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-rw-r--r--lib/cache/cdb_api.h97
1 files changed, 97 insertions, 0 deletions
diff --git a/lib/cache/cdb_api.h b/lib/cache/cdb_api.h
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+/* 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);
+};