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+// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+
+module builtin
+
+// import strings
+
+// B-trees are balanced search trees with all leaves at
+// the same level. B-trees are generally faster than
+// binary search trees due to the better locality of
+// reference, since multiple keys are stored in one node.
+
+// The number for `degree` has been picked through vigor-
+// ous benchmarking but can be changed to any number > 1.
+// `degree` determines the maximum length of each node.
+const (
+ degree = 6
+ mid_index = degree - 1
+ max_len = 2 * degree - 1
+ children_bytes = sizeof(voidptr) * (max_len + 1)
+)
+
+pub struct SortedMap {
+ value_bytes int
+mut:
+ root &mapnode
+pub mut:
+ len int
+}
+
+struct mapnode {
+mut:
+ children &voidptr
+ len int
+ keys [11]string // TODO: Should use `max_len`
+ values [11]voidptr // TODO: Should use `max_len`
+}
+
+fn new_sorted_map(n int, value_bytes int) SortedMap { // TODO: Remove `n`
+ return SortedMap{
+ value_bytes: value_bytes
+ root: new_node()
+ len: 0
+ }
+}
+
+fn new_sorted_map_init(n int, value_bytes int, keys &string, values voidptr) SortedMap {
+ mut out := new_sorted_map(n, value_bytes)
+ for i in 0 .. n {
+ unsafe {
+ out.set(keys[i], &byte(values) + i * value_bytes)
+ }
+ }
+ return out
+}
+
+// The tree is initialized with an empty node as root to
+// avoid having to check whether the root is null for
+// each insertion.
+fn new_node() &mapnode {
+ return &mapnode{
+ children: 0
+ len: 0
+ }
+}
+
+// This implementation does proactive insertion, meaning
+// that splits are done top-down and not bottom-up.
+fn (mut m SortedMap) set(key string, value voidptr) {
+ mut node := m.root
+ mut child_index := 0
+ mut parent := &mapnode(0)
+ for {
+ if node.len == max_len {
+ if isnil(parent) {
+ parent = new_node()
+ m.root = parent
+ }
+ parent.split_child(child_index, mut node)
+ if key == parent.keys[child_index] {
+ unsafe {
+ C.memcpy(parent.values[child_index], value, m.value_bytes)
+ }
+ return
+ }
+ if key < parent.keys[child_index] {
+ node = unsafe { &mapnode(parent.children[child_index]) }
+ } else {
+ node = unsafe { &mapnode(parent.children[child_index + 1]) }
+ }
+ }
+ mut i := 0
+ for i < node.len && key > node.keys[i] {
+ i++
+ }
+ if i != node.len && key == node.keys[i] {
+ unsafe {
+ C.memcpy(node.values[i], value, m.value_bytes)
+ }
+ return
+ }
+ if isnil(node.children) {
+ mut j := node.len - 1
+ for j >= 0 && key < node.keys[j] {
+ node.keys[j + 1] = node.keys[j]
+ node.values[j + 1] = node.values[j]
+ j--
+ }
+ node.keys[j + 1] = key
+ unsafe {
+ node.values[j + 1] = malloc(m.value_bytes)
+ C.memcpy(node.values[j + 1], value, m.value_bytes)
+ }
+ node.len++
+ m.len++
+ return
+ }
+ parent = node
+ child_index = i
+ node = unsafe { &mapnode(node.children[child_index]) }
+ }
+}
+
+fn (mut n mapnode) split_child(child_index int, mut y mapnode) {
+ mut z := new_node()
+ z.len = mid_index
+ y.len = mid_index
+ for j := mid_index - 1; j >= 0; j-- {
+ z.keys[j] = y.keys[j + degree]
+ z.values[j] = y.values[j + degree]
+ }
+ if !isnil(y.children) {
+ z.children = unsafe { &voidptr(malloc(int(children_bytes))) }
+ for jj := degree - 1; jj >= 0; jj-- {
+ unsafe {
+ z.children[jj] = y.children[jj + degree]
+ }
+ }
+ }
+ unsafe {
+ if isnil(n.children) {
+ n.children = &voidptr(malloc(int(children_bytes)))
+ }
+ n.children[n.len + 1] = n.children[n.len]
+ }
+ for j := n.len; j > child_index; j-- {
+ n.keys[j] = n.keys[j - 1]
+ n.values[j] = n.values[j - 1]
+ unsafe {
