1# @ajax/mesh-abi-view-doom
2
3programs/doom's view: a DDA raycaster's pose, map, columns and show region.
4
5Part of the mesh contract: the memory, control, snapshot and peer protocols shared by meshd, its GPU
6programs (CUDA kernels, wasm lanes, native workers) and the tools. Every side compiles the same
7definitions, so an offset can never disagree.
8
9```c
10#include "mesh/abi/view_doom.h"
11```
12
13## Ported from
14
15[alpha-rust-mesh](https://github.com/rsafier/alpha-rust-mesh) (Richard Safier, MIT): crates/mesh-abi/src/v2/views.rs (`doom`): WIDTH, D_POS_X, D_POS_Y, D_DIR_X, D_DIR_Y, D_PLANE_X, D_PLANE_Y, D_ROWS, … (43 in all).
16
17Names: Rust's `NAME` is `MESH_NAME`; a constant of a Rust module `m` is `MESH_M_NAME` (unless it already starts with `M_`); a function `f` is `mesh_f` (`mesh_m_f`). Offsets that are `usize` in the Rust are plain integer constants or `size_t` results, `u32` constants carry a `u` suffix, `u64` use `UINT64_C`.
18
19## Device code
20
21The header is freestanding (`<stdint.h>`, `<stddef.h>`, `<stdbool.h>` only): it compiles for the host, `nvptx64-nvidia-cuda` and `wasm32`. Functions the Rust marks `const fn` are `static inline` here. Its tables (string names, field lists) live in `src/`, so device code that uses them links the package for that target.
22
23## Tests
24
25- `tests/constants.c`: every constant against the value the Rust prints (79 checks), and 2 Rust const asserts that call functions
26- `tests/golden.c`: its functions against 261 vectors computed by the Rust on the same inputs
27
28## Differences
29
30`MAP`'s rows are `char[17]` (16 cells and the NUL C adds to a string literal; GCC 15 warns about the Rust layout's unterminated `[u8; 16]`). `PLACE_STATE` and `PLACE_OUT` are arrays of `mesh_doom_region {off, len}`. `SNAP_BYTES` is written out (`D_SHOW + SH_DATA + 2 * OUT_BYTES`) because `show_bytes` is a function, not a constant expression, in C.
31
32## Licence
33
34MIT. See the repository's LICENSE.