lvl.js : implement store api using leveldb

storage/lvl.js

@@ -0,0 +1,71 @@
+var level=require("level");
+
+module.exports.create = function(conf,cb){
+    console.log("Loading leveldb");
+
+    var db=level(conf.levelPath||'./test.level.db'),
+        indices={},
+        Channel={};
+
+    var makeChannel=function(cName){
+        Channel[cName]={
+            lastModified:0,
+            messages:[],
+        };
+    },
+    makeIndex=function(cName){
+        // initializing to negative one means we can increment on inserts
+        // so we always start from zero.
+        indices[cName]=-1;
+    },
+    loadIndex=function(cName, out){
+        indices[cName]=parseInt(out);
+        typeof indices[cName] !== 'number' && 
+            console.error("FOUND A NON-NUMERIC INDEX for channel: %s", cName);
+    },
+    getIndex=function(cName,f){
+        if(typeof indices[cName] !== 'undefined'){
+            f(indices[cName]);
+        }else{
+            // get and increment the channelIndex
+            db.get(cName+'=>index',function(e,out){
+                if(e){
+                    // it doesn't exist, so initialize it
+                    makeIndex(cName);
+                }else{
+                    // it exists. parse it
+                    loadIndex(cName,out);
+                }
+                f(indices[cName]);
+            });
+        }
+    };
+
+    cb({
+        message: function(cName,content,cb){
+            getIndex(cName,function(index){
+                var index = ++indices[cName];
+                db.put(cName+'=>index', ''+index,function(e){
+                    if(e) console.error(e);
+                });
+                db.put(cName+'=>'+index, content, function(err){
+                    if(err){
+                        console.log(err);
+                    }
+                    cb();
+                });
+            });
+        },
+        getMessages: function(cName, cb){
+            /* get all messages relating to a channel */
+            getIndex(cName, function(index){
+                for(var i=index;i>=0;i--){
+                    db.get(cName+'=>'+i,function(e,out){
+                        if(e) return console.error(e);
+                        cb(out);
+                    });
+                }             
+            });
+        },
+    });
+};