add opts.readonly

Author: mafintosh

README.md

@@ -87,9 +87,15 @@ stream you are missing. Please note that this might not guarantee leveldb snapsh
 
 ## API
 
-#### `multileveldown.server(db)`
+#### `multileveldown.server(db, [options])`
 
-Returns a new duplex server stream that you should connect with a client
+Returns a new duplex server stream that you should connect with a client. Options include
+
+``` js
+{
+  readonly: true // make the database be accessible as read only
+}
+```
 
 #### `clientDb = multileveldown.client([options])`
 

server.js

@@ -12,6 +12,7 @@ var DECODERS = [
 ]
 
 module.exports = function (db, opts) {
+  var readonly = !!(opts && opts.readonly)
   var decode = lpstream.decode()
   var encode = lpstream.encode()
   var stream = duplexify(decode, encode)
@@ -44,12 +45,22 @@ module.exports = function (db, opts) {
         return
       }
 
-      switch (tag) {
-        case 0: return onget(req)
-        case 1: return onput(req)
-        case 2: return ondel(req)
-        case 3: return onbatch(req)
-        case 4: return oniterator(req)
+      if (readonly) {
+        switch (tag) {
+          case 0: return onget(req)
+          case 1: return onreadonly(req)
+          case 2: return onreadonly(req)
+          case 3: return onreadonly(req)
+          case 4: return oniterator(req)
+        }
+      } else {
+        switch (tag) {
+          case 0: return onget(req)
+          case 1: return onput(req)
+          case 2: return ondel(req)
+          case 3: return onbatch(req)
+          case 4: return oniterator(req)
+        }
       }
     })
 
@@ -79,6 +90,10 @@ module.exports = function (db, opts) {
       })
     }
 
+    function onreadonly (req) {
+      callback(req.id, new Error('Database is readonly'))
+    }
+
     function onbatch (req) {
       down.batch(req.ops, function (err) {
         callback(req.id, err)

test/basic.js

@@ -37,6 +37,26 @@ tape('put', function (t) {
   })
 })
 
+tape('readonly', function (t) {
+  var db = levelup('no-location', {db: memdown})
+
+  db.put('hello', 'verden')
+
+  var stream = multileveldown.server(db, {readonly: true})
+  var client = multileveldown.client()
+
+  stream.pipe(client.createRpcStream()).pipe(stream)
+
+  client.put('hello', 'world', function (err) {
+    t.ok(err, 'put failed')
+    client.get('hello', function (err, value) {
+      t.error(err, 'no err')
+      t.same(value, 'verden', 'old value')
+      t.end()
+    })
+  })
+})
+
 tape('del', function (t) {
   var db = levelup('no-location', {db: memdown})
   var stream = multileveldown.server(db)