tools/ddbg.dart - sdk.git - Git at Google

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 // Simple interactive debugger shell that connects to the Dart VM's debugger
 // connection port.

 #import("dart:io");
 #import("dart:json");
 #import("dart:math", prefix: "Math");
 #import("dart:utf");


 Map<int, Completer> outstandingCommands;

 Socket vmSock;
 String vmData;
 OutputStream vmStream;
 int seqNum = 0;
 int isolate_id = -1;

 bool verbose = false;

 // The current stack trace, while the VM is paused. It's a list
 // of activation frames.
 List stackTrace;

 // The current activation frame, while the VM is paused.
 Map curFrame;


 void printHelp() {
   print("""
   q   Quit debugger shell
   bt  Show backtrace
   r   Resume execution
   s   Single step
   so  Step over
   si  Step into
   sbp [<file>] <line> Set breakpoint
   rbp <id> Remove breakpoint with given id
   po <id> Print object info for given id
   pl <id> <idx> [<len>] Print list element/slice
   pc <id> Print class info for given id
   ll  List loaded libraries
   plib <id> Print library info for given library id
   slib <id> <true|false> Set library id debuggable
   pg <id> Print all global variables visible within given library id
   ls <lib_id> List loaded scripts in library
   gs <lib_id> <script_url> Get source text of script in library
   epi <none|all|unhandled>  Set exception pause info
   i <id> Interrupt execution of given isolate id
   h   Print help
 """);
 }


 void quitShell() {
   vmStream.close();
   vmSock.close();
   stdin.close();
 }


 Future sendCmd(Map<String, dynamic> cmd) {
   var completer = new Completer();
   int id = cmd["id"];
   outstandingCommands[id] = completer;
   if (verbose) {
     print("sending: '${JSON.stringify(cmd)}'");
   }
   vmStream.writeString(JSON.stringify(cmd));
   return completer.future;
 }


