src/vom/decoder.js - release.js.core - Git at Google

 // Copyright 2015 The Vanadium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 /**
  * @fileoverview Represents a VOM decoder.
  * @private
  */

 module.exports = Decoder;

 var canonicalize = require('../vdl/canonicalize.js');
 var TypeDecoder = require('./type-decoder.js');
 var kind = require('../vdl/kind.js');
 var Registry = require('../vdl/registry.js');
 var types = require('../vdl/types.js');
 var util = require('../vdl/util.js');
 var unwrap = require('../vdl/type-util').unwrap;
 var wiretype = require('../gen-vdl/v.io/v23/vom');
 var nativeTypeRegistry = require('../vdl/native-type-registry');
 var Deferred = require('../lib/deferred');
 var Promise = require('../lib/promise');
 var TaskSequence = require('../lib/task-sequence');
 var promiseFor = require('../lib/async-helper').promiseFor;
 var promiseWhile = require('../lib/async-helper').promiseWhile;

 var endByte = unwrap(wiretype.WireCtrlEnd);
 var nilByte = unwrap(wiretype.WireCtrlNil);

 /**
  * Create a decoder to read objects from the provided message reader.
  * Decode has the option of returning a deeply-wrapped object, or an object only
  * wrapped at the top-level.
  * @param {module:vanadium.vom.ByteArrayMessageReader} reader The message
  * reader.
  * @param {boolean=} deepWrap Whether to deeply wrap. Defaults to false.
  * @param {module:vanadium.vom.TypeDecoder} typeDecoder The type decoder to
  * use.  This can be null.
  * @memberof module:vanadium.vom
  * @constructor
  */
 function Decoder(messageReader, deepWrap, typeDecoder) {
   this._messageReader = messageReader;
   this._typeDecoder = typeDecoder || new TypeDecoder();
   this._deepWrap = false;
   this._tasks = new TaskSequence();
 }

 /*
  * TODO(bprosnitz) We will want to be able to decode when we get callbacks.
  * Revisit this API.
  */
 /**
  * Decodes the next object off of the message reader.
  * @return {object} The next object or null if no more objects are available.
  */
 Decoder.prototype.decode = function(cb) {
   var def = new Deferred(cb);
   var decoder = this;
   this._tasks.addTask(function() {
     return decoder._messageReader.nextMessageType(decoder._typeDecoder).
       then(function(type) {
       if (type === null) {
         return null;
       }
       var reader = decoder._messageReader.rawReader;
       return decoder._decodeValue(type, reader, true);
     }).then(function(v) {
       def.resolve(v);
     }, function(err) {
       def.reject(err);
     });
   });
   return def.promise;
 };

 Decoder.prototype._decodeValue = function(t, reader, shouldWrap) {
   return this._decodeUnwrappedValue(t, reader).then(function(value) {
     // Special: JSValue should be reduced and returned as a native value.
     if (types.JSVALUE.equals(t)) {
       return canonicalize.reduce(value, types.JSVALUE);
     }

     if (nativeTypeRegistry.hasNativeType(t)) {
       return canonicalize.reduce(value, t);
     }
     // If this value should be wrapped, apply the constructor.
     if (t.kind !== kind.TYPEOBJECT && shouldWrap) {
       var Ctor = Registry.lookupOrCreateConstructor(t);
       if (Ctor.prototype._wrappedType) {
         return new Ctor(value);
       }
       if (value !== null && value !== undefined) {
         Object.defineProperty(value, 'constructor', {
           value: Ctor,
         });
       }
     }
     return value;
   });
 };

