/****************************************************************************
	 *   Copyright (C) 2006-2010 by Jason Ansel, Kapil Arya, and Gene Cooperman *
	 *   jansel@csail.mit.edu, kapil@ccs.neu.edu, gene@ccs.neu.edu              *
	 *                                                                          *
	 *   This file is part of the dmtcp/src module of DMTCP (DMTCP:dmtcp/src).  *
	 *                                                                          *
	 *  DMTCP:dmtcp/src is free software: you can redistribute it and/or        *
	 *  modify it under the terms of the GNU Lesser General Public License as   *
	 *  published by the Free Software Foundation, either version 3 of the      *
	 *  License, or (at your option) any later version.                         *
	 *                                                                          *
	 *  DMTCP:dmtcp/src 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 Lesser General Public License for more details.                     *
	 *                                                                          *
	 *  You should have received a copy of the GNU Lesser General Public        *
	 *  License along with DMTCP:dmtcp/src.  If not, see                        *
	 *  <http://www.gnu.org/licenses/>.                                         *
	 ****************************************************************************/
	
	#include "mtcpinterface.h"
	#include "syscallwrappers.h"
	#include  "../jalib/jassert.h"
	
	#include <stdio.h>
	#include <stdlib.h>
	#include <errno.h>
	
	#ifndef EXTERNC
	#define EXTERNC extern "C"
	#endif
	
	//gah!!! signals API is redundant
	
	static bool checkpointSignalBlockedForProcess = false;
	static __thread bool checkpointSignalBlockedForThread = false;
	
	
	static int bannedSignalNumber(){
	  int _determineMtcpSignal(); // from signalwrappers.cpp
	  const int cache = _determineMtcpSignal();
	  return cache;
	}
	
	static int patchBSDMask(int mask){
	  const int allowedMask = ~sigmask(bannedSignalNumber());
	  return mask & allowedMask;
	}
	
	static inline void patchBSDUserMask(int how, const int mask, int *oldmask)
	{
	  const int bannedMask = sigmask(bannedSignalNumber());
	  if (checkpointSignalBlockedForProcess == true) {
	    *oldmask |= bannedMask;
	  } else {
	    *oldmask &= ~bannedMask;
	  }
	
	  if (how == SIG_BLOCK && (mask & bannedMask)) {
	    checkpointSignalBlockedForProcess = true;
	  } else if (how == SIG_SETMASK) {
	    checkpointSignalBlockedForProcess = ((mask & bannedMask) != 0);
	  }
	}
	
	static inline sigset_t patchPOSIXMask(const sigset_t* mask){
	  JASSERT(mask != NULL);
	  sigset_t t = *mask;
	
	  sigdelset(&t, bannedSignalNumber());
	  return t;
	}
	
	static inline void patchPOSIXUserMaskWork(int how, const sigset_t *set, sigset_t *oldset,
	                                          bool checkpointSignalBlocked)
	{
	  if (oldset != NULL) {
	    if (checkpointSignalBlocked == true) {
	      sigaddset(oldset, bannedSignalNumber());
	    } else {
	      sigdelset(oldset, bannedSignalNumber());
	    }
	  }
	
	  if (set != NULL) {
	    if (how == SIG_BLOCK && sigismember(set, bannedSignalNumber())) {
	      checkpointSignalBlocked = true;
	    } else if (how == SIG_UNBLOCK && sigismember(set,bannedSignalNumber())) {
	      checkpointSignalBlocked = false;
	    } else if (how == SIG_SETMASK) {
	      checkpointSignalBlocked = sigismember(set, bannedSignalNumber());
	    }
	  }
	}
	
	static inline void patchPOSIXUserMask(int how, const sigset_t *set, sigset_t *oldset)
	{
	  patchPOSIXUserMaskWork(how, set, oldset, checkpointSignalBlockedForProcess);
	}
	
	/* Multi-threaded version of the above function */
	static inline void patchPOSIXUserMaskMT(int how, const sigset_t *set, sigset_t *oldset)
	{
	  patchPOSIXUserMaskWork(how, set, oldset, checkpointSignalBlockedForThread);
	}
	
	
	//set the handler
	EXTERNC sighandler_t signal(int signum, sighandler_t handler){
	  if(signum == bannedSignalNumber()){
	    return SIG_IGN;
	  }
	  return _real_signal( signum, handler );
	}
	EXTERNC int sigaction(int signum, const struct sigaction *act, struct sigaction *oldact){
	  if(signum == bannedSignalNumber()){
	    act = NULL;
	  }
	  return _real_sigaction( signum, act, oldact);
	}
	EXTERNC int rt_sigaction(int signum, const struct sigaction *act, struct sigaction *oldact){
	  return sigaction (signum, act, oldact);
	  //if(signum == bannedSignalNumber()){
	  //  act = NULL;
	  //}
	  //return _real_rt_sigaction( signum, act, oldact);
	}
	EXTERNC int sigvec(int signum, const struct sigvec *vec, struct sigvec *ovec){
	  if(signum == bannedSignalNumber()){
	    vec = NULL;
	  }
	  return _real_sigvec( signum, vec, ovec );
	}
	
