//! Radix-generic, lexical integer-to-string conversion routines.
//!
//! These routines are optimized for code size: they are significantly
//! slower at the cost of smaller binary size.
#![cfg(feature = "compact")]
#![doc(hidden)]
use lexical_util::algorithm::copy_to_dst;
use lexical_util::constants::FormattedSize;
use lexical_util::digit::digit_to_char;
use lexical_util::num::{AsCast, UnsignedInteger};
// NOTE: Testing our algorithms can be done effectively as:
// table = [
// '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D',
// 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R',
// 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
// ]
// def to_string(value, radix):
// result = ''
// while value >= radix:
// r = value % radix
// value //= radix
// result = table[int(r)] + result
//
// r = value % radix
// result = table[int(r)] + result
//
// return result
/// Write integer to string.
pub trait Compact: UnsignedInteger + FormattedSize {
/// Write our integer to string without optimizations.
///
/// This iterates over the buffer in reverse, and ensures that at least
/// 128 elements exist in the temporary buffer. This ensures that the digits
/// can never overflow, even in base 2. The buffer then must be able to hold
/// at least 128 digits as well, after subslicing the data. This guarantee
/// is likely already made.
fn compact(self, radix: u32, buffer: &mut [u8]) -> usize {
// NOTE: We do not have to validate the buffer length because `copy_to_dst` is
// safe.
assert!(Self::BITS <= 128);
let mut digits: [u8; 128] = [0u8; 128];
let mut index = digits.len();
// Decode all but the last digit.
let radix = Self::from_u32(radix);
let mut value = self;
while value >= radix {
let r = value % radix;
value /= radix;
index -= 1;
digits[index] = digit_to_char(u32::as_cast(r));
}
// Decode last digit.
let r = value;
index -= 1;
digits[index] = digit_to_char(u32::as_cast(r));
let slc = &digits[index..];
copy_to_dst(buffer, slc)
}
}
macro_rules! compact_impl {
($($t:ty)*) => ($(
impl Compact for $t {}
)*)
}
compact_impl! { u8 u16 u32 u64 u128 usize }
