What these files are and where they comes from?
I started to studied hash functions because I need to process a huge file in which it is necessary to search for a certain string. The job of keeping such a large file sorted so that a binary search can be performed on it was out of the question. Instead, I thought about creating a companion file with only two fields per record, the 32-bit hash value and the position (32-bit offset) of each record in the original file, so this much smaller file could be kept sorted more easily. Of course, multiple collisions need to be managed.
I needed a simple and fast hash function. I asked Google Gemini and ChaptGPT and they suggested xxHash, so I selected the xxHash 32-bit flavor for my needs. I reviewed the original xxh32 C++ code and found it to be somewhat confusing, so I wrote my own pure C version that I hope be clearer and simpler. I then translated this code into a highly optimized xxh32.asm MASM32 assembler version that I'm pretty sure will outperform the original code or any other equivalent C or C++ code (although I haven't had time to complete some timing tests).
I then thought that these hashes might also be useful to other users, so I extended my xxh32 function to a complete Windows console program that generates 32-bit hashes from strings supplied in several different forms. The resulting xxHash32.asm program and its xxHash32.exe executable version are also included here.
One option of my program allows to generate the hashes of all the lines in an input file, so I devised to collect the 32-bit hashes in a long "string" and take the xxHash32 from they all. The result is a new 32-bit hash value (I could nickname it "xxh32-squared" as a joke) that can be used to check the integrity of a simple text file when no more requirements are needed.
After that, I wondered if this method could be translated to a Windows Batch file... The technical challenge was interesting because the original code uses several unsigned operations which are not available in the cmd.exe's SET /A command. I had a lot of fun trying to compensate for the inherent limitations of Batch files in a way that was not only functional, but also looked like the original. I finally resolved all the issues and the batch file xxHash32.bat is also included here.
I suspect this Batch version is the slowest one of all different versions published here (after the Bash one). If so, then the fastest and the slowest xxh32 versions are mine! ;)
