oaty/

parser.rs

//! Binary parsing utils.
//!
//! This module should not be used directly, unless you're planning to parse
//! some tables manually.

// This module is adapted from ttf-parser: https://github.com/harfbuzz/ttf-parser/blob/main/src/parser.rs
// Licensed under MIT and Apache 2.0 licenses. Thanks to Yevhenii Reizner

use crate::tag::Tag;
use core::convert::TryInto;
use core::ops::Range;

/// A trait for parsing raw binary data of fixed size.
///
/// This is a low-level, internal trait that should not be used directly.
pub trait TryFromBeBytes: Sized {
    /// Object's raw data size.
    ///
    /// Not always the same as `mem::size_of`.
    const SIZE: usize;

    /// Parses an object from a raw data.
    fn try_parse_from_be_bytes(data: &[u8]) -> Option<Self>;
}

/// A trait for parsing raw binary data of variable size.
///
/// This is a low-level, internal trait that should not be used directly.
pub trait FromSlice<'a>: Sized {
    /// Parses an object from a raw data.
    fn parse(data: &'a [u8]) -> Option<Self>;
}

impl TryFromBeBytes for () {
    const SIZE: usize = 0;

    #[inline]
    fn try_parse_from_be_bytes(_: &[u8]) -> Option<Self> {
        Some(())
    }
}

impl TryFromBeBytes for u8 {
    const SIZE: usize = 1;

    #[inline]
    fn try_parse_from_be_bytes(data: &[u8]) -> Option<Self> {
        data.first().copied()
    }
}

impl TryFromBeBytes for i8 {
    const SIZE: usize = 1;

    #[inline]
    fn try_parse_from_be_bytes(data: &[u8]) -> Option<Self> {
        data.first().copied().map(|n| n as i8)
    }
}

impl TryFromBeBytes for u16 {
    const SIZE: usize = 2;

    #[inline]
    fn try_parse_from_be_bytes(data: &[u8]) -> Option<Self> {
        data.try_into().ok().map(u16::from_be_bytes)
    }
}

impl TryFromBeBytes for i16 {
    const SIZE: usize = 2;

    #[inline]
    fn try_parse_from_be_bytes(data: &[u8]) -> Option<Self> {
        data.try_into().ok().map(i16::from_be_bytes)
    }
}

impl TryFromBeBytes for u32 {
    const SIZE: usize = 4;

    #[inline]
    fn try_parse_from_be_bytes(data: &[u8]) -> Option<Self> {
        data.try_into().ok().map(u32::from_be_bytes)
    }
}

impl TryFromBeBytes for i32 {
    const SIZE: usize = 4;

    #[inline]
    fn try_parse_from_be_bytes(data: &[u8]) -> Option<Self> {
        data.try_into().ok().map(i32::from_be_bytes)
    }
}

impl TryFromBeBytes for u64 {
    const SIZE: usize = 8;

    #[inline]
    fn try_parse_from_be_bytes(data: &[u8]) -> Option<Self> {
        data.try_into().ok().map(u64::from_be_bytes)
    }
}

impl TryFromBeBytes for i64 {
    const SIZE: usize = 8;

    #[inline]
    fn try_parse_from_be_bytes(data: &[u8]) -> Option<Self> {
        data.try_into().ok().map(i64::from_be_bytes)
    }
}

impl TryFromBeBytes for Tag {
    const SIZE: usize = 4;

    #[inline]
    fn try_parse_from_be_bytes(data: &[u8]) -> Option<Self> {
        data.try_into().ok().map(Tag::from_be_bytes)
    }
}

