esrgpcpj/gfsw/gfsw.c

/* $Header: /cvsroot/esrg/sfesrg/esrgpcpj/gfsw/gfsw.c,v 1.30 2009/11/29 02:16:04 dtashley Exp $ */

#include <windows.h>
#include <commdlg.h>

#include <assert.h>
#include <process.h>
#include <stdio.h>

#include "resource.h"

#include "bstrfunc.h"
#include "build_config.h"
#include "crchashfuncs.h"
#include "esrg_md5.h"
#include "esrg_sha512.h"

//--------------------------------------------------------------------------------
//Copyright 2001 David T. Ashley
//-------------------------------------------------------------------------------------------------
//This source code and any program in which it is compiled/used is provided under the GNU GENERAL
//PUBLIC LICENSE, Version 3, full license text below.
//-------------------------------------------------------------------------------------------------
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//APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
//HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
//OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
//THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
//PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
//IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
//ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
//
//  16. Limitation of Liability.
//
//  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
//WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
//THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
//GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
//USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
//DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
//PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
//EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
//SUCH DAMAGES.
//
//  17. Interpretation of Sections 15 and 16.
//
//  If the disclaimer of warranty and limitation of liability provided
//above cannot be given local legal effect according to their terms,
//reviewing courts shall apply local law that most closely approximates
//an absolute waiver of all civil liability in connection with the
//Program, unless a warranty or assumption of liability accompanies a
//copy of the Program in return for a fee.
//
//                     END OF TERMS AND CONDITIONS
//
//            How to Apply These Terms to Your New Programs
//
//  If you develop a new program, and you want it to be of the greatest
//possible use to the public, the best way to achieve this is to make it
//free software which everyone can redistribute and change under these terms.
//
//  To do so, attach the following notices to the program.  It is safest
//to attach them to the start of each source file to most effectively
//state the exclusion of warranty; and each file should have at least
//the "copyright" line and a pointer to where the full notice is found.
//
//    <one line to give the program's name and a brief idea of what it does.>
//    Copyright (C) <year>  <name of author>
//
//    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/>.
//
//Also add information on how to contact you by electronic and paper mail.
//
//  If the program does terminal interaction, make it output a short
//notice like this when it starts in an interactive mode:
//
//    <program>  Copyright (C) <year>  <name of author>
//    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
//    This is free software, and you are welcome to redistribute it
//    under certain conditions; type `show c' for details.
//
//The hypothetical commands `show w' and `show c' should show the appropriate
//parts of the General Public License.  Of course, your program's commands
//might be different; for a GUI interface, you would use an "about box".
//
//  You should also get your employer (if you work as a programmer) or school,
//if any, to sign a "copyright disclaimer" for the program, if necessary.
//For more information on this, and how to apply and follow the GNU GPL, see
//<http://www.gnu.org/licenses/>.
//
//  The GNU General Public License does not permit incorporating your program
//into proprietary programs.  If your program is a subroutine library, you
//may consider it more useful to permit linking proprietary applications with
//the library.  If this is what you want to do, use the GNU Lesser General
//Public License instead of this License.  But first, please read
//<http://www.gnu.org/philosophy/why-not-lgpl.html>.
//-------------------------------------------------------------------------------------------------
//--------------------------------------------------------------------------------
/*
KNOWN DEFECTS
  a)When window has the focus, edit control does not get page 
    ups and downs and arrows.  This means one cannot really use the widget
    without the mouse.  Need to redirect these keystrokes to the 
    edit control.

  b)The OPEN dialog box does not remember previous paths.  I believe this
    is an option I can set with a little storage--need to investigate.
    In any case, very annoying when each time get thrown back into a different
    directory than where I last opened files.

  c)Does not correctly handle file sharing (Dan Parks, Dave Ashley).  
    For example, if one tries to signature a file which is currently 
    open in a word processor, it won't do it.  Need to get sharing 
    behavior right.

SUGGESTIONS FOR FUTURE ENHANCEMENT:

  a)Should sort files before beginning the signaturing (the drag'n'drop
    interface delivers them in an unpredictable order).

  b)Should accomodate more than 200 files (Cory Pratt).  (Limiting factor
    at present time is size of edit window display buffer.)

  c)Should include a SAVE AS option (Raul Selgado).

  d)Should include a print option (Dave Ashley).
*/


#define GFSW_MAXFILES (200)
   //Maximum number of files that will be processed and displayed.
   //Limited to avoid filling up the edit control's buffer.
   
#define GFSW_DISPBUFLEN (55000)
   //The point at which we say the edit control buffer has too
   //many characters in it.

#define GFSW_FILE_READ_BUF_SIZE (0x10000)
   //The number of bytes for each read buffer.  It is difficult to know
   //how to size this value.  On one hand, larger is better, as it 
   //enables the disk to operate in blocks.  On the other hand, too 
   //large is probably not a good idea, as it will take a lot of
   //time to fill the buffer.  Suspect that 16K-64K is about the 
   //optimum, but may go larger, anyway.

static char GFSW_dialog_file_open_buffer[15000];
   //Buffer from the "open files" dialog box, for it to store results
   //in.

static char GFSW_dispbuf[GFSW_DISPBUFLEN+1];
   //The buffer which holds the contents of the edit control (the main control, the
   //text box).  This is a mirror buffer, probably not a very efficient way of doing
   //things.

static int GFSW_use_sound = 1;
   //Remembers the state of the "use sound" option.  Default is YES.

static int GFSW_always_on_top = 1;
   //Remembers whether the main window should always be on top.
   //This can be annoying in some applications, so it can be turned off.

#define WM_USER_EV_CHILD_THREAD_PROGRESS  (WM_USER + 1)
   //The child thread has progress to report (updated information that
   //can be used by the parent).

#define WM_USER_EV_CHILD_THREAD_ENDING    (WM_USER + 2)
   //The child thread is reporting that it is ending.  After this event is
   //posted for the parent, there may be some delay until the thread is actually
   //terminated, so additional OS interaction is required to know the thread
   //is actually dead.

static char GFSW_szAppName[] = "FileHash";
   //The application name.

static WNDPROC GFSW_old_win_edit_handler = NULL;
   //The old edit control handler.  This is used to remember the function pointer,
   //in order to subclass the behavior, because we must catch the drop files event.

static volatile int GFSW_thread_abort_request = 0;
   //This is set TRUE by the main thread if the child thread
   //should abort.  This means the application will terminate
   //(this is the only reason for setting this flag).  This 
   //variable is set by the main thread and read by the
   //child thread.

static DWORD GFSW_parent_thread_id = 0;
   //The thread ID of the parent obtained using the 
   //GetCurrentThreadId() call.  The child needs to know this
   //in order to post a message.

static HWND GFSW_parent_thread_main_window_handle = 0;
   //Window handle of main window.

