add getContext function to the Null Vm (proxy-wasm#14)

* add getContext function to the Null Vm

* format

Author: bianpengyuan

include/proxy-wasm/null_plugin.h

@@ -107,13 +107,13 @@ class NullPlugin : public NullVmPlugin {
   void onDelete(uint64_t context_id);
 
   null_plugin::RootContext *getRoot(string_view root_id);
+  null_plugin::Context *getContext(uint64_t context_id);
 
   void error(string_view message) { wasm_vm_->error(message); }
 
 private:
   null_plugin::Context *ensureContext(uint64_t context_id, uint64_t root_context_id);
   null_plugin::RootContext *ensureRootContext(uint64_t context_id);
-  null_plugin::Context *getContext(uint64_t context_id);
   null_plugin::RootContext *getRootContext(uint64_t context_id);
   null_plugin::ContextBase *getContextBase(uint64_t context_id);
 

include/proxy-wasm/wasm_api_impl.h

@@ -20,9 +20,11 @@
 namespace proxy_wasm {
 namespace null_plugin {
 class RootContext;
+class Context;
 } // namespace null_plugin
 
 null_plugin::RootContext *nullVmGetRoot(string_view root_id);
+null_plugin::Context *nullVmGetContext(uint32_t context_id);
 
 namespace null_plugin {
 
@@ -263,6 +265,7 @@ inline WasmResult proxy_call_foreign_function(const char *function_name, size_t
 #undef WR
 
 inline RootContext *getRoot(string_view root_id) { return nullVmGetRoot(root_id); }
+inline Context *getContext(uint32_t context_id) { return nullVmGetContext(context_id); }
 
 } // namespace null_plugin
 } // namespace proxy_wasm

src/null/null_plugin.cc

@@ -459,4 +459,9 @@ null_plugin::RootContext *nullVmGetRoot(string_view root_id) {
   return static_cast<NullPlugin *>(null_vm->plugin_.get())->getRoot(root_id);
 }
 
+null_plugin::Context *nullVmGetContext(uint32_t context_id) {
+  auto null_vm = static_cast<NullVm *>(current_context_->wasmVm());
+  return static_cast<NullPlugin *>(null_vm->plugin_.get())->getContext(context_id);
+}
+
 } // namespace proxy_wasm