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Favor SmallVec over Box in pluralrules
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This will help avoid heap allocations as most lists are only a few items
long. The only boxed slice that was retained was the SampleRanges, as
this can be of an indeterminate length.
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@gregtatum
gregtatum committed Sep 1, 2021
1 parent 26b1be1 commit 841c72d
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Showing 5 changed files with 53 additions and 42 deletions.
1 change: 1 addition & 0 deletions Cargo.lock
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1 change: 1 addition & 0 deletions components/plurals/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,7 @@ icu_provider = { version = "0.3", path = "../../provider/core", features = ["mac
icu_locid = { version = "0.3", path = "../locid" }
serde = { version = "1.0", default-features = false, features = ["derive", "alloc"], optional = true }
displaydoc = { version = "0.2.3", default-features = false }
smallvec = "1.6"

[dev-dependencies]
criterion = "0.3"
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58 changes: 33 additions & 25 deletions components/plurals/src/rules/ast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,28 +11,29 @@
//! ```
//! use icu::plurals::rules::parse_condition;
//! use icu::plurals::rules::ast::*;
//! use smallvec::{SmallVec,smallvec};
//!
//! let input = "i = 1";
//!
//! let ast = parse_condition(input.as_bytes())
//! .expect("Parsing failed.");
//!
//! assert_eq!(ast, Condition(Box::new([
//! AndCondition(Box::new([
//! assert_eq!(ast, Condition(smallvec![
//! AndCondition(smallvec![
//! Relation {
//! expression: Expression {
//! operand: Operand::I,
//! modulus: None,
//! },
//! operator: Operator::Eq,
//! range_list: RangeList(Box::new([
//! range_list: RangeList(smallvec![
//! RangeListItem::Value(
//! Value(1)
//! )
//! ]))
//! ])
//! }
//! ]))
//! ])));
//! ])
//! ]));
//! ```
//!
//! [`PluralCategory`]: crate::PluralCategory
Expand All @@ -41,6 +42,7 @@
use alloc::boxed::Box;
use alloc::string::String;
use core::ops::RangeInclusive;
use smallvec::SmallVec;

/// A complete AST representation of a plural rule.
/// Comprises a vector of [`AndConditions`] and optionally a set of [`Samples`].
Expand Down Expand Up @@ -98,25 +100,26 @@ pub struct Rule {
/// ```
/// use icu::plurals::rules::ast::*;
/// use icu::plurals::rules::parse_condition;
/// use smallvec::{SmallVec,smallvec};
///
/// let condition = Condition(Box::new([
/// AndCondition(Box::new([Relation {
/// let condition = Condition(smallvec![
/// AndCondition(smallvec![Relation {
/// expression: Expression {
/// operand: Operand::I,
/// modulus: None,
/// },
/// operator: Operator::Eq,
/// range_list: RangeList(Box::new([RangeListItem::Value(Value(5))])),
/// }])),
/// AndCondition(Box::new([Relation {
/// range_list: RangeList(smallvec![RangeListItem::Value(Value(5))]),
/// }]),
/// AndCondition(smallvec![Relation {
/// expression: Expression {
/// operand: Operand::V,
/// modulus: None,
/// },
/// operator: Operator::Eq,
/// range_list: RangeList(Box::new([RangeListItem::Value(Value(2))])),
/// }])),
/// ]));
/// range_list: RangeList(smallvec![RangeListItem::Value(Value(2))]),
/// }]),
/// ]);
///
/// assert_eq!(
/// condition,
Expand All @@ -127,7 +130,7 @@ pub struct Rule {
///
/// [`AndConditions`]: AndCondition
#[derive(Debug, Clone, PartialEq)]
pub struct Condition(pub Box<[AndCondition]>);
pub struct Condition(pub SmallVec<[AndCondition; 2]>);

/// An incomplete AST representation of a plural rule. Comprises a vector of [`Relations`].
///
Expand All @@ -143,32 +146,33 @@ pub struct Condition(pub Box<[AndCondition]>);
/// Can be represented by the AST:
///
/// ```
/// use icu::plurals::rules::ast::*;
/// use icu_plurals::rules::ast::*;
/// use smallvec::{SmallVec,smallvec};
///
/// AndCondition(Box::new([
/// AndCondition(smallvec![
/// Relation {
/// expression: Expression {
/// operand: Operand::I,
/// modulus: None,
/// },
/// operator: Operator::Eq,
/// range_list: RangeList(Box::new([RangeListItem::Value(Value(5))])),
/// range_list: RangeList(smallvec![RangeListItem::Value(Value(5))]),
/// },
/// Relation {
/// expression: Expression {
/// operand: Operand::V,
/// modulus: None,
/// },
/// operator: Operator::NotEq,
/// range_list: RangeList(Box::new([RangeListItem::Value(Value(2))])),
/// range_list: RangeList(smallvec![RangeListItem::Value(Value(2))]),
/// },
/// ]));
/// ]);
///
/// ```
///
/// [`Relations`]: Relation
#[derive(Debug, Clone, PartialEq)]
pub struct AndCondition(pub Box<[Relation]>);
pub struct AndCondition(pub SmallVec<[Relation; 2]>);