+ n.children[j] = n.children[j - 1]
+ }
+ }
+ n.keys[child_index] = y.keys[mid_index]
+ n.values[child_index] = y.values[mid_index]
+ unsafe {
+ n.children[child_index] = voidptr(y)
+ n.children[child_index + 1] = voidptr(z)
+ }
+ n.len++
+}
+
+fn (m SortedMap) get(key string, out voidptr) bool {
+ mut node := m.root
+ for {
+ mut i := node.len - 1
+ for i >= 0 && key < node.keys[i] {
+ i--
+ }
+ if i != -1 && key == node.keys[i] {
+ unsafe {
+ C.memcpy(out, node.values[i], m.value_bytes)
+ }
+ return true
+ }
+ if isnil(node.children) {
+ break
+ }
+ node = unsafe { &mapnode(node.children[i + 1]) }
+ }
+ return false
+}
+
+fn (m SortedMap) exists(key string) bool {
+ if isnil(m.root) { // TODO: find out why root can be nil
+ return false
+ }
+ mut node := m.root
+ for {
+ mut i := node.len - 1
+ for i >= 0 && key < node.keys[i] {
+ i--
+ }
+ if i != -1 && key == node.keys[i] {
+ return true
+ }
+ if isnil(node.children) {
+ break
+ }
+ node = unsafe { &mapnode(node.children[i + 1]) }
+ }
+ return false
+}
+
+fn (n &mapnode) find_key(k string) int {
+ mut idx := 0
+ for idx < n.len && n.keys[idx] < k {
+ idx++
+ }
+ return idx
+}
+
+fn (mut n mapnode) remove_key(k string) bool {
+ idx := n.find_key(k)
+ if idx < n.len && n.keys[idx] == k {
+ if isnil(n.children) {
+ n.remove_from_leaf(idx)
+ } else {
+ n.remove_from_non_leaf(idx)
+ }
+ return true
+ } else {
+ if isnil(n.children) {
+ return false
+ }
+ flag := if idx == n.len { true } else { false }
+ if unsafe { &mapnode(n.children[idx]) }.len < degree {
+ n.fill(idx)
+ }
+
+ mut node := &mapnode(0)
+ if flag && idx > n.len {
+ node = unsafe { &mapnode(n.children[idx - 1]) }
+ } else {
+ node = unsafe { &mapnode(n.children[idx]) }
+ }
+ return node.remove_key(k)
+ }
+}
+
+fn (mut n mapnode) remove_from_leaf(idx int) {
+ for i := idx + 1; i < n.len; i++ {
+ n.keys[i - 1] = n.keys[i]
+ n.values[i - 1] = n.values[i]
+ }
+ n.len--
+}
+
+fn (mut n mapnode) remove_from_non_leaf(idx int) {
+ k := n.keys[idx]
+ if unsafe { &mapnode(n.children[idx]) }.len >= degree {
+ mut current := unsafe { &mapnode(n.children[idx]) }
+ for !isnil(current.children) {
+ current = unsafe { &mapnode(current.children[current.len]) }
+ }
+ predecessor := current.keys[current.len - 1]
+ n.keys[idx] = predecessor
+ n.values[idx] = current.values[current.len - 1]
+ mut node := unsafe { &mapnode(n.children[idx]) }
+ node.remove_key(predecessor)
+ } else if unsafe { &mapnode(n.children[idx + 1]) }.len >= degree {
+ mut current := unsafe { &mapnode(n.children[idx + 1]) }
+ for !isnil(current.children) {
+ current = unsafe { &mapnode(current.children[0]) }
+ }
+ successor := current.keys[0]
+ n.keys[idx] = successor
+ n.values[idx] = current.values[0]
+ mut node := unsafe { &mapnode(n.children[idx + 1]) }
+ node.remove_key(successor)
+ } else {
+ n.merge(idx)
+ mut node := unsafe { &mapnode(n.children[idx]) }
+ node.remove_key(k)
+ }
+}
+
+fn (mut n mapnode) fill(idx int) {
+ if idx != 0 && unsafe { &mapnode(n.children[idx - 1]) }.len >= degree {
+ n.borrow_from_prev(idx)
+ } else if idx != n.len && unsafe { &mapnode(n.children[idx + 1]) }.len >= degree {
+ n.borrow_from_next(idx)
+ } else if idx != n.len {
+ n.merge(idx)
+ } else {
+ n.merge(idx - 1)
+ }
+}
+
+fn (mut n mapnode) borrow_from_prev(idx int) {
+ mut child := unsafe { &mapnode(n.children[idx]) }
+ mut sibling := unsafe { &mapnode(n.children[idx - 1]) }
+ for i := child.len - 1; i >= 0; i-- {
+ child.keys[i + 1] = child.keys[i]
+ child.values[i + 1] = child.values[i]
+ }
+ if !isnil(child.children) {
+ for i := child.len; i >= 0; i-- {
