4 * This file is part of LyX, the document processor.
5 * Licence details can be found in the file COPYING.
9 * Full author contact details are available in file CREDITS.
12 #ifndef LYX_TRIVSTRING_H
13 #define LYX_TRIVSTRING_H
15 #include "support/strfwd.h"
17 #ifdef STD_STRING_USES_COW
23 * Trivial string class with almost no features.
24 * The public interface is a subset of the std::basic_string interface.
25 * The only important feature is that any read-only access does not need
26 * synchronization between multiple threads, i.e. it is thread-safe without
28 * Therefore you can safely use a const trivial_string object in multiple
29 * threads at the same time. This is not the case for std::basic_string in some
30 * STL implementations (e. g. GNU libcstd++, see bug 9336 and
31 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=21334.
32 * This class should not be used for anything else than providing thread-safety.
33 * It should be removed as soon as LyX requires C++11, and all supported STL
34 * implementations provide a C++11 conformant std::basic_string.
36 * If you change anything in this class please ensure that the unit test
37 * tests/check_trivstring.cpp still tests 100% of the public interface.
39 template <typename Char> class trivial_string
42 /// Corresponding std::basic_string
43 typedef std::basic_string<Char, std::char_traits<Char>, std::allocator<Char> > _stdstring;
44 /// Construct an empty string
45 trivial_string() : size_(0), data_(0) {}
46 /// Construct a string from a copy of \p that
47 trivial_string(trivial_string const & that);
48 /// Construct a string from a copy of \p that
49 trivial_string(Char const * that, size_t n);
50 /// Construct a string from a copy of \p that
51 trivial_string(_stdstring const & that);
53 ~trivial_string() { if (!use_sso()) delete[] data_; }
54 /// Assign a copy of \p that
55 trivial_string & operator=(trivial_string const & that);
56 /// Assign a copy of \p that
57 trivial_string & operator=(_stdstring const & that);
58 /// Exchange contents with contents of \p that
59 void swap(trivial_string & that);
60 /// The length of the string, excluding the final 0 character
61 size_t length() const { return size_; }
62 /// Is this string empty?
63 bool empty() const { return size_ == 0; }
64 /// Is this string ordered before, at the same position or after \p other?
65 int compare(trivial_string const & other) const;
66 /// Return substring of length \p n starting at \p pos
67 trivial_string substr(size_t pos = 0, size_t n = _stdstring::npos) const;
68 /// Create a copy as std::basic_string
69 operator _stdstring() const;
70 /// Return a C-compatible string, terminated by a 0 character.
71 /// This is never a copy and only valid for the life time of the trivial_string instance.
72 Char const * c_str() const;
73 /// Return character at position \p i (validity of \i is not checked)
74 Char operator[](size_t i) const;
77 * Whether short string optimization is used.
78 * Short string optimization is a technique where no additional memory
79 * needs to be allocated to store the string contents.
80 * Instead, the memory which would be used to store the pointer to the
81 * character buffer is reinterpreted to be a Char * buffer.
82 * On most 64 bit systems and with Char == char this allows to store
83 * strings of up to 7 characters without allocating additional memory.
85 bool use_sso() const { return (size_ + 1) * sizeof(Char) <= sizeof(Char *); }
86 /// The character storage if sso is used
87 Char * data_sso() { return reinterpret_cast<Char * >(&data_); }
88 /// The character storage if sso is used
89 Char const * data_sso() const { return reinterpret_cast<Char const *>(&data_); }
90 /// The length of the string, excluding the final 0 character
92 /// The character storage
97 /// Comparison operator (needed for std::set etc)
98 template <typename Char> bool operator<(trivial_string<Char> const & lhs, trivial_string<Char> const & rhs);
101 /// Equality operator
102 template <typename Char> bool operator==(trivial_string<Char> const & lhs, trivial_string<Char> const & rhs);
103 template <typename Char> bool operator==(trivial_string<Char> const & lhs, Char const * rhs);
104 template <typename Char> bool operator==(Char const * lhs, trivial_string<Char> const & rhs);
107 /// Stream output operator
108 template <typename Char>
109 std::basic_ostream<Char, std::char_traits<Char> > &
110 operator<<(std::basic_ostream<Char, std::char_traits<Char> > &, trivial_string<Char> const &);