Convert slice hash table and service config code to C++.

2 files changed, 240 insertions, 210 deletions

diff --git a/src/core/lib/transport/service_config.cc b/src/core/lib/transport/service_config.cc
index b1d727419d..e1a55d98ab 100644
--- a/src/core/lib/transport/service_config.cc
+++ b/src/core/lib/transport/service_config.cc
@@ -31,74 +31,30 @@
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
 
-// The main purpose of the code here is to parse the service config in
-// JSON form, which will look like this:
-//
-// {
-//   "loadBalancingPolicy": "string",  // optional
-//   "methodConfig": [  // array of one or more method_config objects
-//     {
-//       "name": [  // array of one or more name objects
-//         {
-//           "service": "string",  // required
-//           "method": "string",  // optional
-//         }
-//       ],
-//       // remaining fields are optional.
-//       // see https://developers.google.com/protocol-buffers/docs/proto3#json
-//       // for format details.
-//       "waitForReady": bool,
-//       "timeout": "duration_string",
-//       "maxRequestMessageBytes": "int64_string",
-//       "maxResponseMessageBytes": "int64_string",
-//     }
-//   ]
-// }
-
-struct grpc_service_config {
-  char* json_string;  // Underlying storage for json_tree.
-  grpc_json* json_tree;
-};
+namespace grpc_core {
 
-grpc_service_config* grpc_service_config_create(const char* json_string) {
-  grpc_service_config* service_config =
-      static_cast<grpc_service_config*>(gpr_malloc(sizeof(*service_config)));
-  service_config->json_string = gpr_strdup(json_string);
-  service_config->json_tree =
-      grpc_json_parse_string(service_config->json_string);
-  if (service_config->json_tree == nullptr) {
+UniquePtr<ServiceConfig> ServiceConfig::Create(const char* json) {
+  UniquePtr<char> json_string(gpr_strdup(json));
+  grpc_json* json_tree = grpc_json_parse_string(json_string.get());
+  if (json_tree == nullptr) {
     gpr_log(GPR_INFO, "failed to parse JSON for service config");
-    gpr_free(service_config->json_string);
-    gpr_free(service_config);
     return nullptr;
   }
-  return service_config;
+  return MakeUnique<ServiceConfig>(std::move(json_string), json_tree);
 }
 
-void grpc_service_config_destroy(grpc_service_config* service_config) {
-  grpc_json_destroy(service_config->json_tree);
-  gpr_free(service_config->json_string);
-  gpr_free(service_config);
-}
+ServiceConfig::ServiceConfig(UniquePtr<char> json_string, grpc_json* json_tree)
+    : json_string_(std::move(json_string)), json_tree_(json_tree) {}
 
-void grpc_service_config_parse_global_params(
-    const grpc_service_config* service_config,
-    void (*process_json)(const grpc_json* json, void* arg), void* arg) {
-  const grpc_json* json = service_config->json_tree;
-  if (json->type != GRPC_JSON_OBJECT || json->key != nullptr) return;
-  for (grpc_json* field = json->child; field != nullptr; field = field->next) {
-    if (field->key == nullptr) return;
-    if (strcmp(field->key, "methodConfig") == 0) continue;
-    process_json(field, arg);
-  }
-}
+ServiceConfig::~ServiceConfig() { grpc_json_destroy(json_tree_); }
 
-const char* grpc_service_config_get_lb_policy_name(
-    const grpc_service_config* service_config) {
-  const grpc_json* json = service_config->json_tree;
-  if (json->type != GRPC_JSON_OBJECT || json->key != nullptr) return nullptr;
+const char* ServiceConfig::GetLoadBalancingPolicyName() const {
+  if (json_tree_->type != GRPC_JSON_OBJECT || json_tree_->key != nullptr) {
+    return nullptr;
+  }
   const char* lb_policy_name = nullptr;
-  for (grpc_json* field = json->child; field != nullptr; field = field->next) {
+  for (grpc_json* field = json_tree_->child; field != nullptr;
+       field = field->next) {
     if (field->key == nullptr) return nullptr;
     if (strcmp(field->key, "loadBalancingPolicy") == 0) {
       if (lb_policy_name != nullptr) return nullptr;  // Duplicate.
@@ -109,8 +65,7 @@ const char* grpc_service_config_get_lb_policy_name(
   return lb_policy_name;
 }
 
