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Add new ssz fn for getting highest set bit

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This commit is contained in:
Paul Hauner 2018-09-13 12:44:26 +10:00
parent e75905421d
commit b6cfceb470
1 changed files with 12 additions and 2 deletions
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14
ssz/src/impl_encode.rs
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@ -14,8 +14,18 @@ macro_rules! impl_encodable_for_uint {
impl Encodable for $type { impl Encodable for $type {
fn ssz_append(&self, s: &mut SszStream) fn ssz_append(&self, s: &mut SszStream)
{ {
// Number of bits required to represent this integer // Number of bits required to represent this integer.
let num_bits = ((*self as f64).log2().floor() as usize) + 1; // This could be optimised at the expense of complexity.
let num_bits = {
let mut n = *self;
let mut r: usize = 0;
while n > 0 {
n >>= 1;
r += 1;
}
r
};
//let num_bits = ((*self as f64).log2().floor() as usize) + 1;
// Number of bytes required to represent this bit // Number of bytes required to represent this bit
let num_bytes = (num_bits + 8 - 1) / 8; let num_bytes = (num_bits + 8 - 1) / 8;
let mut ssz_val: Vec<u8> = Vec::with_capacity(num_bytes); let mut ssz_val: Vec<u8> = Vec::with_capacity(num_bytes);