softposit/p16e1/math/
ceil.rs

1use crate::u16_with_sign;
2
3impl super::P16E1 {
4    pub const fn ceil(self) -> Self {
5        let mut mask = 0x2000_u16;
6        let mut scale = 0_u16;
7
8        let mut ui_a = self.to_bits();
9        let sign = ui_a > 0x8000;
10
11        // sign is True if p_a > NaR.
12        if sign {
13            ui_a = ui_a.wrapping_neg() // A is now |A|.
14        };
15
16        let u_a = if ui_a == 0 {
17            return self;
18        } else if ui_a <= 0x4000 {
19            // 0 <= |pA| < 1 ceiling to zero.(if not negative and whole number)
20            if sign && (ui_a != 0x4000) {
21                0x0
22            } else {
23                0x4000
24            }
25        } else if ui_a <= 0x5000 {
26            // 1 <= x < 2 ceiling to 1 (if not negative and whole number)
27            if sign && (ui_a != 0x5000) {
28                0x4000
29            } else {
30                0x5000
31            }
32        } else if ui_a <= 0x5800 {
33            // 2 <= x < 3 ceiling to 2 (if not negative and whole number)
34            if sign & (ui_a != 0x5800) {
35                0x5000
36            } else {
37                0x5800
38            }
39        } else if ui_a >= 0x7C00 {
40            // If |A| is 256 or greater, leave it unchanged.
41            return self; // This also takes care of the NaR case, 0x8000.
42        } else {
43            // 34% of the cases, we have to decode the posit.
44            while (mask & ui_a) != 0 {
45                // Increment scale by 2 for each regime sign bit.
46                scale += 2; // Regime sign bit is always 1 in this range.
47                mask >>= 1; // Move the mask right, to the next bit.
48            }
49            mask >>= 1; // Skip over termination bit.
50            if (mask & ui_a) != 0 {
51                scale += 1; // If exponent is 1, increment the scale.
52            }
53            mask >>= scale; // Point to the last bit of the integer part.
54
55            mask >>= 1;
56            let mut tmp = ui_a & mask;
57            let bit_n_plus_one = tmp; // "True" if nonzero.
58            ui_a ^= tmp; // Erase the bit, if it was set.
59            tmp = ui_a & (mask - 1); // tmp has any remaining bits = bitsMore
60            ui_a ^= tmp; // Erase those bits, if any were set.
61
62            if !sign && (bit_n_plus_one | tmp) != 0 {
63                ui_a += mask << 1;
64            }
65            ui_a
66        };
67        Self::from_bits(u16_with_sign(u_a, sign))
68    }
69}
softposit/p16e1/math/ceil.rs

softposit/p16e1/math/
ceil.rs
