icao_filter.[ch] from the experimental branch.

icao_filter.h

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+// Part of dump1090, a Mode S message decoder for RTLSDR devices.
+//
+// icao_filter.c: prototypes for ICAO address hashtable
+//
+// Copyright (c) 2014,2015 Oliver Jowett <oliver@mutability.co.uk>
+//
+// This file is free software: you may copy, redistribute and/or modify it  
+// under the terms of the GNU General Public License as published by the
+// Free Software Foundation, either version 2 of the License, or (at your  
+// option) any later version.  
+//
+// This file is distributed in the hope that it will be useful, but  
+// WITHOUT ANY WARRANTY; without even the implied warranty of  
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  
+// General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License  
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#ifndef DUMP1090_ICAO_FILTER_H
+#define DUMP1090_ICAO_FILTER_H
+
+// Call once:
+void icaoFilterInit();
+
+// Add an address to the filter
+void icaoFilterAdd(uint32_t addr);
+
+// Test if the given address matches the filter
+int icaoFilterTest(uint32_t addr);
+
+// Test if the top 16 bits match any previously added address.
+// If they do, returns an arbitrary one of the matched
+// addresses. Returns 0 on failure.
+uint32_t icaoFilterTestFuzzy(uint32_t partial);
+
+// Call this periodically to allow the filter to expire
+// old entries.
+void icaoFilterExpire();
+
+#endif