From 3a9265774c48865547702fe58d127c9fe10338a1 Mon Sep 17 00:00:00 2001
From: Yuchen Pei <me@ypei.me>
Date: Wed, 17 Jan 2018 10:04:48 +0100
Subject: finished Memory.jack

---
 projects/12/Memory.jack | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

(limited to 'projects/12/Memory.jack')

diff --git a/projects/12/Memory.jack b/projects/12/Memory.jack
index 941eec1..b1e67ef 100644
--- a/projects/12/Memory.jack
+++ b/projects/12/Memory.jack
@@ -9,26 +9,72 @@
  * consists of 32,768 words, each holding a 16-bit binary number.
  */ 
 class Memory {
+    static Array memory;
+    static Array heap;
+    static int first;
 
     /** Initializes the class. */
     function void init() {
+        let memory = 0;
+        let heap = 2048;
+        let heap[0] = -1;
+        let heap[1] = 14334;
     }
 
     /** Returns the RAM value at the given address. */
     function int peek(int address) {
+        return memory[address];
     }
 
     /** Sets the RAM value at the given address to the given value. */
     function void poke(int address, int value) {
+        let memory[address] = value;
     }
 
     /** Finds an available RAM block of the given size and returns
      *  a reference to its base address. */
     function int alloc(int size) {
+        var int current;
+        var int size2;
+        var int newLast;
+        let current = 0;
+        let size2 = size + 2;
+        while ((current > -1) & (heap[current + 1] < size2)) {
+            let current = heap[current];
+        }
+        if (current = -1) {
+            String.println("Insufficient space for allocation!");
+            Sys.error(1);
+        } else {
+            let heap[current + 1] = heap[current + 1] - size2;
+            let newLast = current + heap[current + 1] + 2;
+            let heap[newLast] = heap[current];
+            let heap[current] = newLast;
+            let heap[newLast + 1] = size;
+            return heap + newLast + 2;
+        }
     }
 
     /** De-allocates the given object (cast as an array) by making
      *  it available for future allocations. */
     function void deAlloc(Array o) {
+        var int base;
+        var int current;
+        var int prev;
+        let prev = 0;
+        let current = heap[prev];
+        let oBase = o - heap - 2;
+        while ((current > -1) & (~(current = oBase))){
+            let prev = current;
+            let current = heap[current];
+        }
+        if (current = -1) {
+            String.println("The impossible happened");
+            Sys.error(1);
+        } else {
+            let heap[prev] = heap[current]
+            let heap[prev + 1] = heap[prev] - prev - 2;
+            return;
+        }
     }    
 }
-- 
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