Add support for LZMA compressed GET parameters

You can now replace the whole query string with a single `lzma`
parameter having as value an hex encoded LZMA compressed version
of the whole query string as a JSON object.

NEWS.md

@@ -5,6 +5,7 @@
 * Add last_modified field to POST layergroup response (#72)
 * Deprecate signal handler for USR1, add handler for USR2 (#71)
 * Fix support for ampersend characters in CartoCSS
+* Add support for LZMA compressed GET parameters
 
 1.1.8
 -----

lib/cartodb/server_options.js

@@ -5,6 +5,7 @@ var   _          = require('underscore')
     , mapnik     = require('mapnik')
     , crypto     = require('crypto')
     , request    = require('request')
+    , LZMA       = require('lzma/lzma_worker.js').LZMA
   ;
 
 module.exports = function(){
@@ -255,6 +256,42 @@ module.exports = function(){
      */
     me.req2params = function(req, callback){
 
+        if ( req.query.lzma ) {
+
+          // TODO: check ?
+          //console.log("type of req.query.lzma is " + typeof(req.query.lzma));
+          //console.log("req.query.lzma is " + req.query.lzma);
+
+          // Decode
+          var lzma = [];
+          for (var i=0; i<req.query.lzma.length/2; ++i) {
+            var hex = req.query.lzma.substring(i*2, i*2+2);
+            var num = parseInt(hex, "16");
+            if ( num > 127 ) num = 127-num;
+            //console.log(i + " hex: " + hex + " decodes as " + num);
+            lzma.push( num );
+          }
+
+          // Decompress
+          //console.log("LZMA decompression starts with " + lzma);
+          LZMA.decompress(
+            lzma,
+            function(result) {
+              //console.log("LZMA decompression completed, payload: "); console.dir(result);
+              try {
+                req.query = JSON.parse(result);
+                me.req2params(req, callback);
+              } catch (err) { 
+                callback(new Error('Error parsing lzma as JSON: ' + err));
+              }
+            },
+            function(percent) { // progress
+              //console.log("LZMA decompression " + percent + "%");
+            }
+          );
+          return;
+        }
+
         // Whitelist query parameters and attach format
         var good_query = ['sql', 'geom_type', 'cache_buster', 'cache_policy', 'callback', 'interactivity', 'map_key', 'api_key', 'style', 'style_version', 'style_convert' ];
         var bad_query  = _.difference(_.keys(req.query), good_query);

npm-shrinkwrap.json

@@ -332,6 +332,9 @@
     "mapnik": {
       "version": "0.7.22"
     },
+    "lzma": {
+      "version": "1.2.2"
+    },
     "semver": {
       "version": "1.1.3"
     },

package.json

@@ -28,7 +28,8 @@
         "redis": "0.7.2",
         "hiredis": "~0.1.14",
         "request": "2.9.202",
-        "mapnik": "~0.7.14"
+        "mapnik": "~0.7.14",
+        "lzma": "~1.2.2"
     },
     "devDependencies": {
         "mocha": "1.2.1",

test/acceptance/server.js

@@ -7,6 +7,7 @@ var semver      = require('semver');
 var mapnik      = require('mapnik');
 var Step        = require('step');
 var http        = require('http');
+var LZMA        = require('lzma/lzma_worker.js').LZMA;
 var SQLAPIEmu   = require(__dirname + '/../support/SQLAPIEmu.js');
 
 require(__dirname + '/../support/test_helper');
@@ -16,6 +17,27 @@ var serverOptions = require(__dirname + '/../../lib/cartodb/server_options');
 var server = new CartodbWindshaft(serverOptions);
 server.setMaxListeners(0);
 
+// Utility function to compress & encode LZMA
+function lzma_compress_to_hex(payload, mode, callback) {
+  var HEX = [ '0','1','2','3','4','5','6','7',
+              '8','9','a','b','c','d','e','f' ];
+  LZMA.compress(payload, mode, 
+    function(ints) {
+      for (var i=0; i<ints.length; ++i) {
+        if ( ints[i] < 0 ) ints[i] = 127-ints[i];
+        var hi = ints[i] >> 4;
+        var lo = ints[i] & 0x0f;
+        ints[i] = HEX[hi] + HEX[lo];
+      };
+      var hex = ints.join('');
+      callback(null, hex);
+    },
+    function(percent) {
+      //console.log("Compressing: " + percent + "%");
+    }
+  );
+}
+
 suite('server', function() {
 
     var redis_client = redis.createClient(global.environment.redis.port);
@@ -782,6 +804,41 @@ suite('server', function() {
         });
     });
 
+    test("get'ing a tile with url specified 2.1.0 style (lzma version)",  function(done){
+        var qo = {
+          style: test_style_black_210,
+          style_version: '2.1.0',
+          cache_buster: 5
+        };
+        Step (
+          function compressQuery () {
+            //console.log("Compressing starts");
+            var next = this;
+            lzma_compress_to_hex(JSON.stringify(qo), 1, this);
+            //cosole.log("compress returned " + x );
+          },
+          function sendRequest(err, lzma) {
+            //console.log("Compressing ends: " + typeof(lzma) + " - " + lzma);
+            assert.response(server, {
+                headers: {host: 'localhost'},
+                url: '/tiles/test_table/15/16046/12354.png?lzma=' + lzma,
+                method: 'GET',
+                encoding: 'binary'
+            },{}, this);
+          },
+          function checkResponse(res) {
+            assert.equal(res.statusCode, 200, res.statusCode + ': ' + res.body);
+            var ct = res.headers['content-type'];
+            assert.equal(ct, 'image/png');
+            assert.imageEqualsFile(res.body, './test/fixtures/test_table_15_16046_12354_styled_black.png',  2,
+              function(err, similarity) {
+                if (err) throw err;
+                done();
+            });
+          }
+        );
+    });
+
     // See http://github.com/Vizzuality/Windshaft-cartodb/issues/57
     test("GET'ing a tile as anonymous with style set by POST",  function(done){
       var style = querystring.stringify({style: test_style_black_210, style_version: '2.1.0'});