	//set the mask
	EXTERNC int sigblock(int mask){
	  int oldmask = _real_sigblock( patchBSDMask(mask) );
	
	  patchBSDUserMask(SIG_BLOCK, mask, &oldmask);
	
	  return oldmask;
	}
	
	EXTERNC int sigsetmask(int mask){
	  int oldmask = _real_sigsetmask( patchBSDMask(mask) );
	
	  patchBSDUserMask(SIG_SETMASK, mask, &oldmask);
	
	  return oldmask;
	}
	
	EXTERNC int siggetmask(void){
	  int oldmask =  _real_siggetmask();
	
	  patchBSDUserMask(SIG_BLOCK, 0, &oldmask);
	
	  return oldmask;
	}
	
	EXTERNC int sigprocmask(int how, const sigset_t *set, sigset_t *oldset){
	  const sigset_t *orig = set;
	  if (set != NULL) {
	    sigset_t tmp = patchPOSIXMask(set);

	    set = &tmp;

	  }
	

	  int ret = _real_sigprocmask( how, set, oldset );
	
	  if (ret != -1) {
	    patchPOSIXUserMask(how, orig, oldset);
	  }
	  return ret;
	}
	
	EXTERNC int rt_sigprocmask(int how, const sigset_t *set, sigset_t *oldset){
	  return sigprocmask(how, set, oldset);
	//  const sigset_t *orig = set;
	//  if (set != NULL) {
	//    sigset_t tmp = patchPOSIXMask(set);
	//    set = &tmp;
	//  }
	//
	//  int ret = _real_rt_sigprocmask( how, set, oldset );
	//
	//  if (ret != -1) {
	//    patchPOSIXUserMask(how, orig, oldset);
	//  }
	//  return ret;
	}
	
	/*
	 * This wrapper should be thread safe so we use the multithreaded version of
	 * patchPOSIXUserMask function. This will declare the static variables with
	 * __thread to make them thread local.
	 */
	EXTERNC int pthread_sigmask(int how, const sigset_t *set, sigset_t *oldmask){
	  const sigset_t *orig = set;
	  if (set != NULL) {
	    sigset_t tmp = patchPOSIXMask(set);
	    set = &tmp;
	  }
	
	  int ret = _real_pthread_sigmask( how, set, oldmask );
	
	  if (ret != -1) {
	    patchPOSIXUserMaskMT(how, orig, oldmask);
	  }
	
	  return ret;
	}
	
	/*
	 * TODO: man page says that sigwait is implemented via sigtimedwait, however
	 * sigtimedwait can return EINTR (acc. to man page) whereas sigwait won't.
	 * Should we make the wrappers for sigwait/sigtimedwait homogenious??
	 *                                                          -- Kapil
	 */
	EXTERNC int sigwait(const sigset_t *set, int *sig) {
	  if (set != NULL) {
	    sigset_t tmp = patchPOSIXMask(set);
	    set = &tmp;
	  }
	
	  int ret = _real_sigwait( set, sig );
	
	  return ret;
	}
	
	/* 
	 * In sigwaitinfo and sigtimedwait, it is not possible to differentiate between
	 * a MTCP_SIGCKPT and any other signal (that is outside the given signal set)
	 * that might have occured while executing the system call. These system call
	 * will return -1 with errno set to EINTR.
	 * To deal with the situation, we do not remove the MTCP_SIGCKPT from the
	 * signal set (if it is present); instead, we check the return value and if it
	 * turns out to be MTCP_SIGCKPT, we raise the signal once again for this
	 * thread.
	 * Also note that once sigwaitinfo/sigtimedwait returns MTCP_SIGCKPT, we won't
	 * be receiving another MTCP_SIGCKPT until we have called _real_tkill due to
	 * obvious reasons so I believe it is safe to call _real_gettid() here.
	 *                                                              -- Kapil
	 *
	 * Update: 
	 * Another way to write this wrapper would be to remove the STOPSIGNAL from the
	 * user supplied 'set' and then call sigwaitinfo and then we won't need to
	 * raise the STOPSIGNAL ourselves. However, there is a catch. sigwaitinfo will
	 * return 'EINTR' if the wait was interrupted by a signal handler (STOPSIGNAL
	 * in our case), thus we can either call sigwaitinfo again or return the error
	 * to the user code; I would like to do the former.
	 *                                                              -- Kapil
	 */
	EXTERNC int sigwaitinfo(const sigset_t *set, siginfo_t *info)
	{
	  int ret;
	  while ( 1 ) {
	    ret = _real_sigwaitinfo( set, info );
	    if ( ret != bannedSignalNumber() ) {
	      break;
	    }
	    raise(bannedSignalNumber());
	  }
	  return ret;
	}
	
	EXTERNC int sigtimedwait(const sigset_t *set, siginfo_t *info,
	                         const struct timespec *timeout)
	{
	  int ret;
	  while ( 1 ) {
	    ret = _real_sigtimedwait( set, info, timeout );
	    if ( ret != bannedSignalNumber() ) {
	      break;
	    }
	    raise(bannedSignalNumber());
	  }
	  return ret;
	}