feat: port SpriteGfxTable__Init + RingBuffer__Init to Rust (Group A)

First two InitGameState sub-functions ported as hooks:

- SpriteGfxTable__Init (0x541620): fastcall(ECX=base, EDX=count).
Initializes identity permutation + 0xFFFFFFFF lookup table.
15 lines, zero dependencies.

- RingBuffer__Init (0x541060): usercall(EAX=capacity, ESI=struct).
Allocates buffer, initializes 7-DWORD ring buffer struct.
15 lines, only calls wa_malloc.

New file: engine/game_state_init.rs for InitGameState sub-functions.
Headful + headless replay tests PASS.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/openwa-core/src/address.rs

@@ -350,6 +350,10 @@ pub mod va {
     /// PaletteContext__Init (0x5411A0): initialize palette context free-list.
     /// usercall(EAX=context), plain RET.
     pub const PALETTE_CONTEXT_INIT: u32 = 0x0054_11A0;
+    /// SpriteGfxTable__Init (0x541620): fastcall(ECX=base, EDX=count), plain RET.
+    pub const SPRITE_GFX_TABLE_INIT: u32 = 0x0054_1620;
+    /// RingBuffer__Init (0x541060): usercall(EAX=capacity, ESI=struct), plain RET.
+    pub const RING_BUFFER_INIT: u32 = 0x0054_1060;
     /// DDGame__InitDisplayFinal_Maybe (0x56A830): display finalization for non-headless.
     pub const DDGAME_INIT_DISPLAY_FINAL: u32 = 0x0056_A830;
     /// PCLandscape__Constructor (0x57ACB0): constructs 0xB44-byte landscape object.

crates/openwa-core/src/engine/game_state_init.rs

@@ -0,0 +1,52 @@
+//! Pure Rust implementations of DDGame__InitGameState sub-functions.
+//!
+//! Each function is hooked individually so it works regardless of whether
+//! InitGameState itself is Rust or the original WA code.
+
+use crate::wa_alloc::wa_malloc;
+
+/// Pure Rust implementation of SpriteGfxTable__Init (0x541620).
+///
+/// Convention: fastcall(ECX=base, EDX=count), plain RET.
+///
+/// Initializes two parallel arrays:
+/// - `base[0..count]`: identity permutation (index[i] = i)
+/// - `base+0x2000[0..count]`: all 0xFFFFFFFF (unused markers)
+/// Plus 3 trailer fields at +0x3000/+0x3004/+0x3008.
+pub unsafe fn sprite_gfx_table_init(base: *mut u8, count: u32) {
+    for i in 0..count {
+        // Index table: base + i*4 = i
+        *((base as *mut u32).add(i as usize)) = i;
+        // Lookup table: base + 0x2000 + i*4 = 0xFFFFFFFF
+        *((base.add(0x2000) as *mut u32).add(i as usize)) = 0xFFFF_FFFF;
+    }
+    *(base.add(0x3000) as *mut u32) = count;
+    *(base.add(0x3004) as *mut u32) = 0;
+    *(base.add(0x3008) as *mut u32) = count;
+}
+
+/// Pure Rust implementation of RingBuffer__Init (0x541060).
+///
+/// Convention: usercall(EAX=capacity, ESI=struct_ptr), plain RET.
+///
+/// Allocates a zero-filled buffer of `capacity` bytes (aligned + 0x20 header),
+/// then initializes the ring buffer struct (7 DWORDs):
+/// - [0]: data pointer
+/// - [1]: capacity
+/// - [2]-[6]: zeroed (head, tail, count, etc.)
+pub unsafe fn ring_buffer_init(struct_ptr: *mut u8, capacity: u32) {
+    let alloc_size = ((capacity + 3) & !3) + 0x20;
+    let data = wa_malloc(alloc_size);
+    if !data.is_null() {
+        core::ptr::write_bytes(data, 0, capacity as usize);
+    }
+
+    let s = struct_ptr as *mut u32;
+    *s.add(0) = data as u32; // data pointer
+    *s.add(1) = capacity; // capacity
+    *s.add(2) = 0; // field 2
+    *s.add(3) = 0; // field 3
+    *s.add(4) = 0; // field 4
+    *s.add(5) = 0; // field 5
+    *s.add(6) = 0; // field 6
+}

crates/openwa-core/src/engine/mod.rs

@@ -2,6 +2,7 @@ pub mod ddgame;
 pub mod ddgame_wrapper;
 pub mod game_info;
 pub mod game_session;
+pub mod game_state_init;
 pub mod game_timer;
 pub mod net_wrapper;
 

crates/openwa-wormkit/src/replacements/ddgame_init.rs

@@ -18,6 +18,7 @@ use openwa_core::engine::ddgame::{
     bit_grid_init, ddgame_init_fields, ddgame_init_render_indices, display_layer_color_init,
     gfx_dir_find_entry, gfx_dir_load_dir, gfx_resource_create, DDGame,
 };
+use openwa_core::engine::game_state_init::{ring_buffer_init, sprite_gfx_table_init};
 use openwa_core::engine::DDGameWrapper;
 
 // ─── DDGame__InitFields (0x526120) ──────────────────────────────────────────
@@ -200,7 +201,47 @@ pub fn install() -> Result<(), String> {
             va::GFX_DIR_LOAD_DIR,
             load_dir_trampoline as *const (),
         )?;
+
+        hook::install(
+            "SpriteGfxTable__Init",
+            va::SPRITE_GFX_TABLE_INIT,
+            sprite_gfx_table_init_trampoline as *const (),
+        )?;
+
+        hook::install(
+            "RingBuffer__Init",
+            va::RING_BUFFER_INIT,
+            ring_buffer_init_trampoline as *const (),
+        )?;
     }
 
     Ok(())
 }
+
+// ─── SpriteGfxTable__Init (0x541620) ────────────────────────────────────────
+// Convention: fastcall(ECX=base, EDX=count), plain RET.
+
+unsafe extern "fastcall" fn sprite_gfx_table_init_trampoline(base: u32, count: u32) {
+    sprite_gfx_table_init(base as *mut u8, count);
+}
+
+// ─── RingBuffer__Init (0x541060) ────────────────────────────────────────────
+// Convention: usercall(EAX=capacity, ESI=struct_ptr), plain RET.
+
+extern "cdecl" fn impl_ring_buffer_init(struct_ptr: u32, capacity: u32) {
+    unsafe { ring_buffer_init(struct_ptr as *mut u8, capacity) }
+}
+
+#[unsafe(naked)]
+unsafe extern "C" fn ring_buffer_init_trampoline() {
+    core::arch::naked_asm!(
+        "push edx",
+        "push eax",        // capacity (EAX)
+        "push esi",        // struct_ptr (ESI)
+        "call {impl_fn}",
+        "add esp, 8",
+        "pop edx",
+        "ret",
+        impl_fn = sym impl_ring_buffer_init,
+    );
+}