"""
Module to read intel hex files into binary data blobs.
IntelHex files are commonly used to distribute firmware
See: http://en.wikipedia.org/wiki/Intel_HEX
This is a python 3 conversion of the code created by David Braam for the Cura project.
"""
import io

def readHex(filename):
    """
    Read an verify an intel hex file. Return the data as an list of bytes.
    """
    data = []
    extraAddr = 0
    f = io.open(filename, "r")
    for line in f:
        line = line.strip()
        if len(line) < 1:
            continue
        if line[0] != ':':
            raise Exception("Hex file has a line not starting with ':'")
        recLen = int(line[1:3], 16)
        addr = int(line[3:7], 16) + extraAddr
        recType = int(line[7:9], 16)
        if len(line) != recLen * 2 + 11:
            raise Exception("Error in hex file: " + line)
        checkSum = 0
        for i in range(0, recLen + 5):
            checkSum += int(line[i*2+1:i*2+3], 16)
        checkSum &= 0xFF
        if checkSum != 0:
            raise Exception("Checksum error in hex file: " + line)
        
        if recType == 0:#Data record
            while len(data) < addr + recLen:
                data.append(0)
            for i in xrange(0, recLen):
                data[addr + i] = int(line[i*2+9:i*2+11], 16)
        elif recType == 1:	#End Of File record
            pass
        elif recType == 2:	#Extended Segment Address Record
            extraAddr = int(line[9:13], 16) * 16
        else:
            print(recType, recLen, addr, checkSum, line)
    f.close()
    return data