Add Cache API

1 files changed, 54 insertions, 5 deletions

diff --git a/src/memory.rs b/src/memory.rs
index b7e3721..c15bd84 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -1,12 +1,34 @@
-use isa::{Instruction};
+use isa::{self, Instruction};
 use binary::{Binary};
 
+pub type Address = usize;
+
 pub struct Memory {
     memory: Vec<u32>,
 }
 
+#[derive(Clone)]
+struct CacheBlock {
+    valid: bool,
+    tag: u32,
+    contents: Vec<u32>,
+}
+
+// TODO: probably want different caches for different strategies, and
+// investigate how LRU is implemented
+// TODO: use hashtable for a way?
+// TODO: hashtable-based FA cache?
+pub struct Cache {
+    num_sets: usize,
+    num_ways: usize,
+    block_words: usize,
+    cache: Vec<Vec<CacheBlock>>,
+}
+
+// TODO: refactor impls into a MemoryController(?) trait
+
 impl Memory {
-    pub fn new(size: usize, binary: Binary) -> Memory {
+    pub fn new(size: Address, binary: Binary) -> Memory {
         let mut memory = binary.words.clone();
         if size > memory.len() {
             let remainder = size - memory.len();
@@ -17,12 +39,12 @@ impl Memory {
         }
     }
 
-    pub fn read_word(&self, address: usize) -> Option<u32> {
+    pub fn read_word(&self, address: Address) -> Option<isa::Word> {
         // memory is word-addressed but addresses are byte-addressed
         self.memory.get(address / 4).map(Clone::clone)
     }
 
-    pub fn write_word(&mut self, address: usize, value: u32) -> Option<()> {
+    pub fn write_word(&mut self, address: Address, value: isa::Word) -> Option<()> {
         let address = address / 4;
         if address >= self.memory.len() {
             None
@@ -33,7 +55,34 @@ impl Memory {
         }
     }
 
-    pub fn read_instruction(&self, pc: usize) -> Option<Instruction> {
+    pub fn read_instruction(&self, pc: Address) -> Option<Instruction> {
         self.memory.get(pc / 4).map(Clone::clone).map(Instruction::new)
     }
 }
+
+impl Cache {
+    pub fn new(sets: usize, ways: usize, block_words: usize) -> Cache {
+        Cache {
+            num_sets: sets,
+            num_ways: ways,
+            block_words: block_words,
+            cache: vec![vec![CacheBlock {
+                valid: false,
+                tag: 0,
+                contents: vec![0; block_words],
+            }; ways]; sets],
+        }
+    }
+
+    fn read_word(&self, address: Address) -> Option<isa::Word> {
+        None
+    }
+
+    fn write_word(&mut self, address: Address, value: isa::Word) -> Option<()> {
+        None
+    }
+
+    fn invalidate(&mut self, address: Address) {
+        
+    }
+}