 Decoder.prototype._decodeUnwrappedValue = function(t, reader) {
   switch (t.kind) {
     case kind.BOOL:
       return reader.readBool();
     case kind.BYTE:
       return reader.readByte();
     case kind.UINT16:
     case kind.UINT32:
       return reader.readUint();
     case kind.UINT64:
       return reader.readBigUint();
     case kind.INT16:
     case kind.INT32:
       return reader.readInt();
     case kind.INT64:
       return reader.readBigInt();
     case kind.FLOAT32:
     case kind.FLOAT64:
       return reader.readFloat();
     case kind.COMPLEX64:
     case kind.COMPLEX128:
       return reader.readFloat().then(function(real) {
          return reader.readFloat().then(function(imag) {
            return {
              real: real,
              imag: imag
            };
          });
       });
     case kind.STRING:
       return reader.readString();
     case kind.ENUM:
       return this._decodeEnum(t, reader);
     case kind.LIST:
       return this._decodeList(t, reader);
     case kind.ARRAY:
       return this._decodeArray(t, reader);
     case kind.SET:
       return this._decodeSet(t, reader);
     case kind.MAP:
       return this._decodeMap(t, reader);
     case kind.STRUCT:
       return this._decodeStruct(t, reader);
     case kind.UNION:
       return this._decodeUnion(t, reader);
     case kind.ANY:
       return this._decodeAny(reader);
     case kind.OPTIONAL:
       return this._decodeOptional(t, reader);
     case kind.TYPEOBJECT:
       var decoder = this;
       var typeId;
       return reader.readUint().then(function(tId) {
         typeId = tId;
         return decoder._typeDecoder.lookupType(typeId);
       }).then(function(type) {
         if (type === undefined) {
           throw new Error('Undefined type for TYPEOBJECT id ' + typeId);
         }
         return type;
       });

     default:
       return Promise.reject(new Error('Support for decoding kind ' + t.kind +
         ' not yet implemented'));
   }
 };

 Decoder.prototype._decodeEnum = function(t, reader) {
   return reader.readUint().then(function(index) {
     if (t.labels.length <= index) {
       throw new Error('Invalid enum index ' + index);
     }
     return t.labels[index];
   });
 };

 Decoder.prototype._decodeList = function(t, reader) {
   var decoder = this;
   return reader.readUint().then(function(len) {
     return decoder._readSequence(t, len, reader);
   });
 };

 Decoder.prototype._decodeArray = function(t, reader) {
   var decoder = this;
   // Consume the zero byte at the beginning of the array.
   return reader.readByte().then(function(b) {
     if (b !== 0) {
       throw new Error('Unexpected length ' + b);
     }
     return decoder._readSequence(t, t.len, reader);
   });
 };

 Decoder.prototype._readSequence = function(t, len, reader) {
   if (t.elem.kind === kind.BYTE) {
     // Read byte sequences directly into Uint8Arrays.

     // The Uint8Array is created by calling subarray. In node, this means that
     // its buffer points to the whole binary_reader buffer. To fix this, we
     // recreate the Uint8Array here to avoid exposing it.
     return reader._readRawBytes(len).then(function(b) {
       return new Uint8Array(b);
     });
   }

   var arr = new Array(len);
   var i = 0;
   var decoder = this;
   return promiseFor(len, function() {
     return decoder._decodeValue(t.elem, reader, false).then(function(val) {
       arr[i] = val;
       i++;
     });
   }).then(function() {
     return arr;
   });
 };

 Decoder.prototype._decodeSet = function(t, reader) {
   var decoder = this;
   var s = new Set();
   return reader.readUint().then(function(len) {
     return promiseFor(len, function() {
       return decoder._decodeValue(t.key, reader, false).then(function(key) {
         s.add(key);
       });
     });
   }).then(function() {
     return s;
   });
 };

 Decoder.prototype._decodeMap = function(t, reader) {
   var decoder = this;
   return reader.readUint().then(function(len) {
     var m = new Map();
     var i = 0;
     if (len > 0) {
       return decoder._decodeValue(t.key, reader, false).then(handleKey);
     }
     return m;

     function handleKey(key) {
       return decoder._decodeValue(t.elem, reader, false).then(function(value) {
         m.set(key, value);
         i++;
         if (i < len) {
           return decoder._decodeValue(t.key, reader, false).then(handleKey);
         }
         return m;
       });
     }
   });
 };

 Decoder.prototype._decodeStruct = function(t, reader) {
   var decoder = this;
   var Ctor = Registry.lookupOrCreateConstructor(t);
   var obj = Object.create(Ctor.prototype);

   return promiseWhile(notEndByte, readField).then(function() {
     return obj;
   }).then(function(obj) {
     t.fields.forEach(function(field) {
       var name = util.uncapitalize(field.name);
       if (!obj.hasOwnProperty(name)) {
         obj[name] = unwrap(canonicalize.zero(field.type));
       }
     });
     return obj;
   });
   function notEndByte() {
     return reader.tryReadControlByte().then(function(ctrl) {
       if (ctrl === endByte) {
         return false;
       }

       if (ctrl) {
         throw new Error('Unexpected control byte ' + ctrl);
       }
       return true;
     });
   }
   function readField() {
     var name = '';
     return reader.readUint().then(function(nextIndex) {
       if (t.fields.length <= nextIndex) {
         throw new Error('Struct index ' + nextIndex + ' out of bounds');
       }
       var field = t.fields[nextIndex];
       name = util.uncapitalize(field.name);
       return decoder._decodeValue(field.type, reader, false);
     }).then(function(val) {
       obj[name] = val;
     });
   }
 };