static int GFSW_child_thread_is_active = 0;
   //Set TRUE when the child thread is kicked off.  Set
   //FALSE when a message from the child thread is received
   //indicating that the thread has terminated and when the
   //thread is confirmed dead.  This variable is used only
   //by the main thread.

static HANDLE GFSW_child_handle = 0;
   //The handle of the child process.  This is only valid
   //if a thread is active.  This variable is used only
   //by the main thread to check on status.

static unsigned char GFSW_file_read_buf[GFSW_FILE_READ_BUF_SIZE];
   //File read buffer.

struct GFSW_FileInfoStructPerFile
   {
   volatile char fpath[MAX_PATH + 1];
      //The full path to the file, which should be recognized by the operating system.
      //If this string is empty, it is a signal that no file is in this slot.
   volatile int  is_directory_valid;
      //TRUE if the is_directory flag is assigned by the child process and so the 
      //parent can rely on it.
   volatile int  is_directory_error;
      //TRUE if the child process could not obtain directory information.
   volatile int  is_directory;
      //TRUE if the file is actually a directory.  This means it cannot be processed.
   volatile int  file_size_valid;
      //TRUE if file size has been assigned by child (or an attempt to assign it was made).
   volatile int  file_size_error;
      //There was an error in the attempt to obtain file size.
   volatile unsigned __int64 file_size;
      //The number of bytes in the file.
   volatile int  crc32_valid;
      //TRUE if the CRC32 has been assigned, or an attempt was made to assign it.  This
      //means the child has filled in the string.
   volatile char crc32[100];
      //A string representation of the CRC-32, or else an error message from the child.
   volatile int  md5_valid;
      //TRUE if the md5 is valid or an attempt was made.
   volatile char md5[100];
      //A string representation of the MD5 or else an error message from the child.
   volatile int  sha512_valid;
      //TRUE if the SHA512 is valid or an attempt was made.
   volatile char sha512[200];
      //A string representation of the SHA512 or else an error message from the child.
   };

struct GFSW_FileInfoStruct
   {
   volatile struct GFSW_FileInfoStructPerFile file_info[GFSW_MAXFILES];
   volatile int terminated_normally;
   volatile int aborted;
   };


volatile struct GFSW_FileInfoStruct GFSW_file_info;
   //This is the major structure that holds file information.  Here are the three
   //roles it fills:
   //
   //   a)The parent thread fills in this information in preparation for starting
   //     up the child thread.
   //
   //   b)The child thread fills in the information (file size, CRC, MD5) as it
   //     goes down this list, and notifies the parent thread with an event,
   //     which causes the updating of displayed information.
   //
   //   c)After the child thread is absolutely complete, another event is send
   //     to indicate this.


//Function prototypes, to be sure no strange accidents.
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow);
LRESULT CALLBACK GFSW_ReplacementEditProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
static unsigned __stdcall GFSW_ChildThreadFunc(void *pArguments);
static void GFSW_ChildThreadHardSyncStop(void);
static void GFSW_ChildThreadStart(void);
static void GFSW_MakeGenericSound(void);


//Main function for Windows.
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
   {
   HWND         hwnd ;
   HMENU        hmenu;
   MSG          msg ;
   WNDCLASS     wndclass ;

   //Store our current parent thread ID.  The child process will need
   //to know this to post a message.  This is expected to be
   //invariant for the life of the program.
   GFSW_parent_thread_id = GetCurrentThreadId();

   //Zero out the file information block.
   memset((char *)&GFSW_file_info, 0, sizeof(GFSW_file_info));

   wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
   wndclass.lpfnWndProc   = WndProc ;
   wndclass.cbClsExtra    = 0 ;
   wndclass.cbWndExtra    = 0 ;
   wndclass.hInstance     = hInstance ;
   wndclass.hIcon         = LoadIcon (hInstance, MAKEINTRESOURCE(IDI_ICON)) ;
   wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
   wndclass.hbrBackground = (HBRUSH) (COLOR_BTNFACE+1) ;
   wndclass.lpszMenuName  = NULL ;
   wndclass.lpszClassName = GFSW_szAppName ;

   if (!RegisterClass (&wndclass))
      {
      MessageBox (NULL, 
                 TEXT ("Error code from RegisterClass() Win32 API function.    \nMost probable cause is incompatible operating system."), 
                 GFSW_szAppName, 
                 MB_ICONERROR) ;
      return 0 ;
      }
     
   //We need to do some voodoo to figure out how large to make the main window.
   //The feeling is that the window should be as small as possible to display the
   //results from an individual file (the most common application), and if the user
   //wants it bigger s/he can resize it.  Four lines are required (file name, file 
   //size, file CRC-32, and file MD5), so that needs to be the height.  A file
   //MD5 is 128 bits = 32 characters.  In addition, there is the constraint that we
   //cannot go beyond the width and height of a screen.  The guess below is quite
   //crude, assuming that the edit box has a larger font, etc.
   {
   int initial_width = 0;
   int initial_height = 0;

   //Get a crude measure of how big text is.
   initial_width =  LOWORD(GetDialogBaseUnits());
   initial_height = HIWORD(GetDialogBaseUnits());

   //Dope it up linearly.
   initial_width  = (initial_width * 1500)/10;
   initial_height = (initial_height * 150)/10; 

   {
   int temp;

   //Be sure nothing is bigger than 2/3 screen dimensions.
   temp = (GetSystemMetrics(SM_CXFULLSCREEN) * 2) / 3;
   if (initial_width > temp)
      initial_width = temp;
   temp = (GetSystemMetrics(SM_CYFULLSCREEN) * 2) / 3;
   if (initial_height > temp)
      initial_height = temp;
   }

   //Load up the menu resources.  I have verified in documentation that this will be destroyed
   //automatically.
   hmenu = LoadMenu(hInstance, MAKEINTRESOURCE(IDR_GFSW));

   //Create the window.  The "Ex" call is used to make it a topmost window.
   hwnd = CreateWindowEx (
                       WS_EX_TOPMOST,
                       GFSW_szAppName,             // window class name
                       TEXT ("FileHash v0.1"),     // window caption
                       WS_OVERLAPPEDWINDOW,        // window style
                       CW_USEDEFAULT,              // initial x position
                       CW_USEDEFAULT,              // initial y position
                       initial_width,              // initial x size
                       initial_height,             // initial y size
                       NULL,                       // parent window handle
                       hmenu,                      // window menu handle
                       hInstance,                  // program instance handle
                       NULL) ;                     // creation parameters
   }
     
   
   GFSW_parent_thread_main_window_handle = hwnd;

   //This is standard code from Petzold's book.  Don't know _exactly_ what it does, but
   //every Windows program seems to have it.
   ShowWindow (hwnd, iCmdShow) ;
   UpdateWindow (hwnd) ;
     
   while (GetMessage (&msg, NULL, 0, 0))
      {
      TranslateMessage (&msg) ;
      DispatchMessage (&msg) ;
      }

   return msg.wParam ;
   }


//This is the subclass WndProc.   This had to be done to allow the edit 
//control to catch the WM_DROPFILES event.
LRESULT CALLBACK GFSW_ReplacementEditProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
   {
   static int iDeltaPerLine = 120, iAccumDelta = 0;
      //These are for mouse wheel logic.  It may happen in the future that more
      //precise mice without notches are introduced.

