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

2 files changed, 176 insertions, 192 deletions

diff --git a/src/core/lib/slice/slice_hash_table.cc b/src/core/lib/slice/slice_hash_table.cc
deleted file mode 100644
index 9e32321636..0000000000
--- a/src/core/lib/slice/slice_hash_table.cc
+++ /dev/null
@@ -1,147 +0,0 @@
-//
-// Copyright 2016 gRPC authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-//
-
-#include <grpc/support/port_platform.h>
-
-#include "src/core/lib/slice/slice_hash_table.h"
-
-#include <stdbool.h>
-#include <string.h>
-
-#include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
-
-#include "src/core/lib/slice/slice_internal.h"
-#include "src/core/lib/transport/metadata.h"
-
-struct grpc_slice_hash_table {
-  gpr_refcount refs;
-  void (*destroy_value)(void* value);
-  int (*value_cmp)(void* a, void* b);
-  size_t size;
-  size_t max_num_probes;
-  grpc_slice_hash_table_entry* entries;
-};
-
-static bool is_empty(grpc_slice_hash_table_entry* entry) {
-  return entry->value == nullptr;
-}
-
-static void grpc_slice_hash_table_add(grpc_slice_hash_table* table,
-                                      grpc_slice key, void* value) {
-  GPR_ASSERT(value != nullptr);
-  const size_t hash = grpc_slice_hash(key);
-  for (size_t offset = 0; offset < table->size; ++offset) {
-    const size_t idx = (hash + offset) % table->size;
-    if (is_empty(&table->entries[idx])) {
-      table->entries[idx].key = key;
-      table->entries[idx].value = value;
-      // Keep track of the maximum number of probes needed, since this
-      // provides an upper bound for lookups.
-      if (offset > table->max_num_probes) table->max_num_probes = offset;
-      return;
-    }
-  }
-  GPR_ASSERT(false);  // Table should never be full.
-}
-
-grpc_slice_hash_table* grpc_slice_hash_table_create(
-    size_t num_entries, grpc_slice_hash_table_entry* entries,
-    void (*destroy_value)(void* value), int (*value_cmp)(void* a, void* b)) {
-  grpc_slice_hash_table* table =
-      static_cast<grpc_slice_hash_table*>(gpr_zalloc(sizeof(*table)));
-  gpr_ref_init(&table->refs, 1);
-  table->destroy_value = destroy_value;
-  table->value_cmp = value_cmp;
-  // Keep load factor low to improve performance of lookups.
-  table->size = num_entries * 2;
-  const size_t entry_size = sizeof(grpc_slice_hash_table_entry) * table->size;
-  table->entries =
-      static_cast<grpc_slice_hash_table_entry*>(gpr_zalloc(entry_size));
-  for (size_t i = 0; i < num_entries; ++i) {
-    grpc_slice_hash_table_entry* entry = &entries[i];
-    grpc_slice_hash_table_add(table, entry->key, entry->value);
-  }
-  return table;
-}
-
-grpc_slice_hash_table* grpc_slice_hash_table_ref(grpc_slice_hash_table* table) {
-  if (table != nullptr) gpr_ref(&table->refs);
-  return table;
-}
-
-void grpc_slice_hash_table_unref(grpc_slice_hash_table* table) {
-  if (table != nullptr && gpr_unref(&table->refs)) {
-    for (size_t i = 0; i < table->size; ++i) {
-      grpc_slice_hash_table_entry* entry = &table->entries[i];
-      if (!is_empty(entry)) {
-        grpc_slice_unref_internal(entry->key);
-        table->destroy_value(entry->value);
-      }
-    }
-    gpr_free(table->entries);
-    gpr_free(table);
-  }
-}
-
-void* grpc_slice_hash_table_get(const grpc_slice_hash_table* table,
-                                const grpc_slice key) {
-  const size_t hash = grpc_slice_hash(key);
-  // We cap the number of probes at the max number recorded when
-  // populating the table.
-  for (size_t offset = 0; offset <= table->max_num_probes; ++offset) {
-    const size_t idx = (hash + offset) % table->size;
-    if (is_empty(&table->entries[idx])) break;
-    if (grpc_slice_eq(table->entries[idx].key, key)) {
-      return table->entries[idx].value;
-    }
-  }
-  return nullptr;  // Not found.
-}
-
-static int pointer_cmp(void* a, void* b) { return GPR_ICMP(a, b); }
-int grpc_slice_hash_table_cmp(const grpc_slice_hash_table* a,
-                              const grpc_slice_hash_table* b) {
-  int (*const value_cmp_fn_a)(void* a, void* b) =
-      a->value_cmp != nullptr ? a->value_cmp : pointer_cmp;
-  int (*const value_cmp_fn_b)(void* a, void* b) =
-      b->value_cmp != nullptr ? b->value_cmp : pointer_cmp;
-  // Compare value_fns
-  const int value_fns_cmp =
-      GPR_ICMP((void*)value_cmp_fn_a, (void*)value_cmp_fn_b);
-  if (value_fns_cmp != 0) return value_fns_cmp;
-  // Compare sizes
-  if (a->size < b->size) return -1;
-  if (a->size > b->size) return 1;
-  // Compare rows.
-  for (size_t i = 0; i < a->size; ++i) {
-    if (is_empty(&a->entries[i])) {
-      if (!is_empty(&b->entries[i])) {
-        return -1;  // a empty but b non-empty
-      }
-      continue;  // both empty, no need to check key or value
-    } else if (is_empty(&b->entries[i])) {
-      return 1;  // a non-empty but b empty
-    }
-    // neither entry is empty
-    const int key_cmp = grpc_slice_cmp(a->entries[i].key, b->entries[i].key);
-    if (key_cmp != 0) return key_cmp;
-    const int value_cmp =
-        value_cmp_fn_a(a->entries[i].value, b->entries[i].value);
-    if (value_cmp != 0) return value_cmp;
-  }
-  return 0;
-}
diff --git a/src/core/lib/slice/slice_hash_table.h b/src/core/lib/slice/slice_hash_table.h
index 819bb3b5bc..fbe9cc58e8 100644
--- a/src/core/lib/slice/slice_hash_table.h
+++ b/src/core/lib/slice/slice_hash_table.h
@@ -19,52 +19,183 @@
 
