| /*! |
| Lower level primitive types that are useful in a variety of circumstances. |
| |
| # Overview |
| |
| This list represents the principle types in this module and briefly describes |
| when you might want to use them. |
| |
| * [`PatternID`] - A type that represents the identifier of a regex pattern. |
| This is probably the most widely used type in this module (which is why it's |
| also re-exported in the crate root). |
| * [`StateID`] - A type the represents the identifier of a finite automaton |
| state. This is used for both NFAs and DFAs, with the notable exception of |
| the hybrid NFA/DFA. (The hybrid NFA/DFA uses a special purpose "lazy" state |
| identifier.) |
| * [`SmallIndex`] - The internal representation of both a `PatternID` and a |
| `StateID`. Its purpose is to serve as a type that can index memory without |
| being as big as a `usize` on 64-bit targets. The main idea behind this type |
| is that there are many things in regex engines that will, in practice, never |
| overflow a 32-bit integer. (For example, like the number of patterns in a regex |
| or the number of states in an NFA.) Thus, a `SmallIndex` can be used to index |
| memory without peppering `as` casts everywhere. Moreover, it forces callers |
| to handle errors in the case where, somehow, the value would otherwise overflow |
| either a 32-bit integer or a `usize` (e.g., on 16-bit targets). |
| * [`NonMaxUsize`] - Represents a `usize` that cannot be `usize::MAX`. As a |
| result, `Option<NonMaxUsize>` has the same size in memory as a `usize`. This |
| useful, for example, when representing the offsets of submatches since it |
| reduces memory usage by a factor of 2. It is a legal optimization since Rust |
| guarantees that slices never have a length that exceeds `isize::MAX`. |
| */ |
| |
| use core::num::NonZeroUsize; |
| |
| #[cfg(feature = "alloc")] |
| use alloc::vec::Vec; |
| |
| use crate::util::int::{Usize, U16, U32, U64}; |
| |
| /// A `usize` that can never be `usize::MAX`. |
| /// |
| /// This is similar to `core::num::NonZeroUsize`, but instead of not permitting |
| /// a zero value, this does not permit a max value. |
| /// |
| /// This is useful in certain contexts where one wants to optimize the memory |
| /// usage of things that contain match offsets. Namely, since Rust slices |
| /// are guaranteed to never have a length exceeding `isize::MAX`, we can use |
| /// `usize::MAX` as a sentinel to indicate that no match was found. Indeed, |
| /// types like `Option<NonMaxUsize>` have exactly the same size in memory as a |
| /// `usize`. |
| /// |
| /// This type is defined to be `repr(transparent)` for |
| /// `core::num::NonZeroUsize`, which is in turn defined to be |
| /// `repr(transparent)` for `usize`. |
| #[derive(Clone, Copy, Eq, Hash, PartialEq, PartialOrd, Ord)] |
| #[repr(transparent)] |
| pub struct NonMaxUsize(NonZeroUsize); |
| |
| impl NonMaxUsize { |
| /// Create a new `NonMaxUsize` from the given value. |
| /// |
| /// This returns `None` only when the given value is equal to `usize::MAX`. |
| #[inline] |
| pub fn new(value: usize) -> Option<NonMaxUsize> { |
| NonZeroUsize::new(value.wrapping_add(1)).map(NonMaxUsize) |
| } |
| |
| /// Return the underlying `usize` value. The returned value is guaranteed |
| /// to not equal `usize::MAX`. |
| #[inline] |
| pub fn get(self) -> usize { |
| self.0.get().wrapping_sub(1) |
| } |
| } |
| |
| // We provide our own Debug impl because seeing the internal repr can be quite |
| // surprising if you aren't expecting it. e.g., 'NonMaxUsize(5)' vs just '5'. |
| impl core::fmt::Debug for NonMaxUsize { |
| fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result { |
| write!(f, "{:?}", self.get()) |
| } |
| } |
| |
| /// A type that represents a "small" index. |
