1 files changed, 127 insertions, 0 deletions
diff --git a/src/core/lib/slice/slice_hash_table.c b/src/core/lib/slice/slice_hash_table.c
new file mode 100644
index 0000000000..46f807f4a5
--- /dev/null
+++ b/src/core/lib/slice/slice_hash_table.c
@@ -0,0 +1,127 @@
+//
+// 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/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;
+  size_t size;
+  grpc_slice_hash_table_entry* entries;
+};
+
+static bool is_empty(grpc_slice_hash_table_entry* entry) {
+  return entry->vtable == NULL;
+}
+
+// Helper function for insert and get operations that performs quadratic
+// probing (https://en.wikipedia.org/wiki/Quadratic_probing).
+static size_t grpc_slice_hash_table_find_index(
+    const grpc_slice_hash_table* table, const grpc_slice key, bool find_empty) {
+  size_t hash = grpc_slice_hash(key);
+  for (size_t i = 0; i < table->size; ++i) {
+    const size_t idx = (hash + i * i) % table->size;
+    if (is_empty(&table->entries[idx])) {
+      return find_empty ? idx : table->size;
+    }
+    if (grpc_slice_eq(table->entries[idx].key, key)) {
+      return idx;
+    }
+  }
+  return table->size;  // Not found.
+}
+
+static void grpc_slice_hash_table_add(
+    grpc_slice_hash_table* table, grpc_slice key, void* value,
+    const grpc_slice_hash_table_vtable* vtable) {
+  GPR_ASSERT(value != NULL);
+  const size_t idx =
+      grpc_slice_hash_table_find_index(table, key, true /* find_empty */);
+  GPR_ASSERT(idx != table->size);  // Table should never be full.
+  grpc_slice_hash_table_entry* entry = &table->entries[idx];
+  entry->key = grpc_slice_ref_internal(key);
+  entry->value = vtable->copy_value(value);
+  entry->vtable = vtable;
+}
+
+grpc_slice_hash_table* grpc_slice_hash_table_create(
+    size_t num_entries, grpc_slice_hash_table_entry* entries) {
+  grpc_slice_hash_table* table = gpr_malloc(sizeof(*table));
+  memset(table, 0, sizeof(*table));
+  gpr_ref_init(&table->refs, 1);
+  // Quadratic probing gets best performance when the table is no more
+  // than half full.
+  table->size = num_entries * 2;
+  const size_t entry_size = sizeof(grpc_slice_hash_table_entry) * table->size;
+  table->entries = gpr_malloc(entry_size);
+  memset(table->entries, 0, 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, entry->vtable);
+  }
+  return table;
+}
+
+grpc_slice_hash_table* grpc_slice_hash_table_ref(grpc_slice_hash_table* table) {
+  if (table != NULL) gpr_ref(&table->refs);
+  return table;
+}
+
+void grpc_slice_hash_table_unref(grpc_exec_ctx* exec_ctx,
+                                 grpc_slice_hash_table* table) {
+  if (table != NULL && 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(exec_ctx, entry->key);
+        entry->vtable->destroy_value(exec_ctx, 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 idx =
+      grpc_slice_hash_table_find_index(table, key, false /* find_empty */);
+  if (idx == table->size) return NULL;  // Not found.
+  return table->entries[idx].value;
+}