Shared library: Add PerfettoFnv1a to API headers

It's going to be used by the track event data source

Bug: 237053982
Change-Id: I0cf8075dbb4134693c807e7cb37d313b99b8cbfa

include/perfetto/public/BUILD.gn

diff --git a/include/perfetto/public/BUILD.gn b/include/perfetto/public/BUILD.gn
index 44719d3..84c7982 100644
--- a/include/perfetto/public/BUILD.gn
+++ b/include/perfetto/public/BUILD.gn
@@ -24,6 +24,7 @@
 source_set("public") {
   sources = [
     "data_source.h",
+    "fnv1a.h",
     "pb_decoder.h",
     "pb_macros.h",
     "pb_msg.h",

include/perfetto/public/fnv1a.h

diff --git a/include/perfetto/public/fnv1a.h b/include/perfetto/public/fnv1a.h
new file mode 100644
index 0000000..720aeda
--- /dev/null
+++ b/include/perfetto/public/fnv1a.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * 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 INCLUDE_PERFETTO_PUBLIC_FNV1A_H_
+#define INCLUDE_PERFETTO_PUBLIC_FNV1A_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "perfetto/public/compiler.h"
+
+static inline uint64_t PerfettoFnv1a(const void* data, size_t size) {
+  const uint64_t kFnv1a64OffsetBasis = 0xcbf29ce484222325;
+  const uint64_t kFnv1a64Prime = 0x100000001b3;
+
+  uint64_t value = kFnv1a64OffsetBasis;
+
+  for (size_t i = 0; i < size; i++) {
+    value =
+        (value ^ PERFETTO_STATIC_CAST(const uint8_t*, data)[i]) * kFnv1a64Prime;
+  }
+  return value;
+}
+
+#endif  // INCLUDE_PERFETTO_PUBLIC_FNV1A_H_