[−][src]Struct swc_common::Span
A compressed span.
SpanData
is 12 bytes, which is a bit too big to stick everywhere. Span
is a form that only takes up 8 bytes, with less space for the length and
context. The vast majority (99.9%+) of SpanData
instances will fit within
those 8 bytes; any SpanData
whose fields don't fit into a Span
are
stored in a separate interner table, and the Span
will index into that
table. Interning is rare enough that the cost is low, but common enough
that the code is exercised regularly.
An earlier version of this code used only 4 bytes for Span
, but that was
slower because only 80--90% of spans could be stored inline (even less in
very large crates) and so the interner was used a lot more.
Inline (compressed) format:
span.base_or_index == span_data.lo
span.len_or_tag == len == span_data.hi - span_data.lo
(must be<= MAX_LEN
)span.ctxt == span_data.ctxt
(must be<= MAX_CTXT
)
Interned format:
span.base_or_index == index
(indexes into the interner table)span.len_or_tag == LEN_TAG
(high bit set, all other bits are zero)span.ctxt == 0
The inline form uses 0 for the tag value (rather than 1) so that we don't need to mask out the tag bit when getting the length, and so that the dummy span can be all zeroes.
Notes about the choice of field sizes:
base
is 32 bits in bothSpan
andSpanData
, which means thatbase
values never cause interning. The number of bits needed forbase
depends on the crate size. 32 bits allows up to 4 GiB of code in a crate.script-servo
is the largest crate inrustc-perf
, requiring 26 bits for some spans.len
is 15 bits inSpan
(a u16, minus 1 bit for the tag) and 32 bits inSpanData
, which means that largelen
values will cause interning. The number of bits needed forlen
does not depend on the crate size. The most common number of bits forlen
are 0--7, with a peak usually at 3 or 4, and then it drops off quickly from 8 onwards. 15 bits is enough for 99.99%+ of cases, but larger values (sometimes 20+ bits) might occur dozens of times in a typical crate.ctxt
is 16 bits inSpan
and 32 bits inSpanData
, which means that largectxt
values will cause interning. The number of bits needed forctxt
values depend partly on the crate size and partly on the form of the code. No crates inrustc-perf
need more than 15 bits forctxt
, but larger crates might need more than 16 bits.
Methods
impl Span
[src]
pub fn new(lo: BytePos, hi: BytePos, ctxt: SyntaxContext) -> Self
[src]
pub fn data(self) -> SpanData
[src]
impl Span
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pub fn lo(self) -> BytePos
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pub fn with_lo(self, lo: BytePos) -> Span
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pub fn hi(self) -> BytePos
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pub fn with_hi(self, hi: BytePos) -> Span
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pub fn ctxt(self) -> SyntaxContext
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pub fn with_ctxt(self, ctxt: SyntaxContext) -> Span
[src]
pub fn is_dummy(self) -> bool
[src]
Returns true
if this is a dummy span with any hygienic context.
pub fn shrink_to_lo(self) -> Span
[src]
Returns a new span representing an empty span at the beginning of this span
pub fn shrink_to_hi(self) -> Span
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Returns a new span representing an empty span at the end of this span
pub fn substitute_dummy(self, other: Span) -> Span
[src]
Returns self
if self
is not the dummy span, and other
otherwise.
pub fn contains(self, other: Span) -> bool
[src]
Return true if self
fully encloses other
.
pub fn source_equal(self, other: Span) -> bool
[src]
Return true if the spans are equal with regards to the source text.
Use this instead of ==
when either span could be generated code,
and you only care that they point to the same bytes of source text.
pub fn trim_start(self, other: Span) -> Option<Span>
[src]
Returns Some(span)
, where the start is trimmed by the end of other
pub fn to(self, end: Span) -> Span
[src]
Return a Span
that would enclose both self
and end
.
pub fn between(self, end: Span) -> Span
[src]
Return a Span
between the end of self
to the beginning of end
.
pub fn until(self, end: Span) -> Span
[src]
Return a Span
between the beginning of self
to the beginning of
end
.
pub fn from_inner_byte_pos(self, start: usize, end: usize) -> Span
[src]
pub fn apply_mark(self, mark: Mark) -> Span
[src]
pub fn remove_mark(&mut self) -> Mark
[src]
pub fn adjust(&mut self, expansion: Mark) -> Option<Mark>
[src]
pub fn glob_adjust(
&mut self,
expansion: Mark,
glob_ctxt: SyntaxContext
) -> Option<Option<Mark>>
[src]
&mut self,
expansion: Mark,
glob_ctxt: SyntaxContext
) -> Option<Option<Mark>>
pub fn reverse_glob_adjust(
&mut self,
expansion: Mark,
glob_ctxt: SyntaxContext
) -> Option<Option<Mark>>
[src]
&mut self,
expansion: Mark,
glob_ctxt: SyntaxContext
) -> Option<Option<Mark>>
Trait Implementations
impl Clone for Span
[src]
impl Copy for Span
[src]
impl Debug for Span
[src]
impl Default for Span
[src]
impl<'de> Deserialize<'de> for Span
[src]
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error> where
D: Deserializer<'de>,
[src]
D: Deserializer<'de>,
impl Eq for Span
[src]
impl From<Span> for MultiSpan
[src]
impl Hash for Span
[src]
fn hash<__H: Hasher>(&self, state: &mut __H)
[src]
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
1.3.0[src]
H: Hasher,
impl Ord for Span
[src]
fn cmp(&self, rhs: &Self) -> Ordering
[src]
fn max(self, other: Self) -> Self
1.21.0[src]
fn min(self, other: Self) -> Self
1.21.0[src]
fn clamp(self, min: Self, max: Self) -> Self
[src]
impl PartialEq<Span> for Span
[src]
impl PartialOrd<Span> for Span
[src]
fn partial_cmp(&self, rhs: &Self) -> Option<Ordering>
[src]
#[must_use]
fn lt(&self, other: &Rhs) -> bool
1.0.0[src]
#[must_use]
fn le(&self, other: &Rhs) -> bool
1.0.0[src]
#[must_use]
fn gt(&self, other: &Rhs) -> bool
1.0.0[src]
#[must_use]
fn ge(&self, other: &Rhs) -> bool
1.0.0[src]
impl Serialize for Span
[src]
impl Spanned for Span
[src]
impl StructuralEq for Span
[src]
impl StructuralPartialEq for Span
[src]
Auto Trait Implementations
impl RefUnwindSafe for Span
impl Send for Span
impl Sync for Span
impl Unpin for Span
impl UnwindSafe for Span
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
[src]
T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
[src]
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]
T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
[src]
impl<T> DeserializeOwned for T where
T: Deserialize<'de>,
[src]
T: Deserialize<'de>,
impl<T> Erased for T
impl<T> Erased for T
impl<T> From<T> for T
[src]
impl<T, U> Into<U> for T where
U: From<T>,
[src]
U: From<T>,
impl<T> ToOwned for T where
T: Clone,
[src]
T: Clone,
type Owned = T
The resulting type after obtaining ownership.
fn to_owned(&self) -> T
[src]
fn clone_into(&self, target: &mut T)
[src]
impl<T, U> TryFrom<U> for T where
U: Into<T>,
[src]
U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
[src]
impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
[src]
U: TryFrom<T>,