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use crate::GLOBALS;
use crate::{BytePos, SpanData};
use crate::hygiene::SyntaxContext;
use rustc_data_structures::fx::FxHashMap;
use std::hash::{Hash, Hasher};
#[repr(packed)]
pub struct Span(u32);
impl Copy for Span {}
impl Clone for Span {
#[inline]
fn clone(&self) -> Span {
*self
}
}
impl PartialEq for Span {
#[inline]
fn eq(&self, other: &Span) -> bool {
let a = self.0;
let b = other.0;
a == b
}
}
impl Eq for Span {}
impl Hash for Span {
#[inline]
fn hash<H: Hasher>(&self, state: &mut H) {
let a = self.0;
a.hash(state)
}
}
pub const DUMMY_SP: Span = Span(0);
impl Span {
#[inline]
pub fn new(lo: BytePos, hi: BytePos, ctxt: SyntaxContext) -> Self {
encode(&match lo <= hi {
true => SpanData { lo, hi, ctxt },
false => SpanData { lo: hi, hi: lo, ctxt },
})
}
#[inline]
pub fn data(self) -> SpanData {
decode(self)
}
}
const TAG_INLINE: u32 = 0;
const TAG_INTERNED: u32 = 1;
const TAG_MASK: u32 = 1;
const BASE_INDEX: usize = 0;
const LEN_INDEX: usize = 1;
const CTXT_INDEX: usize = 2;
const INLINE_SIZES: [u32; 3] = [24, 7, 0];
const INLINE_OFFSETS: [u32; 3] = [8, 1, 1];
const INTERNED_INDEX_SIZE: u32 = 31;
const INTERNED_INDEX_OFFSET: u32 = 1;
#[inline]
fn encode(sd: &SpanData) -> Span {
let (base, len, ctxt) = (sd.lo.0, sd.hi.0 - sd.lo.0, sd.ctxt.as_u32());
let val = if (base >> INLINE_SIZES[BASE_INDEX]) == 0 &&
(len >> INLINE_SIZES[LEN_INDEX]) == 0 &&
(ctxt >> INLINE_SIZES[CTXT_INDEX]) == 0 {
(base << INLINE_OFFSETS[BASE_INDEX]) | (len << INLINE_OFFSETS[LEN_INDEX]) |
(ctxt << INLINE_OFFSETS[CTXT_INDEX]) | TAG_INLINE
} else {
let index = with_span_interner(|interner| interner.intern(sd));
(index << INTERNED_INDEX_OFFSET) | TAG_INTERNED
};
Span(val)
}
#[inline]
fn decode(span: Span) -> SpanData {
let val = span.0;
let extract = |pos: u32, size: u32| {
let mask = ((!0u32) as u64 >> (32 - size)) as u32;
(val >> pos) & mask
};
let (base, len, ctxt) = if val & TAG_MASK == TAG_INLINE {(
extract(INLINE_OFFSETS[BASE_INDEX], INLINE_SIZES[BASE_INDEX]),
extract(INLINE_OFFSETS[LEN_INDEX], INLINE_SIZES[LEN_INDEX]),
extract(INLINE_OFFSETS[CTXT_INDEX], INLINE_SIZES[CTXT_INDEX]),
)} else {
let index = extract(INTERNED_INDEX_OFFSET, INTERNED_INDEX_SIZE);
return with_span_interner(|interner| *interner.get(index));
};
SpanData { lo: BytePos(base), hi: BytePos(base + len), ctxt: SyntaxContext::from_u32(ctxt) }
}
#[derive(Default)]
pub struct SpanInterner {
spans: FxHashMap<SpanData, u32>,
span_data: Vec<SpanData>,
}
impl SpanInterner {
fn intern(&mut self, span_data: &SpanData) -> u32 {
if let Some(index) = self.spans.get(span_data) {
return *index;
}
let index = self.spans.len() as u32;
self.span_data.push(*span_data);
self.spans.insert(*span_data, index);
index
}
#[inline]
fn get(&self, index: u32) -> &SpanData {
&self.span_data[index as usize]
}
}
#[inline]
fn with_span_interner<T, F: FnOnce(&mut SpanInterner) -> T>(f: F) -> T {
GLOBALS.with(|globals| f(&mut *globals.span_interner.lock()))
}