bitcoin-asmap 0.1.19

// ---------------- [ File: bitcoin-asmap/src/asn.rs ]
/*!
This function, `decodeasn`, decodes an Autonomous System
Number (ASN) from a provided iterator of boolean values. The
iterator `bitpos` represents the current position in the
ASMAP data, and `endpos` represents the end position of the
data. The purpose of this function is to decode an ASN from
the compact representation in the ASMAP data.

The function uses a static vector `ASN_BIT_SIZES`, which
contains a list of possible ASN bit sizes.

The C++ code provided for this function calls the
`DecodeBits` function with `bitpos`, `endpos`, a minimum bit
size of 1, and the `ASN_BIT_SIZES` vector.

In Rust, the `decodeasn` function will have a similar
structure. It will call a Rust implementation of the
`DecodeBits` function with the given iterator, end position,
a minimum bit size of 1, and the `ASN_BIT_SIZES` vector. The
`todo!();` macro is a placeholder that should be replaced
with the Rust implementation that follows the same logic as
the C++ code provided.
*/

crate::ix!();

lazy_static!{
    static ref ASN_BIT_SIZES: Vec<u8> = vec!{15, 16, 17, 18, 19, 20, 21, 22, 23, 24};
}

/// Decode an ASN starting at `*pos` inside `asmap`.
pub fn decodeasn(asmap: &[bool], pos: &mut usize) -> u32 {
    trace!(pos = *pos, "decodeasn");
    decode_bits(asmap, pos, 1, &ASN_BIT_SIZES)
}

/// Helper that counts the number of set bits in a `u32`.
#[inline]
pub fn count_bits(x: u32) -> u32 {
    x.count_ones()
}