handles words>maxprefixlen

cmd/radFS/arttest/main.go

@@ -0,0 +1,15 @@
+package main
+
+import (
+	"github.com/acmpesuecc/radFS/internal/art"
+)
+
+func main() {
+	tree := &art.Tree{}
+
+	tree.Insert([]byte("abbbbbbbc"), "first")
+	tree.Insert([]byte("abbbbbbbcb"), "second")
+	tree.Insert([]byte("abbbbbbbcbc"), "second")
+
+	art.PrintTree(tree.Root(), 0)
+}

internal/art/art.go

@@ -0,0 +1,23 @@
+package art
+
+// TODO: Public API (Tree struct, Insert, Search, Delete)
+
+type Tree struct {
+	root *Node
+}
+
+func (t *Tree) Root() *Node {
+	return t.root
+}
+
+func (t *Tree) Insert(key []byte, value string) {
+	t.root = insert(t.root, value, key, 0)
+}
+
+func (t *Tree) Search(key []byte) (string, bool) {
+	leaf := search(t.root, key, 0) // start from root and depth 0
+	if leaf != nil && isleaf(leaf) {
+		return leaf.leaf.values, true //Node->innerleaf->values
+	}
+	return "", false
+}

internal/art/insert.go

@@ -0,0 +1,86 @@
+package art
+
+import "fmt"
+
+func insert(n *Node, value string, key []byte, depth int) *Node {
+
+	if n == nil {
+		return newleaf(value, key)
+	}
+	if isleaf(n) {
+		new_node := newNode4()
+		oldkey := n.leaf.key
+		i := depth
+		fmt.Println("depth:", depth)
+		fmt.Println("oldkey[depth:]:", string(oldkey[depth:]))
+		fmt.Println("key[depth:]:", string(key[depth:]))
+
+		for i < len(oldkey) && i < len(key) && oldkey[i] == key[i] {
+			prefix_index := i - depth
+			if prefix_index < maxprefixlen { //index goes till 7 so prefix index<8 and not ==8
+				new_node.innerNode.meta.prefix[prefix_index] = key[i] // stores only the till max prefix
+
+			}
+
+			i++
+		}
+
+		new_node.innerNode.meta.prefixlen = i - depth // stores full prefix len even after maxprefixlen
+		depth = i
+
+		new_node = addchild(new_node, keycheck(key, depth), newleaf(value, key))
+
+		new_node = addchild(new_node, keycheck(oldkey, depth), n)
+		fmt.Println("depth:", depth)
+		fmt.Println("oldkey[depth:]:", string(oldkey[depth:]))
+		fmt.Println("key[depth:]:", string(key[depth:]))
+		fmt.Println("                             ")
+		fmt.Println("prefix", string(new_node.innerNode.meta.prefix))
+		return new_node
+
+	}
+	p := checkprefix(n, key, depth)
+	if p != n.innerNode.meta.prefixlen {
+		new_node := newNode4()
+		new_node = addchild(new_node, keycheck(key, depth+p), newleaf(value, key))
+		if p < maxprefixlen {
+			new_node = addchild(new_node, n.innerNode.meta.prefix[p], n)
+
+		} else {
+			leaf := fetchleaf(n)
+			new_node = addchild(new_node, keycheck(leaf.leaf.key, depth+p), n) // the logic is teh leaf will contain the full key with the same prefix
+		}
+
+		new_node.innerNode.meta.prefixlen = p
+		if p < maxprefixlen {
+			copy(new_node.innerNode.meta.prefix, n.innerNode.meta.prefix[:p])
+
+		} else {
+			copy(new_node.innerNode.meta.prefix, n.innerNode.meta.prefix[:maxprefixlen])
+		}
+
+		oldprefixlen := n.innerNode.meta.prefixlen
+		n.innerNode.meta.prefixlen = n.innerNode.meta.prefixlen - (p + 1)
+		if len(n.innerNode.meta.prefix[p+1:oldprefixlen]) < maxprefixlen {
+			copy(n.innerNode.meta.prefix, n.innerNode.meta.prefix[p+1:oldprefixlen])
+
+		} else {
+			copy(n.innerNode.meta.prefix, n.innerNode.meta.prefix[p+1:maxprefixlen])
+		}
+
+		return new_node
+	}
+
+	depth += n.innerNode.meta.prefixlen
+	next, pos := findchild(keycheck(key, depth), n)
+	if next != nil {
+		n.innerNode.children[pos] = insert(next, value, key, depth+1)
+		return n
+
+	} else {
+		n = addchild(n, keycheck(key, depth), newleaf(value, key))
+		return n
+
+	}
+
+}

internal/art/leaf.go

@@ -0,0 +1,18 @@
+package art
+
+// TODO: Leaf node structure for storing values
+
+type leaf struct {
+	key    []byte
+	values string
+}
+
+func newleaf(value string, key []byte) *Node {
+	return &Node{
+		leaf: &leaf{key: key, values: value},
+	}
+
+}
+func isleaf(n *Node) bool {
+	return n.leaf != nil
+}

