path: root/misc.py

def LEB128UnsignedDecode(bytelist):
    result = 0
    shift = 0
    for byte in bytelist:
        result |= (byte & 0x7f) << shift
        if (byte & 0x80) == 0:
            break
        shift += 7
    return(result)

def LEB128SignedDecode(bytelist):
    result = 0
    shift = 0
    for byte in bytelist:
        result |= (byte & 0x7f) << shift
        last_byte = byte
        shift += 7
        if (byte & 0x80) == 0:
            break
    if last_byte & 0x40:
        result |= - (1 << shift)
    return(result)

def LEB128UnsignedEncode(int_val):
    if int_val < 0:
        raise Exception("value must not be negative")
    elif int_val == 0:
        return bytes([0])
    byte_array = bytearray()
    while int_val:
        byte = int_val & 0x7f
        byte_array.append(byte | 0x80)
        int_val >>= 7
    byte_array[-1] ^= 0x80
    return(byte_array)

def LEB128SignedEncode(int_val):
    byte_array = bytearray()
    while True:
        byte = int_val & 0x7f
        byte_array.append(byte | 0x80)
        int_val >>= 7
        if (int_val == 0 and byte&0x40 == 0) or (int_val == -1 and byte&0x40):
            byte_array[-1] ^= 0x80
            break
    return(byte_array)