   //We need to watch for the drop target notification message, and take action 
   //in that case.
   switch(message)
      {
      case WM_DROPFILES:
         {
         int iFiles;
         int i;
         HDROP hDropInfo = (HANDLE)wParam;

         //Do a hard sync stop on the child thread.  This should not take
         //very long.  A new drag'n'drop event will just cause restart
         //with the new set of files.
         GFSW_ChildThreadHardSyncStop();

         //Zero out the file information area and the text buffer mirror.
         memset((char *)&GFSW_file_info, 0, sizeof(GFSW_file_info));
         GFSW_dispbuf[0] = 0;

         // Get the number of files and folders that were dropped.
         iFiles = DragQueryFile (hDropInfo, (DWORD)(-1), (LPSTR)NULL, 0);

         //Copy the paths to the right buffer area.
         for (i=0; (i<iFiles) && (i<GFSW_MAXFILES); i++)
            {
            DragQueryFile (hDropInfo, i, (LPSTR)(GFSW_file_info.file_info[i].fpath), MAX_PATH);
            }

         //Start up the child thread.
         GFSW_ChildThreadStart();

         break;
         }
      case WM_MOUSEWHEEL:
         {
         iAccumDelta += (short) HIWORD (wParam);

         while (iAccumDelta >= iDeltaPerLine)
            {
            SendMessage(hwnd, WM_VSCROLL, SB_PAGEUP, 0);
            iAccumDelta -= iDeltaPerLine;
            //iAccumDelta = 0;
            }

         while (iAccumDelta <= -iDeltaPerLine)
            {
            SendMessage(hwnd, WM_VSCROLL, SB_PAGEDOWN, 0);
            iAccumDelta += iDeltaPerLine;
            //iAccumDelta = 0;
            }

         break;
         }
      }

   //Call the old Window procedure.
   return (CallWindowProc(GFSW_old_win_edit_handler, hwnd, message, wParam, lParam));
   }


//Stages the display buffer in preparation for outputting it out
//to the edit child window.  This function generally interacts
//with the file information data structure even while the
//child thread is running.  This is OK, as race conditions are
//covered.  Essentially, as the child thread proceeds, it updates
//data then afterwards flags it as valid.  This function
//never proceeds into invalid data.
static void GFSW_StageDisplayBuffer(void)
   {
   int dispbufidx;
   int nfiles;
   int len;
   int i;
   char buf[2*MAX_PATH+200];

   //Count the number of files queued, and put that in the buffer.
   dispbufidx = 0;
   nfiles=0;
   for (i=0; i<GFSW_MAXFILES; i++)
      {
      if (GFSW_file_info.file_info[i].fpath[0])
         {
         nfiles++;
         }
      else
         {
         break;
         }
      }
   sprintf_s(buf, sizeof(buf), "Files to signature:  %d.\x0d\x0a", nfiles);
   len = strlen(buf);
   if ((len + dispbufidx + 2) < GFSW_DISPBUFLEN)
      {
      strcpy_s(GFSW_dispbuf+dispbufidx, sizeof(GFSW_dispbuf) - dispbufidx,buf);
      dispbufidx += len;
      }

   //Loop through and output the information for each file.
   for (i=0; i<GFSW_MAXFILES; i++)
      {
      if ((GFSW_file_info.file_info[i].fpath[0]) && (GFSW_file_info.file_info[i].is_directory_valid))
         {
         sprintf_s(buf, sizeof(buf), "--------------------\x0d\x0a");
         len = strlen(buf);
         if ((len + dispbufidx + 2) < GFSW_DISPBUFLEN)
            {
            strcpy_s(GFSW_dispbuf+dispbufidx, sizeof(GFSW_dispbuf)-dispbufidx, buf);
            dispbufidx += len;
            }

         sprintf_s(buf, sizeof(buf), "[%03d/%03d] %s\x0d\x0a", i+1, nfiles, GFSW_file_info.file_info[i].fpath);
         len = strlen(buf);
         if ((len + dispbufidx + 2) < GFSW_DISPBUFLEN)
            {
            strcpy_s(GFSW_dispbuf+dispbufidx, sizeof(GFSW_dispbuf)-dispbufidx, buf);
            dispbufidx += len;
            }

         //If the file is actually a directory or there was an error, we can't
         //do further processing on it.
         if (GFSW_file_info.file_info[i].is_directory_error)
            {
            sprintf_s(buf, sizeof(buf), "\tError obtaining file attributes--cannot process this file.\x0d\x0a");
            len = strlen(buf);
            if ((len + dispbufidx + 2) < GFSW_DISPBUFLEN)
               {
               strcpy_s(GFSW_dispbuf+dispbufidx, sizeof(GFSW_dispbuf)-dispbufidx, buf);
               dispbufidx += len;
               }
            }
         else if (GFSW_file_info.file_info[i].is_directory)
            {
            sprintf_s(buf, sizeof(buf), "\tThis item is a directory and will not be signatured.\x0d\x0a");
            len = strlen(buf);
            if ((len + dispbufidx + 2) < GFSW_DISPBUFLEN)
               {
               strcpy_s(GFSW_dispbuf+dispbufidx, sizeof(GFSW_dispbuf)-dispbufidx, buf);
               dispbufidx += len;
               }
            }
         else
            {
            //This is not a directory.  We can print the rest of the 
            //information.
            //
            //First, the file size.
            if (GFSW_file_info.file_info[i].file_size_valid)
               {
               char buf2[100];

               buf2[0] = 0;  //Just in case conversion doesn't go right.
               sprintf_s(buf2, sizeof(buf2), "%I64u", GFSW_file_info.file_info[i].file_size);
               BSTRFUNC_commanate(buf2);
               sprintf_s(buf, sizeof(buf), "\tSize:\t%s\x0d\x0a", buf2);

               len = strlen(buf);
               if ((len + dispbufidx + 2) < GFSW_DISPBUFLEN)
                  {
                  strcpy_s(GFSW_dispbuf+dispbufidx, sizeof(GFSW_dispbuf)-dispbufidx, buf);
                  dispbufidx += len;
                  }
               }

            //Now, the CRC-32.
            if (GFSW_file_info.file_info[i].crc32_valid)
               {
               sprintf_s(buf, sizeof(buf), "\tCRC-32:\t%s\x0d\x0a", GFSW_file_info.file_info[i].crc32);
               len = strlen(buf);
               if ((len + dispbufidx + 2) < GFSW_DISPBUFLEN)
                  {
                  strcpy_s(GFSW_dispbuf+dispbufidx, sizeof(GFSW_dispbuf)-dispbufidx, buf);
                  dispbufidx += len;
                  }
               }

