feat: Copy event.h from B&A to common repo

This is part of a series of CLs to copy
the KV BYOS clients from B&A to common repo.

Bug: 411430242
Change-Id: I8bfab3ade62fd66003320da395907a9c8c378430
GitOrigin-RevId: 5a29336d8a1bd93f8e0ea3fef0364c6330557d52

Author: Privacy Sandbox Team

src/core/event/BUILD.bazel

@@ -0,0 +1,50 @@
+# Copyright 2025 Google LLC
+#
+# 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.
+
+load("@rules_cc//cc:defs.bzl", "cc_library")
+
+cc_library(
+    name = "constants",
+    hdrs = [
+        "constants.h",
+    ],
+)
+
+cc_library(
+    name = "event_base",
+    srcs = ["event_base.cc"],
+    hdrs = [
+        "event_base.h",
+    ],
+    visibility = ["//visibility:public"],
+    deps = [
+        ":constants",
+        "@google_privacysandbox_servers_common//src/logger:request_context_logger",
+        "@libevent//:event",
+    ],
+)
+
+cc_library(
+    name = "event",
+    srcs = ["event.cc"],
+    hdrs = [
+        "event.h",
+    ],
+    visibility = ["//visibility:public"],
+    deps = [
+        ":constants",
+        "@google_privacysandbox_servers_common//src/logger:request_context_logger",
+        "@libevent//:event",
+    ],
+)

src/core/event/constants.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * 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.
+ */
+
+#ifndef SRC_CORE_EVENT_CONSTANTS_H_
+#define SRC_CORE_EVENT_CONSTANTS_H_
+
+namespace privacy_sandbox::server_common {
+
+// Libevent uses default priority as half of the number of priorities.
+// We needed 2 priorities to begin with (high and default) but configured 3
+// here for future use if we have to configure a low priority event.
+inline constexpr int kNumEventPriorities = 3;
+
+}  // namespace privacy_sandbox::server_common
+
+#endif  // SRC_CORE_EVENT_CONSTANTS_H_

src/core/event/event.cc

@@ -0,0 +1,48 @@
+//  Copyright 2025 Google LLC
+//
+//  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 "src/core/event/event.h"
+
+#include <utility>
+
+#include "event2/event.h"
+#include "event2/event_struct.h"
+
+namespace privacy_sandbox::server_common {
+
+Event::Event(struct event_base* base, evutil_socket_t fd, int16_t event_type,
+             Event::Callback event_callback, void* arg, int priority,
+             struct timeval* event_timeout, OnDelete on_delete,
+             bool add_to_loop)
+    : priority_(priority),
+      event_(event_new(base, fd, event_type, event_callback, arg)),
+      on_delete_(std::move(on_delete)) {
+  event_priority_set(event_, priority_);
+  if (add_to_loop) {
+    event_add(event_, event_timeout);
+  }
+}
+
+struct event* Event::get() { return event_; }
+Event::~Event() {
+  if (event_) {
+    if (on_delete_) {
+      on_delete_(event_);
+    }
+    event_del(event_);
+    event_free(event_);
+  }
+}
+
+}  // namespace privacy_sandbox::server_common

src/core/event/event.h

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * 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.
+ */
+
+#ifndef SRC_CORE_EVENT_EVENT_H_
+#define SRC_CORE_EVENT_EVENT_H_
+
+#include <functional>
+
+#include "event2/event.h"
+#include "event2/event_struct.h"
+#include "src/core/event/constants.h"
+
+namespace privacy_sandbox::server_common {
+
+// Wraps the event used by libevent. This wrapper makes it easier to manage
+// lifecycle of the underlying event.
+class Event {
+ public:
+  using OnDelete = std::function<void(struct event*)>;
+  // Arguments are documented here:
+  // https://libevent.org/doc/event_8h.html#aed2307f3d9b38e07cc10c2607322d758
+  using Callback = void (*)(/*fd or signal=*/int, /*events=*/int16_t,
+                            /*pointer to user provided data=*/void*);
+
+  explicit Event(struct event_base* base, evutil_socket_t fd,
+                 int16_t event_type, Callback event_callback, void* arg,
+                 int priority = kNumEventPriorities / 2,
+                 struct timeval* event_timeout = nullptr,
+                 OnDelete on_delete = nullptr, bool add_to_loop = true);
+  struct event* get();
+  virtual ~Event();
+
+ private:
+  int priority_;
+  struct event* event_ = nullptr;
+  OnDelete on_delete_;
+};
+
+}  // namespace privacy_sandbox::server_common
+
+#endif  // SRC_CORE_EVENT_EVENT_H_

