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Remove most of FlowList
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This needs to be reworked for DST.  Until then, DList<FlowRef> will do.
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@kmcallister
kmcallister committed Sep 20, 2014
1 parent d6ba37c commit 8a7eefe
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Showing 2 changed files with 28 additions and 205 deletions.
14 changes: 1 addition & 13 deletions components/layout/flow.rs
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Expand Up @@ -29,7 +29,7 @@ use css::node_style::StyledNode;
use block::BlockFlow;
use context::LayoutContext;
use floats::Floats;
use flow_list::{FlowList, Link, FlowListIterator, MutFlowListIterator};
use flow_list::{FlowList, FlowListIterator, MutFlowListIterator};
use flow_ref::FlowRef;
use fragment::{Fragment, TableRowFragment, TableCellFragment};
use incremental::RestyleDamage;
Expand Down Expand Up @@ -691,16 +691,6 @@ pub struct BaseFlow {
/// The children of this flow.
pub children: FlowList,

/// The flow's next sibling.
///
/// FIXME(pcwalton): Make this private. Misuse of this can lead to data races.
pub next_sibling: Link,

/// The flow's previous sibling.
///
/// FIXME(pcwalton): Make this private. Misuse of this can lead to data races.
pub prev_sibling: Link,

/* layout computations */
// TODO: min/pref and position are used during disjoint phases of
// layout; maybe combine into a single enum to save space.
Expand Down Expand Up @@ -809,8 +799,6 @@ impl BaseFlow {
restyle_damage: node.restyle_damage(),

children: FlowList::new(),
next_sibling: None,
prev_sibling: None,

intrinsic_inline_sizes: IntrinsicISizes::new(),
position: LogicalRect::zero(writing_mode),
Expand Down
219 changes: 27 additions & 192 deletions components/layout/flow_list.rs
View file
Expand Up @@ -2,295 +2,130 @@
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! A variant of `DList` specialized to store `Flow`s without an extra
//! indirection.

use flow::{Flow, base, mut_base};
use flow::Flow;
use flow_ref::FlowRef;

use std::kinds::marker::ContravariantLifetime;
use std::mem;
use std::ptr;
use std::raw;

pub type Link = Option<FlowRef>;
use std::collections::{Deque, dlist, DList};

// This needs to be reworked now that we have dynamically-sized types in Rust.
// Until then, it's just a wrapper around DList.

#[allow(raw_pointer_deriving)]
pub struct Rawlink<'a> {
object: raw::TraitObject,
marker: ContravariantLifetime<'a>,
}

/// Doubly-linked list of Flows.
///
/// The forward links are strong references.
/// The backward links are weak references.
pub struct FlowList {
length: uint,
list_head: Link,
list_tail: Link,
flows: DList<FlowRef>,
}

/// Double-ended FlowList iterator
pub struct FlowListIterator<'a> {
head: &'a Link,
nelem: uint,
it: dlist::Items<'a, FlowRef>,
}

/// Double-ended mutable FlowList iterator
pub struct MutFlowListIterator<'a> {
head: Rawlink<'a>,
nelem: uint,
}

impl<'a> Rawlink<'a> {
/// Like Option::None for Rawlink
pub fn none() -> Rawlink<'static> {
Rawlink {
object: raw::TraitObject {
vtable: ptr::mut_null(),
data: ptr::mut_null(),
},
marker: ContravariantLifetime,
}
}

/// Like Option::Some for Rawlink
pub fn some(n: &Flow) -> Rawlink {
unsafe {
Rawlink {
object: mem::transmute::<&Flow, raw::TraitObject>(n),
marker: ContravariantLifetime,
}
}
}

pub unsafe fn resolve_mut(&self) -> Option<&'a mut Flow> {
if self.object.data.is_null() {
None
} else {
Some(mem::transmute_copy::<raw::TraitObject, &mut Flow>(&self.object))
}
}
}

/// Set the .prev field on `next`, then return `Some(next)`
unsafe fn link_with_prev(mut next: FlowRef, prev: Option<FlowRef>) -> Link {
mut_base(next.get_mut()).prev_sibling = prev;
Some(next)
it: dlist::MutItems<'a, FlowRef>,
}

impl Collection for FlowList {
/// O(1)
#[inline]
fn is_empty(&self) -> bool {
self.list_head.is_none()
self.flows.is_empty()
}
/// O(1)
#[inline]
fn len(&self) -> uint {
self.length
self.flows.len()
}
}

// This doesn't quite fit the Deque trait because of the need to switch between
// &Flow and ~Flow.
impl FlowList {
/// Provide a reference to the front element, or None if the list is empty
#[inline]
pub fn front<'a>(&'a self) -> Option<&'a Flow> {
self.list_head.as_ref().map(|head| head.get())
self.flows.front().map(|head| head.get())
}

/// Provide a mutable reference to the front element, or None if the list is empty
#[inline]
pub unsafe fn front_mut<'a>(&'a mut self) -> Option<&'a mut Flow> {
self.list_head.as_mut().map(|head| head.get_mut())
self.flows.front_mut().map(|head| head.get_mut())
}

/// Provide a reference to the back element, or None if the list is empty
#[inline]
pub fn back<'a>(&'a self) -> Option<&'a Flow> {
match self.list_tail {
None => None,
Some(ref list_tail) => Some(list_tail.get())
}
self.flows.back().map(|tail| tail.get())
}

