117 lines
3.5 KiB
C++
117 lines
3.5 KiB
C++
// (C) Copyright Jeremy Siek 2004
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_STRINGTOK_HPP
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#define BOOST_STRINGTOK_HPP
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/*
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* stringtok.hpp -- Breaks a string into tokens. This is an example for lib3.
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*
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* Template function looks like this:
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*
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* template <typename Container>
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* void stringtok (Container &l,
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* string const &s,
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* char const * const ws = " \t\n");
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*
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* A nondestructive version of strtok() that handles its own memory and can
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* be broken up by any character(s). Does all the work at once rather than
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* in an invocation loop like strtok() requires.
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*
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* Container is any type that supports push_back(a_string), although using
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* list<string> and deque<string> are indicated due to their O(1) push_back.
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* (I prefer deque<> because op[]/at() is available as well.) The first
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* parameter references an existing Container.
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*
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* s is the string to be tokenized. From the parameter declaration, it can
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* be seen that s is not affected. Since references-to-const may refer to
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* temporaries, you could use stringtok(some_container, readline("")) when
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* using the GNU readline library.
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*
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* The final parameter is an array of characters that serve as whitespace.
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* Whitespace characters default to one or more of tab, space, and newline,
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* in any combination.
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*
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* 'l' need not be empty on entry. On return, 'l' will have the token
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* strings appended.
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*
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*
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* [Example:
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* list<string> ls;
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* stringtok (ls, " this \t is\t\n a test ");
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* for (list<string>::const_iterator i = ls.begin();
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* i != ls.end(); ++i)
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* {
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* cerr << ':' << (*i) << ":\n";
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* }
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*
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* would print
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* :this:
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* :is:
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* :a:
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* :test:
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* -end example]
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*
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* pedwards@jaj.com May 1999
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*/
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#include <string>
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#include <cstring> // for strchr
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/*****************************************************************
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* This is the only part of the implementation that I don't like.
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* It can probably be improved upon by the reader...
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*/
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inline bool
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isws (char c, char const * const wstr)
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{
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using namespace std;
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return (strchr(wstr,c) != NULL);
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}
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namespace boost {
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/*****************************************************************
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* Simplistic and quite Standard, but a bit slow. This should be
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* templatized on basic_string instead, or on a more generic StringT
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* that just happens to support ::size_type, .substr(), and so on.
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* I had hoped that "whitespace" would be a trait, but it isn't, so
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* the user must supply it. Enh, this lets them break up strings on
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* different things easier than traits would anyhow.
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*/
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template <typename Container>
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void
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stringtok (Container &l, std::string const &s, char const * const ws = " \t\n")
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{
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typedef std::string::size_type size_type;
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const size_type S = s.size();
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size_type i = 0;
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while (i < S) {
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// eat leading whitespace
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while ((i < S) && (isws(s[i],ws))) ++i;
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if (i == S) return; // nothing left but WS
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// find end of word
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size_type j = i+1;
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while ((j < S) && (!isws(s[j],ws))) ++j;
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// add word
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l.push_back(s.substr(i,j-i));
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// set up for next loop
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i = j+1;
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}
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}
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} // namespace boost
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#endif // BOOST_STRINGTOK_HPP
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