metadata_utils.hpp

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#pragma once
 
/// @file userver/ugrpc/server/metadata_utils.hpp
/// @brief Utilities to work with the request metadata
 
#include <map>
#include <string_view>
#include <utility>
 
#include <grpcpp/support/string_ref.h>
#include <boost/range/adaptor/map.hpp>
#include <boost/range/adaptor/transformed.hpp>
 
#include <userver/ugrpc/impl/to_string.hpp>
#include <userver/ugrpc/server/call_context.hpp>
#include <userver/utils/assert.hpp>
#include <userver/utils/text.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace ugrpc::server {
 
/// @brief Returns an std::input_range containing std::string_view
/// which are non-owning references to the values of the metadata field.
/// The references must not outlive the call object to avoid undefined behavior.
inline auto GetRepeatedMetadata(const CallContextBase& context, std::string_view field_name) {
    UASSERT(field_name == utils::text::ToLower(field_name));
    const auto& metadata = context.GetServerContext().client_metadata();
    auto [it_begin, it_end] = metadata.equal_range(ugrpc::impl::ToGrpcStringRef(field_name));
 
    using Metadata = std::multimap<grpc::string_ref, grpc::string_ref>;
    return boost::iterator_range<Metadata::const_iterator>(it_begin, it_end) |
           boost::adaptors::transformed([](const std::pair<const grpc::string_ref, grpc::string_ref>& entry) {
               return ugrpc::impl::ToStringView(entry.second);
           });
}
 
}  // namespace ugrpc::server
 
USERVER_NAMESPACE_END