Lua - Handling 64 bits number on 32 bit lua compiler

Question

Currently I am trying to decode data (using lua). Data I have is 64 bit hexadecimal (big endian).

That specific number needs to be converted to little endian. Beside that other bitwise operations are going to be applied later based on the internal logic.

Now, initially I thought that things are going to be easy, having in mind that I can use bitop and simply apply any bitwise operations I would like to.

Now, unfortunately, I have (and please make a note that I am not able to change this), 32 bit lua compiler, hence, I am not simply able to use these operations.

There are 2 questions which I would like to ask:

• If i have hex

  800A000000000000 how can I use 32 bitwise operations (specifically in this case operations like bit.bswap, bit.rshift, bit.lshift from the library i shared above) on this hexadecimal number? Is it possible to split this number on 2 parts, and then apply operations on each of them and then merge them together again? If that is the case, how?

• Do you have any good reference (like a good book) which I can use to familiarize myself with algorithms and what I can do and what I cannot when we are talking about bitwise operations (expecially representing huge numbers using multiple small chunks )

Prior asking this question, I found and read other references to the same subject, but all of them are more related with specific cases (which is hard to understand unless you are familiar with the subject):

1. lua 64-bit transitioning issue
2. Does Lua make use of 64-bit integers?
3. Determine whether Lua compiler runs 32 or 64 bit
4. Comparing signed 64 bit number using 32 bit bitwise operations in Lua

Answer 1

After more detailed investigation regarding this topic, testing and communication with other people which opinion is relevant to this subject, posting an answer:

In this specific case, it really does not matter do you have 32 bit or 64 bit compiler (or device). The biggest integer you are able to represent based on lua doc: 64-bit floats can only represent integers up to 53 bits of precision, and the hex number I used as an example is bigger then that.

This means that any kind of general bit-wise operations are not going to work for these numbers.

Basically, this question can be reconstructed in: "How I can use bit wise operations in lua on full 64 bits?".

Only solution is to use libraries for this one or to implement it by yourself (separating 64 bit number to two 32 bit numbers and implementing bit wise operators by yourself)