j2i.net – Mostly Development, but what ever interests me at the time
Description: Mostly Development, but what ever interests me at the time
I’m working with some data that needs to be hashed in both C# and JavaScript. Usually converting an algorithm across languages is pretty trivial. But in JavaScript the regular numeric type is a double-precision 64-bit number. While this sounds sufficiently large, when used as an integer this only provides 53-bits of precision. As you might imagine, using a 53-bit numeric type on one system and 64-bit on another would result in differences in outcome. This would make hased data between these two functions in
A potential issue with BIGINT is that it can accommodate extremely large values. This isn’t usually a problem, but I need to have identical behaviour for the hash function to have identical results across the languages. Fixing this is simple though. I only need to perform the bitwise AND operation to truncate any bits in the BIGINT beyond position 64. The hast function I’m using was originally found on StackOverflow. This might not be the final Hash function that I use, but for now it works.
A key thing to note in the JavaScript implementation is the n suffix on the numbers. This ensures that they are all using the BIGINT type. Also take note of the bitwise operation with the number 0xFFFFFFFFn . This ensures that the number is truncated and acting like a 64-bit integer.
j2i.net – Mostly Development, but what ever interests me at the time