 Decoder.prototype._decodeOptional = function(t, reader) {
   var decoder = this;
   return reader.peekByte().then(function(isNil) {
     if (isNil === nilByte) {
       // We don't have to wait for the read to finish.
       reader.readByte();
       return null;
     }
     return decoder._decodeValue(t.elem, reader, false);
   });
 };

 Decoder.prototype._decodeAny = function(reader) {
   var decoder = this;
   return reader.tryReadControlByte().then(function(ctrl) {
     if (ctrl === nilByte) {
       return null;
     }

     if (ctrl) {
       throw new Error('Unexpected control byte ' + ctrl);
     }
     var typeId;
     return reader.readUint().then(function(tId) {
       typeId = tId;
       return decoder._typeDecoder.lookupType(typeId);
     }).then(function(type) {
       if (type === undefined) {
         throw new Error('Undefined typeid ' + typeId);
       }
       return decoder._decodeValue(type, reader, true);
     });
   });
 };

 Decoder.prototype._decodeUnion = function(t, reader) {
   var decoder = this;
   var field;
   // Find the Union field that was set and decode its value.
   return reader.readUint().then(function(fieldIndex) {
     if (t.fields.length <= fieldIndex) {
       throw new Error('Union index ' + fieldIndex + ' out of bounds');
     }
     field = t.fields[fieldIndex];
     return decoder._decodeValue(field.type, reader, false);
   }).then(function(val) {
     // Return the Union with a single field set to its decoded value.
     var Ctor = Registry.lookupOrCreateConstructor(t);
     var obj = Object.create(Ctor.prototype);
     obj[util.uncapitalize(field.name)] = val;
     return obj;
   });
 };
	// Copyright 2015 The Vanadium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	/**
	* @fileoverview Represents a VOM decoder.
	* @private
	*/

	module.exports = Decoder;

	var canonicalize = require('../vdl/canonicalize.js');
	var TypeDecoder = require('./type-decoder.js');
	var kind = require('../vdl/kind.js');
	var Registry = require('../vdl/registry.js');
	var types = require('../vdl/types.js');
	var util = require('../vdl/util.js');
	var unwrap = require('../vdl/type-util').unwrap;
	var wiretype = require('../gen-vdl/v.io/v23/vom');
	var nativeTypeRegistry = require('../vdl/native-type-registry');
	var Deferred = require('../lib/deferred');
	var Promise = require('../lib/promise');
	var TaskSequence = require('../lib/task-sequence');
	var promiseFor = require('../lib/async-helper').promiseFor;
	var promiseWhile = require('../lib/async-helper').promiseWhile;

	var endByte = unwrap(wiretype.WireCtrlEnd);
	var nilByte = unwrap(wiretype.WireCtrlNil);

	/**
	* Create a decoder to read objects from the provided message reader.
	* Decode has the option of returning a deeply-wrapped object, or an object only
	* wrapped at the top-level.
	* @param {module:vanadium.vom.ByteArrayMessageReader} reader The message
	* reader.
	* @param {boolean=} deepWrap Whether to deeply wrap. Defaults to false.
	* @param {module:vanadium.vom.TypeDecoder} typeDecoder The type decoder to
	* use. This can be null.
	* @memberof module:vanadium.vom
	* @constructor
	*/
	function Decoder(messageReader, deepWrap, typeDecoder) {
	this._messageReader = messageReader;
	this._typeDecoder = typeDecoder \|\| new TypeDecoder();
	this._deepWrap = false;
	this._tasks = new TaskSequence();
	}