-// Returns the number of names specified in the method config \a json.
-static size_t count_names_in_method_config_json(grpc_json* json) {
+size_t ServiceConfig::CountNamesInMethodConfig(grpc_json* json) {
   size_t num_names = 0;
   for (grpc_json* field = json->child; field != nullptr; field = field->next) {
     if (field->key != nullptr && strcmp(field->key, "name") == 0) {
@@ -124,9 +79,7 @@ static size_t count_names_in_method_config_json(grpc_json* json) {
   return num_names;
 }
 
-// Returns a path string for the JSON name object specified by \a json.
-// Returns NULL on error.  Caller takes ownership of result.
-static char* parse_json_method_name(grpc_json* json) {
+UniquePtr<char> ServiceConfig::ParseJsonMethodName(grpc_json* json) {
   if (json->type != GRPC_JSON_OBJECT) return nullptr;
   const char* service_name = nullptr;
   const char* method_name = nullptr;
@@ -147,116 +100,7 @@ static char* parse_json_method_name(grpc_json* json) {
   char* path;
   gpr_asprintf(&path, "/%s/%s", service_name,
                method_name == nullptr ? "*" : method_name);
-  return path;
+  return UniquePtr<char>(path);
 }
 
-// Parses the method config from \a json.  Adds an entry to \a entries for
-// each name found, incrementing \a idx for each entry added.
-// Returns false on error.
-static bool parse_json_method_config(
-    grpc_json* json, void* (*create_value)(const grpc_json* method_config_json),
-    void* (*ref_value)(void* value), void (*unref_value)(void* value),
-    grpc_slice_hash_table_entry* entries, size_t* idx) {
-  // Construct value.
-  void* method_config = create_value(json);
-  if (method_config == nullptr) return false;
-  // Construct list of paths.
-  bool success = false;
-  gpr_strvec paths;
-  gpr_strvec_init(&paths);
-  for (grpc_json* child = json->child; child != nullptr; child = child->next) {
-    if (child->key == nullptr) continue;
-    if (strcmp(child->key, "name") == 0) {
-      if (child->type != GRPC_JSON_ARRAY) goto done;
-      for (grpc_json* name = child->child; name != nullptr; name = name->next) {
-        char* path = parse_json_method_name(name);
-        if (path == nullptr) goto done;
-        gpr_strvec_add(&paths, path);
-      }
-    }
-  }
-  if (paths.count == 0) goto done;  // No names specified.
-  // Add entry for each path.
-  for (size_t i = 0; i < paths.count; ++i) {
-    entries[*idx].key = grpc_slice_from_copied_string(paths.strs[i]);
-    entries[*idx].value = ref_value(method_config);
-    ++*idx;
-  }
-  success = true;
-done:
-  unref_value(method_config);
-  gpr_strvec_destroy(&paths);
-  return success;
-}
-
-grpc_slice_hash_table* grpc_service_config_create_method_config_table(
-    const grpc_service_config* service_config,
-    void* (*create_value)(const grpc_json* method_config_json),
-    void* (*ref_value)(void* value), void (*unref_value)(void* value)) {
-  const grpc_json* json = service_config->json_tree;
-  // Traverse parsed JSON tree.
-  if (json->type != GRPC_JSON_OBJECT || json->key != nullptr) return nullptr;
-  size_t num_entries = 0;
-  grpc_slice_hash_table_entry* entries = nullptr;
-  for (grpc_json* field = json->child; field != nullptr; field = field->next) {
-    if (field->key == nullptr) return nullptr;
-    if (strcmp(field->key, "methodConfig") == 0) {
-      if (entries != nullptr) return nullptr;  // Duplicate.
-      if (field->type != GRPC_JSON_ARRAY) return nullptr;
-      // Find number of entries.
-      for (grpc_json* method = field->child; method != nullptr;
-           method = method->next) {
-        size_t count = count_names_in_method_config_json(method);
-        if (count <= 0) return nullptr;
-        num_entries += count;
-      }
-      // Populate method config table entries.
-      entries = static_cast<grpc_slice_hash_table_entry*>(
-          gpr_malloc(num_entries * sizeof(grpc_slice_hash_table_entry)));
-      size_t idx = 0;
-      for (grpc_json* method = field->child; method != nullptr;
-           method = method->next) {
-        if (!parse_json_method_config(method, create_value, ref_value,
-                                      unref_value, entries, &idx)) {
-          for (size_t i = 0; i < idx; ++i) {
-            grpc_slice_unref_internal(entries[i].key);
-            unref_value(entries[i].value);
-          }
-          gpr_free(entries);
-          return nullptr;
-        }
-      }
-      GPR_ASSERT(idx == num_entries);
-    }
-  }
-  // Instantiate method config table.
-  grpc_slice_hash_table* method_config_table = nullptr;
-  if (entries != nullptr) {
-    method_config_table = grpc_slice_hash_table_create(num_entries, entries,
-                                                       unref_value, nullptr);
-    gpr_free(entries);
-  }
-  return method_config_table;
-}
-
-void* grpc_method_config_table_get(const grpc_slice_hash_table* table,
-                                   grpc_slice path) {
-  void* value = grpc_slice_hash_table_get(table, path);
-  // If we didn't find a match for the path, try looking for a wildcard
-  // entry (i.e., change "/service/method" to "/service/*").
-  if (value == nullptr) {
-    char* path_str = grpc_slice_to_c_string(path);
-    const char* sep = strrchr(path_str, '/') + 1;
-    const size_t len = static_cast<size_t>(sep - path_str);
-    char* buf = static_cast<char*>(gpr_malloc(len + 2));  // '*' and NUL
-    memcpy(buf, path_str, len);
-    buf[len] = '*';
-    buf[len + 1] = '\0';
-    grpc_slice wildcard_path = grpc_slice_from_copied_string(buf);
-    gpr_free(buf);
-    value = grpc_slice_hash_table_get(table, wildcard_path);
-    grpc_slice_unref_internal(wildcard_path);
-    gpr_free(path_str);
-  }
-  return value;
-}
+}  // namespace grpc_core
diff --git a/src/core/lib/transport/service_config.h b/src/core/lib/transport/service_config.h
index 6517f36802..a65b267d46 100644
--- a/src/core/lib/transport/service_config.h
+++ b/src/core/lib/transport/service_config.h
@@ -20,44 +20,230 @@
 #include <grpc/support/port_platform.h>
 
