diff --git a/src/core/ext/filters/client_channel/client_channel.cc b/src/core/ext/filters/client_channel/client_channel.cc
index 01825a14eb9aa8330302a01e21ad0f4ebc614186..450bb5fd04b4ae8137d9d9d4c8c144546ad98691 100644
--- a/src/core/ext/filters/client_channel/client_channel.cc
+++ b/src/core/ext/filters/client_channel/client_channel.cc
@@ -376,35 +376,39 @@ class CallData {
GRPC_ERROR_NONE);
}
- Iterator Begin() const override {
- static_assert(sizeof(grpc_linked_mdelem*) <= sizeof(Iterator),
+ iterator begin() const override {
+ static_assert(sizeof(grpc_linked_mdelem*) <= sizeof(intptr_t),
"iterator size too large");
- return reinterpret_cast<Iterator>(batch_->list.head);
+ return iterator(this, reinterpret_cast<intptr_t>(batch_->list.head));
}
- bool IsEnd(Iterator it) const override {
- return reinterpret_cast<grpc_linked_mdelem*>(it) == nullptr;
- }
- void Next(Iterator* it) const override {
- *it = reinterpret_cast<Iterator>(
- reinterpret_cast<grpc_linked_mdelem*>(*it)->next);
- }
- StringView Key(Iterator it) const override {
- return StringView(
- GRPC_MDKEY(reinterpret_cast<grpc_linked_mdelem*>(it)->md));
- }
- StringView Value(Iterator it) const override {
- return StringView(
- GRPC_MDVALUE(reinterpret_cast<grpc_linked_mdelem*>(it)->md));
+ iterator end() const override {
+ static_assert(sizeof(grpc_linked_mdelem*) <= sizeof(intptr_t),
+ "iterator size too large");
+ return iterator(this, 0);
}
- void Erase(Iterator* it) override {
+ iterator erase(iterator it) override {
grpc_linked_mdelem* linked_mdelem =
- reinterpret_cast<grpc_linked_mdelem*>(*it);
- *it = reinterpret_cast<Iterator>(linked_mdelem->next);
+ reinterpret_cast<grpc_linked_mdelem*>(GetIteratorHandle(it));
+ intptr_t handle = reinterpret_cast<intptr_t>(linked_mdelem->next);
grpc_metadata_batch_remove(batch_, linked_mdelem);
+ return iterator(this, handle);
}
private:
+ intptr_t IteratorHandleNext(intptr_t handle) const override {
+ grpc_linked_mdelem* linked_mdelem =
+ reinterpret_cast<grpc_linked_mdelem*>(handle);
+ return reinterpret_cast<intptr_t>(linked_mdelem->next);
+ }
+ std::pair<StringView, StringView> IteratorHandleGet(
+ intptr_t handle) const override {
+ grpc_linked_mdelem* linked_mdelem =
+ reinterpret_cast<grpc_linked_mdelem*>(handle);
+ return std::make_pair(StringView(GRPC_MDKEY(linked_mdelem->md)),
+ StringView(GRPC_MDVALUE(linked_mdelem->md)));
+ }
+
CallData* calld_;
grpc_metadata_batch* batch_;
};
diff --git a/src/core/ext/filters/client_channel/lb_policy.h b/src/core/ext/filters/client_channel/lb_policy.h
index dc4bf51cfce9a34eb5072b57ce784eeebcdcba44..bf6efb00fc1ef56a97478606f7486193977ebc4a 100644
--- a/src/core/ext/filters/client_channel/lb_policy.h
+++ b/src/core/ext/filters/client_channel/lb_policy.h
@@ -21,6 +21,8 @@
#include <grpc/support/port_platform.h>
+#include <iterator>
+
#include "src/core/ext/filters/client_channel/server_address.h"
#include "src/core/ext/filters/client_channel/service_config.h"
#include "src/core/ext/filters/client_channel/subchannel_interface.h"
@@ -119,10 +121,31 @@ class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
/// Implemented by the client channel and used by the SubchannelPicker.
class MetadataInterface {
public:
- // Implementations whose iterators fit in intptr_t may internally
- // cast this directly to their iterator type. Otherwise, they may
- // dynamically allocate their iterators and store the address here.
- typedef intptr_t Iterator;
+ class iterator
+ : public std::iterator<std::input_iterator_tag,
+ std::pair<StringView, StringView>, // value_type
+ std::ptrdiff_t, // difference_type
+ std::pair<StringView, StringView>*, // pointer
+ std::pair<StringView, StringView>& // reference
+ > {
+ public:
+ iterator(const MetadataInterface* md, intptr_t handle)
+ : md_(md), handle_(handle) {}
+ iterator& operator++() {
+ handle_ = md_->IteratorHandleNext(handle_);
+ return *this;
+ }
+ bool operator==(iterator other) const {
+ return md_ == other.md_ && handle_ == other.handle_;
+ }
+ bool operator!=(iterator other) const { return !(*this == other); }
+ value_type operator*() const { return md_->IteratorHandleGet(handle_); }
+
+ private:
+ friend class MetadataInterface;
+ const MetadataInterface* md_;
+ intptr_t handle_;
+ };
virtual ~MetadataInterface() = default;
@@ -134,15 +157,22 @@ class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
virtual void Add(StringView key, StringView value) = 0;
/// Iteration interface.
- virtual Iterator Begin() const = 0;
- virtual bool IsEnd(Iterator it) const = 0;
- virtual void Next(Iterator* it) const = 0;
- virtual StringView Key(Iterator it) const = 0;
- virtual StringView Value(Iterator it) const = 0;
-
- /// Removes the element pointed to by \a it, which is modified to
- /// point to the next element.
- virtual void Erase(Iterator* it) = 0;
+ virtual iterator begin() const = 0;
+ virtual iterator end() const = 0;
+
+ /// Removes the element pointed to by \a it.
+ /// Returns an iterator pointing to the next element.
+ virtual iterator erase(iterator it) = 0;
+
+ protected:
+ intptr_t GetIteratorHandle(const iterator& it) const { return it.handle_; }
+
+ private:
+ friend class iterator;
+
+ virtual intptr_t IteratorHandleNext(intptr_t handle) const = 0;
+ virtual std::pair<StringView /*key*/, StringView /*value */>
+ IteratorHandleGet(intptr_t handle) const = 0;
};
/// Arguments used when picking a subchannel for a call.
diff --git a/test/core/util/test_lb_policies.cc b/test/core/util/test_lb_policies.cc
index c4aab3fc3ac540ede8c9895c6094008910da6b8c..684ee656b756a57167d704b19f562791e947ff9b 100644
--- a/test/core/util/test_lb_policies.cc
+++ b/test/core/util/test_lb_policies.cc
@@ -201,13 +201,10 @@ class InterceptRecvTrailingMetadataLoadBalancingPolicy
};
static void LogMetadata(MetadataInterface* metadata) {
- for (MetadataInterface::Iterator it = metadata->Begin();
- !metadata->IsEnd(it); metadata->Next(&it)) {
+ for (const auto& p : *metadata) {
gpr_log(GPR_INFO, " \"%.*s\"=>\"%.*s\"",
- static_cast<int>(metadata->Key(it).size()),
- metadata->Key(it).data(),
- static_cast<int>(metadata->Value(it).size()),
- metadata->Value(it).data());
+ static_cast<int>(p.first.size()), p.first.data(),
+ static_cast<int>(p.second.size()), p.second.data());
}
}
};