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|
/// Wrapper around Vec which supports fast indexing and rotation
///
/// The rotation implemented by grid::Storage is a simple integer addition.
/// Compare with standard library rotation which requires rearranging items in
/// memory.
///
/// As a consequence, the indexing operators need to be reimplemented for this
/// type to account for the 0th element not always being at the start of the
/// allocation.
///
/// Because certain Vec operations are no longer valid on this type, no Deref
/// implementation is provided. Anything from Vec that should be exposed must be
/// done so manually.
use std::ops::{Index, IndexMut};
use index::Line;
/// Maximum number of invisible lines before buffer is resized
const TRUNCATE_STEP: usize = 100;
#[derive(Clone, Debug, Deserialize, Serialize)]
pub struct Storage<T> {
inner: Vec<T>,
zero: usize,
visible_lines: Line,
/// Total number of lines currently active in the terminal (scrollback + visible)
///
/// Shrinking this length allows reducing the number of lines in the scrollback buffer without
/// having to truncate the raw `inner` buffer.
/// As long as `len` is bigger than `inner`, it is also possible to grow the scrollback buffer
/// without any additional insertions.
#[serde(skip)]
len: usize,
}
impl<T: PartialEq> ::std::cmp::PartialEq for Storage<T> {
fn eq(&self, other: &Self) -> bool {
// Make sure length is equal
if self.inner.len() != other.inner.len() {
return false;
}
// Check which vec has the bigger zero
let (ref bigger, ref smaller) = if self.zero >= other.zero {
(self, other)
} else {
(other, self)
};
// Calculate the actual zero offset
let len = self.inner.len();
let bigger_zero = bigger.zero % len;
let smaller_zero = smaller.zero % len;
// Compare the slices in chunks
// Chunks:
// - Bigger zero to the end
// - Remaining lines in smaller zero vec
// - Beginning of smaller zero vec
//
// Example:
// Bigger Zero (6):
// 4 5 6 | 7 8 9 | 0 1 2 3
// C2 C2 C2 | C3 C3 C3 | C1 C1 C1 C1
// Smaller Zero (3):
// 7 8 9 | 0 1 2 3 | 4 5 6
// C3 C3 C3 | C1 C1 C1 C1 | C2 C2 C2
&bigger.inner[bigger_zero..]
== &smaller.inner[smaller_zero..smaller_zero + (len - bigger_zero)]
&& &bigger.inner[..bigger_zero - smaller_zero]
== &smaller.inner[smaller_zero + (len - bigger_zero)..]
&& &bigger.inner[bigger_zero - smaller_zero..bigger_zero]
== &smaller.inner[..smaller_zero]
}
}
impl<T> Storage<T> {
#[inline]
pub fn with_capacity(cap: usize, lines: Line, template: T) -> Storage<T>
where
T: Clone,
{
// Allocate all lines in the buffer, including scrollback history
//
// TODO (jwilm) Allocating each line at this point is expensive and
// delays startup. A nice solution might be having `Row` delay
// allocation until it's actually used.
let inner = vec![template; cap];
Storage {
inner,
zero: 0,
visible_lines: lines - 1,
len: cap,
}
}
/// Increase the number of lines in the buffer
pub fn grow_visible_lines(&mut self, next: Line, template_row: T)
where
T: Clone,
{
// Number of lines the buffer needs to grow
let lines_to_grow = (next - (self.visible_lines + 1)).0;
// Only grow if there are not enough lines still hidden
if lines_to_grow > (self.inner.len() - self.len) {
// Lines to grow additionally to invisible lines
let new_lines_to_grow = lines_to_grow - (self.inner.len() - self.len);
// Get the position of the start of the buffer
let offset = self.zero % self.inner.len();
// Split off the beginning of the raw inner buffer
let mut start_buffer = self.inner.split_off(offset);
// Insert new template rows at the end of the raw inner buffer
let mut new_lines = vec![template_row; new_lines_to_grow];
self.inner.append(&mut new_lines);
// Add the start to the raw inner buffer again
self.inner.append(&mut start_buffer);
// Update the zero to after the lines we just inserted
self.zero = offset + lines_to_grow;
}
// Update visible lines and raw buffer length
self.len += lines_to_grow;
self.visible_lines = next - 1;
}
/// Decrease the number of lines in the buffer
pub fn shrink_visible_lines(&mut self, next: Line) {
// Shrink the size without removing any lines
self.len -= (self.visible_lines - (next - 1)).0;
// Update visible lines
self.visible_lines = next - 1;
// Free memory
if self.inner.len() > self.len() + TRUNCATE_STEP {
self.truncate();
}
}
/// Truncate the invisible elements from the raw buffer
pub fn truncate(&mut self) {
// Calculate shrinkage/offset for indexing
let offset = self.zero % self.inner.len();
let shrinkage = self.inner.len() - self.len;
let shrinkage_start = ::std::cmp::min(offset, shrinkage);
// Create two vectors with correct ordering
let mut split = self.inner.split_off(offset);
// Truncate the buffers
let len = self.inner.len();
let split_len = split.len();
self.inner.truncate(len - shrinkage_start);
split.truncate(split_len - (shrinkage - shrinkage_start));
// Merge buffers again and reset zero
self.zero = self.inner.len();
self.inner.append(&mut split);
}
#[inline]
pub fn len(&self) -> usize {
self.len
}
/// Compute actual index in underlying storage given the requested index.
#[inline]
fn compute_index(&self, requested: usize) -> usize {
(requested + self.zero) % self.inner.len()
}
pub fn swap_lines(&mut self, a: Line, b: Line) {
let offset = self.inner.len() + self.zero + *self.visible_lines;
let a = (offset - *a) % self.inner.len();
let b = (offset - *b) % self.inner.len();
self.inner.swap(a, b);
}
pub fn iter_mut(&mut self) -> IterMut<T> {
IterMut { storage: self, index: 0 }
}
pub fn rotate(&mut self, count: isize) {
debug_assert!(count.abs() as usize <= self.inner.len());
let len = self.inner.len();
self.zero = (self.zero as isize + count + len as isize) as usize % len;
}
// Fast path
pub fn rotate_up(&mut self, count: usize) {
self.zero =
|