Read/write operation works neither good nor bad - c++

Question

I am programming a face detection algorithm. In my code I'm parsing an XML file (in a recursion way, very inefficient takes my about 4 minutes to parse the whole XML file). I'd like to save the XML content using Iosteam binary to a file. I'm using a struct in C++ in order to use the raw data.
My goal is to parse the XML only if the raw data file is not exist.
The method work like this:
If the raw data file is not exist, parse the XML file and save the data to a file.
If the raw data file exist, read the raw data from the file
My problem is: whenever I open the raw data file and read from it. I get to read only small amount of byte from the file, I don't know how much, but in a certain point I receive only 0x00 data on my buffer.
My guess: I believe this has to do with the OS buffer, Which has a certain amount of buffer for read and write operations. I might be wrong about this. Though I'm not sure which one from the operations doesn't work well, it's either the write or read.
I was thinking to write / read the raw data char by char or line by line. In the other hand the file doesn't contain a text, which means that I can't read line by line or char by char.
The raw data size is
size_t datasize = DataSize(); == 196876 (Byte)
Which is retrieve in this function
/* Get the upper bound for predefined cascade size */
size_t CCacadeInterpreter::DataSize()
{
// this is an upper boundary for the whole hidden cascade size
size_t datasize = sizeof(HaarClassifierCascade) * TOTAL_CASCADE+
sizeof(HaarStageClassifier)*TOTAL_STAGES +
sizeof(HaarClassifier) * TOTAL_CLASSIFIERS +
sizeof(void*)*(TOTAL_CASCADE+TOTAL_STAGES+TOTAL_CLASSIFIERS);
return datasize;
}
The method work like this
BYTE * CCacadeInterpreter::Interpreter()
{
printf("|Phase - Load cascade from memory | CCacadeInterpreter::Interpreter | \n");
size_t datasize = DataSize();
// Create a memory structure
nextFreeSpace = pStartMemoryLocation = new BYTE [datasize];
memset(nextFreeSpace,0x00,datasize);
// Try to open a predefined cascade file on the current folder (instead of parsing the file again)
fstream stream;
stream.open(cascadeSavePath); // ...try existing file
if (stream.is_open())
{
stream.seekg(0,ios::beg);
stream.read((char*)pStartMemoryLocation , datasize); // **ream from file**
stream.close();
printf("|Load cascade from saved memory location | CCacadeInterpreter::Interpreter | \n");
printf("Completed\n\n");
stream.close();
return pStartMemoryLocation;
}
// Open the cascade file and parse the cascade xml file
std::fstream cascadeFile;
cascadeFile.open(cascadeDestanationPath, std::fstream::in); // open the file with read only attributes
if (!cascadeFile.is_open())
{
printf("Error: couldn't open cascade XML file\n");
delete pStartMemoryLocation;
return NULL;
}
// Read the file XML file , line by line
string buffer, str;
getline(cascadeFile,str);
while(cascadeFile)
{
buffer+=str;
getline(cascadeFile,str);
}
cascadeFile.close();
split(buffer, '<',m_tokens);
// Parsing begins
pHaarClassifierCascade = (HaarClassifierCascade*)nextFreeSpace;
nextFreeSpace += sizeof(HaarClassifierCascade);
pHaarClassifierCascade->count=0;
pHaarClassifierCascade->orig_window_size_height=20;
pHaarClassifierCascade->orig_window_size_width=20;
m_deptInTree=0;
m_numOfStage = 0;
m_numOfTotalClassifiers=0;
while (m_tokens.size())
{
Parsing();
}
// Save the current cascade into a file
SaveBlockToMemory(pStartMemoryLocation,datasize);
printf("\nCompleted\n\n");
return pStartMemoryLocation;
}
bool CCacadeInterpreter::SaveBlockToMemory(BYTE * pStartMemoryLocation,size_t dataSize)
{
fstream stream;
if (stream.is_open() )
stream.close();
stream.open(cascadeSavePath); // ...try existing file
if (!stream.is_open()) // ...else, create new file...
stream.open(cascadeSavePath, ios_base::in | ios_base::out | ios_base::trunc);
stream.seekg(0,ios::beg);
stream.write((char*)pStartMemoryLocation,dataSize);
stream.close();
return true;
}

Answer 1

Try using the Boost IOstreams library.
It has an easy to use wrrapers for file handling