Question

i have locked my file from 0 to 5 bytes, and i write some character byte by byte but it does not stop writing even if the file is locked, i dont know what is wrong, i have tried every type of flag in createFile function, but no success, please help.

#include <windows.h>
#include <tchar.h>
#include <stdio.h>
#include <strsafe.h>
#include <stdlib.h>

void __cdecl _tmain(int argc, TCHAR *argv[])
{
DWORD dwBytesWritten;
HANDLE hFile;
BOOL filesize= FALSE;
LARGE_INTEGER pl_int;
PLARGE_INTEGER pli_int = &pl_int;
char * Buffer = (char *)malloc (1);
Buffer[0]='0';
printf("Detect Lock Process Started\n");
hFile = CreateFile(argv[1],         // open One.txt
          GENERIC_WRITE|GENERIC_READ,             // open for reading
          FILE_SHARE_READ | FILE_SHARE_WRITE,           // do not share
          NULL,                     // no security
          OPEN_EXISTING,            // existing file only
          FILE_ATTRIBUTE_NORMAL,    // normal file
          NULL);                    // no attr. template

if (hFile == INVALID_HANDLE_VALUE)
{
   printf("Could not open %s\n",argv[1]); 
   return;
}
filesize = GetFileSizeEx(hFile, pli_int);

__int64 fsizes= (__int64)(pli_int->QuadPart);

if (filesize == FALSE)
    printf("Could not get file size\n");
else
    _tprintf(TEXT("%s (%d bytes) \n"), argv[1], fsizes);

bool lock = LockFile(hFile,5,0,10,0);
if (lock == FALSE)
    printf("lockfailed\n");
for(int x=0; x < fsizes; x++)
{
    if (!WriteFile(hFile,Buffer,1,&dwBytesWritten,NULL))
    //if (!ReadFile(hFile,Buffer,1,&dwBytesWritten,NULL))
    {
        printf("File Locked-could not Write file at byte %d\n",x);

    }
    else
        printf("File Written at byte %d\n",x);
}
free(Buffer);
CloseHandle(hFile);

}

THE MAIN PROCESS THAT CALLS THIS PROCESS IS BELOW, i didnt mention it earlier, sorry abt that.

#include <windows.h>
#include <tchar.h>
#include <stdio.h>
#include <strsafe.h>
#include <stdlib.h>

void DisplayError(LPTSTR lpszFunction);

void __cdecl _tmain(int argc, TCHAR *argv[])
{
HANDLE hFile;


if(argc < 4 || argc%2 != 0) //check if low count or odd count
{
    printf("Wrong set of parameters \n");
    printf("Parameters=>  <lockfile> <File Name> (<Lock region Start value> <Lock        reigion Stop value>......)\n");
    return;
}
if (argc > 12)
{
    printf("Too many arguments\n");
    return;
}
// Open the existing file.

hFile = CreateFile(argv[1],         // open One.txt
          GENERIC_READ,             // open for reading
          FILE_SHARE_READ | FILE_SHARE_WRITE,           // do not share
          NULL,                     // no security
          OPEN_EXISTING,            // existing file only
          FILE_ATTRIBUTE_NORMAL,    // normal file
          NULL);                    // no attr. template

if (hFile == INVALID_HANDLE_VALUE)
{
   printf("Could not open %s\n",argv[1]); 
   return;
}


int i=argc-2;
int count[10];
for (int j=0; j<i; j++)
{
    count[j]=_ttoi(argv[2+j]);
}


for(int z=0; z<i; z=z+2)
{
    if(!LockFile(hFile,count[z],0,count[z+1]-count[z],0))
        DisplayError(TEXT("LockFile"));
    else
        printf("file locked from %d to %d bytes\n",count[z],count[z+1]);
} 
STARTUPINFO si;
PROCESS_INFORMATION pi;
printf("Calling Detect Lock\n");
ZeroMemory( &si, sizeof(si) );
si.cb = sizeof(si);
ZeroMemory( &pi, sizeof(pi) );

LPTSTR szCmdline = _tcsdup(TEXT("C:\\detectlock\\Debug\\detectlock.exe ass23.txt"));

if( !CreateProcess( NULL,   // No module name (use command line)
    szCmdline,        // Command line
    NULL,           // Process handle not inheritable
    NULL,           // Thread handle not inheritable
    FALSE,          // Set handle inheritance to FALSE
    0,              // No creation flags
    NULL,           // Use parent's environment block
    NULL,           // Use parent's starting directory 
    &si,            // Pointer to STARTUPINFO structure
    &pi )           // Pointer to PROCESS_INFORMATION structure
) 
{
    printf( "CreateProcess failed (%d)\n", GetLastError() );
    return;
}

// Wait until child process exits.
WaitForSingleObject( pi.hProcess, INFINITE );

// Close process and thread handles. 
CloseHandle( pi.hProcess );
CloseHandle( pi.hThread );
CloseHandle(hFile);
//CloseHandle(hAppend);



}

Answer 1

From the MSDN article for LockFile():

Locks the specified file for exclusive access by the calling process.

Well, that surely worked. Your test is not verifying if another process is locked out of the file.