X-Git-Url: https://git.openstreetmap.org/rails.git/blobdiff_plain/2f6aab7124a59536b66fa5670fe8a59797255440..1d8e66016c4cdf465d06198cfbbfe76613ed3bfc:/public/javascripts/site.js

diff --git a/public/javascripts/site.js b/public/javascripts/site.js
index e0c18a27b..23ea3bc68 100644
--- a/public/javascripts/site.js
+++ b/public/javascripts/site.js
@@ -84,6 +84,20 @@ function updatelinks(lon,lat,zoom,layers,minlon,minlat,maxlon,maxlat) {
       node.style.fontStyle = 'italic';
     }
   }
+
+  node = document.getElementById("shortlinkanchor");
+  if (node) {
+    var args = getArgs(node.href);
+    var code = makeShortCode(lat, lon, zoom);
+    // little hack. may the gods of hardcoding please forgive me, or 
+    // show me the Right way to do it.
+    if (layers && (layers != "B000FTF")) {
+      args["layers"] = layers;
+      node.href = setArgs("/go/" + code, args);
+    } else {
+      node.href = "/go/" + code;
+    }
+  }
 }
 
 function getArgs(url) {
@@ -158,3 +172,34 @@ function i18n(string, keys) {
    
   return string;
 } 
+
+function makeShortCode(lat, lon, zoom) {
+    char_array = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_@";
+    var x = Math.round((lon + 180.0) * ((1 << 30) / 90.0));
+    var y = Math.round((lat +  90.0) * ((1 << 30) / 45.0));
+    // hack around the fact that JS apparently only allows 53-bit integers?!?
+    // note that, although this reduces the accuracy of the process, it's fine for
+    // z18 so we don't need to care for now.
+    var c1 = 0, c2 = 0;
+    for (var i = 31; i > 16; --i) {
+	c1 = (c1 << 1) | ((x >> i) & 1);
+	c1 = (c1 << 1) | ((y >> i) & 1);
+    }
+    for (var i = 16; i > 1; --i) {
+	c2 = (c2 << 1) | ((x >> i) & 1);
+	c2 = (c2 << 1) | ((y >> i) & 1);
+    }
+    var str = "";
+    for (var i = 0; i < Math.ceil((zoom + 8) / 3.0) && i < 5; ++i) {
+	digit = (c1 >> (24 - 6 * i)) & 0x3f;
+	str += char_array.charAt(digit);
+    }
+    for (var i = 5; i < Math.ceil((zoom + 8) / 3.0); ++i) {
+	digit = (c2 >> (24 - 6 * (i - 5))) & 0x3f;
+	str += char_array.charAt(digit);
+    }
+    for (var i = 0; i < ((zoom + 8) % 3); ++i) {
+	str += "=";
+    }
+    return str;
+}