libs/regex/example/snippets/partial_regex_grep.cpp
/*
*
* Copyright (c) 1998-2002
* John Maddock
*
* Use, modification and distribution are subject to the
* Boost Software License, Version 1.0. (See accompanying file
* LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
*
*/
/*
* LOCATION: see http://www.boost.org for most recent version.
* FILE partial_regex_grep.cpp
* VERSION see <boost/version.hpp>
* DESCRIPTION: Search example using partial matches.
*/
#include <boost/regex.hpp>
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <cstring>
#ifdef BOOST_NO_STDC_NAMESPACE
namespace std{ using ::memmove; }
#endif
// match some kind of html tag:
boost::regex e("<[^>]*>");
// count how many:
unsigned int tags = 0;
// saved position of partial match:
const char* next_pos = 0;
bool grep_callback(const boost::match_results<const char*>& m)
{
if(m[0].matched == false)
{
// save position and return:
next_pos = m[0].first;
}
else
++tags;
return true;
}
void search(std::istream& is)
{
char buf[4096];
next_pos = buf + sizeof(buf);
bool have_more = true;
while(have_more)
{
// how much do we copy forward from last try:
std::ptrdiff_t leftover = (buf + sizeof(buf)) - next_pos;
// and how much is left to fill:
std::ptrdiff_t size = next_pos - buf;
// copy forward whatever we have left:
std::memmove(buf, next_pos, leftover);
// fill the rest from the stream:
is.read(buf + leftover, size);
std::streamsize read = is.gcount();
// check to see if we've run out of text:
have_more = read == size;
// reset next_pos:
next_pos = buf + sizeof(buf);
// and then grep:
boost::regex_grep<bool(*)(const boost::cmatch&), const char*>(grep_callback,
static_cast<const char*>(buf),
static_cast<const char*>(buf + read + leftover),
e,
boost::match_default | boost::match_partial);
}
}
int main(int argc, char* argv[])
{
if(argc > 1)
{
for(int i = 1; i < argc; ++i)
{
std::ifstream fs(argv[i]);
if(fs.bad()) continue;
search(fs);
fs.close();
}
}
else
{
std::string one("<META NAME=\"keywords\" CONTENT=\"regex++, regular expressions, regular expression library, C++\">");
std::string what;
while(what.size() < 10000)
{
what.append(one);
what.append(13, ' ');
}
std::stringstream ss;
ss.str(what);
search(ss);
}
std::cout << "total tag count was " << tags << std::endl;
return 0;
}