# hexutil.py
"""Miscellaneous utility routines relating to hex and byte strings"""
# Copyright (c) 2008-2012 Darcy Mason
# This file is part of pydicom, released under a modified MIT license.
#    See the file license.txt included with this distribution, also
#    available at http://pydicom.googlecode.com

from binascii import a2b_hex, b2a_hex
from dicom import in_py3
from dicom.charset import default_encoding


def hex2bytes(hexstring):
    """Return bytestring for a string of hex bytes separated by whitespace

    This is useful for creating specific byte sequences for testing, using
    python's implied concatenation for strings with comments allowed.
    Example:
        hex_string = (
         "08 00 32 10"     # (0008, 1032) SQ "Procedure Code Sequence"
         " 08 00 00 00"    # length 8
         " fe ff 00 e0"    # (fffe, e000) Item Tag
        )
        byte_string = hex2bytes(hex_string)
    Note in the example that all lines except the first must start with a space,
    alternatively the space could end the previous line.
    """
    # This works in both 3.x and 2.x because the first conditional evaluates to
    # true in 2.x so the difference in bytes constructor doesn't matter
    if isinstance(hexstring, bytes):
        return a2b_hex(hexstring.replace(b" ", b""))
    else:
        return a2b_hex(bytes(hexstring.replace(" ", ""), default_encoding))


def bytes2hex(byte_string):
    s = b2a_hex(byte_string)
    if in_py3:
        s = s.decode()
    return " ".join(s[i:i + 2] for i in range(0, len(s), 2))