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use std::marker::PhantomData;
use crate::bucket::BucketInner;
use crate::data::{Data, Ref};
use crate::node::{Node, NodeData, NodeID};
use crate::page::{Page, PageID};
use crate::ptr::Ptr;
#[derive(Clone, Copy)]
pub(crate) enum PageNodeID {
Page(PageID),
Node(NodeID),
}
pub(crate) enum PageNode {
Page(Ptr<Page>),
Node(Ptr<Node>),
}
impl PageNode {
fn leaf(&self) -> bool {
match self {
PageNode::Page(p) => p.page_type == Page::TYPE_LEAF,
PageNode::Node(n) => n.leaf(),
}
}
fn len(&self) -> usize {
match self {
PageNode::Page(p) => p.count as usize,
PageNode::Node(n) => n.data.len(),
}
}
fn index_page(&self, index: usize) -> PageID {
match self {
PageNode::Page(p) => {
if index >= p.count as usize {
return 0;
}
match p.page_type {
Page::TYPE_BRANCH => p.branch_elements()[index].page,
_ => panic!("INVALID PAGE TYPE FOR INDEX_PAGE"),
}
}
PageNode::Node(n) => {
if index >= n.data.len() {
return 0;
}
match &n.data {
NodeData::Branches(b) => b[index].page,
_ => panic!("INVALID NODE TYPE FOR INDEX_PAGE"),
}
}
}
}
fn index(&self, key: &[u8]) -> (usize, bool) {
let result = match self {
PageNode::Page(p) => match p.page_type {
Page::TYPE_LEAF => p.leaf_elements().binary_search_by_key(&key, |e| e.key()),
Page::TYPE_BRANCH => p.branch_elements().binary_search_by_key(&key, |e| e.key()),
_ => panic!("INVALID PAGE TYPE FOR INDEX: {:?}", p.page_type),
},
PageNode::Node(n) => match &n.data {
NodeData::Branches(b) => b.binary_search_by_key(&key, |b| b.key()),
NodeData::Leaves(l) => l.binary_search_by_key(&key, |l| l.key()),
},
};
match result {
Ok(i) => (i, true),
Err(mut i) => {
if i > 0 {
i -= 1;
};
(i, false)
}
}
}
fn val(&self, index: usize) -> Option<Data> {
match self {
PageNode::Page(p) => match p.page_type {
Page::TYPE_LEAF => p.leaf_elements().get(index).map(|e| Data::from_leaf(e)),
_ => panic!("INVALID PAGE TYPE FOR VAL"),
},
PageNode::Node(n) => match &n.data {
NodeData::Leaves(l) => l.get(index).cloned(),
_ => panic!("INVALID NODE TYPE FOR VAL"),
},
}
}
}
pub struct Cursor<'a> {
bucket: Ptr<BucketInner>,
stack: Vec<Elem>,
next_called: bool,
_phantom: PhantomData<&'a ()>,
}
impl<'a> Cursor<'a> {
pub(crate) fn new(b: Ptr<BucketInner>) -> Cursor<'a> {
Cursor {
bucket: b,
stack: vec![],
next_called: false,
_phantom: PhantomData {},
}
}
pub(crate) fn current_id(&self) -> PageNodeID {
let e = self.stack.last().unwrap();
match &e.page_node {
PageNode::Page(p) => PageNodeID::Page(p.id),
PageNode::Node(n) => PageNodeID::Node(n.id),
}
}
pub(crate) fn current_index(&self) -> usize {
let e = self.stack.last().unwrap();
e.index
}
pub fn seek<T: AsRef<[u8]>>(&mut self, key: T) -> bool {
self.next_called = false;
self.stack.clear();
self.search(key.as_ref(), self.bucket.meta.root_page)
}
pub fn current(&self) -> Option<Data> {
match self.stack.last() {
Some(e) => e.page_node.val(e.index),
None => None,
}
}
fn search(&mut self, key: &[u8], page_id: PageID) -> bool {
let page_node = self.bucket.page_node(page_id);
let (index, exact) = page_node.index(key);
let leaf = page_node.leaf();
self.stack.push(Elem { index, page_node });
if leaf {
return exact;
}
let next_page_id = self.stack.last().unwrap().page_node.index_page(index);
if next_page_id == 0 {
return false;
}
self.bucket.add_page_parent(next_page_id, page_id);
self.search(key, next_page_id)
}
pub(crate) fn seek_first(&mut self) {
if self.stack.is_empty() {
let page_node = self.bucket.page_node(self.bucket.meta.root_page);
self.stack.push(Elem {
index: 0,
page_node,
});
}
loop {
let elem = self.stack.last().unwrap();
if elem.page_node.leaf() {
break;
}
if elem.page_node.len() == 0 {
break;
}
let page_node = self.bucket.page_node(elem.page_node.index_page(elem.index));
self.stack.push(Elem {
index: 0,
page_node,
});
}
}
}
impl<'a> Iterator for Cursor<'a> {
type Item = Ref<'a, Data>;
fn next(&mut self) -> Option<Self::Item> {
if self.stack.is_empty() {
self.seek_first();
} else if self.next_called {
loop {
let elem = self.stack.last_mut().unwrap();
if elem.index >= (elem.page_node.len() - 1) {
if self.stack.len() == 1 {
return None;
}
self.stack.pop();
continue;
} else {
elem.index += 1;
}
self.seek_first();
break;
}
}
self.next_called = true;
self.current().map(Ref::new)
}
}
struct Elem {
index: usize,
page_node: PageNode,
}