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| use core::{mem::MaybeUninit, slice, str}; | |
| const HEX_DIGITS_LUT: &[u8] = b"0123456789ABCDEF"; | |
| const MAX_LEN: usize = 20; | |
| pub struct Buffer([MaybeUninit<u8>; MAX_LEN]); | |
| impl Buffer { | |
| #[inline] | |
| pub fn new() -> Buffer { | |
| let bytes = [MaybeUninit::<u8>::uninit(); MAX_LEN]; | |
| Buffer(bytes) | |
| } | |
| #[inline] | |
| pub fn format<I: Integer>(&mut self, i: I) -> &str { | |
| i.write(unsafe { | |
| &mut *(&mut self.0 as *mut [MaybeUninit<u8>; MAX_LEN] | |
| as *mut <I as private::Sealed>::Buffer) | |
| }) | |
| } | |
| } | |
| pub trait Integer: private::Sealed {} | |
| mod private { | |
| pub trait Sealed: Copy { | |
| type Buffer: 'static; | |
| fn write(self, buf: &mut Self::Buffer) -> &str; | |
| } | |
| } | |
| impl Integer for usize {} | |
| impl Integer for isize {} | |
| impl private::Sealed for usize { | |
| type Buffer = [MaybeUninit<u8>; MAX_LEN]; | |
| #[inline] | |
| fn write(self, buf: &mut Self::Buffer) -> &str { | |
| unsafe { | |
| let mut n = self; | |
| if n > 0 { | |
| let mut curr = buf.len() as isize; | |
| let lut = HEX_DIGITS_LUT.as_ptr(); | |
| let buf_ptr = buf.as_mut_ptr() as *mut u8; | |
| while n != 0 { | |
| curr -= 1; | |
| lut.offset((n % 16) as isize) | |
| .copy_to_nonoverlapping(buf_ptr.offset(curr), 1); | |
| n /= 16; | |
| } | |
| let len = buf.len() - curr as usize; | |
| let slice = slice::from_raw_parts(buf_ptr.offset(curr), len); | |
| return str::from_utf8_unchecked(slice); | |
| } | |
| "0" | |
| } | |
| } | |
| } | |
| impl private::Sealed for isize { | |
| type Buffer = [MaybeUninit<u8>; MAX_LEN]; | |
| #[inline] | |
| fn write(self, buf: &mut Self::Buffer) -> &str { | |
| unsafe { | |
| let mut curr = buf.len() as isize; | |
| let buf_ptr = buf.as_mut_ptr() as *mut u8; | |
| let lut = HEX_DIGITS_LUT.as_ptr(); | |
| let is_nonnegative = self >= 0; | |
| let mut n = if is_nonnegative { | |
| self | |
| } else { | |
| self.checked_abs().unwrap_or_else(|| { | |
| curr -= 1; | |
| let value = isize::MAX; | |
| let rem = value % 16; | |
| lut.offset(rem) | |
| .copy_to_nonoverlapping(buf_ptr.offset(curr), 1); | |
| value / 16 + (rem == 15) as isize | |
| }) | |
| }; | |
| while n != 0 { | |
| curr -= 1; | |
| lut.offset(n % 16) | |
| .copy_to_nonoverlapping(buf_ptr.offset(curr), 1); | |
| n /= 16; | |
| } | |
| if !is_nonnegative { | |
| curr -= 1; | |
| buf_ptr.offset(curr).write(b'-'); | |
| } | |
| let len = (buf.len() as isize - curr) as usize; | |
| let slice = slice::from_raw_parts(buf_ptr.offset(curr), len); | |
| str::from_utf8_unchecked(slice) | |
| } | |
| } | |
| } |
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