/// A slice-like container that converts internal binary data only on access.
///
/// Array values are stored in a continuous data chunk.
pub struct LazyArray16<'a, T> {
    data: &'a [u8],
    data_type: core::marker::PhantomData<T>,
}

impl<T> Clone for LazyArray16<'_, T> {
    fn clone(&self) -> Self {
        *self
    }
}
impl<T> Copy for LazyArray16<'_, T> {}

impl<T> Default for LazyArray16<'_, T> {
    #[inline]
    fn default() -> Self {
        LazyArray16 {
            data: &[],
            data_type: core::marker::PhantomData,
        }
    }
}

impl<'a, T: TryFromBeBytes> LazyArray16<'a, T> {
    /// Creates a new `LazyArray`.
    #[inline]
    pub fn new(data: &'a [u8]) -> Self {
        LazyArray16 {
            data,
            data_type: core::marker::PhantomData,
        }
    }

    pub(crate) fn bytes(&self) -> &[u8] {
        self.data
    }

    /// Returns a value at `index`.
    #[inline]
    pub fn get(&self, index: u16) -> Option<T> {
        if index < self.len() {
            let start = usize::from(index) * T::SIZE;
            let end = start + T::SIZE;
            self.data
                .get(start..end)
                .and_then(T::try_parse_from_be_bytes)
        } else {
            None
        }
    }

    /// Returns the last value.
    #[inline]
    pub fn last(&self) -> Option<T> {
        if !self.is_empty() {
            self.get(self.len() - 1)
        } else {
            None
        }
    }

    /// Returns sub-array.
    #[inline]
    pub fn slice(&self, range: Range<u16>) -> Option<Self> {
        let start = usize::from(range.start) * T::SIZE;
        let end = usize::from(range.end) * T::SIZE;
        Some(LazyArray16 {
            data: self.data.get(start..end)?,
            ..LazyArray16::default()
        })
    }

    /// Returns array's length.
    #[inline]
    pub fn len(&self) -> u16 {
        (self.data.len() / T::SIZE) as u16
    }

    /// Checks if array is empty.
    #[inline]
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Performs a binary search by specified `key`.
    #[inline]
    pub fn binary_search(&self, key: &T) -> Option<(u16, T)>
    where
        T: Ord,
    {
        self.binary_search_by(|p| p.cmp(key))
    }

    /// Performs a binary search using specified closure.
    #[inline]
    pub fn binary_search_by<F>(&self, mut f: F) -> Option<(u16, T)>
    where
        F: FnMut(&T) -> core::cmp::Ordering,
    {
        // Based on Rust std implementation.

        use core::cmp::Ordering;

        let mut size = self.len();
        if size == 0 {
            return None;
        }

        let mut base = 0;
        while size > 1 {
            let half = size / 2;
            let mid = base + half;
            // mid is always in [0, size), that means mid is >= 0 and < size.
            // mid >= 0: by definition
            // mid < size: mid = size / 2 + size / 4 + size / 8 ...
            let cmp = f(&self.get(mid)?);
            base = if cmp == Ordering::Greater { base } else { mid };
            size -= half;
        }

        // base is always in [0, size) because base <= mid.
        let value = self.get(base)?;
        if f(&value) == Ordering::Equal {
            Some((base, value))
        } else {
            None
        }
    }
}

impl<'a, T: TryFromBeBytes + core::fmt::Debug + Copy> core::fmt::Debug for LazyArray16<'a, T> {
    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
        f.debug_list().entries(*self).finish()
    }
}

impl<'a, T: TryFromBeBytes> IntoIterator for LazyArray16<'a, T> {
    type Item = T;
    type IntoIter = LazyArrayIter16<'a, T>;

    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        LazyArrayIter16 {
            data: self,
            index: 0,
        }
    }
}

/// An iterator over `LazyArray16`.
#[derive(Clone, Copy)]
#[allow(missing_debug_implementations)]
pub struct LazyArrayIter16<'a, T> {
    data: LazyArray16<'a, T>,
    index: u16,
}

impl<T: TryFromBeBytes> Default for LazyArrayIter16<'_, T> {
    #[inline]
    fn default() -> Self {
        LazyArrayIter16 {
            data: LazyArray16::new(&[]),
            index: 0,
        }
    }
}

impl<'a, T: TryFromBeBytes> Iterator for LazyArrayIter16<'a, T> {
    type Item = T;

