From d3a0cc3a8ba6dfeb64d3faeffdeb6845b60e5840 Mon Sep 17 00:00:00 2001
From: Yuchen Pei <me@ypei.me>
Date: Sat, 20 Jan 2018 15:41:49 +0100
Subject: rearranged the dir for github

- removed tools and pdfs
- rearranged the projects dirs
- added md files
- other minor changes
---
 jackos/Memory.jack | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 jackos/Memory.jack

(limited to 'jackos/Memory.jack')

diff --git a/jackos/Memory.jack b/jackos/Memory.jack
new file mode 100644
index 0000000..54e04aa
--- /dev/null
+++ b/jackos/Memory.jack
@@ -0,0 +1,72 @@
+// 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 memory;
+    static Array heap;
+    static int last;
+
+    /** Initializes the class. */
+    function void init() {
+        let memory = 0;
+        let heap = 2048;
+        let heap[0] = -1;
+        let heap[1] = 14334;
+        let last = 0;
+        return;
+    }
+
+    /** 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;
+        return;
+    }
+
+    /** 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) {
+            do String.println("Insufficient space for allocation!");
+            do Sys.error(1);
+            return -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 oBase;
+        let oBase = o - heap - 2;
+        let heap[oBase] = -1;
+        let heap[last] = oBase;
+        let last = oBase;
+        return;
+    }    
+}
-- 
cgit v1.2.3