lexical_parse_float/
table_binary.rs

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1//! Pre-computed tables for writing non-decimal strings.
2
3#![cfg(feature = "power-of-two")]
4#![cfg(not(feature = "compact"))]
5#![doc(hidden)]
6
7use lexical_util::num::Float;
8
9#[cfg(not(feature = "radix"))]
10use crate::table_decimal::*;
11
12// HELPERS
13// -------
14
15/// Get lookup table for small int powers.
16///
17/// # Safety
18///
19/// Safe as long as the radix provided is valid, and exponent is smaller
20/// than the table for the radix.
21#[inline(always)]
22#[cfg(not(feature = "radix"))]
23pub const fn get_small_int_power(exponent: usize, radix: u32) -> u64 {
24    // NOTE: don't check the radix since we also use it for half radix, or 5.
25    match radix {
26        2 => get_small_int_power2(exponent),
27        4 => get_small_int_power4(exponent),
28        5 => get_small_int_power5(exponent),
29        8 => get_small_int_power8(exponent),
30        10 => get_small_int_power10(exponent),
31        16 => get_small_int_power16(exponent),
32        32 => get_small_int_power32(exponent),
33        _ => unreachable!(),
34    }
35}
36
37/// Get lookup table for small f32 powers.
38#[inline(always)]
39#[cfg(not(feature = "radix"))]
40pub fn get_small_f32_power(exponent: usize, radix: u32) -> f32 {
41    match radix {
42        2 => get_small_f32_power2(exponent),
43        4 => get_small_f32_power4(exponent),
44        8 => get_small_f32_power8(exponent),
45        10 => get_small_f32_power10(exponent),
46        16 => get_small_f32_power16(exponent),
47        32 => get_small_f32_power32(exponent),
48        _ => unreachable!(),
49    }
50}
51
52/// Get lookup table for small f64 powers.
53///
54/// # Safety
55///
56/// Safe as long as the radix provided is valid, and exponent is smaller
57/// than the table for the radix.
58#[inline(always)]
59#[cfg(not(feature = "radix"))]
60pub fn get_small_f64_power(exponent: usize, radix: u32) -> f64 {
61    match radix {
62        2 => get_small_f64_power2(exponent),
63        4 => get_small_f64_power4(exponent),
64        8 => get_small_f64_power8(exponent),
65        10 => get_small_f64_power10(exponent),
66        16 => get_small_f64_power16(exponent),
67        32 => get_small_f64_power32(exponent),
68        _ => unreachable!(),
69    }
70}
71
72//  NOTE:
73//      These functions use the fact that **all** powers-of-two
74//      can be exactly represented and cheaply using bit shifts for
75//      integers, or by setting the exponent directly.
76
77/// Get pre-computed int power of 2.
78#[inline(always)]
79pub const fn get_small_int_power2(exponent: usize) -> u64 {
80    1 << exponent
81}
82
83/// Get pre-computed f32 power of 2.
84#[inline(always)]
85pub fn get_small_f32_power2(exponent: usize) -> f32 {
86    // Can't handle values above the denormal size.
87    debug_assert!(exponent as i32 <= f32::EXPONENT_BIAS - f32::MANTISSA_SIZE);
88    let shift = (f32::EXPONENT_BIAS - f32::MANTISSA_SIZE) as u32;
89    let bits = (exponent as u32 + shift) << f32::MANTISSA_SIZE;
90    f32::from_bits(bits)
91}
92
93/// Get pre-computed f64 power of 2.
94#[inline(always)]
95pub fn get_small_f64_power2(exponent: usize) -> f64 {
96    // Can't handle values above the denormal size.
97    debug_assert!(exponent as i32 <= f64::EXPONENT_BIAS - f64::MANTISSA_SIZE);
98    let shift = (f64::EXPONENT_BIAS - f64::MANTISSA_SIZE) as u64;
99    let bits = (exponent as u64 + shift) << f64::MANTISSA_SIZE;
100    f64::from_bits(bits)
101}
102
103/// Get pre-computed int power of 4.
104#[inline(always)]
105pub const fn get_small_int_power4(exponent: usize) -> u64 {
106    get_small_int_power2(2 * exponent)
107}
108
109/// Get pre-computed f32 power of 4.
110#[inline(always)]
111pub fn get_small_f32_power4(exponent: usize) -> f32 {
112    get_small_f32_power2(2 * exponent)
113}
114
115/// Get pre-computed f64 power of 4.
116#[inline(always)]
117pub fn get_small_f64_power4(exponent: usize) -> f64 {
118    get_small_f64_power2(2 * exponent)
119}
120
121/// Get pre-computed int power of 8.
122#[inline(always)]
123pub const fn get_small_int_power8(exponent: usize) -> u64 {
124    get_small_int_power2(3 * exponent)
125}
126
127/// Get pre-computed f32 power of 8.
128#[inline(always)]
129pub fn get_small_f32_power8(exponent: usize) -> f32 {
130    get_small_f32_power2(3 * exponent)
131}
132
133/// Get pre-computed f64 power of 8.
134#[inline(always)]
135pub fn get_small_f64_power8(exponent: usize) -> f64 {
136    get_small_f64_power2(3 * exponent)
137}
138
139/// Get pre-computed int power of 16.
140#[inline(always)]
141pub const fn get_small_int_power16(exponent: usize) -> u64 {
142    get_small_int_power2(4 * exponent)
143}
144
145/// Get pre-computed f32 power of 16.
146#[inline(always)]
147pub fn get_small_f32_power16(exponent: usize) -> f32 {
148    get_small_f32_power2(4 * exponent)
149}
150
151/// Get pre-computed f64 power of 16.
152#[inline(always)]
153pub fn get_small_f64_power16(exponent: usize) -> f64 {
154    get_small_f64_power2(4 * exponent)
155}
156
157/// Get pre-computed int power of 32.
158#[inline(always)]
159pub const fn get_small_int_power32(exponent: usize) -> u64 {
160    get_small_int_power2(5 * exponent)
161}
162
163/// Get pre-computed f32 power of 32.
164#[inline(always)]
165pub fn get_small_f32_power32(exponent: usize) -> f32 {
166    get_small_f32_power2(5 * exponent)
167}
168
169/// Get pre-computed f64 power of 32.
170#[inline(always)]
171pub fn get_small_f64_power32(exponent: usize) -> f64 {
172    get_small_f64_power2(5 * exponent)
173}
lexical_parse_float/table_binary.rs

lexical_parse_float/
table_binary.rs
