[120], *p;
static const char *magic = "$1$";
/* Refine the Salt first */
sp = salt;
/* If it starts with the magic string, then skip that */
if(!strncmp(sp, magic, strlen(magic)))
sp += strlen(magic);
/* It stops at the first '$', max 8 chars */
for(ep = sp; *ep && *ep != '$' && ep < (sp + 8); ep++)
continue;
/* get the length of the true salt */
sl = ep - sp;
MD5Init(&ctx);
/* The password first, since that is what is most unknown */
MD5Update(&ctx, (const u_char *)pw, strlen(pw));
/* Then our magic string */
MD5Update(&ctx, (const u_char *)magic, strlen(magic));
/* Then the raw salt */
MD5Update(&ctx, (const u_char *)sp, (u_int)sl);
/* Then just as many characters of the MD5(pw,salt,pw) */
MD5Init(&ctx1);
MD5Update(&ctx1, (const u_char *)pw, strlen(pw));
MD5Update(&ctx1, (const u_char *)sp, (u_int)sl);
MD5Update(&ctx1, (const u_char *)pw, strlen(pw));
MD5Final(final, &ctx1);
for(pl = (int)strlen(pw); pl > 0; pl -= MD5_SIZE)
MD5Update(&ctx, (const u_char *)final,
(u_int)(pl > MD5_SIZE ? MD5_SIZE : pl));
/* Don't leave anything around in vm they could use. */
memset(final, 0, sizeof(final));
/* Then something really weird... */
for (i = strlen(pw); i; i >>= 1)
if(i & 1)
MD5Update(&ctx, (const u_char *)final, 1);
else
MD5Update(&ctx, (const u_char *)pw, 1);
/* Now make the output string */
strcpy(passwd, magic);
strncat(passwd, sp, (u_int)sl);
strcat(passwd, "$");
MD5Final(final, &ctx);
/*
* and now, just to make sure things don't run too fast
* On a 60 Mhz Pentium this takes 34 msec, so you would
* need 30 seconds to build a 1000 entry dictionary...
*/
for(i = 0; i < 1000; i++) {
MD5Init(&ctx1);
if(i & 1)
MD5Update(&ctx1, (const u_char *)pw, strlen(pw));
else
MD5Update(&ctx1, (const u_char *)final, MD5_SIZE);
if(i % 3)
MD5Update(&ctx1, (const u_char *)sp, (u_int)sl);
if(i % 7)
MD5Update(&ctx1, (const u_char *)pw, strlen(pw));
if(i & 1)
MD5Update(&ctx1, (const u_char *)final, MD5_SIZE);
else
MD5Update(&ctx1, (const u_char *)pw, strlen(pw));
MD5Final(final, &ctx1);
}
p = passwd + strlen(passwd);
l = (final[ 0]<<16) | (final[ 6]<<8) | final[12];
_crypt_to64(p, l, 4); p += 4;
l = (final[ 1]<<16) | (final[ 7]<<8) | final[13];
_crypt_to64(p, l, 4); p += 4;
l = (final[ 2]<<16) | (final[ 8]<<8) | final[14];
_crypt_to64(p, l, 4); p += 4;
l = (final[ 3]<<16) | (final[ 9]<<8) | final[15];
_crypt_to64(p, l, 4); p += 4;
l = (final[ 4]<<16) | (final[10]<<8) | final[ 5];
_crypt_to64(p, l, 4); p += 4;
l = final[11];
_crypt_to64(p, l, 2); p += 2;
*p = '\0';
/* Don't leave anything around in vm they could use. */
memset(final, 0, sizeof(final));
return (passwd);
}
And, here is my version in C#, along with an expected match.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Security.Cryptography;
using System.IO;
using System.Management;
namespace Test
{
class Program
{
static void Main(string[] args)
{
byte[] salt = Encoding.ASCII.GetBytes("$1$ls3xPLpO$Wu/FQ.PtP2XBCqrM.w847/");
Console.WriteLine("Hash: " + Encoding.ASCII.GetString(salt));
byte[] passkey = Encoding.ASCII.GetBytes("suckit");
byte[] newhash = md5_crypt(passkey, salt);
Console.WriteLine("Hash2: " + Encoding.ASCII.GetString(newhash));
byte[] newhash2 = md5_crypt(passkey, newhash);
Console.WriteLine("Hash3: " + Encoding.ASCII.GetString(newhash2));
Console.ReadKey(true);
}
public static byte[] md5_crypt(byte[] pw, byte[] salt)
{
MemoryStream ctx, ctx1;
ulong l;
int sl, pl;
int i;
byte[] final;
int sp, ep; //** changed pointers to array indices
MemoryStream passwd = new MemoryStream();
byte[] magic = Encoding.ASCII.GetBytes("$1$");
// Refine the salt first
sp = 0; //** Changed to an array index, rather than a pointer.
// If it starts with the magic string, then skip that
if (salt[0] == magic[0] &&
salt[1] == magic[1] &&
salt[2] == magic[2])
{
sp += magic.Length;
}
// It stops at the first '$', max 8 chars
for (ep = sp;