 #include <grpc/support/port_platform.h>
 
-#include "src/core/lib/transport/metadata.h"
+#include <string.h>
 
-/** Hash table implementation.
- *
- * This implementation uses open addressing
- * (https://en.wikipedia.org/wiki/Open_addressing) with linear
- * probing (https://en.wikipedia.org/wiki/Linear_probing).
- *
- * The keys are \a grpc_slice objects.  The values are arbitrary pointers
- * with a common destroy function.
- *
- * Hash tables are intentionally immutable, to avoid the need for locking.
- */
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/gpr/useful.h"
+#include "src/core/lib/gprpp/ref_counted.h"
+#include "src/core/lib/gprpp/ref_counted_ptr.h"
+#include "src/core/lib/slice/slice_internal.h"
+
+/// Hash table implementation.
+///
+/// This implementation uses open addressing
+/// (https://en.wikipedia.org/wiki/Open_addressing) with linear
+/// probing (https://en.wikipedia.org/wiki/Linear_probing).
+///
+/// The keys are \a grpc_slice objects.  The values can be any type.
+///
+/// Hash tables are intentionally immutable, to avoid the need for locking.
+
+namespace grpc_core {
+
+template <typename T>
+class SliceHashTable : public RefCounted<SliceHashTable<T>> {
+ public:
+  struct Entry {
+    grpc_slice key;
+    T value;
+    bool is_set;
+  };
+
+  // Function for comparing values.
+  // TODO(roth): Eliminate this and the Cmp() method from this API once
+  // grpc_channel_args is redesigned to require that keys are unique.
+  typedef int (*ValueCmp)(const T&, const T&);
+
+  /// Creates a new hash table containing \a entries, which is an array
+  /// of length \a num_entries.  Takes ownership of all keys and values in \a
+  /// entries.  If not null, \a value_cmp will be used to compare values in
+  /// the context of \a Cmp(). If null, raw pointer (\a GPR_ICMP) comparison
+  /// will be used.
+  static RefCountedPtr<SliceHashTable> Create(size_t num_entries,
+                                              Entry* entries,
+                                              ValueCmp value_cmp);
+
+  /// Returns the value from the table associated with \a key.
+  /// Returns null if \a key is not found.
+  const T* Get(const grpc_slice& key) const;
+
+  /// Compares \a a vs. \a b.
+  /// A table is considered "smaller" (resp. "greater") if:
+  ///  - GPR_ICMP(a->value_cmp, b->value_cmp) < 1 (resp. > 1),
+  ///  - else, it contains fewer (resp. more) entries,
+  ///  - else, if strcmp(a_key, b_key) < 1 (resp. > 1),
+  ///  - else, if value_cmp(a_value, b_value) < 1 (resp. > 1).
+  static int Cmp(const SliceHashTable& a, const SliceHashTable& b);
+
+ private:
+  // So New() can call our private ctor.
+  template <typename T2, typename... Args>
+  friend T2* New(Args&&... args);
+
+  SliceHashTable(size_t num_entries, Entry* entries, ValueCmp value_cmp);
+  virtual ~SliceHashTable();
+
+  void Add(grpc_slice key, T& value);
+
+  // Default value comparison function, if none specified by caller.
+  static int DefaultValueCmp(const T& a, const T& b) { return GPR_ICMP(a, b); }
+
+  const ValueCmp value_cmp_;
+  const size_t size_;
+  size_t max_num_probes_;
+  Entry* entries_;
+};
+
+//
+// implementation -- no user-serviceable parts below
+//
+
+template <typename T>
+RefCountedPtr<SliceHashTable<T>> SliceHashTable<T>::Create(size_t num_entries,
