boost/pending/stringtok.hpp

   1 //  (C) Copyright Jeremy Siek 2004
   2 //  Distributed under the Boost Software License, Version 1.0. (See
   3 //  accompanying file LICENSE_1_0.txt or copy at
   4 //  http://www.boost.org/LICENSE_1_0.txt)
   5
   6 #ifndef BOOST_STRINGTOK_HPP
   7 #define BOOST_STRINGTOK_HPP
   8
   9 /*
  10  * stringtok.hpp -- Breaks a string into tokens.  This is an example for lib3.
  11  *
  12  * Template function looks like this:
  13  *
  14  *    template <typename Container>
  15  *    void stringtok (Container &l,
  16  *                    string const &s,
  17  *                    char const * const ws = " \t\n");
  18  *
  19  * A nondestructive version of strtok() that handles its own memory and can
  20  * be broken up by any character(s).  Does all the work at once rather than
  21  * in an invocation loop like strtok() requires.
  22  *
  23  * Container is any type that supports push_back(a_string), although using
  24  * list<string> and deque<string> are indicated due to their O(1) push_back.
  25  * (I prefer deque<> because op[]/at() is available as well.)  The first
  26  * parameter references an existing Container.
  27  *
  28  * s is the string to be tokenized.  From the parameter declaration, it can
  29  * be seen that s is not affected.  Since references-to-const may refer to
  30  * temporaries, you could use stringtok(some_container, readline("")) when
  31  * using the GNU readline library.
  32  *
  33  * The final parameter is an array of characters that serve as whitespace.
  34  * Whitespace characters default to one or more of tab, space, and newline,
  35  * in any combination.
  36  *
  37  * 'l' need not be empty on entry.  On return, 'l' will have the token
  38  * strings appended.
  39  *
  40  *
  41  * [Example:
  42  *       list<string>       ls;
  43  *       stringtok (ls, " this  \t is\t\n  a test  ");
  44  *       for (list<string>::const_iterator i = ls.begin();
  45  *            i != ls.end(); ++i)
  46  *       {
  47  *            cerr << ':' << (*i) << ":\n";
  48  *       }
  49  *
  50  *  would print
  51  *       :this:
  52  *       :is:
  53  *       :a:
  54  *       :test:
  55  * -end example]
  56  *
  57  * pedwards@jaj.com  May 1999
  58 */
  59
  60
  61 #include <string>
  62 #include <cstring>    // for strchr
  63
  64
  65 /*****************************************************************
  66  * This is the only part of the implementation that I don't like.
  67  * It can probably be improved upon by the reader...
  68 */
  69
  70     inline bool
  71     isws (char c, char const * const wstr)
  72     {
  73         using namespace std;
  74         return (strchr(wstr,c) != NULL);
  75     }
  76
  77
  78 namespace boost {
  79
  80 /*****************************************************************
  81  * Simplistic and quite Standard, but a bit slow.  This should be
  82  * templatized on basic_string instead, or on a more generic StringT
  83  * that just happens to support ::size_type, .substr(), and so on.
  84  * I had hoped that "whitespace" would be a trait, but it isn't, so
  85  * the user must supply it.  Enh, this lets them break up strings on
  86  * different things easier than traits would anyhow.
  87 */
  88 template <typename Container>
  89 void
  90 stringtok (Container &l, std::string const &s, char const * const ws = " \t\n")
  91 {
  92   typedef std::string::size_type size_type;
  93     const size_type  S = s.size();
  94           size_type  i = 0;
  95
  96     while (i < S) {
  97         // eat leading whitespace
  98         while ((i < S) && (isws(s[i],ws)))  ++i;
  99         if (i == S)  return;  // nothing left but WS
 100
 101         // find end of word
 102         size_type  j = i+1;
 103         while ((j < S) && (!isws(s[j],ws)))  ++j;
 104
 105         // add word
 106         l.push_back(s.substr(i,j-i));
 107
 108         // set up for next loop
 109         i = j+1;
 110     }
 111 }
 112
 113
 114 } // namespace boost
 115
 116 #endif // BOOST_STRINGTOK_HPP