Struct ScratchPool 

pub struct ScratchPool { /* private fields */ }

N-slot pool of ScanScratch buffers — one slot per render thread.

R12.0 introduced this as the host-owned ownership root for per-thread scratch. R12.1 wires it through crate::opticast() (single slot in use). R12.2 will fan slots 0..4 across the four quadrant scan loops via rayon::join; R12.3 will distribute slots across N row strips via par_iter.

Per-frame setters (Self::set_skycast / Self::set_fog / Self::set_side_shades) broadcast to every slot — so once R12.2 fans out, each thread already sees the current frame’s fog / sky / shading state on its private slot.

One slot is ~7.6 MB at 640 × 480 / vsid = 2048 (see PORTING-MULTICORE.md § “Memory cost”). Hosts allocate one pool at startup and reuse it across frames; the rasterizer is the per-frame object that borrows the framebuffer / zbuffer.

Implementations

impl ScratchPool

pub fn new(xres: u32, yres: u32, vsid: u32) -> Self

Single-slot pool — single-threaded rendering. Equivalent to one ScanScratch::new_for_size allocation. The R12.0 default; preserves the pre-R12 single-threaded shape.

pub fn new_parallel(xres: u32, yres: u32, vsid: u32, n_threads: usize) -> Self

n_threads-slot pool. Each slot holds its own ~7.6 MB ScanScratch. Pass the value the host wants rayon to fan out across; n_threads = 0 is treated as 1 so Self::slot_mut(0) is always valid.

R12.1 only consumes slot 0; later sub-substages (R12.2 / R12.3) start indexing additional slots.

pub fn n_threads(&self) -> usize

Number of slots in this pool — one per render thread.

pub fn slot(&self, idx: usize) -> &ScanScratch

Read-only access to one slot.

Panics

If idx >= self.n_threads().

pub fn slot_mut(&mut self, idx: usize) -> &mut ScanScratch

Mutable access to one slot.

Panics

If idx >= self.n_threads().

pub fn set_skycast(&mut self, col: i32, dist: i32)

Per-frame sky (col, dist) push, broadcast to every slot. See ScanScratch::set_skycast.

pub fn set_fog(&mut self, col: i32, max_scan_dist: i32)

Per-frame fog push, broadcast to every slot. See ScanScratch::set_fog.

pub fn set_side_shades( &mut self, top: i8, bot: i8, left: i8, right: i8, up: i8, down: i8, )

Per-frame side-shading push, broadcast to every slot. See ScanScratch::set_side_shades.

Trait Implementations

impl Debug for ScratchPool

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.