+                                                           Entry* entries,
+                                                           ValueCmp value_cmp) {
+  return MakeRefCounted<SliceHashTable<T>>(num_entries, entries, value_cmp);
+}
+
+template <typename T>
+SliceHashTable<T>::SliceHashTable(size_t num_entries, Entry* entries,
+                                  ValueCmp value_cmp)
+    : value_cmp_(value_cmp),
+      // Keep load factor low to improve performance of lookups.
+      size_(num_entries * 2),
+      max_num_probes_(0) {
+  entries_ = static_cast<Entry*>(gpr_zalloc(sizeof(Entry) * size_));
+  for (size_t i = 0; i < num_entries; ++i) {
+    Entry* entry = &entries[i];
+    Add(entry->key, entry->value);
+  }
+}
+
+template <typename T>
+SliceHashTable<T>::~SliceHashTable() {
+  for (size_t i = 0; i < size_; ++i) {
+    Entry& entry = entries_[i];
+    if (entry.is_set) {
+      grpc_slice_unref_internal(entry.key);
+      entry.value.~T();
+    }
+  }
+  gpr_free(entries_);
+}
+
+template <typename T>
+void SliceHashTable<T>::Add(grpc_slice key, T& value) {
+  const size_t hash = grpc_slice_hash(key);
+  for (size_t offset = 0; offset < size_; ++offset) {
+    const size_t idx = (hash + offset) % size_;
+    if (!entries_[idx].is_set) {
+      entries_[idx].is_set = true;
+      entries_[idx].key = key;
+      entries_[idx].value = std::move(value);
+      // Keep track of the maximum number of probes needed, since this
+      // provides an upper bound for lookups.
+      if (offset > max_num_probes_) max_num_probes_ = offset;
+      return;
+    }
+  }
+  GPR_ASSERT(false);  // Table should never be full.
+}
+
+template <typename T>
+const T* SliceHashTable<T>::Get(const grpc_slice& key) const {
+  const size_t hash = grpc_slice_hash(key);
+  // We cap the number of probes at the max number recorded when
+  // populating the table.
+  for (size_t offset = 0; offset <= max_num_probes_; ++offset) {
+    const size_t idx = (hash + offset) % size_;
+    if (!entries_[idx].is_set) break;
+    if (grpc_slice_eq(entries_[idx].key, key)) {
+      return &entries_[idx].value;
+    }
+  }
+  return nullptr;  // Not found.
+}
+
+template <typename T>
+int SliceHashTable<T>::Cmp(const SliceHashTable& a, const SliceHashTable& b) {
+  ValueCmp value_cmp_a =
+      a.value_cmp_ != nullptr ? a.value_cmp_ : DefaultValueCmp;
+  ValueCmp value_cmp_b =
+      b.value_cmp_ != nullptr ? b.value_cmp_ : DefaultValueCmp;
+  // Compare value_fns
+  const int value_fns_cmp = GPR_ICMP((void*)value_cmp_a, (void*)value_cmp_b);
+  if (value_fns_cmp != 0) return value_fns_cmp;
+  // Compare sizes
+  if (a.size_ < b.size_) return -1;
+  if (a.size_ > b.size_) return 1;
+  // Compare rows.
+  for (size_t i = 0; i < a.size_; ++i) {
+    if (!a.entries_[i].is_set) {
+      if (b.entries_[i].is_set) {
+        return -1;  // a empty but b non-empty
+      }
+      continue;  // both empty, no need to check key or value
+    } else if (!b.entries_[i].is_set) {
+      return 1;  // a non-empty but b empty
+    }
+    // neither entry is empty
+    const int key_cmp = grpc_slice_cmp(a.entries_[i].key, b.entries_[i].key);
+    if (key_cmp != 0) return key_cmp;
+    const int value_cmp = value_cmp_a(a.entries_[i].value, b.entries_[i].value);
+    if (value_cmp != 0) return value_cmp;
+  }
+  return 0;
+}
 
