From 115ee12f040d3fbbceef4b81aba639d72315b27e Mon Sep 17 00:00:00 2001
From: Jef Roosens <roosensjef@gmail.com>
Date: Tue, 17 Oct 2023 11:25:51 +0200
Subject: [PATCH] feat(lsm): start store entry implementation

---
 lsm/include/lsm/store.h               | 84 +++++++++++++++++++++++++++
 lsm/src/_include/lsm/store_internal.h | 22 +++++++
 lsm/src/store/lsm_store_entry.c       | 37 ++++++++++++
 3 files changed, 143 insertions(+)
 create mode 100644 lsm/include/lsm/store.h
 create mode 100644 lsm/src/_include/lsm/store_internal.h
 create mode 100644 lsm/src/store/lsm_store_entry.c

diff --git a/lsm/include/lsm/store.h b/lsm/include/lsm/store.h
new file mode 100644
index 0000000..d0fab21
--- /dev/null
+++ b/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
diff --git a/lsm/src/_include/lsm/store_internal.h b/lsm/src/_include/lsm/store_internal.h
new file mode 100644
index 0000000..d0aaed0
--- /dev/null
+++ b/lsm/src/_include/lsm/store_internal.h
@@ -0,0 +1,22 @@
+#ifndef LSM_STORE_INTERNAL
+#define LSM_STORE_INTERNAL
+
+#include "lsm/store.h"
+#include "lsm/str_internal.h"
+
+typedef struct lsm_attr {
+  lsm_attr_type type;
+  lsm_str str;
+} lsm_attr;
+
+struct lsm_entry {
+  lsm_str key;
+  struct {
+    uint64_t count;
+    uint64_t bitmap;
+    lsm_attr *items;
+  } attrs;
+  lsm_str data;
+};
+
+#endif
diff --git a/lsm/src/store/lsm_store_entry.c b/lsm/src/store/lsm_store_entry.c
new file mode 100644
index 0000000..99a2b30
--- /dev/null
+++ b/lsm/src/store/lsm_store_entry.c
@@ -0,0 +1,37 @@
+#include <stdlib.h>
+
+#include "lsm.h"
+#include "lsm/store_internal.h"
+
+lsm_error lsm_entry_init(lsm_entry **ptr) {
+  lsm_entry *entry = calloc(1, sizeof(lsm_entry));
+
+  if (entry == NULL) {
+    return lsm_error_failed_alloc;
+  }
+
+  *ptr = entry;
+
+  return lsm_error_ok;
+}
+
+bool lsm_entry_attr_present(lsm_entry *entry, lsm_attr_type type) {
+  return (entry->attrs.bitmap & type) != 0;
+}
+
+lsm_error lsm_entry_attr_get(lsm_str **out, lsm_entry *entry,
+                             lsm_attr_type type) {
+  if (!lsm_entry_attr_present(entry, type)) {
+    return lsm_error_not_found;
+  }
+
+  for (uint64_t i = 0; i < entry->attrs.count; i++) {
+    if (entry->attrs.items[i].type == type) {
+      *out = &entry->attrs.items[i].str;
+
+      return lsm_error_ok;
+    }
+  }
+
+  return lsm_error_not_found;
+}