 #include <grpc/impl/codegen/grpc_types.h>
+#include <grpc/support/string_util.h>
 
+#include "src/core/lib/gprpp/inlined_vector.h"
+#include "src/core/lib/gprpp/ref_counted_ptr.h"
 #include "src/core/lib/json/json.h"
 #include "src/core/lib/slice/slice_hash_table.h"
 
-typedef struct grpc_service_config grpc_service_config;
-
-grpc_service_config* grpc_service_config_create(const char* json_string);
-void grpc_service_config_destroy(grpc_service_config* service_config);
-
-/// Invokes \a process_json() for each global parameter in the service
-/// config.  \a arg is passed as the second argument to \a process_json().
-void grpc_service_config_parse_global_params(
-    const grpc_service_config* service_config,
-    void (*process_json)(const grpc_json* json, void* arg), void* arg);
-
-/// Gets the LB policy name from \a service_config.
-/// Returns NULL if no LB policy name was specified.
-/// Caller does NOT take ownership.
-const char* grpc_service_config_get_lb_policy_name(
-    const grpc_service_config* service_config);
-
-/// Creates a method config table based on the data in \a json.
-/// The table's keys are request paths.  The table's value type is
-/// returned by \a create_value(), based on data parsed from the JSON tree.
-/// \a ref_value() and \a unref_value() are used to ref and unref values.
-/// Returns NULL on error.
-grpc_slice_hash_table* grpc_service_config_create_method_config_table(
-    const grpc_service_config* service_config,
-    void* (*create_value)(const grpc_json* method_config_json),
-    void* (*ref_value)(void* value), void (*unref_value)(void* value));
-
-/// A helper function for looking up values in the table returned by
-/// \a grpc_service_config_create_method_config_table().
-/// Gets the method config for the specified \a path, which should be of
-/// the form "/service/method".
-/// Returns NULL if the method has no config.
-/// Caller does NOT own a reference to the result.
-void* grpc_method_config_table_get(const grpc_slice_hash_table* table,
-                                   grpc_slice path);
+// The main purpose of the code here is to parse the service config in
+// JSON form, which will look like this:
+//
+// {
+//   "loadBalancingPolicy": "string",  // optional
+//   "methodConfig": [  // array of one or more method_config objects
+//     {
+//       "name": [  // array of one or more name objects
+//         {
+//           "service": "string",  // required
+//           "method": "string",  // optional
+//         }
+//       ],
+//       // remaining fields are optional.
+//       // see
+//       https://developers.google.com/protocol-buffers/docs/proto3#json
+//       // for format details.
+//       "waitForReady": bool,
+//       "timeout": "duration_string",
+//       "maxRequestMessageBytes": "int64_string",
+//       "maxResponseMessageBytes": "int64_string",
+//     }
+//   ]
+// }
+
+namespace grpc_core {
+
+class ServiceConfig {
+ public:
+  /// Creates a new service config from parsing \a json_string.
+  /// Returns null on parse error.
+  static UniquePtr<ServiceConfig> Create(const char* json);
+
+  ~ServiceConfig();
+
+  /// Invokes \a process_json() for each global parameter in the service
+  /// config.  \a arg is passed as the second argument to \a process_json().
+  template <typename T>
+  using ProcessJson = void (*)(const grpc_json*, T*);
+  template <typename T>
+  void ParseGlobalParams(ProcessJson<T> process_json, T* arg) const;
