feat(lsm): start store entry implementation

lsm/include/lsm/store.h

@@ -0,0 +1,84 @@
+#ifndef LSM_STORE
+#define LSM_STORE
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "lsm.h"
+#include "lsm/str.h"
+
+/**
+ * The type of an entry attribute.
+ *
+ * Each type is represented as a single bit of an
+ * integer, so they can be easily combined into a bitmap.
+ */
+typedef enum lsm_attr_type : uint64_t {
+  lsm_attr_type_entry_type = 1 << 0,
+  lsm_attr_type_content_type = 1 << 1
+} lsm_attr_type;
+
+/**
+ * An entry inside an LSM store.
+ *
+ * Each entry consists of the key it's stored behind, zero  or more attributes
+ * (metadata) and a data field. The data field can be stored on disk or
+ * in-memory, depending on the size.
+ */
+typedef struct lsm_entry lsm_entry;
+
+/**
+ * Allocate and initialize a new lsm_entry object.
+ *
+ * @param ptr where to store newly allocated pointer
+ */
+lsm_error lsm_entry_init(lsm_entry **ptr);
+
+/**
+ * Deallocate an existing lsm_entry object.
+ *
+ * @param entry object to deallocate
+ */
+void lsm_entry_free(lsm_entry *entry);
+
+/**
+ * Checks whether the entry has an attribute with the specified type.
+ *
+ * @param entry entry to check
+ * @param type type of attribute to check for
+ */
+bool lsm_entry_attr_present(lsm_entry *entry, lsm_attr_type type);
+
+/**
+ * Retrieve the contents of an attribute from an entry, if present
+ *
+ * @param out where to store pointer to attribute data
+ * @param entry entry to search for
+ * @param type type of attribute to return
+ */
+lsm_error lsm_entry_attr_get(lsm_str **out, lsm_entry *entry,
+                             lsm_attr_type type);
+
+/**
+ * A store consisting of LSM entries.
+ *
+ * A store manages both an in-memory data structure for quick lookup, and a
+ * database file for persistent storage of the contained entries.
+ */
+typedef struct lsm_store lsm_store;
+
+/**
+ * Allocate and initialize a new lsm_store object.
+ *
+ * @param ptr where to store newly allocated pointer
+ */
+lsm_error lsm_store_init(lsm_store **ptr);
+
+/**
+ * Dealocate an existing lsm_store object.
+ *
+ * @param store object to deallocate
+ */
+void lsm_store_free(lsm_store *store);
+
+#endif