WRITER: Basic writing of (short) strings

codeaholics · Jul 27, 2013 · f8f0ec1 · f8f0ec1
1 parent e7e576f
commit f8f0ec1
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Showing 2 changed files with 82 additions and 11 deletions.
diff --git a/lib/writer.js b/lib/writer.js
@@ -33,13 +33,12 @@ function Writer(options) {
     options = options || {};
 
     var self = this;
-    var currentDatabase = 0;
+    var currentDatabase = undefined;
     var encoding = options.encoding || 'utf8';
     var crc = new Crc64();
-    var emptyCrc = new Buffer(8);
+    var outputBuffers = [];
     var expectedNext = ['header'];
-
-    emptyCrc.fill(0);
+    var handlers = {};
 
     self._transform = function(obj, encoding, cb) {
         try {
@@ -50,7 +49,76 @@ function Writer(options) {
     }
 
     function handleObject(obj, cb) {
-        if (!obj || !obj.type || expectedNext.indexOf(obj.type) == -1) throw new Error('Unexpected object received');
-        cb();
+        if (!obj || !obj.type) throw new Error('Unexpected object received');
+        if (expectedNext.indexOf(obj.type) == -1) throw new Error('Unexpected object received: ' + obj.type + '; was expecting one of: ' + expectedNext);
+
+        handlers[obj.type](obj, function() {
+            if (outputBuffers.length) {
+                self.push(Buffer.concat(outputBuffers));
+                outputBuffers = [];
+            }
+            expectedNext = Array.prototype.slice.call(arguments, 0);
+            cb();
+        });
+    }
+
+    handlers.header = function(obj, next) {
+        var header = 'REDIS' + ('000' + obj.version).slice(-4);
+        output(header);
+        next('database', 'end');
+    }
+
+    handlers.database = function(obj, next) {
+        // don't do anything explicit with database objects; switch databases based on the key objects
+        next('database', 'key', 'end');
+    }
+
+    handlers.key = function(obj, next) {
+        if (obj.database != currentDatabase) {
+            switchDatabase(obj.database);
+        }
+
+        handlers[obj.rtype + 'Key'](obj);
+
+        next('database', 'key', 'end');
+    }
+
+    handlers.end = function(obj, next) {
+        output(new Buffer([0xFF]));
+        // TODO: CRC
+        next();
+    }
+
+    handlers.stringKey = function(obj) {
+        output(new Buffer([0x00]));
+        outputBytes(new Buffer(obj.key, encoding));
+        outputBytes(new Buffer(obj.value, encoding));
+    }
+
+    function switchDatabase(n) {
+        output(new Buffer([0xFE]));
+        outputLengthEncoding(n, false);
+        currentDatabase = n;
+    }
+
+    function outputLengthEncoding(n, special) {
+        if (n < 0) throw new Error('Cannot write negative length encoding: ' + n);
+
+        if (!special && n <= 0x3F) {
+            return output(new Buffer([n]));
+        } else {
+            throw new Error('Failed to write length encoding: ' + n);
+        }
+    }
+
+    function outputBytes(buffer) {
+        outputLengthEncoding(buffer.length, false);
+        output(buffer);
+    }
+
+    function output(data) {
+        if (data instanceof Buffer) return outputBuffers.push(data);
+        if (typeof(data) == 'string') return outputBuffers.push(new Buffer(data, 'ascii'));
+        throw new Error('Unknown output data type');
     }
 }
diff --git a/test/writer.js b/test/writer.js
@@ -22,8 +22,8 @@ var Parser = require('../rdb-tools').Parser,
 
 describe('Writer', function() {
     describe('should round-trip', function() {
-        _.each(fs.readdirSync('test/dumps'), function(f) {
-           it.skip(f, roundTripTest.bind(null, f));
+        _.each(fs.readdirSync('test/dumps'), function(f, i) {
+            if (['empty_database.rdb', 'multiple_databases.rdb'].indexOf(f) != -1) it(f, roundTripTest.bind(null, f));
         });
     });
 
@@ -32,7 +32,8 @@ describe('Writer', function() {
                 ['string', 'hello world'],
                 ['null', null],
                 ['undefined', undefined],
-                ['object without type', {}]], function(data) {
+                ['object without type', {}],
+                ['wrong type of object', {type: 'database'}]], function(data) {
             it(data[0], simpleErrorTest.bind(null, data[1]));
         });
     });
@@ -62,19 +63,21 @@ function roundTripTest(f, done) {
         outputCaptives = [];
 
     inputCaptor._transform = function(obj, encoding, cb) {
+        delete obj.offset;
         inputCaptives.push(obj);
         this.push(obj);
         cb();
     }
 
     outputCaptor._write = function(obj, encoding, cb) {
+        delete obj.offset;
         outputCaptives.push(obj);
         cb();
     }
 
     outputCaptor.on('finish', function() {
-        // TODO: check the input and output captive match
-        done('not yet testing');
+        assert.deepEqual(outputCaptives, inputCaptives);
+        done();
     });
 
     inputStream.pipe(parser).pipe(inputCaptor).pipe(writer).pipe(reparser).pipe(outputCaptor);