+
+  /// Gets the LB policy name from \a service_config.
+  /// Returns NULL if no LB policy name was specified.
+  /// Caller does NOT take ownership.
+  const char* GetLoadBalancingPolicyName() const;
+
+  /// Creates a method config table based on the data in \a json.
+  /// The table's keys are request paths.  The table's value type is
+  /// returned by \a create_value(), based on data parsed from the JSON tree.
+  /// Returns null on error.
+  template <typename T>
+  using CreateValue = RefCountedPtr<T> (*)(const grpc_json* method_config_json);
+  template <typename T>
+  RefCountedPtr<SliceHashTable<RefCountedPtr<T>>> CreateMethodConfigTable(
+      CreateValue<T> create_value);
+
+  /// A helper function for looking up values in the table returned by
+  /// \a CreateMethodConfigTable().
+  /// Gets the method config for the specified \a path, which should be of
+  /// the form "/service/method".
+  /// Returns null if the method has no config.
+  /// Caller does NOT own a reference to the result.
+  template <typename T>
+  static RefCountedPtr<T> MethodConfigTableLookup(
+      const SliceHashTable<RefCountedPtr<T>>& table, grpc_slice path);
+
+ private:
+  // So New() can call our private ctor.
+  template <typename T, typename... Args>
+  friend T* New(Args&&... args);
+
+  // Takes ownership of \a json_tree.
+  ServiceConfig(UniquePtr<char> json_string, grpc_json* json_tree);
+
+  // Returns the number of names specified in the method config \a json.
+  static size_t CountNamesInMethodConfig(grpc_json* json);
+
+  // Returns a path string for the JSON name object specified by \a json.
+  // Returns null on error.
+  static UniquePtr<char> ParseJsonMethodName(grpc_json* json);
+
+  // Parses the method config from \a json.  Adds an entry to \a entries for
+  // each name found, incrementing \a idx for each entry added.
+  // Returns false on error.
+  template <typename T>
+  static bool ParseJsonMethodConfig(
+      grpc_json* json, CreateValue<T> create_value,
+      typename SliceHashTable<RefCountedPtr<T>>::Entry* entries, size_t* idx);
+
+  UniquePtr<char> json_string_;  // Underlying storage for json_tree.
+  grpc_json* json_tree_;
+};
+
+//
+// implementation -- no user-serviceable parts below
+//
+
+template <typename T>
+void ServiceConfig::ParseGlobalParams(ProcessJson<T> process_json,
+                                      T* arg) const {
+  if (json_tree_->type != GRPC_JSON_OBJECT || json_tree_->key != nullptr) {
+    return;
+  }
+  for (grpc_json* field = json_tree_->child; field != nullptr;
+       field = field->next) {
+    if (field->key == nullptr) return;
+    if (strcmp(field->key, "methodConfig") == 0) continue;
+    process_json(field, arg);
+  }
+}
+
+template <typename T>
+bool ServiceConfig::ParseJsonMethodConfig(
+    grpc_json* json, CreateValue<T> create_value,
+    typename SliceHashTable<RefCountedPtr<T>>::Entry* entries, size_t* idx) {
+  // Construct value.
+  RefCountedPtr<T> method_config = create_value(json);
+  if (method_config == nullptr) return false;
+  // Construct list of paths.
+  InlinedVector<UniquePtr<char>, 10> paths;
+  for (grpc_json* child = json->child; child != nullptr; child = child->next) {
+    if (child->key == nullptr) continue;
+    if (strcmp(child->key, "name") == 0) {
+      if (child->type != GRPC_JSON_ARRAY) return false;
+      for (grpc_json* name = child->child; name != nullptr; name = name->next) {