(ep + sp < salt.Length) && //** Converted to array indices, and rather than check for null termination, check for the end of the array.
salt[ep] != (byte)'$' &&
ep < (sp + 8);
ep++)
continue;
// Get the length of the true salt
sl = ep - sp;
ctx = MD5Init();
// The password first, since that is what is most unknown
MD5Update(ctx, pw, pw.Length);
// Then our magic string
MD5Update(ctx, magic, magic.Length);
// Then the raw salt
MD5Update(ctx, salt, sp, sl);
// Then just as many characters of the MD5(pw,salt,pw)
ctx1 = MD5Init();
MD5Update(ctx1, pw, pw.Length);
MD5Update(ctx1, salt, sp, sl);
MD5Update(ctx1, pw, pw.Length);
final = MD5Final(ctx1);
for(pl = pw.Length; pl > 0; pl -= final.Length)
MD5Update(ctx, final,
(pl > final.Length ? final.Length : pl));
// Don't leave anything around in vm they could use.
for (i = 0; i < final.Length; i++) final[i] = 0;
// Then something really weird...
for (i = pw.Length; i != 0; i >>= 1)
if((i & 1) != 0)
MD5Update(ctx, final, 1);
else
MD5Update(ctx, pw, 1);
// Now make the output string
passwd.Write(magic, 0, magic.Length);
passwd.Write(salt, sp, sl);
passwd.WriteByte((byte)'$');
final = MD5Final(ctx);
// and now, just to make sure things don't run too fast
// On a 60 Mhz Pentium this takes 34 msec, so you would
// need 30 seconds to build a 1000 entry dictionary...
for(i = 0; i < 1000; i++)
{
ctx1 = MD5Init();
if((i & 1) != 0)
MD5Update(ctx1, pw, pw.Length);
else
MD5Update(ctx1, final, final.Length);
if((i % 3) != 0)
MD5Update(ctx1, salt, sp, sl);
if((i % 7) != 0)
MD5Update(ctx1, pw, pw.Length);
if((i & 1) != 0)
MD5Update(ctx1, final, final.Length);
else
MD5Update(ctx1, pw, pw.Length);
final = MD5Final(ctx1);
}
//** Section changed to use a memory stream, rather than a byte array.
l = (((ulong)final[0]) << 16) | (((ulong)final[6]) << 8) | ((ulong)final[12]);
_crypt_to64(passwd, l, 4);
l = (((ulong)final[1]) << 16) | (((ulong)final[7]) << 8) | ((ulong)final[13]);
_crypt_to64(passwd, l, 4);
l = (((ulong)final[2]) << 16) | (((ulong)final[8]) << 8) | ((ulong)final[14]);
_crypt_to64(passwd, l, 4);
l = (((ulong)final[3]) << 16) | (((ulong)final[9]) << 8) | ((ulong)final[15]);
_crypt_to64(passwd, l, 4);
l = (((ulong)final[4]) << 16) | (((ulong)final[10]) << 8) | ((ulong)final[5]);
_crypt_to64(passwd, l, 4);
l = final[11];
_crypt_to64(passwd, l, 2);
byte[] buffer = new byte[passwd.Length];
passwd.Seek(0, SeekOrigin.Begin);
passwd.Read(buffer, 0, buffer.Length);
return buffer;
}
public static MemoryStream MD5Init()
{
return new MemoryStream();
}
public static void MD5Update(MemoryStream context, byte[] source, int length)
{
context.Write(source, 0, length);
}
public static void MD5Update(MemoryStream context, byte[] source, int offset, int length)
{
context.Write(source, offset, length);
}
public static byte[] MD5Final(MemoryStream context)
{
long location = context.Position;
byte[] buffer = new byte[context.Length];
context.Seek(0, SeekOrigin.Begin);
context.Read(buffer, 0, (int)context.Length);
context.Seek(location, SeekOrigin.Begin);
return MD5.Create().ComputeHash(buffer);
}
// Changed to use a memory stream rather than a character array.
public static void _crypt_to64(MemoryStream s, ulong v, int n)
{
char[] _crypt_a64 = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz".ToCharArray();
while (--n >= 0)
{
s.WriteByte((byte)_crypt_a64[v & 0x3f]);
v >>= 6;
}
}
}
}
What Am I doing wrong? I am making some big assumptions about the workings of the MD5xxxx functions in the FreeBSD version, but it seems to work.
Is this not the actual version used by PHP? Does anyone have any insight?
EDIT:
I downloaded a copy of PHP's source code, and found that it uses the glibc library. So, I downloaded a copy of glibc's source code, found the __md5_crypt_r function, duplicated its functionality, ant it came back with the EXACT same hashes as the FreeBSD version.
Now, I am pretty much stumped. Did PHP 4 use a different method than PHP 5? What is going on?