| /// |
| /// The main idea of this type is to provide something that can index memory, |
| /// but uses less memory than `usize` on 64-bit systems. Specifically, its |
| /// representation is always a `u32` and has `repr(transparent)` enabled. (So |
| /// it is safe to transmute between a `u32` and a `SmallIndex`.) |
| /// |
| /// A small index is typically useful in cases where there is no practical way |
| /// that the index will overflow a 32-bit integer. A good example of this is |
| /// an NFA state. If you could somehow build an NFA with `2^30` states, its |
| /// memory usage would be exorbitant and its runtime execution would be so |
| /// slow as to be completely worthless. Therefore, this crate generally deems |
| /// it acceptable to return an error if it would otherwise build an NFA that |
| /// requires a slice longer than what a 32-bit integer can index. In exchange, |
| /// we can use 32-bit indices instead of 64-bit indices in various places. |
| /// |
| /// This type ensures this by providing a constructor that will return an error |
| /// if its argument cannot fit into the type. This makes it much easier to |
| /// handle these sorts of boundary cases that are otherwise extremely subtle. |
| /// |
| /// On all targets, this type guarantees that its value will fit in a `u32`, |
| /// `i32`, `usize` and an `isize`. This means that on 16-bit targets, for |
| /// example, this type's maximum value will never overflow an `isize`, |
| /// which means it will never overflow a `i16` even though its internal |
| /// representation is still a `u32`. |
| /// |
| /// The purpose for making the type fit into even signed integer types like |
| /// `isize` is to guarantee that the difference between any two small indices |
| /// is itself also a small index. This is useful in certain contexts, e.g., |
| /// for delta encoding. |
| /// |
| /// # Other types |
| /// |
| /// The following types wrap `SmallIndex` to provide a more focused use case: |
| /// |
| /// * [`PatternID`] is for representing the identifiers of patterns. |
| /// * [`StateID`] is for representing the identifiers of states in finite |
| /// automata. It is used for both NFAs and DFAs. |
| /// |
| /// # Representation |
| /// |
| /// This type is always represented internally by a `u32` and is marked as |
| /// `repr(transparent)`. Thus, this type always has the same representation as |
| /// a `u32`. It is thus safe to transmute between a `u32` and a `SmallIndex`. |
| /// |
| /// # Indexing |
| /// |
| /// For convenience, callers may use a `SmallIndex` to index slices. |
| /// |
| /// # Safety |
| /// |
| /// While a `SmallIndex` is meant to guarantee that its value fits into `usize` |
| /// without using as much space as a `usize` on all targets, callers must |
| /// not rely on this property for safety. Callers may choose to rely on this |
| /// property for correctness however. For example, creating a `SmallIndex` with |
| /// an invalid value can be done in entirely safe code. This may in turn result |
| /// in panics or silent logical errors. |
| #[derive( |
| Clone, Copy, Debug, Default, Eq, Hash, PartialEq, PartialOrd, Ord, |
| )] |
| #[repr(transparent)] |
| pub struct SmallIndex(u32); |
| |
| impl SmallIndex { |
| /// The maximum index value. |
| #[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))] |
| pub const MAX: SmallIndex = |
| // FIXME: Use as_usize() once const functions in traits are stable. |
| SmallIndex::new_unchecked(core::i32::MAX as usize - 1); |
| |
| /// The maximum index value. |
| #[cfg(target_pointer_width = "16")] |
| pub const MAX: SmallIndex = |
| SmallIndex::new_unchecked(core::isize::MAX - 1); |
| |
| /// The total number of values that can be represented as a small index. |