+ unsafe {
+ child.children[i + 1] = child.children[i]
+ }
+ }
+ }
+ child.keys[0] = n.keys[idx - 1]
+ child.values[0] = n.values[idx - 1]
+ if !isnil(child.children) {
+ unsafe {
+ child.children[0] = sibling.children[sibling.len]
+ }
+ }
+ n.keys[idx - 1] = sibling.keys[sibling.len - 1]
+ n.values[idx - 1] = sibling.values[sibling.len - 1]
+ child.len++
+ sibling.len--
+}
+
+fn (mut n mapnode) borrow_from_next(idx int) {
+ mut child := unsafe { &mapnode(n.children[idx]) }
+ mut sibling := unsafe { &mapnode(n.children[idx + 1]) }
+ child.keys[child.len] = n.keys[idx]
+ child.values[child.len] = n.values[idx]
+ if !isnil(child.children) {
+ unsafe {
+ child.children[child.len + 1] = sibling.children[0]
+ }
+ }
+ n.keys[idx] = sibling.keys[0]
+ n.values[idx] = sibling.values[0]
+ for i := 1; i < sibling.len; i++ {
+ sibling.keys[i - 1] = sibling.keys[i]
+ sibling.values[i - 1] = sibling.values[i]
+ }
+ if !isnil(sibling.children) {
+ for i := 1; i <= sibling.len; i++ {
+ unsafe {
+ sibling.children[i - 1] = sibling.children[i]
+ }
+ }
+ }
+ child.len++
+ sibling.len--
+}
+
+fn (mut n mapnode) merge(idx int) {
+ mut child := unsafe { &mapnode(n.children[idx]) }
+ sibling := unsafe { &mapnode(n.children[idx + 1]) }
+ child.keys[mid_index] = n.keys[idx]
+ child.values[mid_index] = n.values[idx]
+ for i in 0 .. sibling.len {
+ child.keys[i + degree] = sibling.keys[i]
+ child.values[i + degree] = sibling.values[i]
+ }
+ if !isnil(child.children) {
+ for i := 0; i <= sibling.len; i++ {
+ unsafe {
+ child.children[i + degree] = sibling.children[i]
+ }
+ }
+ }
+ for i := idx + 1; i < n.len; i++ {
+ n.keys[i - 1] = n.keys[i]
+ n.values[i - 1] = n.values[i]
+ }
+ for i := idx + 2; i <= n.len; i++ {
+ unsafe {
+ n.children[i - 1] = n.children[i]
+ }
+ }
+ child.len += sibling.len + 1
+ n.len--
+ // free(sibling)
+}
+
+pub fn (mut m SortedMap) delete(key string) {
+ if m.root.len == 0 {
+ return
+ }
+
+ removed := m.root.remove_key(key)
+ if removed {
+ m.len--
+ }
+
+ if m.root.len == 0 {
+ // tmp := t.root
+ if isnil(m.root.children) {
+ return
+ } else {
+ m.root = unsafe { &mapnode(m.root.children[0]) }
+ }
+ // free(tmp)
+ }
+}
+
+// Insert all keys of the subtree into array `keys`
+// starting at `at`. Keys are inserted in order.
+fn (n &mapnode) subkeys(mut keys []string, at int) int {
+ mut position := at
+ if !isnil(n.children) {
+ // Traverse children and insert
+ // keys inbetween children
+ for i in 0 .. n.len {
+ child := unsafe { &mapnode(n.children[i]) }
+ position += child.subkeys(mut keys, position)
+ keys[position] = n.keys[i]
+ position++
+ }
+ // Insert the keys of the last child
+ child := unsafe { &mapnode(n.children[n.len]) }
+ position += child.subkeys(mut keys, position)
+ } else {
+ // If leaf, insert keys
+ for i in 0 .. n.len {
+ keys[position + i] = n.keys[i]
+ }
+ position += n.len
+ }
+ // Return # of added keys
+ return position - at
+}
+
+pub fn (m &SortedMap) keys() []string {
+ mut keys := []string{len: m.len}
+ if isnil(m.root) || m.root.len == 0 {
+ return keys
+ }
+ m.root.subkeys(mut keys, 0)
+ return keys
+}
+
+fn (mut n mapnode) free() {
+ println('TODO')
+}
+
+pub fn (mut m SortedMap) free() {
+ if isnil(m.root) {
+ return
+ }
+ m.root.free()
+}
+
+pub fn (m SortedMap) print() {
+ println('TODO')
+}
+
+// pub fn (m map_string) str() string {
+// if m.len == 0 {
+// return '{}'
+// }
+// mut sb := strings.new_builder(50)
+// sb.writeln('{')
+// for key, val in m {
+// sb.writeln(' "$key" => "$val"')
+// }
+// sb.writeln('}')
+// return sb.str()
+// }