            //Now, the MD-5.
            if (GFSW_file_info.file_info[i].md5_valid)
               {
               sprintf_s(buf, sizeof(buf), "\tMD-5:\t%s\x0d\x0a", GFSW_file_info.file_info[i].md5);
               len = strlen(buf);
               if ((len + dispbufidx + 2) < GFSW_DISPBUFLEN)
                  {
                  strcpy_s(GFSW_dispbuf+dispbufidx, sizeof(GFSW_dispbuf)-dispbufidx, buf);
                  dispbufidx += len;
                  }
               }

                        //Now, the SHA512.
            if (GFSW_file_info.file_info[i].sha512_valid)
               {
               sprintf_s(buf, sizeof(buf), "\tSHA-512:\t%s\x0d\x0a", GFSW_file_info.file_info[i].sha512);
               len = strlen(buf);
               if ((len + dispbufidx + 2) < GFSW_DISPBUFLEN)
                  {
                  strcpy_s(GFSW_dispbuf+dispbufidx, sizeof(GFSW_dispbuf)-dispbufidx, buf);
                  dispbufidx += len;
                  }
               }
            }
         }
      else
         {
         break;
         }

      }

   //Process the termination condition information.
   if (GFSW_file_info.aborted)
      {
      sprintf_s(buf, sizeof(buf), "-------------------- FILE SIGNATURE ABORTED --------------------");
      }
   else if (GFSW_file_info.terminated_normally)
      {
      sprintf_s(buf, sizeof(buf), "-------------------- FILE SIGNATURE COMPLETE --------------------");
      }
   else
      {
      sprintf_s(buf, sizeof(buf), "-------------------- FILE SIGNATURE IN PROGRESS -------------------");
      }

   len = strlen(buf);
   if ((len + dispbufidx + 2) < GFSW_DISPBUFLEN)
      {
      strcpy_s(GFSW_dispbuf+dispbufidx, sizeof(GFSW_dispbuf)-dispbufidx, buf);
      dispbufidx += len;
      }
   }


//Pushes the display buffer out to the edit cotrol.
static int GFSW_UpdateEditControl(HWND te_wind)
   {
   SetWindowText(te_wind, GFSW_dispbuf);

   //Must set the buffer position (i.e. the display position) to the end.
   //The "/10" assumes that there can't be more than 8 chars or so per line--
   //couldn't find a way to go to the end automatically.
   SendMessage(te_wind,EM_LINESCROLL,0,GFSW_DISPBUFLEN/8);

   return(0);
   }


//This is the Windows procedure and event loop for the 
//main Window.
//
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
   {
   HDC         hdc ;
   PAINTSTRUCT ps ;
   static RECT        rect ;
   static HWND te_wind = 0;

   switch (message)
      {
      case WM_CREATE:
         {
         //Need to get the size of our current window so we can create the
         //child same size.
         //
         GetClientRect (hwnd, &rect);

         te_wind = CreateWindow ("EDIT",                     // window class name
                             "",                         // window caption
                             WS_CHILD|WS_VISIBLE|WS_BORDER|ES_MULTILINE|ES_AUTOVSCROLL|ES_WANTRETURN,        // window style
                             0,                          // initial x position
                             0,                          // initial y position
                             rect.right,                        // initial x size
                             rect.bottom,                         // initial y size
                             hwnd,                       // parent window handle
                             (HMENU) 1,                          // window menu handle
                             ((LPCREATESTRUCT)lParam)->hInstance, // program instance handle
                             NULL) ;                     // creation parameters
         //Print initial usage instructions.
         SetWindowText(te_wind, "To calculate CRC-32 cyclic redundancy codes, MD-5 message digests, "
                                           "and SHA-512 message digests, just "
                               "drag and drop files into this box (from Windows Explorer "
                               "or a similar application), or use the FILE->OPEN "
                               "menu selection.  Text can be freely selected and "
                               "copied from this window (select the desired text "
                               "and use the right mouse button for a popup menu "
                               "which includes COPY).");

         //Tell Windows that this child is a fair drop target for files.
         DragAcceptFiles (te_wind, TRUE);

         //We need to subclass the child window, which is to define a new wndproc
         //for it.
         GFSW_old_win_edit_handler = (WNDPROC) SetWindowLong(te_wind, GWL_WNDPROC, (long) GFSW_ReplacementEditProc);

         return 0 ;
         }
      case WM_SIZE:
         {
         rect.left = 0;
         rect.top = 0;
         rect.right = LOWORD(lParam);
         rect.bottom = HIWORD(lParam);
         MoveWindow(te_wind, 0, 0, rect.right, rect.bottom, TRUE);
         return 0;
         }
      case WM_PAINT:
         {
         hdc = BeginPaint (hwnd, &ps) ;

         GetClientRect (hwnd, &rect) ;
          
         EndPaint (hwnd, &ps) ;
         return 0 ;
         }
      case WM_DESTROY:
         {
         PostQuitMessage (0) ;
         GFSW_ChildThreadHardSyncStop();
         return 0 ;
         }
      //This is a home-spun event which means that there are files to be processed.
      //This is sent once when the drop is initially done and then each time a file
      //is processed another event is used to continue the process, until finally
      //there are no more files to do.
      case WM_USER_EV_CHILD_THREAD_PROGRESS:
         {
         //Just recalc the mirror buffer and redisplay it.
         GFSW_StageDisplayBuffer();
         GFSW_UpdateEditControl(te_wind);
         return 0;
         }
      case WM_USER_EV_CHILD_THREAD_ENDING:
         {
         HMENU hMenu;

         //Just recalc the mirror buffer and redisplay it.
         GFSW_StageDisplayBuffer();
         GFSW_UpdateEditControl(te_wind);
         GFSW_MakeGenericSound();

         hMenu = GetMenu(GFSW_parent_thread_main_window_handle);

         EnableMenuItem(hMenu, ID_ACTIONS_HALTSIGOP, MF_GRAYED);

         return 0;
         }
      case WM_COMMAND:
         {
         switch(LOWORD(wParam))
            {
            case ID_FILE_OPEN_FOR_SIG:
               {
               OPENFILENAME ofn;
               static char szFilter[] = "All Files (*.*)\0*.*\0\0";

