ryu/pretty/
mantissa.rs

1use core::ptr;
2
3use digit_table::*;
4
5#[cfg_attr(feature = "no-panic", inline)]
6pub unsafe fn write_mantissa_long(mut output: u64, mut result: *mut u8) {
7    if (output >> 32) != 0 {
8        // One expensive 64-bit division.
9        let mut output2 = (output - 100_000_000 * (output / 100_000_000)) as u32;
10        output /= 100_000_000;
11
12        let c = output2 % 10_000;
13        output2 /= 10_000;
14        let d = output2 % 10_000;
15        let c0 = (c % 100) << 1;
16        let c1 = (c / 100) << 1;
17        let d0 = (d % 100) << 1;
18        let d1 = (d / 100) << 1;
19        ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c0 as usize), result.offset(-2), 2);
20        ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c1 as usize), result.offset(-4), 2);
21        ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(d0 as usize), result.offset(-6), 2);
22        ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(d1 as usize), result.offset(-8), 2);
23        result = result.offset(-8);
24    }
25    write_mantissa(output as u32, result);
26}
27
28#[cfg_attr(feature = "no-panic", inline)]
29pub unsafe fn write_mantissa(mut output: u32, mut result: *mut u8) {
30    while output >= 10_000 {
31        let c = (output - 10_000 * (output / 10_000)) as u32;
32        output /= 10_000;
33        let c0 = (c % 100) << 1;
34        let c1 = (c / 100) << 1;
35        ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c0 as usize), result.offset(-2), 2);
36        ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c1 as usize), result.offset(-4), 2);
37        result = result.offset(-4);
38    }
39    if output >= 100 {
40        let c = ((output % 100) << 1) as u32;
41        output /= 100;
42        ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c as usize), result.offset(-2), 2);
43        result = result.offset(-2);
44    }
45    if output >= 10 {
46        let c = (output << 1) as u32;
47        ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c as usize), result.offset(-2), 2);
48    } else {
49        *result.offset(-1) = b'0' + output as u8;
50    }
51}