| pub const LIMIT: usize = SmallIndex::MAX.as_usize() + 1; |
| |
| /// The zero index value. |
| pub const ZERO: SmallIndex = SmallIndex::new_unchecked(0); |
| |
| /// The number of bytes that a single small index uses in memory. |
| pub const SIZE: usize = core::mem::size_of::<SmallIndex>(); |
| |
| /// Create a new small index. |
| /// |
| /// If the given index exceeds [`SmallIndex::MAX`], then this returns |
| /// an error. |
| #[inline] |
| pub fn new(index: usize) -> Result<SmallIndex, SmallIndexError> { |
| SmallIndex::try_from(index) |
| } |
| |
| /// Create a new small index without checking whether the given value |
| /// exceeds [`SmallIndex::MAX`]. |
| /// |
| /// Using this routine with an invalid index value will result in |
| /// unspecified behavior, but *not* undefined behavior. In particular, an |
| /// invalid index value is likely to cause panics or possibly even silent |
| /// logical errors. |
| /// |
| /// Callers must never rely on a `SmallIndex` to be within a certain range |
| /// for memory safety. |
| #[inline] |
| pub const fn new_unchecked(index: usize) -> SmallIndex { |
| // FIXME: Use as_u32() once const functions in traits are stable. |
| SmallIndex(index as u32) |
| } |
| |
| /// Like [`SmallIndex::new`], but panics if the given index is not valid. |
| #[inline] |
| pub fn must(index: usize) -> SmallIndex { |
| SmallIndex::new(index).expect("invalid small index") |
| } |
| |
| /// Return this small index as a `usize`. This is guaranteed to never |
| /// overflow `usize`. |
| #[inline] |
| pub const fn as_usize(&self) -> usize { |
| // FIXME: Use as_usize() once const functions in traits are stable. |
| self.0 as usize |
| } |
| |
| /// Return this small index as a `u64`. This is guaranteed to never |
| /// overflow. |
| #[inline] |
| pub const fn as_u64(&self) -> u64 { |
| // FIXME: Use u64::from() once const functions in traits are stable. |
| self.0 as u64 |
| } |
| |
| /// Return the internal `u32` of this small index. This is guaranteed to |
| /// never overflow `u32`. |
| #[inline] |
| pub const fn as_u32(&self) -> u32 { |
| self.0 |
| } |
| |
| /// Return the internal `u32` of this small index represented as an `i32`. |
| /// This is guaranteed to never overflow an `i32`. |
| #[inline] |
| pub const fn as_i32(&self) -> i32 { |
| // This is OK because we guarantee that our max value is <= i32::MAX. |
| self.0 as i32 |
| } |
| |
| /// Returns one more than this small index as a usize. |
| /// |
| /// Since a small index has constraints on its maximum value, adding `1` to |
| /// it will always fit in a `usize`, `u32` and a `i32`. |
| #[inline] |
| pub fn one_more(&self) -> usize { |
| self.as_usize() + 1 |
| } |
| |
| /// Decode this small index from the bytes given using the native endian |
| /// byte order for the current target. |
| /// |
| /// If the decoded integer is not representable as a small index for the |
| /// current target, then this returns an error. |
| #[inline] |
| pub fn from_ne_bytes( |
| bytes: [u8; 4], |
| ) -> Result<SmallIndex, SmallIndexError> { |
| let id = u32::from_ne_bytes(bytes); |
| if id > SmallIndex::MAX.as_u32() { |
| return Err(SmallIndexError { attempted: u64::from(id) }); |
| } |
| Ok(SmallIndex::new_unchecked(id.as_usize())) |
| } |
| |
| /// Decode this small index from the bytes given using the native endian |
| /// byte order for the current target. |
| /// |
| /// This is analogous to [`SmallIndex::new_unchecked`] in that is does not |
| /// check whether the decoded integer is representable as a small index. |
| #[inline] |
| pub fn from_ne_bytes_unchecked(bytes: [u8; 4]) -> SmallIndex { |
| SmallIndex::new_unchecked(u32::from_ne_bytes(bytes).as_usize()) |
| } |
| |
| /// Return the underlying small index integer as raw bytes in native endian |
