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/*
Copyright 2024 Owain Davies
SPDX-License-Identifier: Apache-2.0 OR MIT
*/
use crate::to_twos_complement::{ByteOrder, TwosComplement};
use crate::{Arbi, Digit};
const DIGIT_BYTES: usize = core::mem::size_of::<Digit>();
impl Arbi {
/// Creates an `Arbi` integer from its representation as a byte array
/// in little endian, interpreted as a nonnegative integer.
///
/// If `bytes` is empty, [`Arbi::zero()`] is returned.
///
/// # Examples
/// ```
/// use arbi::Arbi;
///
/// let bytes = [0x78, 0x56, 0x34, 0x12, 0x34, 0x56, 0x78, 0x90];
///
/// let value = Arbi::from_le_bytes(&bytes);
/// assert_eq!(value, 0x9078563412345678_u64);
/// assert_eq!(value, u64::from_le_bytes(bytes));
///
/// let zero = Arbi::from_le_bytes(&[]);
/// assert_eq!(zero, 0);
/// ```
pub fn from_le_bytes(bytes: &[u8]) -> Self {
if bytes.is_empty() {
return Arbi::zero();
}
let full_chunks = bytes.len() / DIGIT_BYTES;
let remainder = bytes.len() % DIGIT_BYTES;
let mut num =
Arbi::with_capacity(full_chunks + usize::from(remainder > 0));
for chunk in bytes.chunks_exact(DIGIT_BYTES) {
let digit = Digit::from_le_bytes(chunk.try_into().unwrap());
num.vec.push(digit);
}
if remainder > 0 {
let mut last_bytes = [0u8; DIGIT_BYTES];
last_bytes[..remainder]
.copy_from_slice(&bytes[full_chunks * DIGIT_BYTES..]);
let last_digit = Digit::from_le_bytes(last_bytes);
num.vec.push(last_digit);
}
num.trim();
num
}
/// Creates an `Arbi` integer from its representation as a byte array
/// in big endian, interpreted as a nonnegative integer.
///
/// If `bytes` is empty, [`Arbi::zero()`] is returned.
///
/// # Examples
/// ```
/// use arbi::Arbi;
///
/// let bytes = [0x12, 0x34, 0x56, 0x78, 0x12, 0x34, 0x56, 0x78];
///
/// let value = Arbi::from_be_bytes(&bytes);
/// assert_eq!(value, 0x1234567812345678_u64);
/// assert_eq!(value, u64::from_be_bytes(bytes));
///
/// let zero = Arbi::from_be_bytes(&[]);
/// assert_eq!(zero, 0);
/// ```
pub fn from_be_bytes(bytes: &[u8]) -> Self {
if bytes.is_empty() {
return Arbi::zero();
}
let full_chunks = bytes.len() / DIGIT_BYTES;
let remainder = bytes.len() % DIGIT_BYTES;
let mut num =
Arbi::with_capacity(full_chunks + usize::from(remainder > 0));
let full_chunks_iter = bytes.chunks_exact(DIGIT_BYTES);
for chunk in full_chunks_iter.rev() {
let digit = Digit::from_be_bytes(chunk.try_into().unwrap());
num.vec.push(digit);
}
if remainder > 0 {
let mut last_bytes = [0u8; DIGIT_BYTES];
last_bytes[DIGIT_BYTES - remainder..]
.copy_from_slice(&bytes[0..remainder]);
let last_digit = Digit::from_be_bytes(last_bytes);
num.vec.push(last_digit);
}
num.trim();
num
}
/// Creates an `Arbi` integer from its representation as a byte array
/// in little endian, interpreted as a signed integer.
///
/// If `bytes` is empty, [`Arbi::zero()`] is returned.
///
/// # Examples
/// ```
/// use arbi::Arbi;
///
/// // Positive
/// let bytes = [0x78, 0x56, 0x34, 0x12, 0x78, 0x56, 0x34, 0x12];
/// let value = Arbi::from_le_bytes_signed(&bytes);
/// assert_eq!(value, 0x1234567812345678_i64);
/// assert_eq!(value, i64::from_le_bytes(bytes));
///
/// // Negative
/// let bytes = [0xb3, 0xb3, 0xb4, 0xb5, 0xb2, 0xb3, 0xb4, 0xb5];
/// let value = Arbi::from_le_bytes_signed(&bytes);
/// assert_eq!(value, i64::from_le_bytes(bytes));
///
/// // Zero
/// let bytes = [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00];
/// let value = Arbi::from_le_bytes_signed(&bytes);
/// assert_eq!(value, 0);
/// assert_eq!(value, i64::from_le_bytes(bytes));
///
/// let zero = Arbi::from_le_bytes_signed(&[]);
/// assert_eq!(zero, 0);
/// ```
pub fn from_le_bytes_signed(bytes: &[u8]) -> Self {
if bytes.is_empty() {
return Arbi::zero();
}
let is_negative = bytes.last().map_or(false, |&b| b & 0x80 != 0);
// TODO: one pass?
let mut num = Self::from_le_bytes(bytes);
if is_negative {
num.vec.to_twos_complement(ByteOrder::Le);
num.negate_mut();
}
num.trim();
num
}
/// Creates an `Arbi` integer from its representation as a byte array
/// in big endian, interpreted as a signed integer.
