Store headers in bloom filter, respond to 100-continue

src/BloomFilter.h

@@ -0,0 +1,65 @@
+/*
+ * Authored by Alex Hultman, 2018-2019.
+ * Intellectual property of third-party.
+
+ * 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 UWS_BLOOMFILTER_H
+#define UWS_BLOOMFILTER_H
+
+/* This filter has a decently low amount of false positives for the
+ * standard and non-standard common request headers */
+
+#include <string_view>
+#include <bitset>
+
+namespace uWS {
+
+struct BloomFilter {
+private:
+    std::bitset<512> filter;
+
+    unsigned int hash1(std::string_view key) {
+        return ((unsigned int)key[key.length() - 1] - (key.length() << 3)) & 511;
+    }
+
+    unsigned int hash2(std::string_view key) {
+        return (((unsigned int)key[0] + (key.length() << 4)) & 511);
+    }
+
+    unsigned int hash3(std::string_view key) {
+        return ((unsigned int)key[key.length() - 2] - 97 - (key.length() << 5)) & 511;
+    }
+
+public:
+    bool mightHave(std::string_view key) {
+        return filter.test(hash1(key)) && filter.test(hash2(key)) && (key.length() < 2 || filter.test(hash3(key)));
+    }
+
+    void add(std::string_view key) {
+        filter.set(hash1(key));
+        filter.set(hash2(key));
+        if (key.length() >= 2) {
+            filter.set(hash3(key));
+        }
+    }
+
+    void reset() {
+        filter.reset();
+    }
+};
+
+}
+
+#endif // UWS_BLOOMFILTER_H