boost/property_tree/string_path.hpp
// ----------------------------------------------------------------------------
// Copyright (C) 2009 Sebastian Redl
//
// Distributed under 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)
//
// For more information, see www.boost.org
// ----------------------------------------------------------------------------
#ifndef BOOST_PROPERTY_TREE_STRING_PATH_HPP_INCLUDED
#define BOOST_PROPERTY_TREE_STRING_PATH_HPP_INCLUDED
#include <boost/property_tree/ptree_fwd.hpp>
#include <boost/property_tree/id_translator.hpp>
#include <boost/property_tree/exceptions.hpp>
#include <boost/property_tree/detail/ptree_utils.hpp>
#include <boost/static_assert.hpp>
#include <boost/assert.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/optional/optional.hpp>
#include <boost/throw_exception.hpp>
#include <algorithm>
#include <string>
#include <iterator>
namespace boost { namespace property_tree
{
namespace detail
{
template <typename Sequence, typename Iterator>
void append_and_preserve_iter(Sequence &s, const Sequence &r,
Iterator &, std::forward_iterator_tag)
{
// Here we boldly assume that anything that is not random-access
// preserves validity. This is valid for the STL sequences.
s.insert(s.end(), r.begin(), r.end());
}
template <typename Sequence, typename Iterator>
void append_and_preserve_iter(Sequence &s, const Sequence &r,
Iterator &it,
std::random_access_iterator_tag)
{
// Convert the iterator to an index, and later back.
typename std::iterator_traits<Iterator>::difference_type idx =
it - s.begin();
s.insert(s.end(), r.begin(), r.end());
it = s.begin() + idx;
}
template <typename Sequence>
inline std::string dump_sequence(const Sequence &)
{
return "<undumpable sequence>";
}
inline std::string dump_sequence(const std::string &s)
{
return s;
}
#ifndef BOOST_NO_STD_WSTRING
inline std::string dump_sequence(const std::wstring &s)
{
return narrow<std::string>(s.c_str());
}
#endif
}
/// Default path class. A path is a sequence of values. Groups of values
/// are separated by the separator value, which defaults to '.' cast to
/// the sequence's value type. The group of values is then passed to the
/// translator to get a key.
///
/// If instantiated with std::string and id_translator\<std::string\>,
/// it accepts paths of the form "one.two.three.four".
///
/// @tparam String Any Sequence. If the sequence does not support random-
/// access iteration, concatenation of paths assumes that
/// insertions at the end preserve iterator validity.
/// @tparam Translator A translator with internal_type == String.
template <typename String, typename Translator>
class string_path
{
BOOST_STATIC_ASSERT((is_same<String,
typename Translator::internal_type>::value));
public:
typedef typename Translator::external_type key_type;
typedef typename String::value_type char_type;
/// Create an empty path.
explicit string_path(char_type separator = char_type('.'));
/// Create a path by parsing the given string.
/// @param value A sequence, possibly with separators, that describes
/// the path, e.g. "one.two.three".
/// @param separator The separator used in parsing. Defaults to '.'.
/// @param tr The translator used by this path to convert the individual
/// parts to keys.
string_path(const String &value, char_type separator = char_type('.'),
Translator tr = Translator());
/// Create a path by parsing the given string.
/// @param value A zero-terminated array of values. Only use if zero-
/// termination makes sense for your type, and your
/// sequence supports construction from it. Intended for
/// string literals.
/// @param separator The separator used in parsing. Defaults to '.'.
/// @param tr The translator used by this path to convert the individual
/// parts to keys.
string_path(const char_type *value,
char_type separator = char_type('.'),
Translator tr = Translator());
// Default copying doesn't do the right thing with the iterator
string_path(const string_path &o);
string_path& operator =(const string_path &o);
/// Take a single element off the path at the front and return it.
key_type reduce();
/// Test if the path is empty.
bool empty() const;
/// Test if the path contains a single element, i.e. no separators.
bool single() const;
/// Get the separator used by this path.
char_type separator() const { return m_separator; }
std::string dump() const {
return detail::dump_sequence(m_value);
}
/// Concatenates two path components
friend string_path operator /(string_path p1, const string_path &p2)
{
p1 /= p2;
return p1;
}
/// Append a second path to this one.
/// @pre o's separator is the same as this one's, or o has no separators
string_path& operator /=(const string_path &o) {
// If it's single, there's no separator. This allows to do
// p /= "piece";
// even for non-default separators.
BOOST_ASSERT((m_separator == o.m_separator
|| o.empty()
|| o.single())
&& "Incompatible paths.");
if(!o.empty()) {
String sub;
if(!this->empty()) {
sub.push_back(m_separator);
}
sub.insert(sub.end(), o.cstart(), o.m_value.end());
detail::append_and_preserve_iter(m_value, sub, m_start,
typename std::iterator_traits<s_iter>::iterator_category());
}
return *this;
}
private:
typedef typename String::iterator s_iter;
typedef typename String::const_iterator s_c_iter;
String m_value;
char_type m_separator;
Translator m_tr;
s_iter m_start;
s_c_iter cstart() const { return m_start; }
};
template <typename String, typename Translator> inline
string_path<String, Translator>::string_path(char_type separator)
: m_separator(separator), m_start(m_value.begin())
{}
template <typename String, typename Translator> inline
string_path<String, Translator>::string_path(const String &value,
char_type separator,
Translator tr)
: m_value(value), m_separator(separator),
m_tr(tr), m_start(m_value.begin())
{}
template <typename String, typename Translator> inline
string_path<String, Translator>::string_path(const char_type *value,
char_type separator,
Translator tr)
: m_value(value), m_separator(separator),
m_tr(tr), m_start(m_value.begin())
{}
template <typename String, typename Translator> inline
string_path<String, Translator>::string_path(const string_path &o)
: m_value(o.m_value), m_separator(o.m_separator),
m_tr(o.m_tr), m_start(m_value.begin())
{
std::advance(m_start, std::distance(o.m_value.begin(), o.cstart()));
}
template <typename String, typename Translator> inline
string_path<String, Translator>&
string_path<String, Translator>::operator =(const string_path &o)
{
m_value = o.m_value;
m_separator = o.m_separator;
m_tr = o.m_tr;
m_start = m_value.begin();
std::advance(m_start, std::distance(o.m_value.begin(), o.cstart()));
return *this;
}
template <typename String, typename Translator>
typename Translator::external_type string_path<String, Translator>::reduce()
{
BOOST_ASSERT(!empty() && "Reducing empty path");
s_iter next_sep = std::find(m_start, m_value.end(), m_separator);
String part(m_start, next_sep);
m_start = next_sep;
if(!empty()) {
// Unless we're at the end, skip the separator we found.
++m_start;
}
if(optional<key_type> key = m_tr.get_value(part)) {
return *key;
}
BOOST_PROPERTY_TREE_THROW(ptree_bad_path("Path syntax error", *this));
}
template <typename String, typename Translator> inline
bool string_path<String, Translator>::empty() const
{
return m_start == m_value.end();
}
template <typename String, typename Translator> inline
bool string_path<String, Translator>::single() const
{
return std::find(static_cast<s_c_iter>(m_start),
m_value.end(), m_separator)
== m_value.end();
}
// By default, this is the path for strings. You can override this by
// specializing path_of for a more specific form of std::basic_string.
template <typename Ch, typename Traits, typename Alloc>
struct path_of< std::basic_string<Ch, Traits, Alloc> >
{
typedef std::basic_string<Ch, Traits, Alloc> _string;
typedef string_path< _string, id_translator<_string> > type;
};
}}
#endif