diff options
Diffstat (limited to 'library/core/src/num/dec2flt/common.rs')
-rw-r--r-- | library/core/src/num/dec2flt/common.rs | 179 |
1 files changed, 31 insertions, 148 deletions
diff --git a/library/core/src/num/dec2flt/common.rs b/library/core/src/num/dec2flt/common.rs index 17957d7e7..11a626485 100644 --- a/library/core/src/num/dec2flt/common.rs +++ b/library/core/src/num/dec2flt/common.rs @@ -1,165 +1,60 @@ //! Common utilities, for internal use only. -use crate::ptr; - /// Helper methods to process immutable bytes. -pub(crate) trait ByteSlice: AsRef<[u8]> { - unsafe fn first_unchecked(&self) -> u8 { - debug_assert!(!self.is_empty()); - // SAFETY: safe as long as self is not empty - unsafe { *self.as_ref().get_unchecked(0) } - } - - /// Get if the slice contains no elements. - fn is_empty(&self) -> bool { - self.as_ref().is_empty() - } - - /// Check if the slice at least `n` length. - fn check_len(&self, n: usize) -> bool { - n <= self.as_ref().len() - } - - /// Check if the first character in the slice is equal to c. - fn first_is(&self, c: u8) -> bool { - self.as_ref().first() == Some(&c) - } - - /// Check if the first character in the slice is equal to c1 or c2. - fn first_is2(&self, c1: u8, c2: u8) -> bool { - if let Some(&c) = self.as_ref().first() { c == c1 || c == c2 } else { false } - } - - /// Bounds-checked test if the first character in the slice is a digit. - fn first_isdigit(&self) -> bool { - if let Some(&c) = self.as_ref().first() { c.is_ascii_digit() } else { false } - } - - /// Check if self starts with u with a case-insensitive comparison. - fn starts_with_ignore_case(&self, u: &[u8]) -> bool { - debug_assert!(self.as_ref().len() >= u.len()); - let iter = self.as_ref().iter().zip(u.iter()); - let d = iter.fold(0, |i, (&x, &y)| i | (x ^ y)); - d == 0 || d == 32 - } - - /// Get the remaining slice after the first N elements. - fn advance(&self, n: usize) -> &[u8] { - &self.as_ref()[n..] - } - - /// Get the slice after skipping all leading characters equal c. - fn skip_chars(&self, c: u8) -> &[u8] { - let mut s = self.as_ref(); - while s.first_is(c) { - s = s.advance(1); - } - s - } - - /// Get the slice after skipping all leading characters equal c1 or c2. - fn skip_chars2(&self, c1: u8, c2: u8) -> &[u8] { - let mut s = self.as_ref(); - while s.first_is2(c1, c2) { - s = s.advance(1); - } - s - } - +pub(crate) trait ByteSlice { /// Read 8 bytes as a 64-bit integer in little-endian order. - unsafe fn read_u64_unchecked(&self) -> u64 { - debug_assert!(self.check_len(8)); - let src = self.as_ref().as_ptr() as *const u64; - // SAFETY: safe as long as self is at least 8 bytes - u64::from_le(unsafe { ptr::read_unaligned(src) }) - } + fn read_u64(&self) -> u64; - /// Try to read the next 8 bytes from the slice. - fn read_u64(&self) -> Option<u64> { - if self.check_len(8) { - // SAFETY: self must be at least 8 bytes. - Some(unsafe { self.read_u64_unchecked() }) - } else { - None - } - } - - /// Calculate the offset of slice from another. - fn offset_from(&self, other: &Self) -> isize { - other.as_ref().len() as isize - self.as_ref().len() as isize - } -} - -impl ByteSlice for [u8] {} - -/// Helper methods to process mutable bytes. -pub(crate) trait ByteSliceMut: AsMut<[u8]> { /// Write a 64-bit integer as 8 bytes in little-endian order. - unsafe fn write_u64_unchecked(&mut self, value: u64) { - debug_assert!