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syntax: Use a ring buffer instead of a dvec and save a bunch of copies. Shaves a second or two off rustc.

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This commit is contained in:
Patrick Walton 2012-06-08 17:17:31 -07:00
parent cdcae39ba3
commit c7c37debe4
1 changed files with 25 additions and 7 deletions
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32
src/libsyntax/parse/parser.rs
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@ -70,7 +70,9 @@ class parser {
let mut token: token::token;
let mut span: span;
let mut last_span: span;
let buffer: dvec<{tok: token::token, span: span}>;
let mut buffer: [mut {tok: token::token, span: span}]/4;
let mut buffer_start: int;
let mut buffer_end: int;
let mut restriction: restriction;
let reader: reader;
let keywords: hashmap<str, ()>;
@ -86,7 +88,14 @@ class parser {
self.token = tok0.tok;
self.span = span0;
self.last_span = span0;
self.buffer = dvec::dvec();
self.buffer = [mut
{tok: tok0.tok, span: span0},
{tok: tok0.tok, span: span0},
{tok: tok0.tok, span: span0},
{tok: tok0.tok, span: span0}
]/4;
self.buffer_start = 0;
self.buffer_end = 0;
self.restriction = UNRESTRICTED;
self.reader = rdr;
self.keywords = token::keyword_table();
@ -98,12 +107,13 @@ class parser {
fn bump() {
self.last_span = self.span;
if self.buffer.len() == 0u {
if self.buffer_start == self.buffer_end {
let next = lexer::next_token(self.reader);
self.token = next.tok;
self.span = mk_sp(next.chpos, self.reader.chpos);
} else {
let next = self.buffer.shift();
let next = self.buffer[self.buffer_start];
self.buffer_start = (self.buffer_start + 1) & 3;
self.token = next.tok;
self.span = next.span;
}
@ -112,13 +122,21 @@ class parser {
self.token = next;
self.span = mk_sp(lo, hi);
}
fn buffer_length() -> int {
if self.buffer_start <= self.buffer_end {
ret self.buffer_end - self.buffer_start;
}
ret (4 - self.buffer_start) + self.buffer_end;
}
fn look_ahead(distance: uint) -> token::token {
while self.buffer.len() < distance {
let dist = distance as int;
while self.buffer_length() < dist {
let next = lexer::next_token(self.reader);
let sp = mk_sp(next.chpos, self.reader.chpos);
self.buffer.push({tok: next.tok, span: sp});
self.buffer[self.buffer_end] = {tok: next.tok, span: sp};
self.buffer_end = (self.buffer_end + 1) & 3;
}
ret self.buffer[distance - 1u].tok;
ret copy self.buffer[(self.buffer_start + dist - 1) & 3].tok;
}
fn fatal(m: str) -> ! {
self.sess.span_diagnostic.span_fatal(copy self.span, m)