using System;
using System.IO;
using System.Net;
using System.Text;
public class GooglePageRank
 {
 ///
 /// Devuelve el PageRank una URL suministrada. 0 a 10 ó
 /// -1 (N/A), que indica que ha existido un error
 /// o la URL no esta indexada.
 ///
 ///URL a testear
 ///
 public static int GetPageRank(string url)
 {
 int rank = -1;
try
 {
 // URL a completar
 url = String.Format("http://toolbarqueries.google.com/tbr" +
 "?client=navclient-auto&features=Rank&ch={0}&q=info:{1}",
 ComputeHash(url), UrlEncode(url));
// Página de descarga
 HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
 StreamReader stream = new StreamReader(request.GetResponse().GetResponseStream());
 string response = stream.ReadToEnd();
// Página de page rank a parsear
 string[] arr = response.Split(':');
 if (arr.Length == 3)
 rank = int.Parse(arr[2]);
 }
 catch (Exception)
 {
 // No hace nada, pero retorna un -1;
 }
 return rank;
 }
///
 /// URL-encodea la URL dada. Útil cuando HttpUtility no está disponible
 ///
 ///URL a encodear
 ///
 private static string UrlEncode(string url)
 {
 StringBuilder builder = new StringBuilder();
foreach (char c in url)
 {
 if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9'))
 builder.Append(c);
 else if (c == ' ')
 builder.Append('+');
 else if ("()*-_.!".IndexOf(c) >= 0)
 builder.Append(c);
 else
 builder.AppendFormat("%{0:X2}", (byte)c);
 }
 return builder.ToString();
 }
///
 /// Calcula un valor hash requerido por Google
 ///
 private static string ComputeHash(string url)
 {
 UInt32 a, b;
 UInt32 c = 0xE6359A60;
 int k = 0;
 int len;
// Modify URL
 url = string.Format("info:{0}", url);
a = b = 0x9E3779B9;
 len = url.Length;
while (len >= 12)
 {
 a += (UInt32)(url[k + 0] + (url[k + 1] << 8) + (url[k + 2] << 16) + (url[k + 3] << 24));
 b += (UInt32)(url[k + 4] + (url[k + 5] << 8) + (url[k + 6] << 16) + (url[k + 7] << 24));
 c += (UInt32)(url[k + 8] + (url[k + 9] << 8) + (url[k + 10] << 16) + (url[k + 11] << 24));
 Mix(ref a, ref b, ref c);
 k += 12;
 len -= 12;
 }
c += (UInt32)url.Length;
 switch (len)
 {
 case 11:
 c += (UInt32)(url[k + 10] << 24);
 goto case 10;
 case 10:
 c += (UInt32)(url[k + 9] << 16);
 goto case 9;
 case 9:
 c += (UInt32)(url[k + 8] << 8);
 goto case 8;
 case 8:
 b += (UInt32)(url[k + 7] << 24);
 goto case 7;
 case 7:
 b += (UInt32)(url[k + 6] << 16);
 goto case 6;
 case 6:
 b += (UInt32)(url[k + 5] << 8);
 goto case 5;
 case 5:
 b += (UInt32)(url[k + 4]);
 goto case 4;
 case 4:
 a += (UInt32)(url[k + 3] << 24);
 goto case 3;
 case 3:
 a += (UInt32)(url[k + 2] << 16);
 goto case 2;
 case 2:
 a += (UInt32)(url[k + 1] << 8);
 goto case 1;
 case 1:
 a += (UInt32)(url[k + 0]);
 break;
 default:
 break;
 }
 Mix(ref a, ref b, ref c);
 return string.Format("6{0}", c);
 }
 ///
 /// ComputeHash() método de ayuda
 ///
 private static void Mix(ref UInt32 a, ref UInt32 b, ref UInt32 c)
 {
 a -= b; a -= c; a ^= c >> 13;
 b -= c; b -= a; b ^= a << 8;
 c -= a; c -= b; c ^= b >> 13;
 a -= b; a -= c; a ^= c >> 12;
 b -= c; b -= a; b ^= a << 16;
 c -= a; c -= b; c ^= b >> 5;
 a -= b; a -= c; a ^= c >> 3;
 b -= c; b -= a; b ^= a << 10;
 c -= a; c -= b; c ^= b >> 15;
 }
 }