src/core/event/event_base.cc

@@ -0,0 +1,41 @@
+//  Copyright 2025 Google LLC
+//
+//  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 "src/core/event/event_base.h"
+
+#include "event2/event.h"
+#include "event2/thread.h"
+
+namespace privacy_sandbox::server_common {
+
+EventBase::EventBase(bool use_pthreads, int num_priorities) {
+  if (use_pthreads) {
+    evthread_use_pthreads();
+  }
+  event_base_ = event_base_new();
+  event_base_priority_init(event_base_, num_priorities);
+  if (server_common::log::PS_VLOG_IS_ON(10)) {
+    event_enable_debug_mode();
+  }
+}
+
+EventBase::~EventBase() {
+  if (event_base_ != nullptr) {
+    event_base_free(event_base_);
+  }
+}
+
+struct event_base* EventBase::get() { return event_base_; }
+
+}  // namespace privacy_sandbox::server_common

src/core/event/event_base.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * 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.
+ */
+
+#ifndef SRC_CORE_EVENT_EVENT_BASE_H_
+#define SRC_CORE_EVENT_EVENT_BASE_H_
+
+#include "event2/event.h"
+#include "event2/thread.h"
+#include "src/core/event/constants.h"
+#include "src/logger/request_context_logger.h"
+
+namespace privacy_sandbox::server_common {
+
+// Wrapper for the libevent structure to hold information and state for a
+// libevent dispatch loop.
+class EventBase {
+ public:
+  explicit EventBase(bool use_pthreads = true,
+                     int num_priorities = kNumEventPriorities);
+  virtual ~EventBase();
+
+  // Gets the underlying event base data type.
+  struct event_base* get();
+
+ private:
+  struct event_base* event_base_ = nullptr;
+};
+
+}  // namespace privacy_sandbox::server_common
+
+#endif  // SRC_CORE_EVENT_EVENT_BASE_H_

third_party/cpp_deps.bzl

@@ -185,6 +185,18 @@ def cpp_dependencies():
         strip_prefix = "flatbuffers-24.3.25",
         urls = ["https://github.com/google/flatbuffers/archive/refs/tags/v24.3.25.zip"],
     )
+    maybe(
+        http_archive,
+        name = "libevent",
+        build_file = "//third_party:libevent.BUILD",
+        patch_args = ["-p1"],
+        patches = [
+            "//third_party:libevent.patch",
+        ],
+        sha256 = "8836ad722ab211de41cb82fe098911986604f6286f67d10dfb2b6787bf418f49",
+        strip_prefix = "libevent-release-2.1.12-stable",
+        urls = ["https://github.com/libevent/libevent/archive/refs/tags/release-2.1.12-stable.zip"],
+    )
     _bazel_deps()
     _container_deps()
     _ts_js_deps()

third_party/libevent-evconfig.patch

@@ -0,0 +1,64 @@
+diff --git a/evconfig-private.h b/evconfig-private.h
+new file mode 100644
+index 0000000..31e6100
+--- /dev/null
++++ b/evconfig-private.h
+@@ -0,0 +1,56 @@
++/* evconfig-private.h.  Generated from evconfig-private.h.in by configure.  */
++/* evconfig-private.h template - see "Configuration Header Templates" */
++/* in AC manual.  Kevin Bowling <kevin.bowling@kev009.com */
++#ifndef EVCONFIG_PRIVATE_H_INCLUDED_
++#define EVCONFIG_PRIVATE_H_INCLUDED_
++
++/* Enable extensions on AIX 3, Interix.  */
++#ifndef _ALL_SOURCE
++# define _ALL_SOURCE 1
++#endif
++/* Enable GNU extensions on systems that have them.  */
++#ifndef _GNU_SOURCE
++# define _GNU_SOURCE 1
++#endif
++/* Enable threading extensions on Solaris.  */
++#ifndef _POSIX_PTHREAD_SEMANTICS
++# define _POSIX_PTHREAD_SEMANTICS 1
++#endif
++/* Enable extensions on HP NonStop.  */
++#ifndef _TANDEM_SOURCE
++# define _TANDEM_SOURCE 1
++#endif
++/* Enable general extensions on Solaris.  */
++#ifndef __EXTENSIONS__
++# define __EXTENSIONS__ 1
++#endif
++
++/* Number of bits in a file offset, on hosts where this is settable. */
++/* #undef _FILE_OFFSET_BITS */
++/* Define for large files, on AIX-style hosts. */
++/* #undef _LARGE_FILES */
++
++/* Define to 1 if on MINIX. */
++#ifndef _MINIX
++/* #undef _MINIX */
++#endif
++
++/* Define to 2 if the system does not provide POSIX.1 features except with
++   this defined. */
++#ifndef _POSIX_1_SOURCE
++/* #undef _POSIX_1_SOURCE */
++#endif
++
++/* Define to 1 if you need to in order for `stat' and other things to work. */
++#ifndef _POSIX_SOURCE
++/* #undef _POSIX_SOURCE */
++#endif
++
++/* Enable POSIX.2 extensions on QNX for getopt */
++#ifdef __QNX__
++# ifndef __EXT_POSIX2
++#  define __EXT_POSIX2
++# endif
++#endif
++
++#endif
+-- 
+2.43.0.472.g3155946c3a-goog