               //Set up for the dialog.
               GFSW_dialog_file_open_buffer[0] = 0;  //Be sure that initial name zero'd out.
               GFSW_dialog_file_open_buffer[1] = 0;

               ofn.lStructSize = sizeof(OPENFILENAME);
               ofn.hwndOwner         = hwnd ;
               ofn.hInstance         = NULL ;
               ofn.lpstrFilter       = szFilter;
               ofn.lpstrCustomFilter = NULL ;
               ofn.nMaxCustFilter    = 0 ;
               ofn.nFilterIndex      = 0 ;
               ofn.lpstrFile         = GFSW_dialog_file_open_buffer;
               ofn.nMaxFile          = sizeof(GFSW_dialog_file_open_buffer) - 1;
               ofn.lpstrFileTitle    = NULL;
               ofn.nMaxFileTitle     = 0;
               ofn.lpstrInitialDir   = NULL ;
               ofn.lpstrTitle        = "Open File(s) For Signature Calculation" ;
               ofn.Flags             = OFN_ALLOWMULTISELECT
                                     | OFN_FILEMUSTEXIST
                                     | OFN_HIDEREADONLY
                                     | OFN_NODEREFERENCELINKS
                                     | OFN_PATHMUSTEXIST
                                     | OFN_EXPLORER
                                     | OFN_SHAREAWARE;           
               ofn.nFileOffset       = 0 ;
               ofn.nFileExtension    = 0 ;
               ofn.lpstrDefExt       = NULL;
               ofn.lCustData         = 0L ;
               ofn.lpfnHook          = NULL ;
               ofn.lpTemplateName    = NULL ;
     
               //Zero out the dialog return area buffer.
               GFSW_dialog_file_open_buffer[0] = 0;
               GFSW_dialog_file_open_buffer[1] = 0;

               if (GetOpenFileName (&ofn))
                  {
                  int dstarridx=0;
                  int srccharidx=0;

                  //There was success and something specified.  This means we must
                  //kill the child thread if it is running.
                  //Do a hard sync stop on the child thread.  This should not take
                  //very long.  A new drag'n'drop event will just cause restart
                  //with the new set of files.
                  GFSW_ChildThreadHardSyncStop();

                  //Zero out the file information area and the text buffer mirror.
                  memset((char *)&GFSW_file_info, 0, sizeof(GFSW_file_info));
                  GFSW_dispbuf[0] = 0;

                  dstarridx=0;
                  srccharidx=0;

                  //Advance to first string terminator.
                  while (GFSW_dialog_file_open_buffer[srccharidx] != 0)
                     srccharidx++;

                  //In the special case where the double-null is encountered immediately, there is
                  //only one file, and full path is specified.
                  //
                  if (!GFSW_dialog_file_open_buffer[srccharidx+1])
                     {
                     strcpy_s((char *)GFSW_file_info.file_info[0].fpath, sizeof(GFSW_file_info.file_info[0].fpath), GFSW_dialog_file_open_buffer);
                     }
                  else
                     {
                     //This is the multiple file case.
                     while ((dstarridx < GFSW_MAXFILES) && (GFSW_dialog_file_open_buffer[srccharidx+1]))
                        {
                        int len;

                        srccharidx++;
                        strcpy_s((char *)GFSW_file_info.file_info[dstarridx].fpath, sizeof(GFSW_file_info.file_info[dstarridx].fpath), GFSW_dialog_file_open_buffer);

                        //Watch out for adding two backslashes.  This can happen if the path
                        //contains only a drive letter ("c:\", for example) so that the OS
                        //adds a path on.
                        len = strlen(GFSW_dialog_file_open_buffer);
                        if ((len != 0) && (GFSW_dialog_file_open_buffer[len-1]=='\\'))
                           {
                           //Do nothing.  Watch out in modifying this.  The "len != 0" test
                           //above is to prevent an access violation in the second test--watch
                           //out when modifying this if-then-else construct.
                           }
                        else
                           {
                           strcat_s((char *)GFSW_file_info.file_info[dstarridx].fpath, sizeof(GFSW_file_info.file_info[dstarridx].fpath), "\\");
                           }
                        strcat_s((char *)GFSW_file_info.file_info[dstarridx].fpath, sizeof(GFSW_file_info.file_info[dstarridx].fpath), GFSW_dialog_file_open_buffer+srccharidx);
                        while (GFSW_dialog_file_open_buffer[srccharidx] != 0)
                           srccharidx++;
                        dstarridx++;
                        }
                     }

                  //Start up the child thread.
                  GFSW_ChildThreadStart();

                  //Redisplay the edit buffer.
                  GFSW_StageDisplayBuffer();
                  GFSW_UpdateEditControl(te_wind);
                  }

               return 0;
               }
            case ID_FILE_EXIT:
               {
               SendMessage(hwnd, WM_CLOSE, 0, 0);
               return 0;
               }
            case ID_ACTIONS_HALTSIGOP:
               {
               GFSW_ChildThreadHardSyncStop();
               GFSW_MakeGenericSound();
               GFSW_StageDisplayBuffer();
               GFSW_UpdateEditControl(te_wind);
               return 0;
               }
            case ID_OPTIONS_USE_SOUND:
               {
               if (GFSW_use_sound)
                  {
                  HMENU hMenu;

                  hMenu = GetMenu(GFSW_parent_thread_main_window_handle);
                  GFSW_use_sound = 0;
                  CheckMenuItem(hMenu, ID_OPTIONS_USE_SOUND, MF_UNCHECKED);
                  }
               else
                  {
                  HMENU hMenu;

                  hMenu = GetMenu(GFSW_parent_thread_main_window_handle);
                  GFSW_use_sound = 1;
                  CheckMenuItem(hMenu, ID_OPTIONS_USE_SOUND, MF_CHECKED);
                  }
               return 0;
               }
            case ID_OPTIONS_WINDOWALWAYSONTOP:
               {
               if (GFSW_always_on_top)
                  {
                  HMENU hMenu;

                  hMenu = GetMenu(GFSW_parent_thread_main_window_handle);
                  GFSW_always_on_top = 0;
                  CheckMenuItem(hMenu, ID_OPTIONS_WINDOWALWAYSONTOP, MF_UNCHECKED);
                  SetWindowPos(GFSW_parent_thread_main_window_handle,
                               HWND_NOTOPMOST,
                               0,
                               0,
                               0,
                               0,
                               SWP_NOMOVE | SWP_NOSIZE | SWP_FRAMECHANGED);
                  }
               else
                  {
                  HMENU hMenu;

                  hMenu = GetMenu(GFSW_parent_thread_main_window_handle);
                  GFSW_always_on_top = 1;
                  CheckMenuItem(hMenu, ID_OPTIONS_WINDOWALWAYSONTOP, MF_CHECKED);
                  SetWindowPos(GFSW_parent_thread_main_window_handle,
                               HWND_TOPMOST,
                               0,
                               0,
                               0,
                               0,
                               SWP_NOMOVE | SWP_NOSIZE | SWP_FRAMECHANGED);
                  }
               return 0;
               }
            case ID_HELP_ABOUT:
               {
               char *msg;
               char *first_line = "FileHash (GUI file message digest widget)\n\n";
               char *second_line = "[Built on " __DATE__ " at " __TIME__ "]\n\n";
                           char *third_line = "Please contact Dave Ashley (DASHLEY@GMAIL.COM) with any issues.";

               msg = malloc(strlen(first_line)+strlen(second_line)+strlen(third_line)+1);

               assert(msg != NULL);