| /// format. |
| #[inline] |
| pub fn to_ne_bytes(&self) -> [u8; 4] { |
| self.0.to_ne_bytes() |
| } |
| } |
| |
| impl<T> core::ops::Index<SmallIndex> for [T] { |
| type Output = T; |
| |
| #[inline] |
| fn index(&self, index: SmallIndex) -> &T { |
| &self[index.as_usize()] |
| } |
| } |
| |
| impl<T> core::ops::IndexMut<SmallIndex> for [T] { |
| #[inline] |
| fn index_mut(&mut self, index: SmallIndex) -> &mut T { |
| &mut self[index.as_usize()] |
| } |
| } |
| |
| #[cfg(feature = "alloc")] |
| impl<T> core::ops::Index<SmallIndex> for Vec<T> { |
| type Output = T; |
| |
| #[inline] |
| fn index(&self, index: SmallIndex) -> &T { |
| &self[index.as_usize()] |
| } |
| } |
| |
| #[cfg(feature = "alloc")] |
| impl<T> core::ops::IndexMut<SmallIndex> for Vec<T> { |
| #[inline] |
| fn index_mut(&mut self, index: SmallIndex) -> &mut T { |
| &mut self[index.as_usize()] |
| } |
| } |
| |
| impl From<u8> for SmallIndex { |
| fn from(index: u8) -> SmallIndex { |
| SmallIndex::new_unchecked(usize::from(index)) |
| } |
| } |
| |
| impl TryFrom<u16> for SmallIndex { |
| type Error = SmallIndexError; |
| |
| fn try_from(index: u16) -> Result<SmallIndex, SmallIndexError> { |
| if u32::from(index) > SmallIndex::MAX.as_u32() { |
| return Err(SmallIndexError { attempted: u64::from(index) }); |
| } |
| Ok(SmallIndex::new_unchecked(index.as_usize())) |
| } |
| } |
| |
| impl TryFrom<u32> for SmallIndex { |
| type Error = SmallIndexError; |
| |
| fn try_from(index: u32) -> Result<SmallIndex, SmallIndexError> { |
| if index > SmallIndex::MAX.as_u32() { |
| return Err(SmallIndexError { attempted: u64::from(index) }); |
| } |
| Ok(SmallIndex::new_unchecked(index.as_usize())) |
| } |
| } |
| |
| impl TryFrom<u64> for SmallIndex { |
| type Error = SmallIndexError; |
| |
| fn try_from(index: u64) -> Result<SmallIndex, SmallIndexError> { |
| if index > SmallIndex::MAX.as_u64() { |
| return Err(SmallIndexError { attempted: index }); |
| } |
| Ok(SmallIndex::new_unchecked(index.as_usize())) |
| } |
| } |
| |
| impl TryFrom<usize> for SmallIndex { |
| type Error = SmallIndexError; |
| |
| fn try_from(index: usize) -> Result<SmallIndex, SmallIndexError> { |
| if index > SmallIndex::MAX.as_usize() { |
| return Err(SmallIndexError { attempted: index.as_u64() }); |
| } |
| Ok(SmallIndex::new_unchecked(index)) |
| } |
| } |
| |
| #[cfg(test)] |
| impl quickcheck::Arbitrary for SmallIndex { |
| fn arbitrary(gen: &mut quickcheck::Gen) -> SmallIndex { |
| use core::cmp::max; |
| |
| let id = max(i32::MIN + 1, i32::arbitrary(gen)).abs(); |
| if id > SmallIndex::MAX.as_i32() { |
| SmallIndex::MAX |
| } else { |
| SmallIndex::new(usize::try_from(id).unwrap()).unwrap() |
| } |
| } |
| } |
| |
| /// This error occurs when a small index could not be constructed. |
| /// |
| /// This occurs when given an integer exceeding the maximum small index value. |
| /// |
| /// When the `std` feature is enabled, this implements the `Error` trait. |
| #[derive(Clone, Debug, Eq, PartialEq)] |
| pub struct SmallIndexError { |
| attempted: u64, |
| } |
| |
| impl SmallIndexError { |
| /// Returns the value that could not be converted to a small index. |
| pub fn attempted(&self) -> u64 { |
| self.attempted |
| } |
| } |
| |
| #[cfg(feature = "std")] |
| impl std::error::Error for SmallIndexError {} |
| |
| impl core::fmt::Display for SmallIndexError { |
| fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result { |
| write!( |
| f, |
| "failed to create small index from {:?}, which exceeds {:?}", |
| self.attempted(), |
| SmallIndex::MAX, |
| ) |
| } |
| } |
| |
| #[derive(Clone, Debug)] |
| pub(crate) struct SmallIndexIter { |
| rng: core::ops::Range<usize>, |
| } |
| |
| impl Iterator for SmallIndexIter { |
| type Item = SmallIndex; |
| |
