devela 0.28.0

A development substrate of coherence.
Documentation 
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// devela::text::ascii::digits::u16

use super::*;
use crate::{AsciiLut, is};

impl Digits<u16> {
    /// The maximum number of decimal digits a `u16` can represent.
    pub const MAX_DIGITS_10: u8 = 5;

    /// The maximum number of hexadecimal digits a `u16` can represent.
    pub const MAX_DIGITS_16: u8 = 4;

    #[doc = _DOC_COUNT_DIGITS_10!()]
    /// # Examples
    /// ```
    /// # use devela::text::Digits;
    /// assert_eq![1, Digits(0_u16).count_digits10()];
    /// assert_eq![4, Digits(9876_u16).count_digits10()];
    /// ```
    #[must_use]
    pub const fn count_digits10(self) -> u8 {
        is![self.0 == 0, 1, self.0.ilog10() as u8 + 1]
    }

    #[doc = _DOC_COUNT_DIGITS_16!()]
    pub const fn count_digits16(self) -> u8 {
        match self.0 {
            0 => 1,
            0x1..=0xF => 1,
            0x10..=0xFF => 2,
            0x100..=0xFFF => 3,
            _ => 4,
        }
    }

    /* digit_at_ */

    /// Returns the ASCII decimal digit at the specified index.
    ///
    /// Returns `b'0'` if the index is beyond the number's decimal digits.
    #[must_use]
    #[inline(always)]
    pub const fn digit_at_index10(self, index: u8) -> u8 {
        is![index >= self.count_digits10(), return b'0'];
        let power = AsciiLut::POWERS10[index as usize] as u16;
        (self.0 / power % 10) as u8 + b'0'
    }

    /// Returns the ASCII decimal digit at the specified index.
    ///
    /// Returns `None` if the index is beyond the number's decimal digits.
    #[must_use]
    pub const fn digit_at_index10_checked(self, index: u8) -> Option<u8> {
        is![index >= self.count_digits10(), return None];
        let power = AsciiLut::POWERS10[index as usize] as u16;
        Some((self.0 / power % 10) as u8 + b'0')
    }

    /// Returns the ASCII hexadecimal digit at the specified index (0 = least significant digit).
    ///
    /// For indices beyond the number's hexadecimal digits, returns the digit `b'0'`.
    #[must_use]
    pub const fn digit_at_index16(self, index: u8) -> u8 {
        let shift = index as u32 * 4;
        let digit = (self.0.unbounded_shr(shift) & 0xF) as usize;
        AsciiLut::DIGITS_BASE36[digit]
    }

    /// Returns `Some(ASCII digit)` if the index is within the number's hexadecimal digits,
    ///
    /// For indices beyond the number's hexadecimal digits, returns `None`.
    #[must_use]
    pub const fn digit_at_index16_checked(self, index: u8) -> Option<u8> {
        is![index >= self.count_digits16(), return None];
        let shift = index as u32 * 4;
        let digit = (self.0.unbounded_shr(shift) & 0xF) as usize;
        Some(AsciiLut::DIGITS_BASE36[digit])
    }

    /* digit_value_at_ */

    /// Returns the numeric value (0-9) of the decimal digit at the specified index.
    ///
    /// Returns `0` if the index is beyond the number's decimal digits.
    #[must_use]
    pub const fn digit_value_at_index10(self, index: u8) -> u8 {
        is![index >= self.count_digits10(), return 0];
        let power = AsciiLut::POWERS10[index as usize] as u16;
        (self.0 / power % 10) as u8
    }
    /// Returns `Some(numeric_value)` (0-9) of the decimal digit at the specified index.
    ///
    /// Returns `None` if the index is beyond the number's decimal digits.
    #[must_use]
    pub const fn digit_value_at_index10_checked(self, index: u8) -> Option<u8> {
        is![index >= self.count_digits10(), return None];
        let power = AsciiLut::POWERS10[index as usize] as u16;
        Some((self.0 / power % 10) as u8)
    }

    /// Returns the numeric value (0-15) of the hexadecimal digit at the specified index.
    ///
    /// Returns `0` if the index is beyond the number's hexadecimal digits.
    #[must_use]
    #[inline(always)]
    pub const fn digit_value_at_index16(self, index: u8) -> u8 {
        let shift = index as u32 * 4;
        (self.0.unbounded_shr(shift) & 0xF) as u8
    }
    /// Returns `Some(numeric_value)` (0-15) if the index is within bounds.
    ///
    /// Returns `None` if the index is beyond the number's hexadecimal digits.
    #[must_use]
    pub const fn digit_value_at_index16_checked(self, index: u8) -> Option<u8> {
        is![index < self.count_digits16(), Some(self.digit_value_at_index16(index)), None]
    }

    //

    #[doc = _DOC_DIGIT_AT_POWER_10!()]
    #[must_use]
    pub(crate) const fn digit_at_power10(self, divisor: u16) -> u8 {
        (self.0 / divisor % 10) as u8 + b'0'
    }
    #[doc = _DOC_DIGIT_AT_POWER_16!()]
    #[must_use]
    pub(crate) const fn digit_at_power16(self, divisor: u16) -> u8 {
        let digit = match divisor {
            0x1 => self.0 & 0xF,
            0x10 => (self.0 >> 4) & 0xF,
            0x100 => (self.0 >> 8) & 0xF,
            0x1000 => (self.0 >> 12) & 0xF,
            _ => (self.0 / divisor) % 16,
        };
        AsciiLut::DIGITS_BASE36[digit as usize]
    }