               if (msg)
                  {
                  strcpy_s(msg, strlen(first_line)+strlen(second_line)+strlen(third_line)+1,   first_line);
                  strcat_s(msg, strlen(first_line)+strlen(second_line)+strlen(third_line)+1,   second_line);
                  strcat_s(msg, strlen(first_line)+strlen(second_line)+strlen(third_line)+1,   third_line);
                  MessageBox (hwnd, 
                              msg, 
                              GFSW_szAppName, 
                              MB_OK|MB_ICONINFORMATION) ;
                  free(msg);
                  }
               return 0 ;
               }
            case ID_HELP_HELP:
               {
               MessageBox (hwnd, 
                           "This program was written by Dave Ashley\n"
                                                   "(DASHLEY@GMAIL.COM).  Please feel free\n"
                           "to correspond by e-mail.",
                           GFSW_szAppName, 
                           MB_OK|MB_ICONINFORMATION) ;
               return 0 ;
               }
            }
         break;
         }
      }

   return DefWindowProc (hwnd, message, wParam, lParam) ;
   }


//This is the child thread which is deployed in order to calculate the CRC-32
//and MD5 of a single file.  This is done because a single-threaded approach
//does not allow the GUI to continue to receive Windows events, and it
//clogs up the desktop with an unmoveable unresponsive blob.  This child
//thread keeps its eye on the abort flag, and will terminate if it sees that.
//It takes its input from the top of the list of filenames, and returns
//the CRC-32 and MD5, whic take some time to compute.
static unsigned __stdcall GFSW_ChildThreadFunc(void *pArguments)
   {
   int fidx;
      //The index of the table entry we're currently processing.
   DWORD file_attributes;
      //The returned file attributes from the OS.
   HANDLE hFile = (HANDLE) -1;
      //The file handle used to get size and to open for reading.  This being
      //not the error value signals that it is valid and will need to be closed.
   DWORD file_size=0;
      //File size obtained from a call to the GetFileSize() function.
   DWORD file_size_high=0;
      //High 32 bits of same.
   DWORD last_error=0;
      //Result of the GetLastError() function.  This is required to properly decode
      //the file size when very large files are involved.
   DWORD rc = 0;
      //Return code from file seek.
   BOOL  rv = 0;

   struct CRCHASHFUNCS_Crc32StateStruct crc32s;
   struct ESRG_MD5_Md5StateStruct md5s;
   struct ESRG_MD5_Md5ResultStruct md5r;
   struct ESRG_SHA512_Sha512StateStruct  sha512s;
   struct ESRG_SHA512_Sha512ResultStruct sha512r;
   int exit_flag = 0;
   DWORD bytes_read = 0;
   unsigned crc32;


   //We have been invoked.  We now just signature files until the list is
   //done or until we are asked to gracefully abort.
   for (
       fidx = 0; 
       (fidx<GFSW_MAXFILES) && (GFSW_file_info.file_info[fidx].fpath[0] != 0) && (!GFSW_thread_abort_request);
       fidx++
       )
      {
      //Set any values here that are critical to have right in case we must abort.
      hFile = (HANDLE) -1;
         //This has to be the error value.  If we abort, need to know whether
         //to try to close this.

      /********************************************************************************/
      /********************************************************************************/
      /*******  F I L E    A T T R I B U T E S  ***************************************/
      /********************************************************************************/
      /********************************************************************************/
      file_attributes = GetFileAttributes((char *)GFSW_file_info.file_info[fidx].fpath);
      if (file_attributes == 0xFFFFFFFF)
         {
         GFSW_file_info.file_info[fidx].is_directory_error = 1;
            //Signal trouble trying to figure out if this is a directory.  This also
            //signals that the OS does not understand the file path, so can't do much.
         }
      else if (file_attributes & FILE_ATTRIBUTE_DIRECTORY)
         {
         GFSW_file_info.file_info[fidx].is_directory = 1;
            //This is a directory.
         }

      //In any case, the is_directory information is now valid.
      GFSW_file_info.file_info[fidx].is_directory_valid = 1;

      /********************************************************************************/
      /********************************************************************************/
      /*******  F I L E    S I Z E  ***************************************************/
      /********************************************************************************/
      /********************************************************************************/
      //If this is a directory or if there was an error getting information, we
      //cannot go forward with finding file size information.
      if (GFSW_file_info.file_info[fidx].is_directory || GFSW_file_info.file_info[fidx].is_directory_error)
         {
         GFSW_file_info.file_info[fidx].file_size_error = 1;
         }
      else
         {
         hFile = CreateFile ((char *)GFSW_file_info.file_info[fidx].fpath,
                             GENERIC_READ,
                             FILE_SHARE_READ | FILE_SHARE_WRITE,
                             NULL,
                             OPEN_EXISTING,
                             FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN,
                             (HANDLE)NULL);
            //Try to open the file to look at it.  The documentation
            //of the CreateFile() call is misleading in the MSDN help.
            //A web reference said that the flag combination above,
            //
            //   FILE_SHARE_READ | FILE_SHARE_WRITE,
            //
            //means "exclude none", i.e. allow others to have file open for both read
            //and write.  This seems to be the right combination to allow
            //the signaturing of documents that are open with Microsoft
            //Word or other applications.  I have no idea what will happen
            //if the file size changes while the file is open, but I
            //assume that the EOF will become true or there will be an error,
            //either of which will terminate processing of the file.
         if (hFile == (HANDLE) -1)
            {
            //Open error.  Can't go further.
            GFSW_file_info.file_info[fidx].file_size_error = 1;
            }
         else
            {
            //Try to obtain the file size.
            file_size = GetFileSize(hFile, &file_size_high);

            //Try to get the error flags, which we may need.
            last_error = GetLastError();
 
            //There is some voodoo involved with file size and the
            //error code.  This is documented in the GetFileSize() docs.
            if ((file_size == 0xFFFFFFFF) && (last_error != NO_ERROR))
               {
               GFSW_file_info.file_info[fidx].file_size_error = 1;
               }
            else
               {
               unsigned __int64 lo, hi, composite;
               //If we're here, we have a clean size.  Convert it and display it.

