reworked regex directory structure to match boost requirements.

[SVN r9752]

example/snippets/partial_regex_grep.cpp

@@ -0,0 +1,82 @@
+
+#include <iostream>
+#include <fstream>
+#include <sstream>
+#include <string>
+#include <boost/regex.hpp>
+
+// match some kind of html tag:
+boost::regex e("<[^>]*>");
+// count how many:
+unsigned int tags = 0;
+// saved position of partial match:
+char* next_pos = 0;
+
+bool grep_callback(const boost::match_results<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:
+      unsigned leftover = (buf + sizeof(buf)) - next_pos;
+      // and how much is left to fill:
+      unsigned size = next_pos - buf;
+      // copy forward whatever we have left:
+      memcpy(buf, next_pos, leftover);
+      // fill the rest from the stream:
+      unsigned read = is.readsome(buf + leftover, size);
+      // 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(grep_callback,
+                        buf,
+                        buf + read + leftover,
+                        e,
+                        boost::match_default | boost::match_partial);
+   }
+}
+
+int main(int argc, char* argv[])
+{
+   if(argc > 1)
+   {
+      for(unsigned int i = 1; i < argc; ++i)
+      {
+         std::ifstream fs(argv[i]);
+         if(fs.bad()) continue;
+         search(fs);
+      }
+   }
+   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;
+}
+