Introduce a format parsing context

This context will be used by the various formatters to parse replacement
fields.

Author: trflynn89

Makefile

@@ -21,10 +21,13 @@ $(eval $(call EXCLUDE_FROM_STYLE_ENFORCEMENT, extern/))
 # 3. Ignore external third-party files.
 # 4. Ignore literal_parser.hpp - this file is entirely constexpr functions that do not execute at
 #    runtime, which llvm-cov doesn't seem to recognize.
+# 5. Ignore format_parameter_type.hpp - this file is entirely constexpr functions that do not
+#    execute at runtime, which llvm-cov doesn't seem to recognize.
 $(eval $(call EXCLUDE_FROM_COVERAGE, test/))
 $(eval $(call EXCLUDE_FROM_COVERAGE, bench/))
 $(eval $(call EXCLUDE_FROM_COVERAGE, extern/))
 $(eval $(call EXCLUDE_FROM_COVERAGE, fly/types/numeric/detail/literal_parser.hpp))
+$(eval $(call EXCLUDE_FROM_COVERAGE, fly/types/string/detail/format_parameter_type.hpp))
 
 # Paths to exclude from generation of compilation database.
 $(eval $(call EXCLUDE_FROM_COMPILATION_DATABASE, extern/))

build/win/libfly/libfly.vcxproj

@@ -231,7 +231,9 @@
     <ClInclude Include="..\..\..\fly\types\string\detail\classifier.hpp" />
     <ClInclude Include="..\..\..\fly\types\string\detail\converter.hpp" />
     <ClInclude Include="..\..\..\fly\types\string\detail\format_context.hpp" />
+    <ClInclude Include="..\..\..\fly\types\string\detail\format_parameter_type.hpp" />
     <ClInclude Include="..\..\..\fly\types\string\detail\format_parameters.hpp" />
+    <ClInclude Include="..\..\..\fly\types\string\detail\format_parse_context.hpp" />
     <ClInclude Include="..\..\..\fly\types\string\detail\format_specifier.hpp" />
     <ClInclude Include="..\..\..\fly\types\string\detail\format_string.hpp" />
     <ClInclude Include="..\..\..\fly\types\string\detail\stream_util.hpp" />

build/win/libfly/libfly.vcxproj.filters

@@ -298,9 +298,15 @@
     <ClInclude Include="..\..\..\fly\types\string\detail\format_context.hpp">
       <Filter>types\string\detail</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\..\fly\types\string\detail\format_parameter_type.hpp">
+      <Filter>types\string\detail</Filter>
+    </ClInclude>
     <ClInclude Include="..\..\..\fly\types\string\detail\format_parameters.hpp">
       <Filter>types\string\detail</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\..\fly\types\string\detail\format_parse_context.hpp">
+      <Filter>types\string\detail</Filter>
+    </ClInclude>
     <ClInclude Include="..\..\..\fly\types\string\detail\format_specifier.hpp">
       <Filter>types\string\detail</Filter>
     </ClInclude>

fly/types/string/detail/format_parameter_type.hpp

@@ -0,0 +1,66 @@
+#pragma once
+
+#include "fly/types/string/detail/string_traits.hpp"
+
+#include <cstdint>
+
+namespace fly::detail {
+
+/**
+ * Enumerated list of supported format parameter types.
+ */
+enum class ParameterType : std::uint8_t
+{
+    Generic,
+    Character,
+    String,
+    Pointer,
+    Integral,
+    FloatingPoint,
+    Boolean,
+};
+
+/**
+ * Map a format parameter type to the ParameterType enumeration.
+ *
+ * @tparam T The format parameter type.
+ *
+ * @return The mapped ParameterType enumeration.
+ */
+template <typename T>
+constexpr ParameterType infer_parameter_type()
+{
+    using U = std::remove_cvref_t<T>;
+
+    if constexpr (is_supported_character_v<U>)
+    {
+        return ParameterType::Character;
+    }
+    else if constexpr (is_like_supported_string_v<U>)
+    {
+        return ParameterType::String;
+    }
+    else if constexpr (std::is_pointer_v<U> || std::is_null_pointer_v<U>)
+    {
+        return ParameterType::Pointer;
+    }
+    else if constexpr (
+        BasicFormatTraits::is_integer_v<U> || BasicFormatTraits::is_default_formatted_enum_v<U>)
+    {
+        return ParameterType::Integral;
+    }
+    else if constexpr (std::is_floating_point_v<U>)
+    {
+        return ParameterType::FloatingPoint;
+    }
+    else if constexpr (std::is_same_v<U, bool>)
+    {
+        return ParameterType::Boolean;
+    }
+    else
+    {
+        return ParameterType::Generic;
+    }
+}
+
+} // namespace fly::detail

