[geodisambig] Bloom filter implementation for quick probabilistic set membership tests before hitting disk. 100% recall and bounded precision, saves disk seeks for keys that definitely do not exist (useful for Geonames disambiguation-related lookups and in-process deduping).

src/bloom.h

@@ -0,0 +1,31 @@
+#ifndef BLOOM_H
+#define BLOOM_H
+
+#include <stdlib.h>
+#include <stdbool.h>
+
+#define SALT_CONSTANT 0x66e8c41d
+
+typedef struct bloom_filter {
+    uint64_t capacity;
+    double error;
+    uint64_t num_bits;
+    uint64_t num_bytes;
+    uint32_t num_hashes;
+
+    double bits_per_entry;
+    unsigned char *filter;
+    bool ready;
+} bloom_filter_t;
+
+
+bloom_filter_t *bloom_filter_new(uint64_t capacity, double error);
+
+int bloom_filter_check(bloom_filter_t *self, const char *key, size_t len);
+int bloom_filter_add(bloom_filter_t *self, const char *key, size_t len);
+
+void bloom_filter_print(bloom_filter_t *self);
+
+void bloom_filter_destroy(bloom_filter_t *self);
+
+#endif