Refactor hash table code into its own module and use it for method_config as well as method_config_table.

2 files changed, 221 insertions, 0 deletions

diff --git a/src/core/lib/transport/hashtable.c b/src/core/lib/transport/hashtable.c
new file mode 100644
index 0000000000..89e2640969
--- /dev/null
+++ b/src/core/lib/transport/hashtable.c
@@ -0,0 +1,139 @@
+//
+// Copyright 2016, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+
+#include "src/core/lib/transport/hashtable.h"
+
+#include <stdbool.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/transport/metadata.h"
+
+struct grpc_hash_table {
+  gpr_refcount refs;
+  size_t num_entries;
+  grpc_hash_table_entry* entries;
+};
+
+// Helper function for insert and get operations that performs quadratic
+// probing (https://en.wikipedia.org/wiki/Quadratic_probing).
+static size_t grpc_hash_table_find_index(
+    grpc_hash_table* table, grpc_mdstr* key, bool find_empty) {
+  for (size_t i = 0; i < table->num_entries; ++i) {
+    const size_t idx = (key->hash + i * i) % table->num_entries;
+    if (table->entries[idx].key == NULL)
+      return find_empty ? idx : table->num_entries;
+    if (table->entries[idx].key == key) return idx;
+  }
+  return table->num_entries;  // Not found.
+}
+
+static void grpc_hash_table_add(grpc_hash_table* table, grpc_mdstr* key,
+                                void* value,
+                                const grpc_hash_table_vtable* vtable) {
+  GPR_ASSERT(value != NULL);
+  const size_t idx =
+      grpc_hash_table_find_index(table, key, true /* find_empty */);
+  // This can happen if the table is full.
+  GPR_ASSERT(idx != table->num_entries);
+  grpc_hash_table_entry* entry = &table->entries[idx];
+  entry->key = GRPC_MDSTR_REF(key);
+  entry->value = vtable->copy_value(value);
+  entry->vtable = vtable;
+}
+
+grpc_hash_table* grpc_hash_table_create(size_t num_entries,
+                                        grpc_hash_table_entry* entries) {
+  grpc_hash_table* table = gpr_malloc(sizeof(*table));
+  memset(table, 0, sizeof(*table));
+  gpr_ref_init(&table->refs, 1);
+  // Quadratic chaining gets best performance when the table is no more
+  // than half full.
+  table->num_entries = num_entries * 2;
+  const size_t entry_size = sizeof(grpc_hash_table_entry) * table->num_entries;
+  table->entries = gpr_malloc(entry_size);
+  memset(table->entries, 0, entry_size);
+  for (size_t i = 0; i < num_entries; ++i) {
+    grpc_hash_table_entry* entry = &entries[i];
+    grpc_hash_table_add(table, entry->key, entry->value, entry->vtable);
+  }
+  return table;
+}
+
+grpc_hash_table* grpc_hash_table_ref(grpc_hash_table* table) {
+  if (table != NULL) gpr_ref(&table->refs);
+  return table;
+}
+
+int grpc_hash_table_unref(grpc_hash_table* table) {
+  if (table != NULL && gpr_unref(&table->refs)) {
+    for (size_t i = 0; i < table->num_entries; ++i) {
+      grpc_hash_table_entry* entry = &table->entries[i];
+      if (entry->key != NULL) {
+        GRPC_MDSTR_UNREF(entry->key);
+        entry->vtable->destroy_value(entry->value);
+      }
+    }
+    gpr_free(table->entries);
+    gpr_free(table);
+    return 1;
+  }
+  return 0;
+}
+
+void* grpc_hash_table_get(grpc_hash_table* table, grpc_mdstr* key) {
+  const size_t idx =
+      grpc_hash_table_find_index(table, key, false /* find_empty */);
+  if (idx == table->num_entries) return NULL;  // Not found.
+  return table->entries[idx].value;
+}
+
+int grpc_hash_table_cmp(grpc_hash_table* table1, grpc_hash_table* table2) {
+  // Compare by num_entries.
+  if (table1->num_entries < table2->num_entries) return -1;
+  if (table1->num_entries > table2->num_entries) return 1;
+  for (size_t i = 0; i < table1->num_entries; ++i) {
+    grpc_hash_table_entry* e1 = &table1->entries[i];
+    grpc_hash_table_entry* e2 = &table2->entries[i];
+    // Compare keys by hash value.
+    if (e1->key->hash < e2->key->hash) return -1;
+    if (e1->key->hash > e2->key->hash) return 1;
+    // Compare by vtable (pointer equality).
+    if (e1->vtable < e2->vtable) return -1;
+    if (e1->vtable > e2->vtable) return 1;
+    // Compare values via vtable.
+    const int value_result = e1->vtable->compare_value(e1->value, e2->value);
+    if (value_result != 0) return value_result;
+  }
+  return 0;
+}
diff --git a/src/core/lib/transport/hashtable.h b/src/core/lib/transport/hashtable.h
new file mode 100644
index 0000000000..93f0642c17
--- /dev/null
+++ b/src/core/lib/transport/hashtable.h
@@ -0,0 +1,82 @@
+/*
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef GRPC_CORE_LIB_TRANSPORT_HASHTABLE_H
+#define GRPC_CORE_LIB_TRANSPORT_HASHTABLE_H
+
+#include "src/core/lib/transport/metadata.h"
+
+/** Hash table implementation.
+ *
+ * This implementation uses open addressing
+ * (https://en.wikipedia.org/wiki/Open_addressing) with quadratic
+ * probing (https://en.wikipedia.org/wiki/Quadratic_probing).
+ * This means that the hash table is of fixed size and cannot contain
+ * more than that number of elements.
+ *
+ * The keys are grpc_mdstr objects.  The values are arbitrary pointers
+ * with a common vtable.
+ *
+ * Hash tables are intentionally immutable, to avoid the need for locking.
+ */
+
+typedef struct grpc_hash_table grpc_hash_table;
+
+typedef struct grpc_hash_table_vtable {
+  void (*destroy_value)(void* value);
+  void* (*copy_value)(void* value);
+  int (*compare_value)(void* value1, void* value2);
+} grpc_hash_table_vtable;
+
+typedef struct grpc_hash_table_entry {
+  grpc_mdstr* key;
+  void* value;  /* Must not be NULL. */
+  const grpc_hash_table_vtable* vtable;
+} grpc_hash_table_entry;
+
+/** Creates a new hash table of containing \a entries, which is an array
+    of length \a num_entries.
+    Creates its own copy of all keys and values from \a entries. */
+grpc_hash_table* grpc_hash_table_create(size_t num_entries,
+                                        grpc_hash_table_entry* entries);
+
+grpc_hash_table* grpc_hash_table_ref(grpc_hash_table* table);
+/** Returns 1 when \a table is destroyed. */
+int grpc_hash_table_unref(grpc_hash_table* table);
+
+/** Returns the value from \a table associated with \a key.
+    Returns NULL if \a key is not found. */
+void* grpc_hash_table_get(grpc_hash_table* table, grpc_mdstr* key);
+
+/** Compares two hash tables. */
+int grpc_hash_table_cmp(grpc_hash_table* table1, grpc_hash_table* table2);
+
+#endif /* GRPC_CORE_LIB_TRANSPORT_HASHTABLE_H */