1 files changed, 97 insertions, 0 deletions
diff --git a/lib/cache/cdb_api.h b/lib/cache/cdb_api.h
new file mode 100644
index 0000000..fcca8a9
--- /dev/null
+++ b/lib/cache/cdb_api.h
@@ -0,0 +1,97 @@
+/*  Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
+ *  SPDX-License-Identifier: GPL-3.0-or-later
+*/
+
+#pragma once
+
+#include <stdint.h>
+
+#include <libknot/db/db.h>
+
+/* Cache options. */
+struct kr_cdb_opts {
+	const char *path; /*!< Cache URI path. */
+	size_t maxsize;   /*!< Suggested cache size in bytes; pass 0 to keep unchanged/default. */
+};
+
+struct kr_cdb_stats {
+	uint64_t open;
+	uint64_t close;
+	uint64_t count;
+	uint64_t count_entries;
+	uint64_t clear;
+	uint64_t commit;
+	uint64_t read;
+	uint64_t read_miss;
+	uint64_t write;
+	uint64_t remove;
+	uint64_t remove_miss;
+	uint64_t match;
+	uint64_t match_miss;
+	uint64_t read_leq;
+	uint64_t read_leq_miss;
+	double usage_percent;
+};
+
+/*! Pointer to a cache structure.
+ *
+ * This struct is opaque and never defined; the purpose is to get better
+ * type safety than with void *.
+ */
+typedef struct kr_cdb *kr_cdb_pt;
+
+/*! Cache database API.
+  * This is a simplified version of generic DB API from libknot,
+  * that is tailored to caching purposes.
+  */
+struct kr_cdb_api {
+	const char *name;
+
+	/* Context operations */
+
+	int (*open)(kr_cdb_pt *db, struct kr_cdb_stats *stat, struct kr_cdb_opts *opts, knot_mm_t *mm);
+	void (*close)(kr_cdb_pt db, struct kr_cdb_stats *stat);
+	int (*count)(kr_cdb_pt db, struct kr_cdb_stats *stat);
+	int (*clear)(kr_cdb_pt db, struct kr_cdb_stats *stat);
+
+	/** Run after a row of operations to release transaction/lock if needed. */
+	int (*commit)(kr_cdb_pt db, struct kr_cdb_stats *stat);
+
+	/* Data access */
+
+	int (*read)(kr_cdb_pt db, struct kr_cdb_stats *stat,
+			const knot_db_val_t *key, knot_db_val_t *val, int maxcount);
+	int (*write)(kr_cdb_pt db, struct kr_cdb_stats *stat, const knot_db_val_t *key,
+			knot_db_val_t *val, int maxcount);
+
+	/** Remove maxcount keys.
+	 * \returns the number of successfully removed keys or the first error code
+	 * It returns on first error, but ENOENT is not considered an error. */
+	int (*remove)(kr_cdb_pt db, struct kr_cdb_stats *stat,
+			knot_db_val_t keys[], int maxcount);
+
+	/* Specialised operations */
+
+	/** Find key-value pairs that are prefixed by the given key, limited by maxcount.
+	 * \return the number of pairs or negative error. */
+	int (*match)(kr_cdb_pt db, struct kr_cdb_stats *stat,
+			knot_db_val_t *key, knot_db_val_t keyval[][2], int maxcount);
+
+	/** Less-or-equal search (lexicographic ordering).
+	 * On successful return, key->data and val->data point to DB-owned data.
+	 * return: 0 for equality, > 0 for less, < 0 kr_error */
+	int (*read_leq)(kr_cdb_pt db, struct kr_cdb_stats *stat,
+			knot_db_val_t *key, knot_db_val_t *val);
+
+	/** Return estimated space usage (0--100). */
+	double (*usage_percent)(kr_cdb_pt db);
+
+	/** Return the current cache size limit in bytes; could be cached by check_health(). */
+	size_t (*get_maxsize)(kr_cdb_pt db);
+
+	/** Perform maintenance.
+	 * In LMDB case it checks whether data.mdb is still the same
+	 * and reopens it if it isn't; it errors out if the file doesn't exist anymore.
+	 * \return 0 if OK, 1 if reopened OK, < 0 kr_error */
+	int (*check_health)(kr_cdb_pt db, struct kr_cdb_stats *stat);
+};