ryu 0.2.0

Fast floating point to string conversion
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154

mod exponent;
mod mantissa;

use core::{mem, ptr};

use self::exponent::*;
use self::mantissa::*;
use d2s;
use d2s::*;
use f2s;
use f2s::*;

#[cfg(feature = "no-panic")]
use no_panic::no_panic;

#[cfg_attr(must_use_return, must_use)]
#[cfg_attr(feature = "no-panic", no_panic)]
pub unsafe fn d2s_buffered_n(f: f64, result: *mut u8) -> usize {
    let bits = mem::transmute::<f64, u64>(f).to_le();
    let sign = ((bits >> (DOUBLE_MANTISSA_BITS + DOUBLE_EXPONENT_BITS)) & 1) != 0;
    let ieee_mantissa = bits & ((1u64 << DOUBLE_MANTISSA_BITS) - 1);
    let ieee_exponent =
        (bits >> DOUBLE_MANTISSA_BITS) as u32 & ((1u32 << DOUBLE_EXPONENT_BITS) - 1);

    let mut index = 0isize;
    if sign {
        *result = b'-';
        index += 1;
    }

    if ieee_exponent == 0 && ieee_mantissa == 0 {
        ptr::copy_nonoverlapping(b"0.0".as_ptr(), result.offset(index), 3);
        return sign as usize + 3;
    }

    let v = d2d(ieee_mantissa, ieee_exponent);

    let length = d2s::decimal_length(v.mantissa) as isize;
    let k = v.exponent as isize;
    let kk = length + k; // 10^(kk-1) <= v < 10^kk
    debug_assert!(k >= -324);

    if 0 <= k && kk <= 16 {
        // 1234e7 -> 12340000000.0
        write_mantissa_long(v.mantissa, result.offset(index + length));
        for i in length..kk {
            *result.offset(index + i) = b'0';
        }
        *result.offset(index + kk) = b'.';
        *result.offset(index + kk + 1) = b'0';
        index as usize + kk as usize + 2
    } else if 0 < kk && kk <= 16 {
        // 1234e-2 -> 12.34
        write_mantissa_long(v.mantissa, result.offset(index + length + 1));
        ptr::copy(result.offset(index + 1), result.offset(index), kk as usize);
        *result.offset(index + kk) = b'.';
        index as usize + length as usize + 1
    } else if -6 < kk && kk <= 0 {
        // 1234e-6 -> 0.001234
        *result.offset(index) = b'0';
        *result.offset(index + 1) = b'.';
        let offset = 2 - kk;
        for i in 2..offset {
            *result.offset(index + i) = b'0';
        }
        write_mantissa_long(v.mantissa, result.offset(index + length + offset));
        index as usize + length as usize + offset as usize
    } else if length == 1 {
        // 1e30
        *result.offset(index) = b'0' + v.mantissa as u8;
        *result.offset(index + 1) = b'e';
        index as usize + 2 + write_exponent3(kk - 1, result.offset(index + 2))
    } else {
        // 1234e30 -> 1.234e33
        write_mantissa_long(v.mantissa, result.offset(index + length + 1));
        *result.offset(index) = *result.offset(index + 1);
        *result.offset(index + 1) = b'.';
        *result.offset(index + length + 1) = b'e';
        index as usize
            + length as usize
            + 2
            + write_exponent3(kk - 1, result.offset(index + length + 2))
    }
}

#[cfg_attr(must_use_return, must_use)]
#[cfg_attr(feature = "no-panic", no_panic)]
pub unsafe fn f2s_buffered_n(f: f32, result: *mut u8) -> usize {
    let bits = mem::transmute::<f32, u32>(f).to_le();
    let sign = ((bits >> (FLOAT_MANTISSA_BITS + FLOAT_EXPONENT_BITS)) & 1) != 0;
    let ieee_mantissa = bits & ((1u32 << FLOAT_MANTISSA_BITS) - 1);
    let ieee_exponent =
        ((bits >> FLOAT_MANTISSA_BITS) & ((1u32 << FLOAT_EXPONENT_BITS) - 1)) as u32;

    let mut index = 0isize;
    if sign {
        *result = b'-';
        index += 1;
    }

    if ieee_exponent == 0 && ieee_mantissa == 0 {
        ptr::copy_nonoverlapping(b"0.0".as_ptr(), result.offset(index), 3);
        return sign as usize + 3;
    }

    let v = f2d(ieee_mantissa, ieee_exponent);

    let length = f2s::decimal_length(v.mantissa) as isize;
    let k = v.exponent as isize;
    let kk = length + k; // 10^(kk-1) <= v < 10^kk
    debug_assert!(k >= -45);

    if 0 <= k && kk <= 13 {
        // 1234e7 -> 12340000000.0
        write_mantissa(v.mantissa, result.offset(index + length));
        for i in length..kk {
            *result.offset(index + i) = b'0';
        }
        *result.offset(index + kk) = b'.';
        *result.offset(index + kk + 1) = b'0';
        index as usize + kk as usize + 2
    } else if 0 < kk && kk <= 13 {
        // 1234e-2 -> 12.34
        write_mantissa(v.mantissa, result.offset(index + length + 1));
        ptr::copy(result.offset(index + 1), result.offset(index), kk as usize);
        *result.offset(index + kk) = b'.';
        index as usize + length as usize + 1
    } else if -6 < kk && kk <= 0 {
        // 1234e-6 -> 0.001234
        *result.offset(index) = b'0';
        *result.offset(index + 1) = b'.';
        let offset = 2 - kk;
        for i in 2..offset {
            *result.offset(index + i) = b'0';
        }
        write_mantissa(v.mantissa, result.offset(index + length + offset));
        index as usize + length as usize + offset as usize
    } else if length == 1 {
        // 1e30
        *result.offset(index) = b'0' + v.mantissa as u8;
        *result.offset(index + 1) = b'e';
        index as usize + 2 + write_exponent2(kk - 1, result.offset(index + 2))
    } else {
        // 1234e30 -> 1.234e33
        write_mantissa(v.mantissa, result.offset(index + length + 1));
        *result.offset(index) = *result.offset(index + 1);
        *result.offset(index + 1) = b'.';
        *result.offset(index + length + 1) = b'e';
        index as usize
            + length as usize
            + 2
            + write_exponent2(kk - 1, result.offset(index + length + 2))
    }
}