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        self.index += 1; // TODO: check
        self.data.get(self.index - 1)
    }

    #[inline]
    fn count(self) -> usize {
        usize::from(self.data.len().saturating_sub(self.index))
    }
}

/// A slice-like container that converts internal binary data only on access.
///
/// This is a low-level, internal structure that should not be used directly.
#[derive(Clone, Copy)]
pub struct LazyArray32<'a, T> {
    data: &'a [u8],
    data_type: core::marker::PhantomData<T>,
}

impl<T> Default for LazyArray32<'_, T> {
    #[inline]
    fn default() -> Self {
        LazyArray32 {
            data: &[],
            data_type: core::marker::PhantomData,
        }
    }
}

impl<'a, T: TryFromBeBytes> LazyArray32<'a, T> {
    /// Creates a new `LazyArray`.
    #[inline]
    pub fn new(data: &'a [u8]) -> Self {
        LazyArray32 {
            data,
            data_type: core::marker::PhantomData,
        }
    }

    /// Returns a value at `index`.
    #[inline]
    pub fn get(&self, index: u32) -> Option<T> {
        if index < self.len() {
            let start = (index as usize) * T::SIZE;
            let end = start + T::SIZE;
            self.data
                .get(start..end)
                .and_then(T::try_parse_from_be_bytes)
        } else {
            None
        }
    }

    /// Returns array's length.
    #[inline]
    pub fn len(&self) -> u32 {
        (self.data.len() / T::SIZE) as u32
    }

    /// Checks if the array is empty.
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Performs a binary search by specified `key`.
    #[inline]
    pub fn binary_search(&self, key: &T) -> Option<(u32, T)>
    where
        T: Ord,
    {
        self.binary_search_by(|p| p.cmp(key))
    }

    /// Performs a binary search using specified closure.
    #[inline]
    pub fn binary_search_by<F>(&self, mut f: F) -> Option<(u32, T)>
    where
        F: FnMut(&T) -> core::cmp::Ordering,
    {
        // Based on Rust std implementation.

        use core::cmp::Ordering;

        let mut size = self.len();
        if size == 0 {
            return None;
        }

        let mut base = 0;
        while size > 1 {
            let half = size / 2;
            let mid = base + half;
            // mid is always in [0, size), that means mid is >= 0 and < size.
            // mid >= 0: by definition
            // mid < size: mid = size / 2 + size / 4 + size / 8 ...
            let cmp = f(&self.get(mid)?);
            base = if cmp == Ordering::Greater { base } else { mid };
            size -= half;
        }

        // base is always in [0, size) because base <= mid.
        let value = self.get(base)?;
        if f(&value) == Ordering::Equal {
            Some((base, value))
        } else {
            None
        }
    }
}

impl<'a, T: TryFromBeBytes + core::fmt::Debug + Copy> core::fmt::Debug for LazyArray32<'a, T> {
    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
        f.debug_list().entries(*self).finish()
    }
}

impl<'a, T: TryFromBeBytes> IntoIterator for LazyArray32<'a, T> {
    type Item = T;
    type IntoIter = LazyArrayIter32<'a, T>;

    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        LazyArrayIter32 {
            data: self,
            index: 0,
        }
    }
}

/// An iterator over `LazyArray32`.
#[derive(Clone, Copy)]
#[allow(missing_debug_implementations)]
pub struct LazyArrayIter32<'a, T> {
    data: LazyArray32<'a, T>,
    index: u32,
}

impl<'a, T: TryFromBeBytes> Iterator for LazyArrayIter32<'a, T> {
    type Item = T;

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        self.index += 1; // TODO: check
        self.data.get(self.index - 1)
    }

    #[inline]
    fn count(self) -> usize {
        self.data.len().saturating_sub(self.index) as usize
    }
}

