Create bloom filter class header filer (#10841)

Firestore/core/src/remote/bloom_filter.h

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2023 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 FIRESTORE_CORE_SRC_REMOTE_BLOOM_FILTER_H_
+#define FIRESTORE_CORE_SRC_REMOTE_BLOOM_FILTER_H_
+
+#include <string>
+#include <vector>
+#include "absl/strings/string_view.h"
+
+namespace firebase {
+namespace firestore {
+namespace remote {
+
+class BloomFilter final {
+ public:
+  BloomFilter(std::vector<uint8_t> bitmap, int32_t padding, int32_t hash_count);
+
+  // Copyable & movable.
+  BloomFilter(const BloomFilter&) = default;
+  BloomFilter(BloomFilter&&) = default;
+  BloomFilter& operator=(const BloomFilter&) = default;
+  BloomFilter& operator=(BloomFilter&&) = default;
+
+  /**
+   * Check whether the given string is a possible member of the bloom filter. It
+   * might return false positive result, ie, the given string is not a member of
+   * the bloom filter, but the method returned true.
+   *
+   * @param value the string to be tested for membership.
+   * @return true if the given string might be contained in the bloom filter, or
+   * false if the given string is definitely not contained in the bloom filter.
+   */
+  bool MightContain(absl::string_view value) const;
+
+  // Get the `bit_count_` field. Used for testing purpose.
+  int32_t bit_count() const {
+    return bit_count_;
+  }
+
+ private:
+  // The number of bits in the bloom filter. Guaranteed to be non-negative, and
+  // less than the max number of bits `bitmap_` can represent, i.e.,
+  // bitmap_.size() * 8.
+  int32_t bit_count_ = 0;
+
+  // The number of hash functions used to construct the filter. Guaranteed to be
+  // non-negative.
+  int32_t hash_count_ = 0;
+
+  // Bloom filter's bitmap.
+  std::vector<uint8_t> bitmap_;
+};
+
+}  // namespace remote
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_SRC_REMOTE_BLOOM_FILTER_H_