mega65-adventure VS json65

What are you on about, can you clarify? Rust can compile in no-std/embedded style just as fine (or better) than C can for basically any ARM or RISCV based processor, and quick googling shows this hal for nearly all pi needs and even MEGA65 is "as supported" (read: not at all officially by anything, fan-only) as any current C compiler. Setting up rust for a new target, so long as the code-gen is supported somehow by LLVM, LLVM plugin, LLVM IR transpiler (and maybe libgcc-jit sort of soon) is just as painful or unpainful as setting up a whole team to work via C/C++ with comparable testing harnesses. This doesn't mean easy and is an area Rust is still improving rapidly by the various enterprise agencies (Ferrous systems, Oxide, more I can't remember...) who specifically want to bring rust to such low end hardware because frankly both C and C++ suck with vendor proprietary tool chains and quirks.

JSON parser written in 6502 assembly language\ (69 comments)

The "Library organization" section [1] explains that the json65.s file is the core of the library and the only code necessary to build the library. The additional C code provides a handy tree structure and a callback to pass to the parsing engine.

However, because SAX is a callback-oriented parsing method, you can design your own data structure and write your own callback functions and do without this tree structure.

The additional C code provides similar nice-to-haves, such as string pool interning, a function to print out the aforementioned tree structure, and a wrapper function to parse json from a file.

[1] https://github.com/ppelleti/json65#library-organization