	/*
	* TODO(bprosnitz) We will want to be able to decode when we get callbacks.
	* Revisit this API.
	*/
	/**
	* Decodes the next object off of the message reader.
	* @return {object} The next object or null if no more objects are available.
	*/
	Decoder.prototype.decode = function(cb) {
	var def = new Deferred(cb);
	var decoder = this;
	this._tasks.addTask(function() {
	return decoder._messageReader.nextMessageType(decoder._typeDecoder).
	then(function(type) {
	if (type === null) {
	return null;
	}
	var reader = decoder._messageReader.rawReader;
	return decoder._decodeValue(type, reader, true);
	}).then(function(v) {
	def.resolve(v);
	}, function(err) {
	def.reject(err);
	});
	});
	return def.promise;
	};

	Decoder.prototype._decodeValue = function(t, reader, shouldWrap) {
	return this._decodeUnwrappedValue(t, reader).then(function(value) {
	// Special: JSValue should be reduced and returned as a native value.
	if (types.JSVALUE.equals(t)) {
	return canonicalize.reduce(value, types.JSVALUE);
	}

	if (nativeTypeRegistry.hasNativeType(t)) {
	return canonicalize.reduce(value, t);
	}
	// If this value should be wrapped, apply the constructor.
	if (t.kind !== kind.TYPEOBJECT && shouldWrap) {
	var Ctor = Registry.lookupOrCreateConstructor(t);
	if (Ctor.prototype._wrappedType) {
	return new Ctor(value);
	}
	if (value !== null && value !== undefined) {
	Object.defineProperty(value, 'constructor', {
	value: Ctor,
	});
	}
	}
	return value;
	});
	};

	Decoder.prototype._decodeUnwrappedValue = function(t, reader) {
	switch (t.kind) {
	case kind.BOOL:
	return reader.readBool();
	case kind.BYTE:
	return reader.readByte();
	case kind.UINT16:
	case kind.UINT32:
	return reader.readUint();
	case kind.UINT64:
	return reader.readBigUint();
	case kind.INT16:
	case kind.INT32:
	return reader.readInt();
	case kind.INT64:
	return reader.readBigInt();
	case kind.FLOAT32:
	case kind.FLOAT64:
	return reader.readFloat();
	case kind.COMPLEX64:
	case kind.COMPLEX128:
	return reader.readFloat().then(function(real) {
	return reader.readFloat().then(function(imag) {
	return {
	real: real,
	imag: imag
	};
	});
	});
	case kind.STRING:
	return reader.readString();
	case kind.ENUM:
	return this._decodeEnum(t, reader);
	case kind.LIST:
	return this._decodeList(t, reader);
	case kind.ARRAY:
	return this._decodeArray(t, reader);
	case kind.SET:
	return this._decodeSet(t, reader);
	case kind.MAP:
	return this._decodeMap(t, reader);
	case kind.STRUCT:
	return this._decodeStruct(t, reader);
	case kind.UNION:
	return this._decodeUnion(t, reader);
	case kind.ANY:
	return this._decodeAny(reader);
	case kind.OPTIONAL:
	return this._decodeOptional(t, reader);
	case kind.TYPEOBJECT:
	var decoder = this;
	var typeId;
	return reader.readUint().then(function(tId) {
	typeId = tId;
	return decoder._typeDecoder.lookupType(typeId);
	}).then(function(type) {
	if (type === undefined) {
	throw new Error('Undefined type for TYPEOBJECT id ' + typeId);
	}
	return type;
	});

	default:
	return Promise.reject(new Error('Support for decoding kind ' + t.kind +
	' not yet implemented'));
	}
	};

	Decoder.prototype._decodeEnum = function(t, reader) {
	return reader.readUint().then(function(index) {
	if (t.labels.length <= index) {
	throw new Error('Invalid enum index ' + index);
	}
	return t.labels[index];
	});
	};

	Decoder.prototype._decodeList = function(t, reader) {
	var decoder = this;
	return reader.readUint().then(function(len) {
	return decoder._readSequence(t, len, reader);
	});
	};

	Decoder.prototype._decodeArray = function(t, reader) {
	var decoder = this;
	// Consume the zero byte at the beginning of the array.
	return reader.readByte().then(function(b) {
	if (b !== 0) {
	throw new Error('Unexpected length ' + b);
	}
	return decoder._readSequence(t, t.len, reader);
	});
	};

	Decoder.prototype._readSequence = function(t, len, reader) {
	if (t.elem.kind === kind.BYTE) {
	// Read byte sequences directly into Uint8Arrays.