(self.as_mut().len() >= 8); - let dst = self.as_mut().as_mut_ptr() as *mut u64; - // NOTE: we must use `write_unaligned`, since dst is not - // guaranteed to be properly aligned. Miri will warn us - // if we use `write` instead of `write_unaligned`, as expected. - // SAFETY: safe as long as self is at least 8 bytes - unsafe { - ptr::write_unaligned(dst, u64::to_le(value)); - } - } -} + fn write_u64(&mut self, value: u64); -impl ByteSliceMut for [u8] {} + /// Calculate the offset of a slice from another. + fn offset_from(&self, other: &Self) -> isize; -/// Bytes wrapper with specialized methods for ASCII characters. -#[derive(Debug, Clone, Copy, PartialEq, Eq)] -pub(crate) struct AsciiStr<'a> { - slc: &'a [u8], + /// Iteratively parse and consume digits from bytes. + /// Returns the same bytes with consumed digits being + /// elided. + fn parse_digits(&self, func: impl FnMut(u8)) -> &Self; } -impl<'a> AsciiStr<'a> { - pub fn new(slc: &'a [u8]) -> Self { - Self { slc } +impl ByteSlice for [u8] { + #[inline(always)] // inlining this is crucial to remove bound checks + fn read_u64(&self) -> u64 { + let mut tmp = [0; 8]; + tmp.copy_from_slice(&self[..8]); + u64::from_le_bytes(tmp) } - /// Advance the view by n, advancing it in-place to (n..). - pub unsafe fn step_by(&mut self, n: usize) -> &mut Self { - // SAFETY: safe as long n is less than the buffer length - self.slc = unsafe { self.slc.get_unchecked(n..) }; - self + #[inline(always)] // inlining this is crucial to remove bound checks + fn write_u64(&mut self, value: u64) { + self[..8].copy_from_slice(&value.to_le_bytes()) } - /// Advance the view by n, advancing it in-place to (1..). - pub unsafe fn step(&mut self) -> &mut Self { - // SAFETY: safe as long as self is not empty - unsafe { self.step_by(1) } + #[inline] + fn offset_from(&self, other: &Self) -> isize { + other.len() as isize - self.len() as isize } - /// Iteratively parse and consume digits from bytes. - pub fn parse_digits(&mut self, mut func: impl FnMut(u8)) { - while let Some(&c) = self.as_ref().first() { + #[inline] + fn parse_digits(&self, mut func: impl FnMut(u8)) -> &Self { + let mut s = self; + + // FIXME: Can't use s.split_first() here yet, + // see https://github.com/rust-lang/rust/issues/109328 + while let [c, s_next @ ..] = s { let c = c.wrapping_sub(b'0'); if c < 10 { func(c); - // SAFETY: self cannot be empty - unsafe { - self.step(); - } + s = s_next; } else { break; } } - } -} -impl<'a> AsRef<[u8]> for AsciiStr<'a> { - #[inline] - fn as_ref(&self) -> &[u8] { - self.slc + s } } -impl<'a> ByteSlice for AsciiStr<'a> {} - /// Determine if 8 bytes are all decimal digits. /// This does not care about the order in which the bytes were loaded. pub(crate) fn is_8digits(v: u64) -> bool { @@ -168,19 +63,6 @@ pub(crate) fn is_8digits(v: u64) -> bool { (a | b) & 0x8080_8080_8080_8080 == 0 } -/// Iteratively parse and consume digits from bytes. -pub(crate) fn parse_digits(s: &mut &[u8], mut f: impl FnMut(u8)) { - while let Some(&c) = s.get(0) { - let c = c.wrapping_sub(b'0'); - if c < 10 { - f(c); - *s = s.advance(1); - } else { - break; - } - } -} - /// A custom 64-bit floating point type, representing `f * 2^e`. /// e is biased, so it be directly shifted into the exponent bits. #[derive(Debug, Copy, Clone, PartialEq, Eq, Default)] @@ -192,6 +74,7 @@ pub struct BiasedFp { } impl BiasedFp { + #[inline] pub const fn zero_pow2(e: i32) -> Self { Self { f: 0, e } } |