    /// Converts a `u16` into a byte array of `5` ASCII decimal digits with leading zeros.
    ///
    /// You can trim the leading zeros with `Slice::`[`trim_leading()`][crate::Slice::trim_leading].
    #[must_use]
    pub const fn digits10(self) -> [u8; Self::MAX_DIGITS_10 as usize] {
        [
            //                    54321
            //                    65535    ← u16::MAX
            self.digit_at_power10(10000), // 5 digits
            self.digit_at_power10(1000),
            self.digit_at_power10(100),
            self.digit_at_power10(10),
            self.digit_at_power10(1),
        ]
    }
    /// Converts a `u16` into a byte array of `4` ASCII digits with leading zeros.
    ///
    /// You can trim the leading zeros with `Slice::`[`trim_leading()`][crate::Slice::trim_leading].
    pub const fn digits16(self) -> [u8; Self::MAX_DIGITS_16 as usize] {
        [
            //                      4321
            //                      FFFF    ← u16::MAX
            self.digit_at_power16(0x1000), // 4 digits
            self.digit_at_power16(0x100),
            self.digit_at_power16(0x10),
            self.digit_at_power16(0x1),
        ]
    }

    /// Writes 1..=5 decimal digits without leading zeros starting at `offset`,
    /// returning the number of bytes written.
    #[inline(always)]
    const fn write_digits10_inner(self, buf: &mut [u8], offset: usize) -> usize {
        let n = self.0;
        if n < 10 {
            buf[offset] = n as u8 + b'0';
            1
        } else if n < 100 {
            buf[offset] = (n / 10) as u8 + b'0';
            buf[offset + 1] = (n % 10) as u8 + b'0';
            2
        } else if n < 1000 {
            buf[offset] = (n / 100) as u8 + b'0';
            buf[offset + 1] = ((n / 10) % 10) as u8 + b'0';
            buf[offset + 2] = (n % 10) as u8 + b'0';
            3
        } else if n < 10000 {
            buf[offset] = (n / 1000) as u8 + b'0';
            buf[offset + 1] = ((n / 100) % 10) as u8 + b'0';
            buf[offset + 2] = ((n / 10) % 10) as u8 + b'0';
            buf[offset + 3] = (n % 10) as u8 + b'0';
            4
        } else {
            buf[offset] = (n / 10000) as u8 + b'0';
            buf[offset + 1] = ((n / 1000) % 10) as u8 + b'0';
            buf[offset + 2] = ((n / 100) % 10) as u8 + b'0';
            buf[offset + 3] = ((n / 10) % 10) as u8 + b'0';
            buf[offset + 4] = (n % 10) as u8 + b'0';
            5
        }
    }

    #[doc = _DOC_WRITE_DIGITS_10!(5)]
    pub const fn write_digits10(self, buf: &mut [u8], offset: usize) -> usize {
        let len = self.count_digits10() as usize;
        is![len > buf.len().saturating_sub(offset), return 0];
        self.write_digits10_inner(buf, offset)
    }
    #[doc = _DOC_WRITE_DIGITS_10_NONZERO!(5)]
    pub const fn write_digits10_nonzero(self, buf: &mut [u8], offset: usize) -> usize {
        is![self.0 == 0, return 0];
        self.write_digits10(buf, offset)
    }
    #[doc = _DOC_WRITE_DIGITS_10_FAST!(5)]
    pub const fn write_digits10_fast(self, buf: &mut [u8], offset: usize) -> usize {
        const MAX: usize = Digits::<u16>::MAX_DIGITS_10 as usize;
        is![MAX > buf.len().saturating_sub(offset), return 0];
        self.write_digits10_inner(buf, offset)
    }
    #[doc = _DOC_WRITE_DIGITS_10_FAST_NONZERO!(5)]
    pub const fn write_digits10_fast_nonzero(self, buf: &mut [u8], offset: usize) -> usize {
        is![self.0 == 0, return 0];
        self.write_digits10_fast(buf, offset)
    }

    /// Converts a three-digit decimal number to the corresponding `2` ASCII digits.
    ///
    /// # Panics
    /// This function panics in debug if the given number is > 99.
    #[must_use]
    pub const fn digits10_2(self) -> [u8; 2] {
        debug_assert![self.0 <= 99];
        [self.digit_at_power10(10), self.digit_at_power10(1)]
    }

    /// Converts a three-digit decimal number to the corresponding `3` ASCII digits.
    ///
    /// # Panics
    /// This function panics in debug if the given number is > 999.
    #[must_use]
    pub const fn digits10_3(self) -> [u8; 3] {
        debug_assert![self.0 <= 999];
        [self.digit_at_power10(100), self.digit_at_power10(10), self.digit_at_power10(1)]
    }

    /// Converts a four-digit decimal number to the corresponding `4` ASCII digits.
    ///
    /// # Panics
    /// This function panics in debug if the given number is > 9999.
    #[must_use]
    pub const fn digits10_4(self) -> [u8; 4] {
        debug_assert![self.0 <= 9999];
        [
            self.digit_at_power10(1000),
            self.digit_at_power10(100),
            self.digit_at_power10(10),
            self.digit_at_power10(1),
        ]
    }
}