/// An incomplete AST representation of a plural rule. Comprises an [`Expression`], an [`Operator`], and a [`RangeList`].
///
Expand All @@ -185,14 +189,15 @@ pub struct AndCondition(pub Box<[Relation]>);
///
/// ```
/// use icu::plurals::rules::ast::*;
/// use smallvec::{SmallVec,smallvec};
///
/// Relation {
/// expression: Expression {
/// operand: Operand::I,
/// modulus: None,
/// },
/// operator: Operator::Eq,
/// range_list: RangeList(Box::new([RangeListItem::Value(Value(3))])),
/// range_list: RangeList(smallvec![RangeListItem::Value(Value(3))]),
/// };
///
/// ```
Expand Down Expand Up @@ -304,17 +309,18 @@ pub enum Operand {
///
/// ```
/// use icu::plurals::rules::ast::*;
/// use smallvec::{SmallVec,smallvec};
///
/// RangeList(Box::new([
/// RangeList(smallvec![
/// RangeListItem::Value(Value(5)),
/// RangeListItem::Value(Value(7)),
/// RangeListItem::Value(Value(9)),
/// ]));
/// ]);
/// ```
///
/// [`RangeListItems`]: RangeListItem
#[derive(Debug, Clone, PartialEq)]
pub struct RangeList(pub Box<[RangeListItem]>);
pub struct RangeList(pub SmallVec<[RangeListItem; 2]>);

/// An enum of items that appear in a [`RangeList`]: `Range` or a `Value`.
///
Expand Down Expand Up @@ -408,6 +414,8 @@ pub struct Samples {
///
/// ```
/// use icu::plurals::rules::ast::*;
/// use smallvec::{SmallVec,smallvec};
///
/// SampleList {
/// sample_ranges: Box::new([
/// SampleRange {
Expand Down
19 changes: 10 additions & 9 deletions components/plurals/src/rules/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -57,39 +57,40 @@
//! ```
//! use icu::plurals::rules::parse_condition;
//! use icu::plurals::rules::ast::*;
//! use smallvec::{SmallVec,smallvec};
//!
//! let input = "i = 1 and v = 0 @integer 1";
//!
//! let ast = parse_condition(input.as_bytes())
//! .expect("Parsing failed.");
//! assert_eq!(ast, Condition(Box::new([
//! AndCondition(Box::new([
//! assert_eq!(ast, Condition(smallvec![
//! AndCondition(smallvec![
//! Relation {
//! expression: Expression {
//! operand: Operand::I,
//! modulus: None,
//! },
//! operator: Operator::Eq,
//! range_list: RangeList(Box::new([
//! range_list: RangeList(smallvec![
//! RangeListItem::Value(
//! Value(1)
//! )
//! ]))
//! ])
//! },
//! Relation {
//! expression: Expression {
//! operand: Operand::V,
//! modulus: None,
//! },
//! operator: Operator::Eq,
//! range_list: RangeList(Box::new([
//! range_list: RangeList(smallvec![
//! RangeListItem::Value(
//! Value(0)
//! )
//! ]))
//! },
//! ])),
//! ])));
//! ])
//! }
//! ]),
//! ]));
//! ```
//!
//! Finally, we can pass this [`AST`] (in fact, just the [`Condition`] node),
Expand Down
16 changes: 8 additions & 8 deletions components/plurals/src/rules/parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,9 +7,9 @@ use super::lexer::{Lexer, Token};
use alloc::string::String;
use alloc::string::ToString;
use alloc::vec;
use alloc::vec::Vec;
use core::iter::Peekable;
use displaydoc::Display;
use smallvec::smallvec;

#[derive(Display, Debug, PartialEq, Eq)]
#[allow(clippy::enum_variant_names)]
Expand Down Expand Up @@ -118,12 +118,12 @@ impl<'p> Parser<'p> {
}

fn get_condition(&mut self) -> Result<ast::Condition, ParserError> {
let mut result = vec![];
let mut result = smallvec![];

if let Some(cond) = self.get_and_condition()? {
result.push(cond);
} else {
return Ok(ast::Condition(result.into_boxed_slice()));
return Ok(ast::Condition(result));
}

while self.take_if(Token::Or) {
Expand All @@ -134,12 +134,12 @@ impl<'p> Parser<'p> {
}
}
// If lexer is not done, error?
Ok(ast::Condition(result.into_boxed_slice()))
Ok(ast::Condition(result))
}

fn get_and_condition(&mut self) -> Result<Option<ast::AndCondition>, ParserError> {
if let Some(relation) = self.get_relation()? {
let mut rel = vec![relation];
let mut rel = smallvec![relation];

while self.take_if(Token::And) {
if let Some(relation) = self.get_relation()? {
Expand All @@ -148,7 +148,7 @@ impl<'p> Parser<'p> {
return Err(ParserError::ExpectedRelation);
}
}
Ok(Some(ast::AndCondition(rel.into_boxed_slice())))
Ok(Some(ast::AndCondition(rel)))
} else {
Ok(None)
}
Expand Down Expand Up @@ -188,14 +188,14 @@ impl<'p> Parser<'p> {
}

fn get_range_list(&mut self) -> Result<ast::RangeList, ParserError> {
let mut range_list = Vec::with_capacity(1);
let mut range_list = smallvec![];
loop {
range_list.push(self.get_range_list_item()?);
if !self.take_if(Token::Comma) {
break;
}
}
Ok(ast::RangeList(range_list.into_boxed_slice()))
Ok(ast::RangeList(range_list))
}

fn take_if(&mut self, token: Token) -> bool {
Expand Down

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