bjoernager/rust
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Eliminate left and right cursors in favor of ring buffer

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This commit is contained in:
David Tolnay 2022-01-18 20:19:10 -08:00
parent cc66a7ff20
commit 4d3faae5cd
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GPG key ID: F9BA143B95FF6D82
2 changed files with 33 additions and 30 deletions
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43
compiler/rustc_ast_pretty/src/pp.rs
View file

@ -206,10 +206,6 @@ pub struct Printer {
margin: isize, margin: isize,
/// Number of spaces left on line /// Number of spaces left on line
space: isize, space: isize,
/// Index of left side of input stream
left: usize,
/// Index of right side of input stream
right: usize,
/// Ring-buffer of tokens and calculated sizes /// Ring-buffer of tokens and calculated sizes
buf: RingBuffer<BufEntry>, buf: RingBuffer<BufEntry>,
/// Running size of stream "...left" /// Running size of stream "...left"
@ -245,8 +241,6 @@ impl Printer {
out: String::new(), out: String::new(),
margin: linewidth as isize, margin: linewidth as isize,
space: linewidth as isize, space: linewidth as isize,
left: 0,
right: 0,
buf: RingBuffer::new(), buf: RingBuffer::new(),
left_total: 0, left_total: 0,
right_total: 0, right_total: 0,
@ -281,22 +275,18 @@ impl Printer {
if self.scan_stack.is_empty() { if self.scan_stack.is_empty() {
self.left_total = 1; self.left_total = 1;
self.right_total = 1; self.right_total = 1;
self.right = self.left;
self.buf.clear(); self.buf.clear();
} else {
self.right += 1;
} }
self.buf.push(BufEntry { token: Token::Begin(b), size: -self.right_total }); let right = self.buf.push(BufEntry { token: Token::Begin(b), size: -self.right_total });
self.scan_stack.push_front(self.right); self.scan_stack.push_front(right);
} }
fn scan_end(&mut self) { fn scan_end(&mut self) {
if self.scan_stack.is_empty() { if self.scan_stack.is_empty() {
self.print_end(); self.print_end();
} else { } else {
self.right += 1; let right = self.buf.push(BufEntry { token: Token::End, size: -1 });
self.buf.push(BufEntry { token: Token::End, size: -1 }); self.scan_stack.push_front(right);
self.scan_stack.push_front(self.right);
} }
} }
@ -304,14 +294,12 @@ impl Printer {
if self.scan_stack.is_empty() { if self.scan_stack.is_empty() {
self.left_total = 1; self.left_total = 1;
self.right_total = 1; self.right_total = 1;
self.right = self.left;
self.buf.clear(); self.buf.clear();
} else { } else {
self.check_stack(0); self.check_stack(0);
self.right += 1;
} }
self.buf.push(BufEntry { token: Token::Break(b), size: -self.right_total }); let right = self.buf.push(BufEntry { token: Token::Break(b), size: -self.right_total });
self.scan_stack.push_front(self.right); self.scan_stack.push_front(right);
self.right_total += b.blank_space; self.right_total += b.blank_space;
} }
@ -319,7 +307,6 @@ impl Printer {
if self.scan_stack.is_empty() { if self.scan_stack.is_empty() {
self.print_string(&s); self.print_string(&s);
} else { } else {
self.right += 1;
let len = s.len() as isize; let len = s.len() as isize;
self.buf.push(BufEntry { token: Token::String(s), size: len }); self.buf.push(BufEntry { token: Token::String(s), size: len });
self.right_total += len; self.right_total += len;
@ -329,22 +316,22 @@ impl Printer {
fn check_stream(&mut self) { fn check_stream(&mut self) {
while self.right_total - self.left_total > self.space { while self.right_total - self.left_total > self.space {
if self.scan_stack.back() == Some(&self.left) { if *self.scan_stack.back().unwrap() == self.buf.index_of_first() {
self.scan_stack.pop_back().unwrap(); self.scan_stack.pop_back().unwrap();
self.buf[self.left].size = SIZE_INFINITY; self.buf.first_mut().unwrap().size = SIZE_INFINITY;
} }
self.advance_left(); self.advance_left();
if self.left == self.right { if self.buf.is_empty() {
break; break;
} }
} }
} }
fn advance_left(&mut self) { fn advance_left(&mut self) {
let mut left_size = self.buf[self.left].size; let mut left_size = self.buf.first().unwrap().size;
while left_size >= 0 { while left_size >= 0 {
let left = self.buf[self.left].token.clone(); let left = self.buf.first().unwrap().token.clone();
let len = match left { let len = match left {
Token::Break(b) => b.blank_space, Token::Break(b) => b.blank_space,
@ -360,14 +347,12 @@ impl Printer {
self.left_total += len; self.left_total += len;
if self.left == self.right { self.buf.advance_left();
if self.buf.is_empty() {
break; break;
} }
self.buf.advance_left(); left_size = self.buf.first().unwrap().size;
self.left += 1;
left_size = self.buf[self.left].size;
} }
} }

20
compiler/rustc_ast_pretty/src/pp/ring.rs
View file

@ -22,8 +22,14 @@ impl<T> RingBuffer<T> {
RingBuffer { data: VecDeque::new(), offset: 0 } RingBuffer { data: VecDeque::new(), offset: 0 }
} }
pub fn push(&mut self, value: T) { pub fn is_empty(&self) -> bool {
self.data.is_empty()
}
pub fn push(&mut self, value: T) -> usize {
let index = self.offset + self.data.len();
self.data.push_back(value); self.data.push_back(value);
index
} }
pub fn advance_left(&mut self) { pub fn advance_left(&mut self) {
@ -35,6 +41,18 @@ impl<T> RingBuffer<T> {
self.data.clear(); self.data.clear();
} }
pub fn index_of_first(&self) -> usize {
self.offset
}
pub fn first(&self) -> Option<&T> {
self.data.front()
}
pub fn first_mut(&mut self) -> Option<&mut T> {
self.data.front_mut()
}
pub fn last(&self) -> Option<&T> { pub fn last(&self) -> Option<&T> {
self.data.back() self.data.back()
} }