squiid/rust
1
0
Fork 0
Code Issues Pull requests Projects Activity

Grow scan_stack in the conventional direction

Browse source 
The pretty printer algorithm involves 2 VecDeques: a ring-buffer of
tokens and a deque of ring-buffer indices. Confusingly, those two deques
were being grown in opposite directions for no good reason. Ring-buffer
pushes would go on the "back" of the ring-buffer (i.e. higher indices)
while scan_stack pushes would go on the "front" (i.e. lower indices).
This commit flips the scan_stack accesses to grow the scan_stack and
ring-buffer in the same direction, where push does the same
operation as a Vec push i.e. inserting on the high-index end.
This commit is contained in:
David Tolnay 2022-01-19 18:27:26 -08:00
parent eec6016ec3
commit d81740ed2a
No known key found for this signature in database
GPG key ID: F9BA143B95FF6D82
1 changed files with 9 additions and 9 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

18
compiler/rustc_ast_pretty/src/pp.rs
View file

@ -266,7 +266,7 @@ impl Printer {
self.buf.clear();
}
let right = self.buf.push(BufEntry { token: Token::Begin(b), size: -self.right_total });
self.scan_stack.push_front(right);
self.scan_stack.push_back(right);
}
fn scan_end(&mut self) {
@ -274,7 +274,7 @@ impl Printer {
self.print_end();
} else {
let right = self.buf.push(BufEntry { token: Token::End, size: -1 });
self.scan_stack.push_front(right);
self.scan_stack.push_back(right);
}
}
@ -287,7 +287,7 @@ impl Printer {
self.check_stack(0);
}
let right = self.buf.push(BufEntry { token: Token::Break(b), size: -self.right_total });
self.scan_stack.push_front(right);
self.scan_stack.push_back(right);
self.right_total += b.blank_space;
}
@ -304,8 +304,8 @@ impl Printer {
fn check_stream(&mut self) {
while self.right_total - self.left_total > self.space {
if *self.scan_stack.back().unwrap() == self.buf.index_of_first() {
self.scan_stack.pop_back().unwrap();
if *self.scan_stack.front().unwrap() == self.buf.index_of_first() {
self.scan_stack.pop_front().unwrap();
self.buf.first_mut().unwrap().size = SIZE_INFINITY;
}
self.advance_left();
@ -345,25 +345,25 @@ impl Printer {
}
fn check_stack(&mut self, mut k: usize) {
while let Some(&x) = self.scan_stack.front() {
while let Some(&x) = self.scan_stack.back() {
let mut entry = &mut self.buf[x];
match entry.token {
Token::Begin(_) => {
if k == 0 {
break;
}
self.scan_stack.pop_front().unwrap();
self.scan_stack.pop_back().unwrap();
entry.size += self.right_total;
k -= 1;
}
Token::End => {
// paper says + not =, but that makes no sense.
self.scan_stack.pop_front().unwrap();
self.scan_stack.pop_back().unwrap();
entry.size = 1;
k += 1;
}
_ => {
self.scan_stack.pop_front().unwrap();
self.scan_stack.pop_back().unwrap();
entry.size += self.right_total;
if k == 0 {
break;