               //Play the bit games to get the size.
               lo = (unsigned __int64)file_size;
               hi = (unsigned __int64)file_size_high;
               composite = lo + (hi << 32);
               GFSW_file_info.file_info[fidx].file_size = composite;
               }
            }
         }

      //The file size information is now valid in any case.
      GFSW_file_info.file_info[fidx].file_size_valid = 1;

      //At this point there is potentially progress to report to
      //the main thread.  We will sit and spin until the main
      //thread will accept a posted event announcing progress
      //or until we are aborted.
      while (!PostMessage(GFSW_parent_thread_main_window_handle,
                          WM_USER_EV_CHILD_THREAD_PROGRESS,
                          0,
                          0)
             &&
             !GFSW_thread_abort_request)
         {
         Sleep(1000);  //Wait 1 second until trying again.
                       //1000ms is a long time for a modern computer,
                       //and this should be OK to ease the load if
                       //the system is seriously busy or something.
         }
 
      /********************************************************************************/
      /********************************************************************************/
      /*******  F I L E    C R C - 3 2,    M D - 5,    A N D    S H A - 5 1 2   *******/
      /********************************************************************************/
      /********************************************************************************/
      if (hFile == (HANDLE) -1)      
         {
         //File handle signals an error condition.  We cannot
         //even read the file for CRC-32, MD-5, and SHA-512.  Just set info
         //and boogie.
         strcpy_s((char *)GFSW_file_info.file_info[fidx].crc32,  sizeof(GFSW_file_info.file_info[fidx].crc32),  "INVALID FILE HANDLE");
         strcpy_s((char *)GFSW_file_info.file_info[fidx].md5,    sizeof(GFSW_file_info.file_info[fidx].md5),    "INVALID FILE HANDLE");
         strcpy_s((char *)GFSW_file_info.file_info[fidx].sha512, sizeof(GFSW_file_info.file_info[fidx].sha512), "INVALID FILE HANDLE");
         }
      else
         {
         //This is the meat of the matter where we read the file contents and do
         //the hash calculations.  The assumption made is the the buffer size
         //will be somewhere in the range of 16K-1M, so that the time to process
         //that much data is fairly small.  This should be enough granularity 
         //for a graceful voluntary thread abort.
         //
         //Rewind the file to positon 0.
         rc = SetFilePointer(hFile, 0, NULL, FILE_BEGIN);
         if (rc == 0xFFFFFFFF)
            {
            strcpy_s((char *)GFSW_file_info.file_info[fidx].crc32,  sizeof(GFSW_file_info.file_info[fidx].crc32),  "FILE SEEK ERROR");
            strcpy_s((char *)GFSW_file_info.file_info[fidx].md5,    sizeof(GFSW_file_info.file_info[fidx].md5),    "FILE SEEK ERROR");
            strcpy_s((char *)GFSW_file_info.file_info[fidx].sha512, sizeof(GFSW_file_info.file_info[fidx].sha512), "FILE SEEK ERROR");
            goto file_read_loop_endpoint;
            }

         //Initialize the CRC-32 and MD-5 state blocks.
         CRCHASHFUNCS_Crc32StateStructOpen(&crc32s);
         ESRG_MD5_Md5StateStructOpen(&md5s);
         ESRG_SHA512_Sha512StateStructOpen(&sha512s);

         //Iterate through, reading the file and processing the blocks.  In the case
         //of an abort, we assign the strings appropriately.

         exit_flag = 0;
         while (!exit_flag)
            {
            rv = ReadFile(hFile, GFSW_file_read_buf, GFSW_FILE_READ_BUF_SIZE, &bytes_read, NULL);

            //Add whatever has been read to the running calculation.
            if (bytes_read)
               {
               CRCHASHFUNCS_Crc32StateStructAddData(&crc32s,  GFSW_file_read_buf, bytes_read);
               ESRG_MD5_Md5StateStructAddData      (&md5s,    GFSW_file_read_buf, bytes_read);
               ESRG_SHA512_Sha512StateStructAddData(&sha512s, GFSW_file_read_buf, bytes_read);
               }

            //Process error conditions.
            if (!rv)
               {
               strcpy_s((char *)GFSW_file_info.file_info[fidx].crc32,  sizeof(GFSW_file_info.file_info[fidx].crc32),  "FILE READ ERROR");
               strcpy_s((char *)GFSW_file_info.file_info[fidx].md5,    sizeof(GFSW_file_info.file_info[fidx].md5),    "FILE READ ERROR");
               strcpy_s((char *)GFSW_file_info.file_info[fidx].sha512, sizeof(GFSW_file_info.file_info[fidx].sha512), "FILE READ ERROR");
               goto file_read_loop_endpoint;
               }

            if (!bytes_read)
               {
               //This is the no-error abort when we hit the end of the file naturally.
               exit_flag = 1;
               }
            else if (GFSW_thread_abort_request)
               {
               strcpy_s((char *)GFSW_file_info.file_info[fidx].crc32,  sizeof(GFSW_file_info.file_info[fidx].crc32),  "OPERATION ABORTED");
               strcpy_s((char *)GFSW_file_info.file_info[fidx].md5,    sizeof(GFSW_file_info.file_info[fidx].md5),    "OPERATION ABORTED");
               strcpy_s((char *)GFSW_file_info.file_info[fidx].sha512, sizeof(GFSW_file_info.file_info[fidx].sha512), "OPERATION ABORTED");
               goto file_read_loop_endpoint;
               }
            }

         //This is the natural fallthrough when there was no error.
         //
         //Close up the CRC-32 structure.
         crc32 = CRCHASHFUNCS_Crc32Extract(&crc32s);
         CRCHASHFUNCS_Crc32StateStructClose(&crc32s);

         //Close up the MD-5 structure.
         ESRG_MD5_Md5StateStructClose(&md5s, &md5r);

                 //Close up the SHA-512 structure.
         ESRG_SHA512_Sha512StateStructClose(&sha512s, &sha512r);

         //Form up a CRC-32 string.
         sprintf_s((char *)GFSW_file_info.file_info[fidx].crc32, sizeof(GFSW_file_info.file_info[fidx].crc32), "%8.8X", crc32);

         //Form up an MD-5 string.
         strcpy_s((char *)GFSW_file_info.file_info[fidx].md5,    sizeof(GFSW_file_info.file_info[fidx].md5), md5r.md5_chars);

         //Form up an SHA-512 string.
         strcpy_s((char *)GFSW_file_info.file_info[fidx].sha512, sizeof(GFSW_file_info.file_info[fidx].sha512), sha512r.sha512_chars);

         //Report progress to parent thread.
         while (!PostMessage(GFSW_parent_thread_main_window_handle,
                             WM_USER_EV_CHILD_THREAD_PROGRESS,
                             0,
                             0))
            {
            Sleep(1000);  //Wait 1 second until trying again.
            }

         file_read_loop_endpoint: ;
         }

      //In any case both CRC32 and MD5 info filled in.
      GFSW_file_info.file_info[fidx].crc32_valid  = 1;
      GFSW_file_info.file_info[fidx].md5_valid    = 1;
      GFSW_file_info.file_info[fidx].sha512_valid = 1;

      //If the file handle is valid (i.e. we opened the file) we must
      //close it, regardless of cause.
      if (hFile != (HANDLE)-1)
         {
         BOOL close_result;

         close_result = CloseHandle(hFile);

         if (!close_result)
            {
            strcpy_s((char *)GFSW_file_info.file_info[fidx].crc32,  sizeof(GFSW_file_info.file_info[fidx].crc32),  "FILE HANDLE CLOSE ERROR");
            strcpy_s((char *)GFSW_file_info.file_info[fidx].md5,    sizeof(GFSW_file_info.file_info[fidx].md5),    "FILE HANDLE CLOSE ERROR");
            strcpy_s((char *)GFSW_file_info.file_info[fidx].sha512, sizeof(GFSW_file_info.file_info[fidx].sha512), "FILE HANDLE CLOSE ERROR");
            }
         }
      } // End for() each table entry loop.  