-typedef struct grpc_slice_hash_table grpc_slice_hash_table;
-
-typedef struct grpc_slice_hash_table_entry {
-  grpc_slice key;
-  void* value; /* Must not be NULL. */
-} grpc_slice_hash_table_entry;
-
-/** Creates a new hash table of containing \a entries, which is an array
-    of length \a num_entries.  Takes ownership of all keys and values in \a
-    entries.  Values will be cleaned up via \a destroy_value(). If not NULL, \a
-    value_cmp will be used to compare values in the context of \a
-    grpc_slice_hash_table_cmp. If NULL, raw pointer (\a GPR_ICMP) comparison
-    will be used. */
-grpc_slice_hash_table* grpc_slice_hash_table_create(
-    size_t num_entries, grpc_slice_hash_table_entry* entries,
-    void (*destroy_value)(void* value), int (*value_cmp)(void* a, void* b));
-
-grpc_slice_hash_table* grpc_slice_hash_table_ref(grpc_slice_hash_table* table);
-void grpc_slice_hash_table_unref(grpc_slice_hash_table* table);
-
-/** Returns the value from \a table associated with \a key.
-    Returns NULL if \a key is not found. */
-void* grpc_slice_hash_table_get(const grpc_slice_hash_table* table,
-                                const grpc_slice key);
-
-/** Compares \a a vs. \a b.
- * A table is considered "smaller" (resp. "greater") if:
- *  - GPR_ICMP(a->value_cmp, b->value_cmp) < 1 (resp. > 1),
- *  - else, it contains fewer (resp. more) entries,
- *  - else, if strcmp(a_key, b_key) < 1 (resp. > 1),
- *  - else, if value_cmp(a_value, b_value) < 1 (resp. > 1). */
-int grpc_slice_hash_table_cmp(const grpc_slice_hash_table* a,
-                              const grpc_slice_hash_table* b);
+}  // namespace grpc_core
 
 #endif /* GRPC_CORE_LIB_SLICE_SLICE_HASH_TABLE_H */