feat: page caching layer for vfs

[lunaix-os.git] / lunaix-os / kernel / ds / btrie.c

diff --git a/lunaix-os/kernel/ds/btrie.c b/lunaix-os/kernel/ds/btrie.c
new file mode 100644 (file)
index 0000000..92f034b
--- /dev/null
+++ b/lunaix-os/kernel/ds/btrie.c
@@ -0,0 +1,120 @@
+/**
+ * @file btrie.c
+ * @author Lunaixsky
+ * @brief Bitwise trie tree implementation for sparse array.
+ * @version 0.1
+ * @date 2022-08-01
+ *
+ * @copyright Copyright (c) 2022
+ *
+ */
+
+#include <lunaix/ds/btrie.h>
+#include <lunaix/mm/valloc.h>
+#include <lunaix/spike.h>
+
+#define BTRIE_INSERT 1
+
+struct btrie_node*
+__btrie_traversal(struct btrie* root, uint32_t index, int options)
+{
+    index = index >> root->truncated;
+    uint32_t lz = index ? ROUNDDOWN(31 - __builtin_clz(index), BTRIE_BITS) : 0;
+    uint32_t bitmask = ((1 << BTRIE_BITS) - 1) << lz;
+    uint32_t i = 0;
+    struct btrie_node* tree = root->btrie_root;
+
+    // Time complexity: O(log_2(log_2(N))) where N is the index to lookup
+    while (lz && tree) {
+        i = (index & bitmask) >> lz;
+        struct btrie_node *subtree = 0, *pos, *n;
+
+        llist_for_each(pos, n, &tree->children, siblings)
+        {
+            if (pos->index == i) {
+                subtree = pos;
+                break;
+            }
+        }
+
+        if (!subtree && (options & BTRIE_INSERT)) {
+            struct btrie_node* new_tree = vzalloc(sizeof(struct btrie_node));
+            new_tree->index = i;
+            new_tree->parent = tree;
+            llist_init_head(&new_tree->children);
+
+            llist_append(&tree->children, &new_tree->siblings);
+            llist_append(&root->btrie_root->nodes, &new_tree->nodes);
+            tree = new_tree;
+        } else {
+            tree = subtree;
+        }
+        bitmask = bitmask >> BTRIE_BITS;
+        lz -= BTRIE_BITS;
+    }
+
+    return tree;
+}
+
+void
+btrie_init(struct btrie* btrie, uint32_t trunc_bits)
+{
+    btrie->btrie_root = vzalloc(sizeof(struct btrie_node));
+    llist_init_head(&btrie->btrie_root->nodes);
+    btrie->truncated = trunc_bits;
+}
+
+void*
+btrie_get(struct btrie* root, uint32_t index)
+{
+    struct btrie_node* node = __btrie_traversal(root, index, 0);
+    if (!node) {
+        return NULL;
+    }
+    return node->data;
+}
+
+void
+btrie_set(struct btrie* root, uint32_t index, void* data)
+{
+    struct btrie_node* node = __btrie_traversal(root, index, BTRIE_INSERT);
+    node->data = data;
+}
+
+void
+__btrie_remove(struct btrie_node* node)
+{
+    struct btrie_node* parent = node->parent;
+    if (parent) {
+        llist_delete(&node->siblings);
+        llist_delete(&node->nodes);
+        vfree(node);
+        if (llist_empty(&parent->children)) {
+            __btrie_remove(parent);
+        }
+    }
+}
+
+void*
+btrie_remove(struct btrie* root, uint32_t index)
+{
+    struct btrie_node* node = __btrie_traversal(root, index, 0);
+    if (!node) {
+        return 0;
+    }
+    void* data = node->data;
+    __btrie_remove(node);
+    return data;
+}
+
+void
+btrie_release(struct btrie* tree)
+{
+    struct btrie_node *pos, *n;
+    llist_for_each(pos, n, &tree->btrie_root->nodes, nodes)
+    {
+        vfree(pos);
+    }
+
+    vfree(tree->btrie_root);
+}
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