Re: find a pattern in binary file

Kai-Uwe Bux <>
Fri, 20 Jun 2008 20:13:13 -0400
Ivan wrote:

On Jun 20, 1:11?pm, vizzz <> wrote:

Hi there,
i need to find an hex pattern like 0x650A1010 in a binary file.
i can make a small algorithm that fetch all the file for the match,
but this file is huge, and i'm scared about performances.
Is there any stl method for a fast search?

Hmmm... I had a look at this and ran accross a simple problem. How do
you read a binary file and just echo the HEX for byte to the screen.

#include <iostream>
#include <ostream>
#include <fstream>
#include <iterator>
#include <iomanip>
#include <algorithm>
#include <cassert>

class print_hex {

  std::ostream * ostr_ptr;
  unsigned int line_length;
  unsigned int index;


  print_hex ( std::ostream & str_ref, unsigned int length )
    : ostr_ptr( &str_ref )
    , line_length ( length )
    , index ( 0 )

  void operator() ( unsigned char ch ) {
    if ( index >= line_length ) {
      (*ostr_ptr) << std::hex << std::setw(2) << std::setfill( '0' )
                  << (unsigned int)(ch) << '\n';
      index = 0;
    } else {
      (*ostr_ptr) << std::hex << std::setw(2) << std::setfill( '0' )
                  << (unsigned int)(ch) << ' ';


int main ( int argn, char ** args ) {
  assert( argn == 2 );
  std::ifstream in ( args[1] );
  std::for_each( std::istreambuf_iterator< char >( in ),
                 std::istreambuf_iterator< char >(),
                 print_hex( std::cout, 25 ) );
  std::cout << '\n';

The issue is the c++ read function doesn't return number of bytes
read... so on the last read into a buffer how do you know how many
characters to print?

Have a look at readsome().


Kai-Uwe Bux

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