/// A [`LazyArray16`]-like container, but data is accessed by offsets.
///
/// Unlike [`LazyArray16`], internal storage is not continuous.
///
/// Multiple offsets can point to the same data.
#[derive(Clone, Copy)]
pub struct LazyOffsetArray16<'a, T: FromSlice<'a>> {
    data: &'a [u8],
    // Zero offsets must be ignored.
    offsets: LazyArray16<'a, u16>,
    data_type: core::marker::PhantomData<T>,
}

impl<'a, T: FromSlice<'a>> LazyOffsetArray16<'a, T> {
    /// Creates a new `LazyOffsetArray16`.
    #[allow(dead_code)]
    pub fn new(data: &'a [u8], offsets: LazyArray16<'a, u16>) -> Self {
        Self {
            data,
            offsets,
            data_type: core::marker::PhantomData,
        }
    }

    /// Parses `LazyOffsetArray16` from raw data.
    #[allow(dead_code)]
    pub fn parse(data: &'a [u8]) -> Option<Self> {
        let mut s = Stream::new(data);
        let count = s.read::<u16>()?;
        let offsets = s.read_array16(count)?;
        Some(Self {
            data,
            offsets,
            data_type: core::marker::PhantomData,
        })
    }

    /// Returns a value at `index`.
    #[inline]
    pub fn get(&self, index: u16) -> Option<T> {
        let offset = usize::from(self.offsets.get(index).filter(|offset| *offset != 0)?);
        self.data.get(offset..).and_then(T::parse)
    }

    /// Returns array's length.
    #[inline]
    pub fn len(&self) -> u16 {
        self.offsets.len()
    }

    /// Checks if array is empty.
    #[inline]
    #[allow(dead_code)]
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }
}

impl<'a, T: FromSlice<'a> + core::fmt::Debug + Copy> core::fmt::Debug for LazyOffsetArray16<'a, T> {
    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
        f.debug_list().entries(*self).finish()
    }
}

/// An iterator over [`LazyOffsetArray16`] values.
#[derive(Clone, Copy)]
#[allow(missing_debug_implementations)]
pub struct LazyOffsetArrayIter16<'a, T: FromSlice<'a>> {
    array: LazyOffsetArray16<'a, T>,
    index: u16,
}

impl<'a, T: FromSlice<'a>> IntoIterator for LazyOffsetArray16<'a, T> {
    type Item = T;
    type IntoIter = LazyOffsetArrayIter16<'a, T>;

    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        LazyOffsetArrayIter16 {
            array: self,
            index: 0,
        }
    }
}

impl<'a, T: FromSlice<'a>> Iterator for LazyOffsetArrayIter16<'a, T> {
    type Item = T;

    fn next(&mut self) -> Option<Self::Item> {
        if self.index < self.array.len() {
            self.index += 1;
            self.array.get(self.index - 1)
        } else {
            None
        }
    }

    #[inline]
    fn count(self) -> usize {
        usize::from(self.array.len().saturating_sub(self.index))
    }
}

/// A streaming binary parser.
#[derive(Clone, Default, Debug)]
pub struct Stream<'a> {
    data: &'a [u8],
    offset: usize,
}

impl<'a> Stream<'a> {
    /// Creates a new `Stream` parser.
    #[inline]
    pub fn new(data: &'a [u8]) -> Self {
        Stream { data, offset: 0 }
    }

    /// Creates a new `Stream` parser at offset.
    ///
    /// Returns `None` when `offset` is out of bounds.
    #[inline]
    pub fn new_at(data: &'a [u8], offset: usize) -> Option<Self> {
        if offset <= data.len() {
            Some(Stream { data, offset })
        } else {
            None
        }
    }

    /// Checks that stream reached the end of the data.
    #[inline]
    pub fn at_end(&self) -> bool {
        self.offset >= self.data.len()
    }