///
/// If `bytes` is empty, [`Arbi::zero()`] is returned.
///
/// # Examples
/// ```
/// use arbi::Arbi;
///
/// // Positive
/// let bytes = [0x12, 0x34, 0x56, 0x78, 0x12, 0x34, 0x56, 0x78];
/// let value = Arbi::from_be_bytes_signed(&bytes);
/// assert_eq!(value, 0x1234567812345678_i64);
/// assert_eq!(value, i64::from_be_bytes(bytes));
///
/// // Negative
/// let bytes = [0xb5, 0xb4, 0xb3, 0xb2, 0xb5, 0xb4, 0xb3, 0xb3];
/// let value = Arbi::from_be_bytes_signed(&bytes);
/// assert_eq!(value, i64::from_be_bytes(bytes));
///
/// // Zero
/// let bytes = [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00];
/// let value = Arbi::from_be_bytes_signed(&bytes);
/// assert_eq!(value, 0);
/// assert_eq!(value, i64::from_be_bytes(bytes));
///
/// let zero = Arbi::from_be_bytes_signed(&[]);
/// assert_eq!(zero, 0);
/// ```
pub fn from_be_bytes_signed(bytes: &[u8]) -> Self {
if bytes.is_empty() {
return Arbi::zero();
}
let is_negative = bytes[0] & 0x80 != 0;
// TODO: one pass?
let mut num = Self::from_be_bytes(bytes);
if is_negative {
num.vec.to_twos_complement(ByteOrder::Le);
num.neg = true;
}
num.trim();
num
}
/// Creates an integer value from its memory representation as a byte array
/// in native endianness, interpreted as a nonnegative integer.
///
/// # Examples
/// ```
/// use arbi::Arbi;
///
/// let bytes = if cfg!(target_endian = "big") {
/// [0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]
/// } else {
/// [0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]
/// };
///
/// let a = Arbi::from_ne_bytes(&bytes);
/// assert_eq!(a, 0x1234567890123456_i64);
/// assert_eq!(a, i64::from_ne_bytes(bytes));
/// ```
pub fn from_ne_bytes(bytes: &[u8]) -> Self {
if cfg!(target_endian = "big") {
Self::from_be_bytes(bytes)
} else {
Self::from_le_bytes(bytes)
}
}
/// Creates an integer value from its memory representation as a byte array
/// in native endianness, interpreted as a signed integer.
///
/// # Examples
/// ```
/// use arbi::Arbi;
///
/// let bytes = if cfg!(target_endian = "big") {
/// [0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]
/// } else {
/// [0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]
/// };
///
/// let a = Arbi::from_ne_bytes_signed(&bytes);
/// assert_eq!(a, 0x1234567890123456_i64);
/// assert_eq!(a, i64::from_ne_bytes(bytes));
/// ```
pub fn from_ne_bytes_signed(bytes: &[u8]) -> Self {
if cfg!(target_endian = "big") {
Self::from_be_bytes_signed(bytes)
} else {
Self::from_le_bytes_signed(bytes)
}
}
}
#[cfg(test)]
mod tests {
use super::*;
extern crate std;
use crate::util::test::{get_seedable_rng, Rng};
#[test]
fn test_random_from_le_bytes_signed() {
let (mut rng, _) = get_seedable_rng();
// i64
for _ in 0..i16::MAX {
let mut bytes = [0u8; 8];
rng.fill(&mut bytes);
let expected_value = i64::from_le_bytes(bytes);
let arbi_value = Arbi::from_le_bytes_signed(&bytes);
assert_eq!(
arbi_value, expected_value,
"Test failed for bytes: {:?}, arbi: {}",
bytes, arbi_value
);
let expected_value = i64::from_be_bytes(bytes);
let arbi_value = Arbi::from_be_bytes_signed(&bytes);
assert_eq!(
arbi_value, expected_value,
"Test failed for bytes: {:?}, arbi: {}",
bytes, arbi_value
);
let expected_value = i64::from_ne_bytes(bytes);
let arbi_value = Arbi::from_ne_bytes_signed(&bytes);
assert_eq!(
arbi_value, expected_value,
"Test failed for bytes: {:?}, arbi: {}",
bytes, arbi_value
);
}
// i128
for _ in 0..i16::MAX {
let mut bytes = [0u8; 16];
rng.fill(&mut bytes);
let expected_value = i128::from_le_bytes(bytes);
let arbi_value = Arbi::from_le_bytes_signed(&bytes);
assert_eq!(
arbi_value, expected_value,
"Test failed for bytes: {:?}, arbi: {}",
bytes, arbi_value
);
let expected_value = i128::from_be_bytes(bytes);
let arbi_value = Arbi::from_be_bytes_signed(&bytes);
assert_eq!(
arbi_value, expected_value,
"Test failed for bytes: {:?}, arbi: {}",
bytes, arbi_value
);
let expected_value = i128::from_ne_bytes(bytes);
let arbi_value = Arbi::from_ne_bytes_signed(&bytes);
assert_eq!(
arbi_value, expected_value,
"Test failed for bytes: {:?}, arbi: {}",
bytes, arbi_value
);
}
}
}