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solutions_only/project 12/Memory.jack

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+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/12/Memory.jack
+
+/**
+ * This library provides two services: direct access to the computer's main
+ * memory (RAM), and allocation and recycling of memory blocks. The Hack RAM
+ * consists of 32,768 words, each holding a 16-bit binary number.
+ */ 
+class Memory {
+    static Array mem;
+    /** Initializes the class. */
+    function void init() {
+        let mem = 0;
+        let mem[2048] = 14334;
+        let mem[2049] = -1;
+        return;
+    }
+
+    /** Returns the RAM value at the given address. */
+    function int peek(int address) {
+        return mem[address];
+    }
+
+    /** Sets the RAM value at the given address to the given value. */
+    function void poke(int address, int value) {
+        let mem[address] = value;
+        return;
+    }
+
+    /** Finds an available RAM block of the given size and returns
+     *  a reference to its base address. */
+    function int alloc(int size) {
+        var Array current_block;
+        var int tmp;
+        let current_block = 2048;
+        if (size < 0){
+            do Sys.error(5);
+        }
+        if (size = 0){
+            let size = 1;
+        }
+        while (current_block[0] < (size + 2)) {
+            let current_block = current_block[1];
+        }
+        let current_block[0] = current_block[0] - size - 2;
+        let current_block = current_block + current_block[0] + 2;
+        let current_block[0] = size;
+        return current_block + 2;
+    }
+
+    /** De-allocates the given object (cast as an array) by making
+     *  it available for future allocations. */
+    function void deAlloc(Array o) {
+         var Array current_block;
+         let current_block = 2048;
+         let o[1]= current_block[1];
+         let current_block[1] = o;
+         return;
+
+    }    
+}