Add constexprs buffers - refs boostorg#54

* allows several operations on buffer types to be constexpr * ensure old execution path is still used at runtime, to avoid any performance regression Signed-off-by: Julien Blanc <[email protected]>
Julien-Blanc-tgcm · Sep 9, 2024 · afcf0b0 · afcf0b0
1 parent be21291
commit afcf0b0
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Showing 5 changed files with 156 additions and 97 deletions.
diff --git a/include/boost/endian/arithmetic.hpp b/include/boost/endian/arithmetic.hpp
@@ -184,53 +184,53 @@ class endian_arithmetic
 
 #ifndef BOOST_ENDIAN_NO_CTORS
 
-    endian_arithmetic() = default;
+    BOOST_ENDIAN_CONSTEXPR endian_arithmetic() = default;
 
-    BOOST_ENDIAN_EXPLICIT_OPT endian_arithmetic( T val ) BOOST_NOEXCEPT: buf_( val )
+    BOOST_ENDIAN_EXPLICIT_OPT BOOST_ENDIAN_CONSTEXPR endian_arithmetic( T val ) BOOST_NOEXCEPT: buf_( val )
     {
     }
 
 #endif
 
-    endian_arithmetic& operator=( T val ) BOOST_NOEXCEPT
+    BOOST_ENDIAN_CXX20_CONSTEXPR endian_arithmetic& operator=( T val ) BOOST_NOEXCEPT
     {
         buf_ = val;
         return *this;
     }
 
-    value_type value() const BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR value_type value() const BOOST_NOEXCEPT
     {
         return buf_.value();
     }
 
-    unsigned char const * data() const BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR unsigned char const * data() const BOOST_NOEXCEPT
     {
         return buf_.data();
     }
 
-    unsigned char * data() BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR unsigned char * data() BOOST_NOEXCEPT
     {
         return buf_.data();
     }
 
-    operator value_type() const BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR operator value_type() const BOOST_NOEXCEPT
     {
         return this->value();
     }
 
-    operator buffer_type& () BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR operator buffer_type& () BOOST_NOEXCEPT
     {
         return buf_;
     }
 
-    operator buffer_type const& () BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR operator buffer_type const& () BOOST_NOEXCEPT
     {
         return buf_;
     }
 
     // operators
 
-    T operator+() const BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR T operator+() const BOOST_NOEXCEPT
     {
         return this->value();
     }

diff --git a/include/boost/endian/buffers.hpp b/include/boost/endian/buffers.hpp
@@ -219,27 +219,27 @@ class endian_buffer<Order, T, n_bits, align::no>
 
 #ifndef BOOST_ENDIAN_NO_CTORS
 
-    endian_buffer() = default;
+    BOOST_ENDIAN_CONSTEXPR endian_buffer() = default;
 
-    explicit endian_buffer( T val ) BOOST_NOEXCEPT
+    explicit BOOST_ENDIAN_CONSTEXPR endian_buffer( T val ) BOOST_NOEXCEPT
     {
         boost::endian::endian_store<T, n_bits / 8, Order>( value_, val );
     }
 
 #endif
 
-    endian_buffer& operator=( T val ) BOOST_NOEXCEPT
+    BOOST_ENDIAN_CXX20_CONSTEXPR endian_buffer& operator=( T val ) BOOST_NOEXCEPT
     {
         boost::endian::endian_store<T, n_bits / 8, Order>( value_, val );
         return *this;
     }
 
-    value_type value() const BOOST_NOEXCEPT
+    BOOST_ENDIAN_CXX20_CONSTEXPR value_type value() const BOOST_NOEXCEPT
     {
         return boost::endian::endian_load<T, n_bits / 8, Order>( value_ );
     }
 
-    unsigned char const * data() const BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR unsigned char const * data() const BOOST_NOEXCEPT
     {
         return value_;
     }
@@ -274,27 +274,27 @@ class endian_buffer<Order, T, n_bits, align::yes>
 
 #ifndef BOOST_ENDIAN_NO_CTORS
 
-    endian_buffer() = default;
+    BOOST_ENDIAN_CONSTEXPR endian_buffer() = default;
 
-    explicit endian_buffer( T val ) BOOST_NOEXCEPT
+    explicit BOOST_ENDIAN_CONSTEXPR endian_buffer( T val ) BOOST_NOEXCEPT
     {
         boost::endian::endian_store<T, n_bits / 8, Order>( value_, val );
     }
 
 #endif
 
-    endian_buffer& operator=( T val ) BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR endian_buffer& operator=( T val ) BOOST_NOEXCEPT
     {
         boost::endian::endian_store<T, n_bits / 8, Order>( value_, val );
         return *this;
     }
 
-    value_type value() const BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR value_type value() const BOOST_NOEXCEPT
     {
         return boost::endian::endian_load<T, n_bits / 8, Order>( value_ );
     }
 
-    unsigned char const * data() const BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR unsigned char const * data() const BOOST_NOEXCEPT
     {
         return value_;
     }
@@ -323,26 +323,26 @@ class endian_buffer<order::native, T, n_bits, align::yes>
 
 #ifndef BOOST_ENDIAN_NO_CTORS
 
-    endian_buffer() = default;
+    BOOST_ENDIAN_CONSTEXPR endian_buffer() = default;
 
-    explicit endian_buffer( T val ) BOOST_NOEXCEPT: value_( val )
+    explicit BOOST_ENDIAN_CONSTEXPR endian_buffer( T val ) BOOST_NOEXCEPT: value_( val )
     {
     }
 
 #endif
 
-    endian_buffer& operator=( T val ) BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR endian_buffer& operator=( T val ) BOOST_NOEXCEPT
     {
         value_ = val;
         return *this;
     }
 
-    value_type value() const BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR value_type value() const BOOST_NOEXCEPT
     {
         return value_;
     }
 
-    unsigned char const * data() const BOOST_NOEXCEPT
+    BOOST_ENDIAN_CONSTEXPR unsigned char const * data() const BOOST_NOEXCEPT
     {
         return reinterpret_cast< unsigned char const* >( &value_ );
     }

diff --git a/include/boost/endian/detail/constexpr.hpp b/include/boost/endian/detail/constexpr.hpp
@@ -0,0 +1,16 @@
+#ifndef BOOST_ENDIAN_DETAIL_CONSTEXPR_HPP_INCLUDED
+#define BOOST_ENDIAN_DETAIL_CONSTEXPR_HPP_INCLUDED
+
+// Copyright 2024 Julien Blanc
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#if __cpp_lib_is_constant_evaluated >= 201802L && __cpp_lib_bit_cast >= 201806L
+#define BOOST_ENDIAN_CXX20_CONSTEXPR constexpr
+#define BOOST_ENDIAN_HAS_CXX20_CONSTEXPR 1
+#else
+#define BOOST_ENDIAN_CXX20_CONSTEXPR inline
+#define BOOST_ENDIAN_HAS_CXX20_CONSTEXPR 0
+#endif
+
+#endif  // BOOST_ENDIAN_DETAIL_CONSTEXPR_HPP_INCLUDED