{
 "metadata": {
  "name": "",
  "signature": "sha256:4a14f929c77abfd0a54b26e2baa48a2c7f478d22968a4f6231afc128a12dd480"
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "heading",
     "level": 1,
     "metadata": {},
     "source": [
      "Chapter 20: Low-Level Programming"
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example xor.c, Page 515"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "KEY='&'\n",
      "orig=raw_input()\n",
      "orig_char=list(orig)\n",
      "new_char=[]\n",
      "\n",
      "def sxor(s1,s2):    \n",
      "    return ''.join(chr(ord(a) ^ ord(b)) for a,b in zip(s1,s2))\n",
      "for i in orig_char:\n",
      "    N=sxor(i,KEY)\n",
      "    new_char.append(N)\n",
      "print ''.join(new_char)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "name": "stdout",
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Trust not him with your secrets, who, when left alone in your room, turns over your papers. Johann Kaspar Lavater \n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "rTSUR\u0006HIR\u0006NOK\u0006QORN\u0006_IST\u0006UCETCRU\n",
        "\u0006QNI\n",
        "\u0006QNCH\u0006JC@R\u0006GJIHC\u0006OH\u0006_IST\u0006TIIK\n",
        "\u0006RSTHU\u0006IPCT\u0006_IST\u0006VGVCTU\b\u0006lINGHH\u0006mGUVGT\u0006jGPGRCT\u0006\n"
       ]
      }
     ],
     "prompt_number": 17
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example viewmemory.c, Page 521"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "from itertools import product\n",
      "def main():\n",
      "    \n",
      "    addr=\"\"\n",
      "    i=0\n",
      "    n=0\n",
      "    print \"Address of main function: %s\" % hex(id(main))\n",
      "    print \"Address of addr variable: %s\" % hex(id(addr))\n",
      "    addr=raw_input( \"Enter a (hex) address: \")\n",
      "    n=int(raw_input( \"Enter number of bytes to view: \"))\n",
      "    #printf(\"\\n\");\n",
      "    print \" Address     Bytes     Characters\\n\"\n",
      "    print \" - - - - - - - - - - - - - - - - - - - - - - \"\n",
      "    ptr = addr;\n",
      "    for nn in range(n,0,-10):\n",
      "        print \"%8s \"% hex(id(addr))\n",
      "       # for i,i in product(range(0//10), range(0//n)) :\n",
      "            #print \"%.2X \", *(ptr + i));  \n",
      "        #for (; i <10; i++)\n",
      "           # printf(\" \");                    #pointer dereferencing not in python\n",
      "        #printf(\" \");\n",
      "        #for (i = 0; i < 10 && i < n; i++) {\n",
      "           # BYTE ch = *(ptr + i);\n",
      "            #if (!isprint(ch))\n",
      "            #    ch = '.';\n",
      "           # printf(\"%c\", ch);\n",
      "    #}\n",
      "        #printf(\"\\n\");\n",
      "        #ptr += 10;\n",
      "    #} \n",
      "    #return 0;\n",
      "    #}\n",
      "if  __name__=='__main__':\n",
      "    main()"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Address of main function: 0x4117eb8L\n",
        "Address of addr variable: 0x1c3c148L\n"
       ]
      },
      {
       "name": "stdout",
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Enter a (hex) address: 8048000\n"
       ]
      },
      {
       "name": "stdout",
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Enter number of bytes to view: 40\n"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        " Address     Bytes     Characters\n",
        "\n",
        " - - - - - - - - - - - - - - - - - - - - - - \n",
        "0x41884b8L \n",
        "0x41884b8L \n",
        "0x41884b8L \n",
        "0x41884b8L \n"
       ]
      }
     ],
     "prompt_number": 11
    }
   ],
   "metadata": {}
  }
 ]
}