    /// Jumps to the end of the stream.
    ///
    /// Useful to indicate that we parsed all the data.
    #[inline]
    pub fn jump_to_end(&mut self) {
        self.offset = self.data.len();
    }

    /// Returns the current offset.
    #[inline]
    pub fn offset(&self) -> usize {
        self.offset
    }

    /// Returns the trailing data.
    ///
    /// Returns `None` when `Stream` is reached the end.
    #[inline]
    pub fn tail(&self) -> Option<&'a [u8]> {
        self.data.get(self.offset..)
    }

    /// Advances by `FromData::SIZE`.
    ///
    /// Doesn't check bounds.
    #[inline]
    pub fn skip<T: TryFromBeBytes>(&mut self) {
        self.advance(T::SIZE);
    }

    /// Advances by the specified `len`.
    ///
    /// Doesn't check bounds.
    #[inline]
    pub fn advance(&mut self, len: usize) {
        self.offset += len;
    }

    /// Advances by the specified `len` and checks for bounds.
    #[inline]
    pub fn advance_checked(&mut self, len: usize) -> Option<()> {
        if self.offset + len <= self.data.len() {
            self.advance(len);
            Some(())
        } else {
            None
        }
    }

    /// Parses the type from the steam.
    ///
    /// Returns `None` when there is not enough data left in the stream
    /// or the type parsing failed.
    #[inline]
    pub fn read<T: TryFromBeBytes>(&mut self) -> Option<T> {
        self.read_bytes(T::SIZE)
            .and_then(T::try_parse_from_be_bytes)
    }

    /// Parses the type from the steam at offset.
    #[inline]
    pub fn read_at<T: TryFromBeBytes>(data: &[u8], offset: usize) -> Option<T> {
        data.get(offset..offset + T::SIZE)
            .and_then(T::try_parse_from_be_bytes)
    }

    /// Reads N bytes from the stream.
    #[inline]
    pub fn read_bytes(&mut self, len: usize) -> Option<&'a [u8]> {
        // An integer overflow here on 32bit systems is almost guarantee to be caused
        // by an incorrect parsing logic from the caller side.
        // Simply using `checked_add` here would silently swallow errors, which is not what we want.
        debug_assert!(self.offset as u64 + len as u64 <= u32::MAX as u64);

        let v = self.data.get(self.offset..self.offset + len)?;
        self.advance(len);
        Some(v)
    }

    /// Reads the next `count` types as a slice.
    #[inline]
    pub fn read_array16<T: TryFromBeBytes>(&mut self, count: u16) -> Option<LazyArray16<'a, T>> {
        let len = usize::from(count) * T::SIZE;
        self.read_bytes(len).map(LazyArray16::new)
    }

    /// Reads the next `count` types as a slice.
    #[inline]
    pub fn read_array32<T: TryFromBeBytes>(&mut self, count: u32) -> Option<LazyArray32<'a, T>> {
        let len = count as usize * T::SIZE;
        self.read_bytes(len).map(LazyArray32::new)
    }

    #[allow(dead_code)]
    #[inline]
    pub fn read_at_offset16(&mut self, data: &'a [u8]) -> Option<&'a [u8]> {
        let offset = usize::from(self.read::<u16>()?);
        data.get(offset..)
    }
}

#[inline]
pub fn i16_bound(min: i16, val: i16, max: i16) -> i16 {
    use core::cmp;
    cmp::max(min, cmp::min(max, val))
}

#[inline]
pub fn f32_bound(min: f32, val: f32, max: f32) -> f32 {
    debug_assert!(min.is_finite());
    debug_assert!(val.is_finite());
    debug_assert!(max.is_finite());

    if val > max {
        return max;
    } else if val < min {
        return min;
    }

    val
}

pub fn round4(value: usize) -> usize {
    match value.checked_add(3) {
        Some(value_plus_3) => value_plus_3 & !3,
        None => value,
    }
}