RLE: encode by two symbols - c++

Question

I've created RLE encoding function, which encodes sequences like "A1A1B7B7B7B7" to such strings: "#A12#B74".
void encode(const char *input_path, const char *output_path)
{ // Begin of SBDLib::SBIMask::encode
std::fstream input(input_path, std::ios_base::in | std::ios_base::binary);
std::fstream output(output_path, std::ios_base::out | std::ios_base::binary);
int size = 0; // Set size variable
input.seekg(0, std::ios::end); // Move to EOF
size = input.tellg(); // Tell position
input.seekg(0); // Move to the beginning
int i = 1; // Create encoding counter
int counter = 0; // Create color counter
int cbyte1, cbyte2; // Create current color bytes
int pbyte1 = 0x0; int pbyte2 = 0x0; // Create previous color bytes
while (((cbyte1 = input.get()) != EOF && (cbyte2 = input.get()) != EOF)
|| input.tellg() >= size)
{ // Begin of while
// If current bytes are not equal to previous bytes
// or cursor is at the end of the input file, write
// binary data to file; don't do it if previous bytes
// were not set from 0x0 to any other integer.
if (((cbyte1 != pbyte1 || cbyte2 != pbyte2)
|| (input.tellg() == size))
&& (pbyte1 != 0x0 && pbyte2 != 0x0))
{ // Begin of main if
output << SEPARATOR; // Write separator to file
output.write(reinterpret_cast<const char*>(&pbyte1), 1);
output.write(reinterpret_cast<const char*>(&pbyte2), 1);
output << std::hex << counter; // Write separator, bytes and count
counter = 1; // Reset counter
} // End of main if
else counter++; // Increment counter
pbyte1 = cbyte1; pbyte2 = cbyte2; // Set previous bytes
} // End of main while
} // End of encode
However, function is not as fast as I need. This is the second version of function, I've already improved it to make it faster, but it is still too slow. Do you have any ideas how to improve? I'm lack of ideas.

Answer 1

Depending on the size of data you are reading from files it might be a good idea not to read single charcaters but a chunk of data from your input file at once. This might be a lot faster than accessing the input file on the disk for each input character.
Pseudo code example:
char dataArray[100];
while( !EOF )
{
input.get( &dataArray[0], 100 ); // read a block of data not a single charater
process( dataArray ); // process one line
}