initial commit

dsa-emu/src/memory/mainstore.rs

@@ -0,0 +1,60 @@
+use fxhash::FxHashMap;
+
+use crate::memory::PhysAddr;
+
+type Page = [u8; 4096];
+
+pub struct MainStore {
+    pages: FxHashMap<PhysAddr, Page>,
+}
+
+impl MainStore {
+    pub fn new() -> Self {
+        Self {
+            pages: FxHashMap::default(),
+        }
+    }
+
+    #[inline(always)]
+    const fn segment_addr(addr: PhysAddr) -> (PhysAddr, usize) {
+        (addr & !(0xFFF), (addr & 0xFFF) as usize)
+    }
+
+    #[inline]
+    pub fn read_byte(&self, addr: PhysAddr) -> u8 {
+        let (page, offset) = Self::segment_addr(addr);
+        self.pages.get(&page).map(|p| p[offset]).unwrap_or(0)
+    }
+
+    #[inline]
+    pub fn read_word(&self, addr: PhysAddr) -> u32 {
+        let (page, offset) = Self::segment_addr(addr);
+        let page = self.pages.get(&page).unwrap_or(&[0; 4096]);
+        u32::from_be_bytes(page[offset..=offset + 3].try_into().unwrap())
+    }
+
+    #[inline]
+    pub fn read_page(&self, addr: PhysAddr) -> &[u8] {
+        self.pages.get(&addr).unwrap_or(&[0; 4096])
+    }
+
+    #[inline]
+    pub fn write_byte(&mut self, addr: PhysAddr, value: u8) {
+        let (page, offset) = Self::segment_addr(addr);
+        self.pages.entry(page).or_insert_with(|| [0; 4096])[offset] = value;
+    }
+
+    #[inline]
+    pub fn write_word(&mut self, addr: PhysAddr, value: u32) {
+        let (page, offset) = Self::segment_addr(addr);
+        let page = self.pages.entry(page).or_insert_with(|| [0; 4096]);
+        page[offset..=offset + 3].copy_from_slice(&value.to_be_bytes());
+    }
+
+    #[inline]
+    pub fn write_page(&mut self, addr: PhysAddr, value: &[u8; 4096]) {
+        let (page, offset) = Self::segment_addr(addr);
+        let page = self.pages.entry(page).or_insert_with(|| [0; 4096]);
+        page[offset..offset + value.len()].copy_from_slice(value);
+    }
+}