I've been building a bytecode VM in Rust and recently implemented NaN boxing for value representation. Sharing here for anyone interested.

I needed all VM values (booleans, integers, string pool indices, bytecode references) to fit in 64 bits (stack is Vec).

My implementation encodes 5 distinct types using a 3-bit tag and 32-bit payload, all within a single u64. It also has 15 unused bits, they may be used later for types expansion.

I'm using a 64-bit layout:

• Bits 63-51: Quiet NaN signature (0x7FFC...)
• Bits 50-18: 32-bit payload (integers, string pool indices, etc.)
• Bits 17-3: Unused/ (15 bits)
• Bits 2-0: 3-bit type tag

So it allows me to have 5 tagged types: TRUE_VAL, FALSE_VAL, STRING_VAL, CALLDATA_VAL, U32_VAL

cross-posted from: https://lemmy.ml/post/41182690

Here is my winter holiday project. Current scope and known issues are listed in readme, so thoughts and ideas on them are welcome ^_^

Here is my winter holiday project. Current scope and known issues are listed in readme, so thoughts and ideas on them are welcome ^_^

It is said that a visitor once came to the home of Nobel Prize–winning physicist Niels Bohr and, having noticed a horseshoe hung above the entrance, asked incredulously if the professor believed horseshoes brought good luck. “No,” Bohr replied, “but I am told that they bring luck even to those who do not believe in them.”

My opinion:

• Interesting concept of a Dark Forest & cosmic sociology axioms.
• Unpleasant characters: Ye Wenjie (narcissistic and psychopathic), Cheng Xin (a kind billionaire lol).
• Disappointing ending—the last few chapters feel weak.

Bonus: Absolutely fascinating interpretation of the first book by @yogthos@lemmy.ml.

It's quite easy to read, the book seems to urge action before the foe becomes too strong...

Rust ownership is a fundamental part of the language.

I’ve summarized the basic concepts here as a learning exercise for myself.

I’m sharing this to gather feedback, corrections, and suggestions.

Feel free to offer improvements wherever needed!

link to crate : https://crates.io/crates/st7567_rs