   //Report completion to parent thread.
   if (GFSW_thread_abort_request)
         GFSW_file_info.aborted = 1;
   else
         GFSW_file_info.terminated_normally = 1;

   while (!PostMessage(GFSW_parent_thread_main_window_handle,
                       WM_USER_EV_CHILD_THREAD_ENDING,
                       0,
                       0))
      {
      Sleep(1000);  //Wait 1 second until trying again.
      }

   return 0;
   }


//This function does a hard sync stop on the child thread if it is running.
//If not running, returns immediately.  Because the time to CRC32 or MD5 a
//single buffer is negligible, it shouldn't take long for the thread to 
//gracefully end itself.
static void GFSW_ChildThreadHardSyncStop(void)
   {
   if (GFSW_child_thread_is_active)
      {
      HMENU hMenu;

      GFSW_thread_abort_request = 1;

      WaitForSingleObject(GFSW_child_handle, INFINITE);

      //The thread is done.
      GFSW_child_thread_is_active = 0;
      GFSW_thread_abort_request   = 0;
      GFSW_child_handle           = 0;

      hMenu = GetMenu(GFSW_parent_thread_main_window_handle);

      EnableMenuItem(hMenu, ID_ACTIONS_HALTSIGOP, MF_GRAYED);
      }
   }


//Starts up a child thread.
static void GFSW_ChildThreadStart(void)
   {
   unsigned thread_id;
     //We just discard this.

   //We don't dare start up our single child thread unless none is already running.
   //In the release version, such an error is just ignored, but in the debug version,
   //hard stop.
   assert(!GFSW_child_thread_is_active);

   if (!GFSW_child_thread_is_active)
      {
      //Test compilation of second thread invocation.
      GFSW_child_handle = (HANDLE) _beginthreadex(NULL, 
                                                  0, 
                                                  &GFSW_ChildThreadFunc, 
                                                  NULL,
                                                  0,
                                                  &thread_id);
      if (!GFSW_child_handle)
         {
         //This is an error return from _beginthreadex.
         assert(0);
         }
      else
         {
         HMENU hMenu;

         GFSW_child_thread_is_active = 1;

         hMenu = GetMenu(GFSW_parent_thread_main_window_handle);

         EnableMenuItem(hMenu, ID_ACTIONS_HALTSIGOP, MF_ENABLED);
         }
      }
   }


//Makes a generic sound to alert user.  Honors the GFSW_use_sound state.
//
static void GFSW_MakeGenericSound(void)
   {
   if (GFSW_use_sound)
      {
      MessageBeep(MB_ICONEXCLAMATION);
      }
   }


/******************************************************************************
** $Log: gfsw.c,v $
** Revision 1.30  2009/11/29 02:16:04  dtashley
** Passed final review.
**
** Revision 1.29  2009/11/28 18:17:03  dtashley
** Development edits.
**
** Revision 1.28  2009/11/28 02:00:09  dtashley
** SHA-512 function calls added.
**
** Revision 1.27  2009/11/28 00:09:41  dtashley
** Addition of SHA512 module.
**
** Revision 1.26  2009/11/27 22:30:37  dtashley
** Warnings from newer version of Visual Studio addressed.
**
** Revision 1.25  2002/06/24 05:01:12  dtashley
** Additional documentation added for CreateFile() call.
**
** Revision 1.24  2002/06/23 07:11:55  dtashley
** Defect where would not CRC/MD5 files which were open in an application
** has been corrected.
**
** Revision 1.23  2002/05/21 06:11:07  dtashley
** Addition of version information including date and time compiled.
** Feedback from Dan Parks, Cory Pratt, and Raul Selgado moved to
** top of file and more tersely stated.
**
** Revision 1.22  2002/05/19 05:16:36  dtashley
** Additional usability by Cory Pratt added.
**
** Revision 1.21  2002/05/15 20:07:47  dtashley
** Feedback from Dan Parks, Dick McKamie, and Raul Selgado added.  This
** feedback represents things to do.
**
** Revision 1.20  2002/05/15 04:56:23  dtashley
** Minor issue with two contiguous backslashes appearing in file paths
** corrected.
**
** Revision 1.19  2002/05/14 09:50:36  dtashley
** Nearing completion of initial release of GFSW.
**
** Revision 1.18  2002/05/14 07:32:51  dtashley
** Safety checkin.
**
** Revision 1.17  2002/05/06 07:11:24  dtashley
** Safety checkin.
**
** Revision 1.16  2002/05/04 09:07:51  dtashley
** Substantial strides towards completion.
**
** Revision 1.15  2002/05/03 09:42:04  dtashley
** Completion of work on laptop.  Current solution has trouble when doing
** an exit while child thread running--need to see if this also happens
** on Win2k and resolve.  Near completion.
**
** Revision 1.14  2002/05/03 07:31:16  dtashley
** Preparing to work on laptop again.
**
** Revision 1.13  2002/05/03 05:08:28  dtashley
** Work complete on laptop.
**
** Revision 1.12  2002/05/03 04:31:30  dtashley
** Checkins before working on laptop computer.
**
** Revision 1.11  2002/05/03 00:32:23  dtashley
** Checkins before working on laptop computer.
**
** Revision 1.10  2002/05/02 12:08:59  dtashley
** Edits on laptop towards multithreading.
**
** Revision 1.9  2002/05/02 04:06:25  dtashley
** MD5 module working correctly, pending review of code.
**
** Revision 1.8  2002/05/01 21:51:44  dtashley
** Completion of MD5 implementation.  Implementation does not work correctly,
** and need to debug.  Noticed in MD5 result that first hex digit of MD5 digest
** is always "8"--this is definitely a problem as this can't happen in practice.
** Checking in for baseline to debug.
**
** Revision 1.7  2002/04/30 05:31:21  dtashley
** Minor mouse wheel handling change.  Suspect that somehow integer counts
** were getting out of sync.  May need to resolve later.
**
** Revision 1.6  2002/04/30 05:03:42  dtashley
** Final checkin before addition of MD5.
**
** Revision 1.5  2002/04/30 00:03:12  dtashley
** Code straightened up--ready for line-by-line review.
**
** Revision 1.4  2002/04/29 19:43:54  dtashley
** Safety checkin.
**
** Revision 1.3  2002/04/29 06:18:04  dtashley
** Evening safety checkin.
**
** Revision 1.2  2002/04/28 06:15:48  dtashley
** Safety checkin.
**
** Revision 1.1  2002/04/28 05:37:39  dtashley
** Initial checkin.
*******************************************************************************
** End of GFSW.C. */