	// The Uint8Array is created by calling subarray. In node, this means that
	// its buffer points to the whole binary_reader buffer. To fix this, we
	// recreate the Uint8Array here to avoid exposing it.
	return reader._readRawBytes(len).then(function(b) {
	return new Uint8Array(b);
	});
	}

	var arr = new Array(len);
	var i = 0;
	var decoder = this;
	return promiseFor(len, function() {
	return decoder._decodeValue(t.elem, reader, false).then(function(val) {
	arr[i] = val;
	i++;
	});
	}).then(function() {
	return arr;
	});
	};

	Decoder.prototype._decodeSet = function(t, reader) {
	var decoder = this;
	var s = new Set();
	return reader.readUint().then(function(len) {
	return promiseFor(len, function() {
	return decoder._decodeValue(t.key, reader, false).then(function(key) {
	s.add(key);
	});
	});
	}).then(function() {
	return s;
	});
	};

	Decoder.prototype._decodeMap = function(t, reader) {
	var decoder = this;
	return reader.readUint().then(function(len) {
	var m = new Map();
	var i = 0;
	if (len > 0) {
	return decoder._decodeValue(t.key, reader, false).then(handleKey);
	}
	return m;

	function handleKey(key) {
	return decoder._decodeValue(t.elem, reader, false).then(function(value) {
	m.set(key, value);
	i++;
	if (i < len) {
	return decoder._decodeValue(t.key, reader, false).then(handleKey);
	}
	return m;
	});
	}
	});
	};

	Decoder.prototype._decodeStruct = function(t, reader) {
	var decoder = this;
	var Ctor = Registry.lookupOrCreateConstructor(t);
	var obj = Object.create(Ctor.prototype);

	return promiseWhile(notEndByte, readField).then(function() {
	return obj;
	}).then(function(obj) {
	t.fields.forEach(function(field) {
	var name = util.uncapitalize(field.name);
	if (!obj.hasOwnProperty(name)) {
	obj[name] = unwrap(canonicalize.zero(field.type));
	}
	});
	return obj;
	});
	function notEndByte() {
	return reader.tryReadControlByte().then(function(ctrl) {
	if (ctrl === endByte) {
	return false;
	}

	if (ctrl) {
	throw new Error('Unexpected control byte ' + ctrl);
	}
	return true;
	});
	}
	function readField() {
	var name = '';
	return reader.readUint().then(function(nextIndex) {
	if (t.fields.length <= nextIndex) {
	throw new Error('Struct index ' + nextIndex + ' out of bounds');
	}
	var field = t.fields[nextIndex];
	name = util.uncapitalize(field.name);
	return decoder._decodeValue(field.type, reader, false);
	}).then(function(val) {
	obj[name] = val;
	});
	}
	};

	Decoder.prototype._decodeOptional = function(t, reader) {
	var decoder = this;
	return reader.peekByte().then(function(isNil) {
	if (isNil === nilByte) {
	// We don't have to wait for the read to finish.
	reader.readByte();
	return null;
	}
	return decoder._decodeValue(t.elem, reader, false);
	});
	};

	Decoder.prototype._decodeAny = function(reader) {
	var decoder = this;
	return reader.tryReadControlByte().then(function(ctrl) {
	if (ctrl === nilByte) {
	return null;
	}

	if (ctrl) {
	throw new Error('Unexpected control byte ' + ctrl);
	}
	var typeId;
	return reader.readUint().then(function(tId) {
	typeId = tId;
	return decoder._typeDecoder.lookupType(typeId);
	}).then(function(type) {
	if (type === undefined) {
	throw new Error('Undefined typeid ' + typeId);
	}
	return decoder._decodeValue(type, reader, true);
	});
	});
	};

	Decoder.prototype._decodeUnion = function(t, reader) {
	var decoder = this;
	var field;
	// Find the Union field that was set and decode its value.
	return reader.readUint().then(function(fieldIndex) {
	if (t.fields.length <= fieldIndex) {
	throw new Error('Union index ' + fieldIndex + ' out of bounds');
	}
	field = t.fields[fieldIndex];
	return decoder._decodeValue(field.type, reader, false);
	}).then(function(val) {
	// Return the Union with a single field set to its decoded value.
	var Ctor = Registry.lookupOrCreateConstructor(t);
	var obj = Object.create(Ctor.prototype);
	obj[util.uncapitalize(field.name)] = val;
	return obj;
	});
	};