Merge pull request #20 from dertseha/flac-ignoredLastBlock

Flac ignored last block

lib/flac.js

@@ -1,12 +1,123 @@
+/* jshint node:true, sub:true, globalstrict:true */
+"use strict";
+
 var util = require('util');
 var events = require('events');
 var strtok = require('strtok');
-var fs = require('fs');
 var common = require('./common');
 
+var DataDecoder = function(data) {
+  this.data = data;
+  this.offset = 0;
+};
+
+DataDecoder.prototype.readInt32 = function() {
+  var value = strtok.UINT32_LE.get(this.data, this.offset);
+
+  this.offset += 4;
+
+  return value;
+};
+
+DataDecoder.prototype.readStringUtf8 = function() {
+  var len = this.readInt32();
+  var value = this.data.toString('utf8', this.offset, this.offset + len);
+
+  this.offset += len;
+
+  return value;
+};
+
+var finishedState = {
+  parse: function(context) {
+    return this;
+  },
+  getExpectedType: function() {
+    return strtok.DONE;
+  }
+};
+
+var BlockDataState = function(type, length, nextStateFactory) {
+  this.type = type;
+  this.length = length;
+  this.nextStateFactory = nextStateFactory;
+};
+
+BlockDataState.prototype.parse = function(context, data) {
+  if (this.type === 4) {
+    var decoder = new DataDecoder(data);
+    var vendorString = decoder.readStringUtf8();
+    var commentListLength = decoder.readInt32();
+    var comment;
+    var split;
+    var i;
+
+    for (i = 0; i < commentListLength; i++) {
+      comment = decoder.readStringUtf8();
+      split = comment.split('=');
+      context.emit(split[0].toUpperCase(), split[1]);
+    }
+  } else if (this.type === 6) {
+    var picture = common.readVorbisPicture(data);
+    context.emit('METADATA_BLOCK_PICTURE', picture);
+  }
+
+  return this.nextStateFactory();
+};
+
+BlockDataState.prototype.getExpectedType = function() {
+  return new strtok.BufferType(this.length);
+};
+
+var blockHeaderState = {
+  parse: function(context, data) {
+    var header = {
+      lastBlock: (data[0] & 0x80) == 0x80,
+      type: data[0] & 0x7f,
+      length: strtok.UINT24_BE.get(data, 1)
+    };
+    var followingStateFactory = header.lastBlock ? function() {
+        context.emit('done');
+        return finishedState;
+      } : function() {
+        return blockHeaderState;
+      };
+
+    return new BlockDataState(header.type, header.length, followingStateFactory);
+  },
+  getExpectedType: function() {
+    return new strtok.BufferType(4);
+  }
+};
+
+var idState = {
+  parse: function(context, data) {
+    if (data !== 'fLaC') {
+      throw new Error('expected flac header but was not found');
+    }
+
+    return blockHeaderState;
+  },
+  getExpectedType: function() {
+    return new strtok.StringType(4);
+  }
+};
+
+var startState = {
+  parse: function(context) {
+    return idState;
+  },
+  getExpectedType: function() {
+    return strtok.DONE;
+  }
+};
+
 var Flac = module.exports = function(stream) {
   events.EventEmitter.call(this);
   this.stream = stream;
+
+  this.currentState = startState;
+
   this.parse();
 };
 
@@ -17,66 +128,11 @@ Flac.prototype.parse = function() {
 
   strtok.parse(self.stream, function(v, cb) {
     try {
-      if (!v) {
-        cb.position = 'ID';
-        return new strtok.StringType(4);
-      }
-
-      if (cb.position === 'ID') {
-        if (v !== 'fLaC') {
-          throw new Error('expected flac header but was not found');
-        }
-
-        cb.position = 'METADATA_BLOCK_HEADER';
-        return new strtok.BufferType(4);
-      }
-
-      if (cb.position === 'METADATA_BLOCK_HEADER') {
-        cb.blockHeader = {
-          last_metadata_block: (v[0] & 0x80) == 0x80,
-          block_type: v[0] & 0x7f,
-          length: strtok.UINT24_BE.get(v, 1)
-        }
-
-        if (cb.blockHeader.last_metadata_block) {
-          self.emit('done');
-          return strtok.DONE;
-        }
-
-        cb.position = 'METADATA_BLOCK_DATA';
-        return new strtok.BufferType(cb.blockHeader.length);
-      }
-
-      if (cb.position === 'METADATA_BLOCK_DATA') {
-        if (cb.blockHeader.block_type === 4) {
-          var offset = 0;
-          var vendorLen = strtok.UINT32_LE.get(v, offset);
-          offset += 4;
-          var vendorString = v.toString('utf8', offset, offset += vendorLen);
-          var commentListLength = strtok.UINT32_LE.get(v, offset);
-          offset += 4;
-
-          for (var i = 0; i < commentListLength; i++) {
-            var len = strtok.UINT32_LE.get(v, offset);
-            offset += 4;
-            var comment = v.toString('utf8', offset, offset += len);
-            var split = comment.split('=');
-            self.emit(split[0].toUpperCase(), split[1]);
-          }
-        }
-        if (cb.blockHeader.block_type === 6) {
-          var picture = common.readVorbisPicture(v);
-          self.emit('METADATA_BLOCK_PICTURE', picture);
-        }
-
-        cb.position = 'METADATA_BLOCK_HEADER';
-        return new strtok.BufferType(4);
-      }
-
-
+      self.currentState = self.currentState.parse(self, v);
     } catch (exception) {
+      self.currentState = finishedState;
       self.emit('done', exception);
-      return strtok.DONE;
     }
+    return self.currentState.getExpectedType();
   });
 };