+        UniquePtr<char> path = ParseJsonMethodName(name);
+        if (path == nullptr) return false;
+        paths.push_back(std::move(path));
+      }
+    }
+  }
+  if (paths.size() == 0) return false;  // No names specified.
+  // Add entry for each path.
+  for (size_t i = 0; i < paths.size(); ++i) {
+    entries[*idx].key = grpc_slice_from_copied_string(paths[i].get());
+    entries[*idx].value = method_config;  // Takes a new ref.
+    ++*idx;
+  }
+  // Success.
+  return true;
+}
+
+template <typename T>
+RefCountedPtr<SliceHashTable<RefCountedPtr<T>>>
+ServiceConfig::CreateMethodConfigTable(CreateValue<T> create_value) {
+  // Traverse parsed JSON tree.
+  if (json_tree_->type != GRPC_JSON_OBJECT || json_tree_->key != nullptr) {
+    return nullptr;
+  }
+  size_t num_entries = 0;
+  typename SliceHashTable<RefCountedPtr<T>>::Entry* entries = nullptr;
+  for (grpc_json* field = json_tree_->child; field != nullptr;
+       field = field->next) {
+    if (field->key == nullptr) return nullptr;
+    if (strcmp(field->key, "methodConfig") == 0) {
+      if (entries != nullptr) return nullptr;  // Duplicate.
+      if (field->type != GRPC_JSON_ARRAY) return nullptr;
+      // Find number of entries.
+      for (grpc_json* method = field->child; method != nullptr;
+           method = method->next) {
+        size_t count = CountNamesInMethodConfig(method);
+        if (count <= 0) return nullptr;
+        num_entries += count;
+      }
+      // Populate method config table entries.
+      entries = static_cast<typename SliceHashTable<RefCountedPtr<T>>::Entry*>(
+          gpr_zalloc(num_entries *
+                     sizeof(typename SliceHashTable<RefCountedPtr<T>>::Entry)));
+      size_t idx = 0;
+      for (grpc_json* method = field->child; method != nullptr;
+           method = method->next) {
+        if (!ParseJsonMethodConfig(method, create_value, entries, &idx)) {
+          for (size_t i = 0; i < idx; ++i) {
+            grpc_slice_unref_internal(entries[i].key);
+            entries[i].value.reset();
+          }
+          gpr_free(entries);
+          return nullptr;
+        }
+      }
+      GPR_ASSERT(idx == num_entries);
+    }
+  }
+  // Instantiate method config table.
+  RefCountedPtr<SliceHashTable<RefCountedPtr<T>>> method_config_table;
+  if (entries != nullptr) {
+    method_config_table =
+        SliceHashTable<RefCountedPtr<T>>::Create(num_entries, entries, nullptr);
+    gpr_free(entries);
+  }
+  return method_config_table;
+}
+
+template <typename T>
+RefCountedPtr<T> ServiceConfig::MethodConfigTableLookup(
+    const SliceHashTable<RefCountedPtr<T>>& table, grpc_slice path) {
+  const RefCountedPtr<T>* value = table.Get(path);
+  // If we didn't find a match for the path, try looking for a wildcard
+  // entry (i.e., change "/service/method" to "/service/*").
+  if (value == nullptr) {
+    char* path_str = grpc_slice_to_c_string(path);
+    const char* sep = strrchr(path_str, '/') + 1;
+    const size_t len = (size_t)(sep - path_str);
+    char* buf = (char*)gpr_malloc(len + 2);  // '*' and NUL
+    memcpy(buf, path_str, len);
+    buf[len] = '*';
+    buf[len + 1] = '\0';
+    grpc_slice wildcard_path = grpc_slice_from_copied_string(buf);
+    gpr_free(buf);
+    value = table.Get(wildcard_path);
+    grpc_slice_unref_internal(wildcard_path);
+    gpr_free(path_str);
+  }
+  return RefCountedPtr<T>(*value);
+}
+
+}  // namespace grpc_core
 
 #endif /* GRPC_CORE_LIB_TRANSPORT_SERVICE_CONFIG_H */