fly/types/string/detail/format_parse_context.hpp

@@ -0,0 +1,204 @@
+#pragma once
+
+#include "fly/types/string/detail/format_parameter_type.hpp"
+#include "fly/types/string/detail/string_traits.hpp"
+#include "fly/types/string/lexer.hpp"
+
+#include <cstddef>
+#include <string_view>
+
+namespace fly::detail {
+
+/**
+ * Provides access to the format string parsing state consisting of the format string being parsed,
+ * and the format parameter types and indices.
+ *
+ * @author Timothy Flynn ([email protected])
+ * @version April 25, 2021
+ */
+template <typename CharType>
+class BasicFormatParseContext
+{
+    using traits = BasicStringTraits<CharType>;
+    using view_type = typename traits::view_type;
+
+public:
+    /**
+     * Constructor.
+     *
+     * @param format The format string to be parsed.
+     * @param parameters Pointer to a list of parameter types to be formatted.
+     * @param parameters_size Size of the parameter types list.
+     */
+    template <std::size_t N>
+    constexpr explicit BasicFormatParseContext(
+        const CharType (&format)[N],
+        const ParameterType *parameters,
+        std::size_t parameters_size) noexcept;
+
+    /**
+     * Parse the optional position argument of the current replacement field. If a position was not
+     * found, the position is observed to be the next format parameter in order.
+     *
+     * It is an error if the format string has a mix of manual and automatic positioning.
+     *
+     * @return The parsed or observed format parameter position.
+     */
+    constexpr std::size_t next_position();
+
+    /**
+     * Retrieve the type of the format parameter at the provided index.
+     *
+     * @param index The index of the format parameter.
+     *
+     * @return If the index exists, the format parameter type. Otherwise, an uninitialized value.
+     */
+    constexpr std::optional<ParameterType> parameter_type(std::size_t position);
+
+    /**
+     * @return The lexer for parsing the format string.
+     */
+    constexpr fly::BasicLexer<CharType> &lexer();
+
+    /**
+     * @return A string view into the format string.
+     */
+    constexpr view_type view() const;
+
+    /**
+     * Record an error that was encountered while parsing the format string.
+     *
+     * If invoked from a constant-evaluation context, this will raise a compilation error because
+     * this method is purposefully non-constexpr. This results in an attempt to invoke a
+     * non-constant expression from a constant context, which is erroneous. The error message from
+     * the caller should be displayed in the terminal.
+     *
+     * If not invoked from a constant-evaluation context, this will store the error message.
+     *
+     * @param error A message describing the error that was encountered.
+     */
+    void on_error(const char *error);
+
+    /**
+     * If an error was stored from a non-constant-evaluated context, returns whether an error was
+     * encountered while parsing the format string.
+     *
+     * @return True if an error was encountered while parsing.
+     */
+    constexpr bool has_error() const;
+
+    /**
+     * If an error was stored from a non-constant-evaluated context, returns the last error that was
+     * encountered while parsing the format string.
+     *
+     * @return The error (if any) that was encountered while parsing the format string.
+     */
+    std::string error() const;
+
+private:
+    BasicFormatParseContext(BasicFormatParseContext &&) = delete;
+    BasicFormatParseContext &operator=(BasicFormatParseContext &&) = delete;
+
+    BasicFormatParseContext(const BasicFormatParseContext &) = delete;
+    BasicFormatParseContext &operator=(const BasicFormatParseContext &) = delete;
+
+    fly::BasicLexer<CharType> m_lexer;
+
+    const ParameterType *m_parameters;
+    std::size_t m_parameters_size;
+
+    std::size_t m_next_position {0};
+    bool m_expect_no_positions_specified {false};
+    bool m_expect_all_positions_specified {false};
+
+    std::string_view m_error;
+};
+
+//==================================================================================================
+template <typename CharType>
+template <std::size_t N>
+constexpr BasicFormatParseContext<CharType>::BasicFormatParseContext(
+    const CharType (&format)[N],
+    const ParameterType *parameters,
+    std::size_t parameters_size) noexcept :
+    m_lexer(format),
+    m_parameters(parameters),
+    m_parameters_size(parameters_size)
+{
+}
+
+//==================================================================================================
+template <typename CharType>
+constexpr std::size_t BasicFormatParseContext<CharType>::next_position()
+{
+    std::size_t position = 0;
+
+    if (auto specified_position = m_lexer.consume_number(); specified_position)
+    {
+        m_expect_all_positions_specified = true;
+        position = static_cast<std::size_t>(*specified_position);
+    }
+    else
+    {
+        m_expect_no_positions_specified = true;
+        position = m_next_position++;
+    }
+
+    if (m_expect_all_positions_specified && m_expect_no_positions_specified)
+    {
+        on_error("Argument position must be provided on all or not on any specifier");
+    }
+
+    return position;
+}
+
+//==================================================================================================
+template <typename CharType>
+constexpr std::optional<ParameterType>
+BasicFormatParseContext<CharType>::parameter_type(std::size_t position)
+{
+    if (position >= m_parameters_size)
+    {
+        on_error("Argument position exceeds number of provided arguments");
+        return std::nullopt;
+    }
+
+    return m_parameters[position];
+}
+
+//==================================================================================================
+template <typename CharType>
+constexpr inline fly::BasicLexer<CharType> &BasicFormatParseContext<CharType>::lexer()
+{
+    return m_lexer;
+}
+
+//==================================================================================================
+template <typename CharType>
+constexpr auto BasicFormatParseContext<CharType>::view() const -> view_type
+{
+    return m_lexer.view();
+}
+
+//==================================================================================================
+template <typename CharType>
+void BasicFormatParseContext<CharType>::on_error(const char *error)
+{
+    m_error = error;
+}
+
+//==================================================================================================
+template <typename CharType>
+constexpr bool BasicFormatParseContext<CharType>::has_error() const
+{
+    return !m_error.empty();
+}
+
+//==================================================================================================
+template <typename CharType>
+std::string BasicFormatParseContext<CharType>::error() const
+{
+    return std::string(m_error.data(), m_error.size());
+}
+
+} // namespace fly::detail