// 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;

    }    
}