void CLogViewer::OnActivate(UINT nState, CWnd* pWndOther, BOOL bMinimized)
{
CDialog::OnActivate(nState, pWndOther, bMinimized);
if (!_init)
{
PrintHelpText();
_init = true;
}
}
int main(int argc, char *argv[])
{
LARGE_INTEGER FileSize, AmountToRead = { 0 };
DWORD BytesRead = 0;
char ReadBuffer[1024] = {};
// NTFS supports paths up to 32767. If path is greater than MAX_PATH (260,) need to prefix with \\?\.
// It's OK if we always prefix with \\?\, even with short file paths.
char FilePath[32000] = { '\\', '\\', '?', '\\', 0 };
int StartFromEndOfFile = 0;
int ReadInLines = 0;
if (argc != 5)
{
PrintHelpText();
return(1);
}
// Loop through all command-line arguments, convert them to lower case,
// then validate them.
// E.g. C:\> readpart c:\files\huge.log last 1024 bytes
for (int ArgNumber = 1; ArgNumber < argc; ArgNumber++)
{
char *arg = argv[ArgNumber];
for (int y = 0; y < strlen(arg); y++)
arg[y] = (char)tolower(arg[y]);
// We are on the first argument, i.e. file path
if (ArgNumber == 1)
{
if (strlen(arg) > sizeof(FilePath))
{
printf("\nThe specified file path is too long.\n");
return(1);
}
for (int z = 0; z < strlen(arg); z++)
FilePath[z + 4] = arg[z];
}
// We are on the second argument, i.e. first or last
if (ArgNumber == 2)
{
if (strcmp(arg, "last") == 0)
{
StartFromEndOfFile = 1;
}
else if (strcmp(arg, "first") == 0)
{
// Do nothing because StartFromEndOfFile is already false by default.
}
else
{
printf("\nSecond argument must be either \"first\" or \"last\"!\n");
return(1);
}
}
// We are on the third argument, i.e. a number of bytes or number of lines
if (ArgNumber == 3)
{
AmountToRead.QuadPart = strtoull(arg, NULL, 10);
if (AmountToRead.QuadPart < 1 || AmountToRead.QuadPart > 107374182400)
{
printf("\nNumber of bytes or lines to read was out of range!\n");
return(1);
}
}
// We are on the fourth argument, i.e. bytes or lines
if (ArgNumber == 4)
{
if (strcmp(arg, "bytes") == 0)
{
// Do nothing because ReadInLines is already 0 by default.
}
else if (strcmp(arg, "lines") == 0)
{
ReadInLines = 1;
}
else
{
printf("\nFourth argument must be either \"bytes\" or \"lines\"!\n");
return(1);
}
}
}
HANDLE FileHandle = CreateFile(FilePath,
GENERIC_READ,
FILE_SHARE_READ,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL);
if (FileHandle == INVALID_HANDLE_VALUE)
{
printf("\nCould not open file! (Error Code %d)\n", GetLastError());
return(1);
}
if (GetFileSizeEx(FileHandle, &FileSize) == 0)
{
printf("\nUnable to get file size! (Error Code %d)\n", GetLastError());
return(1);
}
if (AmountToRead.QuadPart >= FileSize.QuadPart)
{
AmountToRead.QuadPart = FileSize.QuadPart;
}
DWORD64 TotalBytesRead = 0;
DWORD NewLinesFound = 0;
if (StartFromEndOfFile)
{
if (ReadInLines)
{
// Read the last X lines from the file.
LARGE_INTEGER CurrentFilePosition = FileSize;
while (TotalBytesRead < (DWORD64)FileSize.QuadPart)
{
if (NewLinesFound >= AmountToRead.QuadPart)
break;
char SingleCharReadBuffer = 0;
if (SetFilePointerEx(FileHandle, CurrentFilePosition, NULL, FILE_BEGIN) == 0)
{
printf("\nUnable to seek to position in file! (Error Code %d)\n", GetLastError());
return(1);
}
if (ReadFile(FileHandle, &SingleCharReadBuffer, 1, &BytesRead, NULL) == 0)
{
printf("\nUnable to read from file! (Error Code %d)\n", GetLastError());
return(1);
}
if (SingleCharReadBuffer == '\n')
NewLinesFound++;
TotalBytesRead++;
CurrentFilePosition.QuadPart--;
}
while (ReadFile(FileHandle, ReadBuffer, sizeof(ReadBuffer), &BytesRead, NULL) && BytesRead)
{
for (DWORD x = 0; x < BytesRead; x++)
printf("%c", ReadBuffer[x]);
}
}
else
{
// Read the last X bytes from the file.
// Set the file pointer to negative AmountToRead bytes from the end of file.
AmountToRead.QuadPart *= -1;
if (SetFilePointerEx(FileHandle, AmountToRead, NULL, FILE_END) == 0)
{
printf("\nUnable to seek to position in file! (Error Code %d)\n", GetLastError());
return(1);
}
while (ReadFile(FileHandle, ReadBuffer, sizeof(ReadBuffer), &BytesRead, NULL) && BytesRead)
{
for (DWORD x = 0; x < BytesRead; x++)
printf("%c", ReadBuffer[x]);
}
}
}
else
{
if (ReadInLines)
{
// Read the first X lines from the file.
while (TotalBytesRead < (DWORD64)FileSize.QuadPart)
{
if (NewLinesFound >= AmountToRead.QuadPart)
break;
DWORD64 BytesRemaining = (DWORD64)FileSize.QuadPart - TotalBytesRead;
if (BytesRemaining < sizeof(ReadBuffer))
ReadFile(FileHandle, ReadBuffer, (DWORD)BytesRemaining, &BytesRead, NULL);
else
ReadFile(FileHandle, ReadBuffer, sizeof(ReadBuffer), &BytesRead, NULL);
TotalBytesRead += BytesRead;
for (DWORD x = 0; x < BytesRead; x++)
{
if (ReadBuffer[x] == '\n')
NewLinesFound++;
if (NewLinesFound >= AmountToRead.QuadPart)
break;
printf("%c", ReadBuffer[x]);
}
}
}
else
{
// Read number of bytes starting from the beginning of the file.
while (TotalBytesRead < (DWORD64)AmountToRead.QuadPart)
{
DWORD64 BytesRemaining = (DWORD64)AmountToRead.QuadPart - TotalBytesRead;
if (BytesRemaining < sizeof(ReadBuffer))
ReadFile(FileHandle, ReadBuffer, (DWORD)BytesRemaining, &BytesRead, NULL);
else
ReadFile(FileHandle, ReadBuffer, sizeof(ReadBuffer), &BytesRead, NULL);
TotalBytesRead += BytesRead;
for (DWORD x = 0; x < BytesRead; x++)
printf("%c", ReadBuffer[x]);
}
}
}
printf("\n");
return(0);
}