| fn next(&mut self) -> Option<SmallIndex> { |
| if self.rng.start >= self.rng.end { |
| return None; |
| } |
| let next_id = self.rng.start + 1; |
| let id = core::mem::replace(&mut self.rng.start, next_id); |
| // new_unchecked is OK since we asserted that the number of |
| // elements in this iterator will fit in an ID at construction. |
| Some(SmallIndex::new_unchecked(id)) |
| } |
| } |
| |
| macro_rules! index_type_impls { |
| ($name:ident, $err:ident, $iter:ident, $withiter:ident) => { |
| impl $name { |
| /// The maximum value. |
| pub const MAX: $name = $name(SmallIndex::MAX); |
| |
| /// The total number of values that can be represented. |
| pub const LIMIT: usize = SmallIndex::LIMIT; |
| |
| /// The zero value. |
| pub const ZERO: $name = $name(SmallIndex::ZERO); |
| |
| /// The number of bytes that a single value uses in memory. |
| pub const SIZE: usize = SmallIndex::SIZE; |
| |
| /// Create a new value that is represented by a "small index." |
| /// |
| /// If the given index exceeds the maximum allowed value, then this |
| /// returns an error. |
| #[inline] |
| pub fn new(value: usize) -> Result<$name, $err> { |
| SmallIndex::new(value).map($name).map_err($err) |
| } |
| |
| /// Create a new value without checking whether the given argument |
| /// exceeds the maximum. |
| /// |
| /// Using this routine with an invalid value will result in |
| /// unspecified behavior, but *not* undefined behavior. In |
| /// particular, an invalid ID value is likely to cause panics or |
| /// possibly even silent logical errors. |
| /// |
| /// Callers must never rely on this type to be within a certain |
| /// range for memory safety. |
| #[inline] |
| pub const fn new_unchecked(value: usize) -> $name { |
| $name(SmallIndex::new_unchecked(value)) |
| } |
| |
| /// Like `new`, but panics if the given value is not valid. |
| #[inline] |
| pub fn must(value: usize) -> $name { |
| $name::new(value).expect(concat!( |
| "invalid ", |
| stringify!($name), |
| " value" |
| )) |
| } |
| |
| /// Return the internal value as a `usize`. This is guaranteed to |
| /// never overflow `usize`. |
| #[inline] |
| pub const fn as_usize(&self) -> usize { |
| self.0.as_usize() |
| } |
| |
| /// Return the internal value as a `u64`. This is guaranteed to |
| /// never overflow. |
| #[inline] |
| pub const fn as_u64(&self) -> u64 { |
| self.0.as_u64() |
| } |
| |
| /// Return the internal value as a `u32`. This is guaranteed to |
| /// never overflow `u32`. |
| #[inline] |
| pub const fn as_u32(&self) -> u32 { |
| self.0.as_u32() |
| } |
| |
| /// Return the internal value as a i32`. This is guaranteed to |
| /// never overflow an `i32`. |
| #[inline] |
| pub const fn as_i32(&self) -> i32 { |
| self.0.as_i32() |
| } |
| |
| /// Returns one more than this value as a usize. |
| /// |
| /// Since values represented by a "small index" have constraints |
| /// on their maximum value, adding `1` to it will always fit in a |
| /// `usize`, `u32` and a `i32`. |
| #[inline] |
| pub fn one_more(&self) -> usize { |
| self.0.one_more() |
| } |
| |
| /// Decode this value from the bytes given using the native endian |
| /// byte order for the current target. |
| /// |
| /// If the decoded integer is not representable as a small index |
| /// for the current target, then this returns an error. |
| #[inline] |
| pub fn from_ne_bytes(bytes: [u8; 4]) -> Result<$name, $err> { |
| SmallIndex::from_ne_bytes(bytes).map($name).map_err($err) |
| } |
| |
| /// Decode this value from the bytes given using the native endian |
| /// byte order for the current target. |
| /// |
| /// This is analogous to `new_unchecked` in that is does not check |
| /// whether the decoded integer is representable as a small index. |
| #[inline] |
| pub fn from_ne_bytes_unchecked(bytes: [u8; 4]) -> $name { |
