redis/detail/coroutine.hpp

0001 //
0002 // Copyright (c) 2025 Marcelo Zimbres Silva (mzimbres@gmail.com),
0003 // Ruben Perez Hidalgo (rubenperez038 at gmail dot com)
0004 //
0005 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0006 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0007 //
0008
0009 #ifndef BOOST_REDIS_DETAIL_COROUTINE_HPP
0010 #define BOOST_REDIS_DETAIL_COROUTINE_HPP
0011
0012 // asio::coroutine uses __COUNTER__ internally, which can trigger
0013 // ODR violations if we use them in header-only code. These manifest as
0014 // extremely hard-to-debug bugs only present in release builds.
0015 // Use this instead when doing coroutines in non-template code.
0016 // Adapted from Boost.MySQL.
0017
0018 // Coroutine state is represented as an integer (resume_point_var).
0019 // Every yield gets assigned a unique value (resume_point_id).
0020 // Yielding sets the next resume point, returns, and sets a case label for re-entering.
0021 // Coroutines need to switch on resume_point_var to re-enter.
0022
0023 // Enclosing this in a scope allows placing the macro inside a brace-less for/while loop
0024 // The empty scope after the case label is required because labels can't be at the end of a compound statement
0025 #define BOOST_REDIS_YIELD(resume_point_var, resume_point_id, ...) \
0026    {                                                              \
0027       resume_point_var = resume_point_id;                         \
0028       return {__VA_ARGS__};                                       \
0029       case resume_point_id:                                       \
0030       {                                                           \
0031       }                                                           \
0032    }
0033
0034 #define BOOST_REDIS_CORO_INITIAL case 0:
0035
0036 #endif