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28
29/// \file utils/format/formatter.hpp
30/// Provides the definition of the utils::format::formatter class.
31///
32/// The utils::format::formatter class is a poor man's replacement for the
33/// Boost.Format library, as it is much simpler and has less dependencies.
34///
35/// Be aware that the formatting supported by this module is NOT compatible
36/// with printf(3) nor with Boost.Format.  The general syntax for a
37/// placeholder in a formatting string is:
38///
39///     %[0][width][.precision]s
40///
41/// In particular, note that the only valid formatting specifier is %s: the
42/// library deduces what to print based on the type of the variable passed
43/// in, not based on what the format string says.  Also, note that the only
44/// valid padding character is 0.
45
46#if !defined(UTILS_FORMAT_FORMATTER_HPP)
47#define UTILS_FORMAT_FORMATTER_HPP
48
49#include <sstream>
50#include <string>
51
52namespace utils {
53namespace format {
54
55
56/// Mechanism to format strings similar to printf.
57///
58/// A formatter always maintains the original format string but also holds a
59/// partial expansion.  The partial expansion is immutable in the context of a
60/// formatter instance, but calls to operator% return new formatter objects with
61/// one less formatting placeholder.
62///
63/// In general, one can format a string in the following manner:
64///
65/// \code
66/// const std::string s = (formatter("%s %s") % "foo" % 5).str();
67/// \endcode
68///
69/// which, following the explanation above, would correspond to:
70///
71/// \code
72/// const formatter f1("%s %s");
73/// const formatter f2 = f1 % "foo";
74/// const formatter f3 = f2 % 5;
75/// const std::string s = f3.str();
76/// \endcode
77class formatter {
78    /// The original format string provided by the user.
79    std::string _format;
80
81    /// The current "expansion" of the format string.
82    ///
83    /// This field gets updated on every call to operator%() to have one less
84    /// formatting placeholder.
85    std::string _expansion;
86
87    /// The position of _expansion from which to scan for placeholders.
88    std::string::size_type _last_pos;
89
90    /// The position of the first placeholder in the current expansion.
91    std::string::size_type _placeholder_pos;
92
93    /// The first placeholder in the current expansion.
94    std::string _placeholder;
95
96    /// Stream used to format any possible argument supplied by operator%().
97    std::ostringstream* _oss;
98
99    formatter replace(const std::string&) const;
100
101    void init(void);
102    formatter(const std::string&, const std::string&,
103              const std::string::size_type);
104
105public:
106    explicit formatter(const std::string&);
107    ~formatter(void);
108
109    const std::string& str(void) const;
110    operator const std::string&(void) const;
111
112    template< typename Type > formatter operator%(const Type&) const;
113    formatter operator%(const bool&) const;
114};
115
116
117}  // namespace format
118}  // namespace utils
119
120
121#endif  // !defined(UTILS_FORMAT_FORMATTER_HPP)
122