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dev: refactor from_byte #432

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Oct 18, 2023
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44 changes: 37 additions & 7 deletions crates/utils/src/helpers.cairo
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,8 @@ use utils::constants::{
POW_256_16,
};
use keccak::u128_split;
use traits::DivRem;
use integer::U32TryIntoNonZero;


/// Ceils a number of bits to the next word (32 bytes)
Expand Down Expand Up @@ -526,16 +528,44 @@ impl U256Impl of U256Trait {
#[generate_trait]
impl ByteArrayExt of ByteArrayExTrait {
fn from_bytes(mut bytes: Span<u8>) -> ByteArray {
//TODO(eni): optimize deserialization of Span<u8> to ByteArray;
// we can just deserialize bytes by chunks of 31, skipping pending_word
// checks
let mut arr: ByteArray = Default::default();
let (nb_full_words, pending_word_len) = DivRem::div_rem(
bytes.len(), 31_u32.try_into().unwrap()
);
let mut i = 0;
loop {
match bytes.pop_front() {
Option::Some(byte) => { arr.append_byte(*byte); },
Option::None => { break; }
}
if i == nb_full_words {
break;
};
let mut word: felt252 = 0;
let mut j = 0;
loop {
if j == 31 {
break;
};
word = word * POW_256_1.into() + (*bytes.pop_front().unwrap()).into();
j += 1;
};
arr.data.append(word.try_into().unwrap());
i += 1;
};

if pending_word_len == 0 {
return arr;
};

let mut pending_word: felt252 = 0;
let mut i = 0;

loop {
if i == pending_word_len {
break;
};
pending_word = pending_word * POW_256_1.into() + (*bytes.pop_front().unwrap()).into();
i += 1;
};
arr.pending_word_len = pending_word_len;
arr.pending_word = pending_word;
arr
}
}
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