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// Copyright 2017 The Servo Project Developers. See the
// COPYRIGHT file at the top-level directory of this distribution.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Bidi Embedding Level
//!
//! See [`Level`](struct.Level.html) for more details.
//!
use std::convert::{From, Into};
use super::char_data::BidiClass;
/// Embedding Level
///
/// Embedding Levels are numbers between 0 and 126 (inclusive), where even values denote a
/// left-to-right (LTR) direction and odd values a right-to-left (RTL) direction.
///
/// This struct maintains a *valid* status for level numbers, meaning that creating a new level, or
/// mutating an existing level, with the value smaller than `0` (before conversion to `u8`) or
/// larger than 125 results in an `Error`.
///
#[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
pub struct Level(u8);
pub const LTR_LEVEL: Level = Level(0);
pub const RTL_LEVEL: Level = Level(1);
const MAX_DEPTH: u8 = 125;
/// During explicit level resolution, embedding level can go as high as `max_depth`.
pub const MAX_EXPLICIT_DEPTH: u8 = MAX_DEPTH;
/// During implicit level resolution, embedding level can go as high as `max_depth + 1`.
pub const MAX_IMPLICIT_DEPTH: u8 = MAX_DEPTH + 1;
/// Errors that can occur on Level creation or mutation
#[derive(Debug, PartialEq)]
pub enum Error {
/// Out-of-range (invalid) embedding level number.
OutOfRangeNumber,
}
impl Level {
/// New LTR level with smallest number value (0).
#[inline]
pub fn ltr() -> Level {
LTR_LEVEL
}
/// New RTL level with smallest number value (1).
#[inline]
pub fn rtl() -> Level {
RTL_LEVEL
}
/// Maximum depth of the directional status stack during implicit resolutions.
pub fn max_implicit_depth() -> u8 {
MAX_IMPLICIT_DEPTH
}
/// Maximum depth of the directional status stack during explicit resolutions.
pub fn max_explicit_depth() -> u8 {
MAX_EXPLICIT_DEPTH
}
// == Inquiries ==
/// Create new level, fail if number is larger than `max_depth + 1`.
#[inline]
pub fn new(number: u8) -> Result<Level, Error> {
if number <= MAX_IMPLICIT_DEPTH {
Ok(Level(number))
} else {
Err(Error::OutOfRangeNumber)
}
}
/// Create new level, fail if number is larger than `max_depth`.
#[inline]
pub fn new_explicit(number: u8) -> Result<Level, Error> {
if number <= MAX_EXPLICIT_DEPTH {
Ok(Level(number))
} else {
Err(Error::OutOfRangeNumber)
}
}
// == Inquiries ==
/// The level number.
#[inline]
pub fn number(&self) -> u8 {
self.0
}
/// If this level is left-to-right.
#[inline]
pub fn is_ltr(&self) -> bool {
self.0 % 2 == 0
}
/// If this level is right-to-left.
#[inline]
pub fn is_rtl(&self) -> bool {
self.0 % 2 == 1
}
// == Mutators ==
/// Raise level by `amount`, fail if number is larger than `max_depth + 1`.
#[inline]
pub fn raise(&mut self, amount: u8) -> Result<(), Error> {
match self.0.checked_add(amount) {
Some(number) => {
if number <= MAX_IMPLICIT_DEPTH {
self.0 = number;
Ok(())
} else {
Err(Error::OutOfRangeNumber)
}
}
None => Err(Error::OutOfRangeNumber),
}
}
/// Raise level by `amount`, fail if number is larger than `max_depth`.
#[inline]
pub fn raise_explicit(&mut self, amount: u8) -> Result<(), Error> {
match self.0.checked_add(amount) {
Some(number) => {
if number <= MAX_EXPLICIT_DEPTH {
self.0 = number;
Ok(())
} else {
Err(Error::OutOfRangeNumber)
}
}
None => Err(Error::OutOfRangeNumber),
}
}
/// Lower level by `amount`, fail if number goes below zero.
#[inline]
pub fn lower(&mut self, amount: u8) -> Result<(), Error> {
match self.0.checked_sub(amount) {
Some(number) => {
self.0 = number;
Ok(())
}
None => Err(Error::OutOfRangeNumber),
}
}
// == Helpers ==
/// The next LTR (even) level greater than this, or fail if number is larger than `max_depth`.
#[inline]
pub fn new_explicit_next_ltr(&self) -> Result<Level, Error> {
Level::new_explicit((self.0 + 2) & !1)
}
/// The next RTL (odd) level greater than this, or fail if number is larger than `max_depth`.
#[inline]
pub fn new_explicit_next_rtl(&self) -> Result<Level, Error> {
Level::new_explicit((self.0 + 1) | 1)
}
/// The lowest RTL (odd) level greater than or equal to this, or fail if number is larger than
/// `max_depth + 1`.
#[inline]
pub fn new_lowest_ge_rtl(&self) -> Result<Level, Error> {
Level::new(self.0 | 1)
}
/// Generate a character type based on a level (as specified in steps X10 and N2).