/// Provide a mutable reference to the back element, or None if the list is empty
#[inline]
pub unsafe fn back_mut<'a>(&'a mut self) -> Option<&'a mut Flow> {
// Can't use map() due to error:
// lifetime of `tail` is too short to guarantee its contents can be safely reborrowed
match self.list_tail {
None => None,
Some(ref mut tail) => {
let x: &mut Flow = tail.get_mut();
Some(mem::transmute_copy(&x))
}
}
self.flows.back_mut().map(|tail| tail.get_mut())
}

/// Add an element first in the list
///
/// O(1)
pub fn push_front(&mut self, mut new_head: FlowRef) {
unsafe {
match self.list_head {
None => {
self.list_tail = Some(new_head.clone());
self.list_head = link_with_prev(new_head, None);
}
Some(ref mut head) => {
mut_base(new_head.get_mut()).prev_sibling = None;
mut_base(head.get_mut()).prev_sibling = Some(new_head.clone());
mem::swap(head, &mut new_head);
mut_base(head.get_mut()).next_sibling = Some(new_head);
}
}
self.length += 1;
}
self.flows.push_front(new_head);
}

/// Remove the first element and return it, or None if the list is empty
///
/// O(1)
pub fn pop_front(&mut self) -> Option<FlowRef> {
self.list_head.take().map(|mut front_node| {
self.length -= 1;
unsafe {
match mut_base(front_node.get_mut()).next_sibling.take() {
Some(node) => self.list_head = link_with_prev(node, None),
None => self.list_tail = None,
}
}
front_node
})
self.flows.pop_front()
}

/// Add an element last in the list
///
/// O(1)
pub fn push_back(&mut self, new_tail: FlowRef) {
if self.list_tail.is_none() {
return self.push_front(new_tail);
}

let old_tail = self.list_tail.clone();
self.list_tail = Some(new_tail.clone());
let mut tail = (*old_tail.as_ref().unwrap()).clone();
let tail_clone = Some(tail.clone());
unsafe {
mut_base(tail.get_mut()).next_sibling = link_with_prev(new_tail, tail_clone);
}
self.length += 1;
self.flows.push_back(new_tail);
}

/// Create an empty list
#[inline]
pub fn new() -> FlowList {
FlowList {
list_head: None,
list_tail: None,
length: 0,
flows: DList::new(),
}
}

/// Provide a forward iterator
#[inline]
pub fn iter<'a>(&'a self) -> FlowListIterator<'a> {
FlowListIterator {
nelem: self.len(),
head: &self.list_head,
it: self.flows.iter(),
}
}

/// Provide a forward iterator with mutable references
#[inline]
pub fn mut_iter<'a>(&'a mut self) -> MutFlowListIterator<'a> {
let len = self.len();
let head_raw = match self.list_head {
Some(ref mut h) => Rawlink::some(h.get()),
None => Rawlink::none(),
};
MutFlowListIterator {
nelem: len,
head: head_raw,
it: self.flows.mut_iter(),
}
}
}

#[unsafe_destructor]
impl Drop for FlowList {
fn drop(&mut self) {
// Dissolve the list in backwards direction
// Just dropping the list_head can lead to stack exhaustion
// when length is >> 1_000_000
let mut tail = mem::replace(&mut self.list_tail, None);
loop {
let new_tail = match tail {
None => break,
Some(ref mut prev) => {
let prev_base = mut_base(prev.get_mut());
prev_base.next_sibling.take();
prev_base.prev_sibling.clone()
}
};
tail = new_tail
}
self.length = 0;
self.list_head = None;
}
}

impl<'a> Iterator<&'a Flow> for FlowListIterator<'a> {
impl<'a> Iterator<&'a Flow + 'a> for FlowListIterator<'a> {
#[inline]
fn next(&mut self) -> Option<&'a Flow> {
if self.nelem == 0 {
return None;
}
self.head.as_ref().map(|head| {
let head_base = base(head.get());
self.nelem -= 1;
self.head = &head_base.next_sibling;
let ret: &Flow = head.get();
ret
})
fn next(&mut self) -> Option<&'a Flow + 'a> {
self.it.next().map(|x| x.get())
}

#[inline]
fn size_hint(&self) -> (uint, Option<uint>) {
(self.nelem, Some(self.nelem))
self.it.size_hint()
}
}

impl<'a> Iterator<&'a mut Flow> for MutFlowListIterator<'a> {
impl<'a> Iterator<&'a mut Flow + 'a> for MutFlowListIterator<'a> {
#[inline]
fn next(&mut self) -> Option<&'a mut Flow> {
if self.nelem == 0 {
return None;
}
unsafe {
self.head.resolve_mut().map(|next| {
self.nelem -= 1;
self.head = match mut_base(next).next_sibling {
Some(ref mut node) => {
let x: &mut Flow = node.get_mut();
// NOTE: transmute needed here to break the link
// between x and next so that it is no longer
// borrowed.
mem::transmute(Rawlink::some(x))
}
None => Rawlink::none(),
};
next
})
}
fn next(&mut self) -> Option<&'a mut Flow + 'a> {
self.it.next().map(|x| x.get_mut())
}

#[inline]
fn size_hint(&self) -> (uint, Option<uint>) {
(self.nelem, Some(self.nelem))
self.it.size_hint()
}
}

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