| $name(SmallIndex::from_ne_bytes_unchecked(bytes)) |
| } |
| |
| /// Return the underlying integer as raw bytes in native endian |
| /// format. |
| #[inline] |
| pub fn to_ne_bytes(&self) -> [u8; 4] { |
| self.0.to_ne_bytes() |
| } |
| |
| /// Returns an iterator over all values from 0 up to and not |
| /// including the given length. |
| /// |
| /// If the given length exceeds this type's limit, then this |
| /// panics. |
| pub(crate) fn iter(len: usize) -> $iter { |
| $iter::new(len) |
| } |
| } |
| |
| // We write our own Debug impl so that we get things like PatternID(5) |
| // instead of PatternID(SmallIndex(5)). |
| impl core::fmt::Debug for $name { |
| fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result { |
| f.debug_tuple(stringify!($name)).field(&self.as_u32()).finish() |
| } |
| } |
| |
| impl<T> core::ops::Index<$name> for [T] { |
| type Output = T; |
| |
| #[inline] |
| fn index(&self, index: $name) -> &T { |
| &self[index.as_usize()] |
| } |
| } |
| |
| impl<T> core::ops::IndexMut<$name> for [T] { |
| #[inline] |
| fn index_mut(&mut self, index: $name) -> &mut T { |
| &mut self[index.as_usize()] |
| } |
| } |
| |
| #[cfg(feature = "alloc")] |
| impl<T> core::ops::Index<$name> for Vec<T> { |
| type Output = T; |
| |
| #[inline] |
| fn index(&self, index: $name) -> &T { |
| &self[index.as_usize()] |
| } |
| } |
| |
| #[cfg(feature = "alloc")] |
| impl<T> core::ops::IndexMut<$name> for Vec<T> { |
| #[inline] |
| fn index_mut(&mut self, index: $name) -> &mut T { |
| &mut self[index.as_usize()] |
| } |
| } |
| |
| impl From<u8> for $name { |
| fn from(value: u8) -> $name { |
| $name(SmallIndex::from(value)) |
| } |
| } |
| |
| impl TryFrom<u16> for $name { |
| type Error = $err; |
| |
| fn try_from(value: u16) -> Result<$name, $err> { |
| SmallIndex::try_from(value).map($name).map_err($err) |
| } |
| } |
| |
| impl TryFrom<u32> for $name { |
| type Error = $err; |
| |
| fn try_from(value: u32) -> Result<$name, $err> { |
| SmallIndex::try_from(value).map($name).map_err($err) |
| } |
| } |
| |
| impl TryFrom<u64> for $name { |
| type Error = $err; |
| |
| fn try_from(value: u64) -> Result<$name, $err> { |
| SmallIndex::try_from(value).map($name).map_err($err) |
| } |
| } |
| |
| impl TryFrom<usize> for $name { |
| type Error = $err; |
| |
| fn try_from(value: usize) -> Result<$name, $err> { |
| SmallIndex::try_from(value).map($name).map_err($err) |
| } |
| } |
| |
| #[cfg(test)] |
| impl quickcheck::Arbitrary for $name { |
| fn arbitrary(gen: &mut quickcheck::Gen) -> $name { |
| $name(SmallIndex::arbitrary(gen)) |
| } |
| } |
| |
| /// This error occurs when a value could not be constructed. |
| /// |
| /// This occurs when given an integer exceeding the maximum allowed |
| /// value. |
| /// |
| /// When the `std` feature is enabled, this implements the `Error` |
| /// trait. |
| #[derive(Clone, Debug, Eq, PartialEq)] |
| pub struct $err(SmallIndexError); |
| |
| impl $err { |
| /// Returns the value that could not be converted to an ID. |
| pub fn attempted(&self) -> u64 { |
| self.0.attempted() |
| } |
| } |
| |
| #[cfg(feature = "std")] |
| impl std::error::Error for $err {} |
| |
| impl core::fmt::Display for $err { |
| fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result { |
| write!( |
| f, |
| "failed to create {} from {:?}, which exceeds {:?}", |
| stringify!($name), |
| self.attempted(), |
| $name::MAX, |
| ) |
| } |
| } |
| |
| #[derive(Clone, Debug)] |
| pub(crate) struct $iter(SmallIndexIter); |
| |
| impl $iter { |
| fn new(len: usize) -> $iter { |
| assert!( |
| len <= $name::LIMIT, |
| "cannot create iterator for {} when number of \ |
| elements exceed {:?}", |
| stringify!($name), |
| $name::LIMIT, |
| ); |
| $iter(SmallIndexIter { rng: 0..len }) |
