from __future__ import annotations

import re

_HEX_RE = re.compile(r"[0-9a-fA-F]")

def parse_hex_input(s: str) -> bytes:

"""Parse a variety of common hex/byte literal formats into raw bytes.

Accepts:

- Inline escaped: \x90\x90\x48...

- C-style: 0x90,0x90,0x48 or 0x90 0x90 0x48

- Raw hex: 909048...

- With whitespace, commas, newlines

"""

if not s:

return b""

s = s.strip()

# Inline \x.. sequences

if "\\x" in s:

pairs = re.findall(r"\\x([0-9a-fA-F]{2})", s)

if not pairs:

raise ValueError("No valid \\xHH sequences found")

return bytes(int(p, 16) for p in pairs)

# Remove 0x prefixes and non-hex separators

cleaned = re.sub(r"0x", "", s, flags=re.IGNORECASE)

cleaned = re.sub(r"[^0-9a-fA-F]", "", cleaned)

if not cleaned:

return b""

if len(cleaned) % 2 != 0:

raise ValueError("Odd-length hex string after cleaning")

try:

return bytes.fromhex(cleaned)

except ValueError as e:

raise ValueError(f"Invalid hex input: {e}")

def count_nulls(b: bytes) -> int:

return sum(1 for x in b if x == 0)