blob: 43a33a6aa43bc7fc12919757f229583340ae606f (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
|
/* single header b-tree implementation by Abdellah El Morabit */
#ifndef B_TREE_H
#define B_TREE_H
// maximum height of the tree the lower the lower the lower amount
// of disk reads which translates into faster?
#define B_TREE_ORDER 4
typedef struct b_tree_node b_tree_node;
struct b_tree_node
{
// store the values
string8 keys[B_TREE_ORDER - 1];
// TODO(nasr): replace with someting more generic?
// NOTE(nasr): cons of void * -> no type safety
// is there a way to still have some sort of that?
void *payload_per_key[B_TREE_ORDER - 1];
b_tree_node *parent;
// handle to store children faster than linked list
// because now we can iteratate over the nodes instead of having cache misses
// when jumping through linked nodes
b_tree_node *children[B_TREE_ORDER];
// this shouldnt change things but could be a performance improvement on a bigger scale??
s32 *max_children;
// NOTE(nasr): reference count ::: check how many leaves are using this node
// also not needed for now because we don't free individual node because of arena allocator
// s32 *refc;
s32 key_count;
b32 leaf;
};
typedef struct b_tree b_tree;
struct b_tree
{
// NOTE(nasr): make sure this always stays in memory
// so that initial fetch never requires a disk read
b_tree_node *root;
};
#ifdef B_TREE_IMPLEMENTATION
///////////////////////////////////////////////////////////////////////////////
//- b_tree.c
// TODO(nasr): 1. splitting the tree when getting too big? (horizontally) 2. joining trees?
internal b_tree_node *
btree_node_alloc(mem_arena *arena)
{
b_tree_node *node = PushStructZero(arena, b_tree_node);
node->leaf = 1;
return node;
}
// NOTE(nasr): @return the index of of the found element
internal s32
btree_node_find_pos(mem_arena *arena, string8 value, b_tree_node *node)
{
for (s32 index = 0; index < node->key_count && string8_cmp(node->keys[i], value) < 0; ++index);
return i;
}
internal void
b_tree_create(mem_arena *arena, b_tree *tree)
{
tree->root = btree_node_alloc(arena);
tree->root->leaf = 1;
tree->root->key_count = 0;
}
// NOTE(nasr): nodes that get passed as parameters should've already been loaded into memory
internal void
b_tree_search(b_tree_node *node, string8 key)
{
s32 found_index = btree_node_find_pos(node, key);
s32 i = 0;
if (found_index < node->key_count && string_compare(node->keys[index], key) == 0)
{
return node->rows[i];
}
if (node->leaf)
{
return NULL;
}
return b_tree_search(node->children[i], key);
return NULL;
}
internal void
b_tree_insert(b_tree_node *current_node)
{
if(current_node->leaf)
{
}
}
internal void
b_tree_write()
{
// TODO(nasr): write the b_tree to disk
}
#endif /* B_TREE_IMPLEMENTATION */
#endif /* B_TREE_H */
|
