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libsyntax/pp: replace manual ring buffer with a VecDeque
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@birkenfeld
birkenfeld committed May 1, 2016
1 parent 3eef083 commit 4186169
Showing 1 changed file with 19 additions and 52 deletions.
71 changes: 19 additions & 52 deletions src/libsyntax/print/pp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,7 @@
//! line (which it can't) and so naturally place the content on its own line to
//! avoid combining it with other lines and making matters even worse.

use std::collections::VecDeque;
use std::fmt;
use std::io;

Expand Down Expand Up @@ -164,7 +165,7 @@ pub fn mk_printer<'a>(out: Box<io::Write+'a>, linewidth: usize) -> Printer<'a> {
debug!("mk_printer {}", linewidth);
let token = vec![Token::Eof; n];
let size = vec![0; n];
let scan_stack = vec![0; n];
let scan_stack = VecDeque::with_capacity(n);
Printer {
out: out,
buf_len: n,
Expand All @@ -177,9 +178,6 @@ pub fn mk_printer<'a>(out: Box<io::Write+'a>, linewidth: usize) -> Printer<'a> {
left_total: 0,
right_total: 0,
scan_stack: scan_stack,
scan_stack_empty: true,
top: 0,
bottom: 0,
print_stack: Vec::new(),
pending_indentation: 0
}
Expand Down Expand Up @@ -241,9 +239,8 @@ pub fn mk_printer<'a>(out: Box<io::Write+'a>, linewidth: usize) -> Printer<'a> {
/// approximation for purposes of line breaking).
///
/// The "input side" of the printer is managed as an abstract process called
/// SCAN, which uses 'scan_stack', 'scan_stack_empty', 'top' and 'bottom', to
/// manage calculating 'size'. SCAN is, in other words, the process of
/// calculating 'size' entries.
/// SCAN, which uses 'scan_stack', to manage calculating 'size'. SCAN is, in
/// other words, the process of calculating 'size' entries.
///
/// The "output side" of the printer is managed by an abstract process called
/// PRINT, which uses 'print_stack', 'margin' and 'space' to figure out what to
Expand Down Expand Up @@ -286,13 +283,7 @@ pub struct Printer<'a> {
/// Begin (if there is any) on top of it. Stuff is flushed off the
/// bottom as it becomes irrelevant due to the primary ring-buffer
/// advancing.
scan_stack: Vec<usize> ,
/// Top==bottom disambiguator
scan_stack_empty: bool,
/// Index of top of scan_stack
top: usize,
/// Index of bottom of scan_stack
bottom: usize,
scan_stack: VecDeque<usize> ,
/// Stack of blocks-in-progress being flushed by print
print_stack: Vec<PrintStackElem> ,
/// Buffered indentation to avoid writing trailing whitespace
Expand All @@ -311,15 +302,15 @@ impl<'a> Printer<'a> {
debug!("pp Vec<{},{}>", self.left, self.right);
match token {
Token::Eof => {
if !self.scan_stack_empty {
if !self.scan_stack.is_empty() {
self.check_stack(0);
self.advance_left()?;
}
self.indent(0);
Ok(())
}
Token::Begin(b) => {
if self.scan_stack_empty {
if self.scan_stack.is_empty() {
self.left_total = 1;
self.right_total = 1;
self.left = 0;
Expand All @@ -334,7 +325,7 @@ impl<'a> Printer<'a> {
Ok(())
}
Token::End => {
if self.scan_stack_empty {
if self.scan_stack.is_empty() {
debug!("pp End/print Vec<{},{}>", self.left, self.right);
self.print(token, 0)
} else {
Expand All @@ -348,7 +339,7 @@ impl<'a> Printer<'a> {
}
}
Token::Break(b) => {
if self.scan_stack_empty {
if self.scan_stack.is_empty() {
self.left_total = 1;
self.right_total = 1;
self.left = 0;
Expand All @@ -365,7 +356,7 @@ impl<'a> Printer<'a> {
Ok(())
}
Token::String(s, len) => {
if self.scan_stack_empty {
if self.scan_stack.is_empty() {
debug!("pp String('{}')/print Vec<{},{}>",
s, self.left, self.right);
self.print(Token::String(s, len), len)
Expand All @@ -387,12 +378,10 @@ impl<'a> Printer<'a> {
if self.right_total - self.left_total > self.space {
debug!("scan window is {}, longer than space on line ({})",
self.right_total - self.left_total, self.space);
if !self.scan_stack_empty {
if self.left == self.scan_stack[self.bottom] {
debug!("setting {} to infinity and popping", self.left);
let scanned = self.scan_pop_bottom();
self.size[scanned] = SIZE_INFINITY;
}
if Some(&self.left) == self.scan_stack.back() {
debug!("setting {} to infinity and popping", self.left);
let scanned = self.scan_pop_bottom();
self.size[scanned] = SIZE_INFINITY;
}
self.advance_left()?;
if self.left != self.right {
Expand All @@ -403,38 +392,16 @@ impl<'a> Printer<'a> {
}
pub fn scan_push(&mut self, x: usize) {
debug!("scan_push {}", x);
if self.scan_stack_empty {
self.scan_stack_empty = false;
} else {
self.top += 1;
self.top %= self.buf_len;
assert!(self.top != self.bottom);
}
self.scan_stack[self.top] = x;
self.scan_stack.push_front(x);
}
pub fn scan_pop(&mut self) -> usize {
assert!(!self.scan_stack_empty);
let x = self.scan_stack[self.top];
if self.top == self.bottom {
self.scan_stack_empty = true;
} else {
self.top += self.buf_len - 1; self.top %= self.buf_len;
}
x
self.scan_stack.pop_front().unwrap()
}
pub fn scan_top(&mut self) -> usize {
assert!(!self.scan_stack_empty);
self.scan_stack[self.top]
*self.scan_stack.front().unwrap()
}
pub fn scan_pop_bottom(&mut self) -> usize {
assert!(!self.scan_stack_empty);
let x = self.scan_stack[self.bottom];
if self.top == self.bottom {
self.scan_stack_empty = true;
} else {
self.bottom += 1; self.bottom %= self.buf_len;
}
x
self.scan_stack.pop_back().unwrap()
}
pub fn advance_right(&mut self) {
self.right += 1;
Expand Down Expand Up @@ -476,7 +443,7 @@ impl<'a> Printer<'a> {
Ok(())
}
pub fn check_stack(&mut self, k: isize) {
if !self.scan_stack_empty {
if !self.scan_stack.is_empty() {
let x = self.scan_top();
match self.token[x] {
Token::Begin(_) => {
Expand Down

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