| } |
| } |
| |
| impl Iterator for $iter { |
| type Item = $name; |
| |
| fn next(&mut self) -> Option<$name> { |
| self.0.next().map($name) |
| } |
| } |
| |
| /// An iterator adapter that is like std::iter::Enumerate, but attaches |
| /// small index values instead. It requires `ExactSizeIterator`. At |
| /// construction, it ensures that the index of each element in the |
| /// iterator is representable in the corresponding small index type. |
| #[derive(Clone, Debug)] |
| pub(crate) struct $withiter<I> { |
| it: I, |
| ids: $iter, |
| } |
| |
| impl<I: Iterator + ExactSizeIterator> $withiter<I> { |
| fn new(it: I) -> $withiter<I> { |
| let ids = $name::iter(it.len()); |
| $withiter { it, ids } |
| } |
| } |
| |
| impl<I: Iterator + ExactSizeIterator> Iterator for $withiter<I> { |
| type Item = ($name, I::Item); |
| |
| fn next(&mut self) -> Option<($name, I::Item)> { |
| let item = self.it.next()?; |
| // Number of elements in this iterator must match, according |
| // to contract of ExactSizeIterator. |
| let id = self.ids.next().unwrap(); |
| Some((id, item)) |
| } |
| } |
| }; |
| } |
| |
| /// The identifier of a regex pattern, represented by a [`SmallIndex`]. |
| /// |
| /// The identifier for a pattern corresponds to its relative position among |
| /// other patterns in a single finite state machine. Namely, when building |
| /// a multi-pattern regex engine, one must supply a sequence of patterns to |
| /// match. The position (starting at 0) of each pattern in that sequence |
| /// represents its identifier. This identifier is in turn used to identify and |
| /// report matches of that pattern in various APIs. |
| /// |
| /// See the [`SmallIndex`] type for more information about what it means for |
| /// a pattern ID to be a "small index." |
| /// |
| /// Note that this type is defined in the |
| /// [`util::primitives`](crate::util::primitives) module, but it is also |
| /// re-exported at the crate root due to how common it is. |
| #[derive(Clone, Copy, Default, Eq, Hash, PartialEq, PartialOrd, Ord)] |
| #[repr(transparent)] |
| pub struct PatternID(SmallIndex); |
| |
| /// The identifier of a finite automaton state, represented by a |
| /// [`SmallIndex`]. |
| /// |
| /// Most regex engines in this crate are built on top of finite automata. Each |
| /// state in a finite automaton defines transitions from its state to another. |
| /// Those transitions point to other states via their identifiers, i.e., a |
| /// `StateID`. Since finite automata tend to contain many transitions, it is |
| /// much more memory efficient to define state IDs as small indices. |
| /// |
| /// See the [`SmallIndex`] type for more information about what it means for |
| /// a state ID to be a "small index." |
| #[derive(Clone, Copy, Default, Eq, Hash, PartialEq, PartialOrd, Ord)] |
| #[repr(transparent)] |
| pub struct StateID(SmallIndex); |
| |
| index_type_impls!(PatternID, PatternIDError, PatternIDIter, WithPatternIDIter); |
| index_type_impls!(StateID, StateIDError, StateIDIter, WithStateIDIter); |
| |
| /// A utility trait that defines a couple of adapters for making it convenient |
| /// to access indices as "small index" types. We require ExactSizeIterator so |
| /// that iterator construction can do a single check to make sure the index of |
| /// each element is representable by its small index type. |
| pub(crate) trait IteratorIndexExt: Iterator { |
| fn with_pattern_ids(self) -> WithPatternIDIter<Self> |
| where |
| Self: Sized + ExactSizeIterator, |
| { |
| WithPatternIDIter::new(self) |
| } |
| |
| fn with_state_ids(self) -> WithStateIDIter<Self> |
| where |
| Self: Sized + ExactSizeIterator, |
| { |
| WithStateIDIter::new(self) |
| } |
| } |
| |
| impl<I: Iterator> IteratorIndexExt for I {} |
