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#[inline(always)]
pub fn id_to_fieldnorm(id: u8) -> u32 {
FIELD_NORMS_TABLE[id as usize]
}
#[inline(always)]
pub fn fieldnorm_to_id(fieldnorm: u32) -> u8 {
FIELD_NORMS_TABLE
.binary_search(&fieldnorm)
.unwrap_or_else(|idx| idx - 1) as u8
}
#[cfg_attr(feature = "cargo-clippy", allow(clippy::unreadable_literal))]
pub const FIELD_NORMS_TABLE: [u32; 256] = [
0, 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, 42, 44, 46, 48, 50, 52, 54, 56, 60,
64, 68, 72, 76, 80, 84, 88, 96, 104, 112, 120, 128, 136, 144, 152, 168, 184, 200, 216, 232,
248, 264, 280, 312, 344, 376, 408, 440, 472, 504, 536, 600, 664, 728, 792, 856, 920, 984,
1_048, 1176, 1304, 1432, 1560, 1688, 1816, 1944, 2072, 2328, 2584, 2840, 3096, 3352, 3608,
3864, 4120, 4632, 5144, 5656, 6168, 6680, 7192, 7704, 8216, 9240, 10264, 11288, 12312, 13336,
14360, 15384, 16408, 18456, 20504, 22552, 24600, 26648, 28696, 30744, 32792, 36888, 40984,
45080, 49176, 53272, 57368, 61464, 65560, 73752, 81944, 90136, 98328, 106520, 114712, 122904,
131096, 147480, 163864, 180248, 196632, 213016, 229400, 245784, 262168, 294936, 327704, 360472,
393240, 426008, 458776, 491544, 524312, 589848, 655384, 720920, 786456, 851992, 917528, 983064,
1048600, 1179672, 1310744, 1441816, 1572888, 1703960, 1835032, 1966104, 2097176, 2359320,
2621464, 2883608, 3145752, 3407896, 3670040, 3932184, 4194328, 4718616, 5242904, 5767192,
6291480, 6815768, 7340056, 7864344, 8388632, 9437208, 10485784, 11534360, 12582936, 13631512,
14680088, 15728664, 16777240, 18874392, 20971544, 23068696, 25165848, 27263000, 29360152,
31457304, 33554456, 37748760, 41943064, 46137368, 50331672, 54525976, 58720280, 62914584,
67108888, 75497496, 83886104, 92274712, 100663320, 109051928, 117440536, 125829144, 134217752,
150994968, 167772184, 184549400, 201326616, 218103832, 234881048, 251658264, 268435480,
301989912, 335544344, 369098776, 402653208, 436207640, 469762072, 503316504, 536870936,
603979800, 671088664, 738197528, 805306392, 872415256, 939524120, 1006632984, 1073741848,
1207959576, 1342177304, 1476395032, 1610612760, 1744830488, 1879048216, 2013265944,
];
#[cfg(test)]
mod tests {
use super::{fieldnorm_to_id, id_to_fieldnorm, FIELD_NORMS_TABLE};
#[test]
fn test_decode_code() {
assert_eq!(fieldnorm_to_id(0), 0);
assert_eq!(fieldnorm_to_id(1), 1);
for i in 0..41 {
assert_eq!(fieldnorm_to_id(i), i as u8);
}
assert_eq!(fieldnorm_to_id(41), 40);
assert_eq!(fieldnorm_to_id(42), 41);
for id in 43..256 {
let field_norm = FIELD_NORMS_TABLE[id];
assert_eq!(id_to_fieldnorm(id as u8), field_norm);
assert_eq!(fieldnorm_to_id(field_norm), id as u8);
assert_eq!(fieldnorm_to_id(field_norm - 1), id as u8 - 1);
assert_eq!(fieldnorm_to_id(field_norm + 1), id as u8);
}
}
#[test]
fn test_u32_max() {
assert_eq!(fieldnorm_to_id(u32::max_value()), u8::max_value());
}
#[test]
fn test_fieldnorm_byte() {
// const expression are not really a thing
// yet... Therefore we do things the other way around.
// The array is defined as a const,
// and we check in the unit test that the const
// value is matching the logic.
const IDENTITY_PART: u8 = 24u8;
fn decode_field_norm_exp_part(b: u8) -> u32 {
let bits = (b & 0b00000111) as u32;
let shift = b >> 3;
if shift == 0 {
bits
} else {
(bits | 8u32) << ((shift - 1u8) as u32)
}
}
fn decode_fieldnorm_byte(b: u8) -> u32 {
if b < IDENTITY_PART {
b as u32
} else {
(IDENTITY_PART as u32) + decode_field_norm_exp_part(b - IDENTITY_PART)
}
}
for i in 0..256 {
assert_eq!(FIELD_NORMS_TABLE[i], decode_fieldnorm_byte(i as u8));
}
}
}
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