#[inline]
pub fn bidi_class(&self) -> BidiClass {
if self.is_rtl() {
BidiClass::R
} else {
BidiClass::L
}
}
pub fn vec(v: &[u8]) -> Vec<Level> {
v.iter().map(|&x| x.into()).collect()
}
}
/// If levels has any RTL (odd) level
///
/// This information is usually used to skip re-ordering of text when no RTL level is present
#[inline]
pub fn has_rtl(levels: &[Level]) -> bool {
levels.iter().any(|&lvl| lvl.is_rtl())
}
impl Into<u8> for Level {
/// Convert to the level number
#[inline]
fn into(self) -> u8 {
self.number()
}
}
impl From<u8> for Level {
/// Create level by number
#[inline]
fn from(number: u8) -> Level {
Level::new(number).expect("Level number error")
}
}
/// Used for matching levels in conformance tests
impl<'a> PartialEq<&'a str> for Level {
#[inline]
fn eq(&self, s: &&'a str) -> bool {
*s == "x" || *s == self.0.to_string()
}
}
/// Used for matching levels in conformance tests
impl<'a> PartialEq<String> for Level {
#[inline]
fn eq(&self, s: &String) -> bool {
self == &s.as_str()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_new() {
assert_eq!(Level::new(0), Ok(Level(0)));
assert_eq!(Level::new(1), Ok(Level(1)));
assert_eq!(Level::new(10), Ok(Level(10)));
assert_eq!(Level::new(125), Ok(Level(125)));
assert_eq!(Level::new(126), Ok(Level(126)));
assert_eq!(Level::new(127), Err(Error::OutOfRangeNumber));
assert_eq!(Level::new(255), Err(Error::OutOfRangeNumber));
}
#[test]
fn test_new_explicit() {
assert_eq!(Level::new_explicit(0), Ok(Level(0)));
assert_eq!(Level::new_explicit(1), Ok(Level(1)));
assert_eq!(Level::new_explicit(10), Ok(Level(10)));
assert_eq!(Level::new_explicit(125), Ok(Level(125)));
assert_eq!(Level::new_explicit(126), Err(Error::OutOfRangeNumber));
assert_eq!(Level::new_explicit(255), Err(Error::OutOfRangeNumber));
}
#[test]
fn test_is_ltr() {
assert_eq!(Level(0).is_ltr(), true);
assert_eq!(Level(1).is_ltr(), false);
assert_eq!(Level(10).is_ltr(), true);
assert_eq!(Level(11).is_ltr(), false);
assert_eq!(Level(124).is_ltr(), true);
assert_eq!(Level(125).is_ltr(), false);
}
#[test]
fn test_is_rtl() {
assert_eq!(Level(0).is_rtl(), false);
assert_eq!(Level(1).is_rtl(), true);
assert_eq!(Level(10).is_rtl(), false);
assert_eq!(Level(11).is_rtl(), true);
assert_eq!(Level(124).is_rtl(), false);
assert_eq!(Level(125).is_rtl(), true);
}
#[test]
fn test_raise() {
let mut level = Level::ltr();
assert_eq!(level.number(), 0);
assert!(level.raise(100).is_ok());
assert_eq!(level.number(), 100);
assert!(level.raise(26).is_ok());
assert_eq!(level.number(), 126);
assert!(level.raise(1).is_err()); // invalid!
assert!(level.raise(250).is_err()); // overflow!
assert_eq!(level.number(), 126);
}
#[test]
fn test_raise_explicit() {
let mut level = Level::ltr();
assert_eq!(level.number(), 0);
assert!(level.raise_explicit(100).is_ok());
assert_eq!(level.number(), 100);
assert!(level.raise_explicit(25).is_ok());
assert_eq!(level.number(), 125);
assert!(level.raise_explicit(1).is_err()); // invalid!
assert!(level.raise_explicit(250).is_err()); // overflow!
assert_eq!(level.number(), 125);
}
#[test]
fn test_lower() {
let mut level = Level::rtl();
assert_eq!(level.number(), 1);
assert!(level.lower(1).is_ok());
assert_eq!(level.number(), 0);
assert!(level.lower(1).is_err()); // underflow!
assert!(level.lower(250).is_err()); // underflow!
assert_eq!(level.number(), 0);
}
#[test]
fn test_has_rtl() {
assert_eq!(has_rtl(&Level::vec(&[0, 0, 0])), false);
assert_eq!(has_rtl(&Level::vec(&[0, 1, 0])), true);
assert_eq!(has_rtl(&Level::vec(&[0, 2, 0])), false);
assert_eq!(has_rtl(&Level::vec(&[0, 125, 0])), true);
assert_eq!(has_rtl(&Level::vec(&[0, 126, 0])), false);
}
#[test]
fn test_into() {
let level = Level::rtl();
assert_eq!(1u8, level.into());
}
#[test]
fn test_vec() {
assert_eq!(
Level::vec(&[0, 1, 125]),
vec![Level(0), Level(1), Level(125)]
);
}
#[test]
fn test_str_eq() {
assert_eq!(Level::vec(&[0, 1, 4, 125]), vec!["0", "1", "x", "125"]);
assert_ne!(Level::vec(&[0, 1, 4, 125]), vec!["0", "1", "5", "125"]);
}
#[test]
fn test_string_eq() {
assert_eq!(
Level::vec(&[0, 1, 4, 125]),
vec!["0".to_string(), "1".to_string(), "x".to_string(), "125".to_string()]
);
}
}
#[cfg(all(feature = "serde", test))]
mod serde_tests {
use serde_test::{Token, assert_tokens};
use super::*;
#[test]
fn test_statics() {
assert_tokens(
&Level::ltr(),
&[Token::NewtypeStruct { name: "Level" }, Token::U8(0)],
);
assert_tokens(
&Level::rtl(),
&[Token::NewtypeStruct { name: "Level" }, Token::U8(1)],
);
}
#[test]
fn test_new() {
let level = Level::new(42).unwrap();
assert_tokens(
&level,
&[Token::NewtypeStruct { name: "Level" }, Token::U8(42)],
);
}
}