Alright, so here is the answer:
PHP uses the glibc implementation of the crypt function. (attached: C# implementation)
The reason my old passwords are not matching the hash is because the Linux box my old website (hosted by GoDaddy) sat on had a non-standard hashing algorithm. (Possibly to fix some of the WEIRD stuff done in the algorithm.)
However, I have tested the following implementation against glibc's unit tests and against a windows install of PHP. Both tests were passed 100%.
EDIT
Here is the link: (moved to a Github Gist)
https://gist.github.com/1092558

The crypt() function in PHP uses whatever hash algorithm the underlying operating system provides for encrypting the data - have a look at its documentation. So the first step should be to find out, how the data was encrypted (what hashing algorithm was used). Once you know that, it should be trivial to find the same algorithm for C#.

You can always system() (or whatever the C# static function is called) out to a php command-line script that does the crypt for you.
I would recommend forcing a password change though after successful login. Then you can have a flag that indicates if the user has changed. Once everyone has changed you can dump the php call.

Just reuse the php implementation... Make sure php's crypt libraries are in your system environment path...
You may need to update your interop method to make sure your string marshaling/charset is correct... you can then use the original hashing algorithm.
[DllImport("crypt.dll", CharSet=CharSet.ASCII)]
private static extern string crypt(string password, string salt);
public bool ValidLogin(string username, string password)
{
string hash = crypt(password, null);
...
}

It does not look trivial.
UPDATE: Originally I wrote: "The PHP Crypt function does not look like a standard hash. Why not? Who knows." As pointed out in the comments, the PHP crypt() is the same as used in BSD for passwd crypt. I don't know if that is a dejure standard, but it is defacto standard. So.
I stand by my position that it does not appear to be trivial.
Rather than porting the code, you might consider keeping the old PHP running, and use it strictly for password validation of old passwords. As users change their passwords, use a new hashing algorithm, something a little more "open". You would have to store the hash, as well as the "flavor of hash" for each user.