internal/art/node.go

@@ -0,0 +1,38 @@
+package art
+
+// TODO: Interfaces and shared node header (meta)
+
+type NodeType int
+
+const (
+	Node4 NodeType = iota
+	Node16
+	Node48
+	Node256
+)
+const (
+	Node4max   = 4
+	Node16Max  = 16
+	Node48Max  = 48
+	Node256Max = 256
+
+	maxprefixlen = 8
+)
+
+type Node struct {
+	innerNode *innerNode
+	leaf      *leaf
+}
+
+type innerNode struct {
+	nodeType     NodeType
+	keys         []byte
+	children     []*Node
+	num_children int
+	meta         meta
+}
+
+type meta struct {
+	prefix    []byte
+	prefixlen int
+}

internal/art/node16.go

@@ -0,0 +1,15 @@
+package art
+
+// TODO: Node16 implementation
+func newNode16() *Node {
+	in := &innerNode{
+		nodeType:     Node16,
+		keys:         make([]byte, Node16Max),
+		children:     make([]*Node, Node16Max),
+		num_children: 0,
+		meta: meta{
+			prefix: make([]byte, maxprefixlen),
+		},
+	}
+	return &Node{innerNode: in}
+}

internal/art/node256.go

@@ -0,0 +1,16 @@
+package art
+
+// TODO: Node256 implementation (direct map)
+
+func newNode256() *Node {
+	in := &innerNode{
+		nodeType:     Node256,
+		children:     make([]*Node, Node256Max),
+		num_children: 0,
+
+		meta: meta{
+			prefix: make([]byte, maxprefixlen),
+		},
+	}
+	return &Node{innerNode: in}
+}

internal/art/node4.go

@@ -0,0 +1,15 @@
+package art
+
+func newNode4() *Node {
+	in := &innerNode{
+		nodeType:     Node4,
+		keys:         make([]byte, Node4max),
+		children:     make([]*Node, Node4max),
+		num_children: 0,
+		meta: meta{
+			prefix: make([]byte, maxprefixlen),
+		},
+	}
+	return &Node{innerNode: in}
+
+}

internal/art/node48.go

@@ -0,0 +1,15 @@
+package art
+
+// TODO: Node48 implementation (indirection layer)
+func newNode48() *Node {
+	in := &innerNode{
+		nodeType:     Node48,
+		keys:         make([]byte, Node256Max),
+		children:     make([]*Node, Node48Max),
+		num_children: 0,
+		meta: meta{
+			prefix: make([]byte, maxprefixlen),
+		},
+	}
+	return &Node{innerNode: in}
+}

internal/art/print_tree.go

@@ -0,0 +1,42 @@
+package art
+
+import "fmt"
+
+func PrintTree(n *Node, level int) {
+	if n == nil {
+		return
+	}
+
+	indent := ""
+	for i := 0; i < level; i++ {
+		indent += "  "
+	}
+
+	if isleaf(n) {
+		fmt.Println(indent + "Leaf: " + string(n.leaf.key))
+		return
+	}
+
+	in := n.innerNode
+
+	prefixlen := in.meta.prefixlen
+	prefix := ""
+	if prefixlen < maxprefixlen {
+		prefix = string(in.meta.prefix[:prefixlen])
+
+	} else {
+		leaf := fetchleaf(n)
+		prefix = string(leaf.leaf.key)
+	}
+
+	fmt.Println(indent+"Node(prefix=\""+prefix+"\", prefixLen=", prefixlen, ")")
+
+	// Print children
+	for i := 0; i < len(in.keys); i++ {
+		if in.children[i] != nil {
+			fmt.Printf("%s Edge('%c' | %d):\t", indent, in.keys[i], in.keys[i])
+
+			PrintTree(in.children[i], level+1)
+		}
+	}
+}

internal/art/search.go

@@ -0,0 +1,41 @@
+package art
+
+func search(n *Node, key []byte, depth int) *Node {
+	// Base case: nil node means we've reached a dead end.
+	// Key does not exist in this path of the tree.
+	if n == nil {
+		return nil
+	}
+
+	// Reached a leaf node, do a full key comparison.
+	// Necessary because path compression may have skipped bytes.
+	if isleaf(n) {
+		if string(n.leaf.key) == string(key) {
+			return n
+		}
+		return nil
+	}
+
+	// Check if the compressed prefix at this node matches the search key.
+	// If any byte mismatches, the entire subtree is irrelevant.
+	if n.innerNode.meta.prefixlen > 0 {
+		p := checkprefix(n, key, depth)
+		if p != n.innerNode.meta.prefixlen {
+			return nil
+		}
+		depth += n.innerNode.meta.prefixlen
+	}
+
+	// Get the next byte to branch on at current depth.
+	// Returns 0 (terminator) if key is exhausted.
+	k := keycheck(key, depth)
+
+	// Find the child corresponding to byte k and recurse deeper.
+	// Return nil if no child exists for this byte.
+	next, _ := findchild(k, n)
+	if next != nil {
+		return search(next, key, depth+1)
+	}
+
+	return nil
+}