 void processCommand(String cmdLine) {
   seqNum++;
   var args = cmdLine.split(' ');
   if (args.length == 0) {
     return;
   }
   var command = args[0];
   var simple_commands =
       { 'r':'resume', 's':'stepOver', 'si':'stepInto', 'so':'stepOut'};
   if (simple_commands[command] != null) {
     var cmd = { "id": seqNum,
                 "command": simple_commands[command],
                 "params": { "isolateId" : isolate_id } };
     sendCmd(cmd).then((result) => handleGenericResponse(result));
     stackTrace = curFrame = null;
   } else if (command == "bt") {
     var cmd = { "id": seqNum,
                 "command": "getStackTrace",
                 "params": { "isolateId" : isolate_id } };
     sendCmd(cmd).then((result) => handleStackTraceResponse(result));
   } else if (command == "ll") {
     var cmd = { "id": seqNum,
                 "command": "getLibraries",
                 "params": { "isolateId" : isolate_id } };
     sendCmd(cmd).then((result) => handleGetLibraryResponse(result));
   } else if (command == "sbp" && args.length >= 2) {
     var url, line;
     if (args.length == 2) {
       url = stackTrace[0]["location"]["url"];
       line = Math.parseInt(args[1]);
     } else {
       url = args[1];
       line = Math.parseInt(args[2]);
     }
     var cmd = { "id": seqNum,
                 "command": "setBreakpoint",
                 "params": { "isolateId" : isolate_id,
                             "url": url,
                             "line": line }};
     sendCmd(cmd).then((result) => handleSetBpResponse(result));
   } else if (command == "rbp" && args.length == 2) {
     var cmd = { "id": seqNum,
                 "command": "removeBreakpoint",
                 "params": { "isolateId" : isolate_id,
                             "breakpointId": Math.parseInt(args[1]) } };
     sendCmd(cmd).then((result) => handleGenericResponse(result));
   } else if (command == "ls" && args.length == 2) {
     var cmd = { "id": seqNum,
                 "command": "getScriptURLs",
                 "params": { "isolateId" : isolate_id,
                             "libraryId": Math.parseInt(args[1]) } };
     sendCmd(cmd).then((result) => handleGetScriptsResponse(result));
   } else if (command == "po" && args.length == 2) {
     var cmd = { "id": seqNum,
                 "command": "getObjectProperties",
                 "params": { "isolateId" : isolate_id,
                             "objectId": Math.parseInt(args[1]) } };
     sendCmd(cmd).then((result) => handleGetObjPropsResponse(result));
   } else if (command == "pl" && args.length >= 3) {
      var cmd;
      if (args.length == 3) {
        cmd = { "id": seqNum,
                "command": "getListElements",
                "params": { "isolateId" : isolate_id,
                            "objectId": Math.parseInt(args[1]),
                            "index": Math.parseInt(args[2]) } };
     } else {
        cmd = { "id": seqNum,
                "command": "getListElements",
                "params": { "isolateId" : isolate_id,
                            "objectId": Math.parseInt(args[1]),
                            "index": Math.parseInt(args[2]),
                            "length": Math.parseInt(args[3]) } };
     }
     sendCmd(cmd).then((result) => handleGetListResponse(result));
   } else if (command == "pc" && args.length == 2) {
     var cmd = { "id": seqNum,
                 "command": "getClassProperties",
                 "params": { "isolateId" : isolate_id,
                             "classId": Math.parseInt(args[1]) } };
     sendCmd(cmd).then((result) => handleGetClassPropsResponse(result));
   } else if (command == "plib" && args.length == 2) {
     var cmd = { "id": seqNum,
                 "command": "getLibraryProperties",
                 "params": {"isolateId" : isolate_id,
                            "libraryId": Math.parseInt(args[1]) } };
     sendCmd(cmd).then((result) => handleGetLibraryPropsResponse(result));
   } else if (command == "slib" && args.length == 3) {
     var cmd = { "id": seqNum,
                 "command": "setLibraryProperties",
                 "params": {"isolateId" : isolate_id,
                            "libraryId": Math.parseInt(args[1]),
                            "debuggingEnabled": args[2] } };
     sendCmd(cmd).then((result) => handleSetLibraryPropsResponse(result));
   } else if (command == "pg" && args.length == 2) {
     var cmd = { "id": seqNum,
                 "command": "getGlobalVariables",
                 "params": { "isolateId" : isolate_id,
                             "libraryId": Math.parseInt(args[1]) } };
     sendCmd(cmd).then((result) => handleGetGlobalVarsResponse(result));
   } else if (command == "gs" && args.length == 3) {
     var cmd = { "id": seqNum,
                 "command":  "getScriptSource",
                 "params": { "isolateId" : isolate_id,
                             "libraryId": Math.parseInt(args[1]),
                             "url": args[2] } };
     sendCmd(cmd).then((result) => handleGetSourceResponse(result));
   } else if (command == "epi" && args.length == 2) {
     var cmd = { "id": seqNum,
                 "command":  "setPauseOnException",
                 "params": { "isolateId" : isolate_id,
                             "exceptions": args[1] } };
     sendCmd(cmd).then((result) => handleGenericResponse(result));
   } else if (command == "i" && args.length == 2) {
     var cmd = { "id": seqNum,
                 "command": "interrupt",
                 "params": { "isolateId": Math.parseInt(args[1]) } };
     sendCmd(cmd).then((result) => handleGenericResponse(result));
   } else if (command == "q") {
     quitShell();
   } else if (command == "h") {
     printHelp();
   } else {
     print("command '$command' not understood, try h for help");
   }
 }


 String remoteObject(value) {
   var kind = value["kind"];
   var text = value["text"];
   var id = value["objectId"];
   if (kind == "string") {
     return "(string, id $id) '$text'";
   } else if (kind == "list") {
     var len = value["length"];
     return "(list, id $id, len $len) $text";
   } else if (kind == "object") {
     return "(obj, id $id) $text";
   } else {
     return "$text";
   }
 }


 printNamedObject(obj) {
   var name = obj["name"];
   var value = obj["value"];
   print("  $name = ${remoteObject(value)}");
 }


 handleGetObjPropsResponse(response) {
   Map props = response["result"];
   int class_id = props["classId"];
   if (class_id == -1) {
     print("  null");
     return;
   }
   List fields = props["fields"];
   print("  class id: $class_id");
   for (int i = 0; i < fields.length; i++) {
     printNamedObject(fields[i]);
   }
 }

 handleGetListResponse(response) {
   Map result = response["result"];
   if (result["elements"] != null) {
     // List slice.
     var index = result["index"];
     var length = result["length"];
     List elements = result["elements"];
     assert(length == elements.length);
     for (int i = 0; i < length; i++) {
       var kind = elements[i]["kind"];
       var text = elements[i]["text"];
       print("  ${index + i}: ($kind) $text");
     }
   } else {
     // One element, a remote object.
     print(result);
     print("  ${remoteObject(result)}");
   }
 }


 handleGetClassPropsResponse(response) {
   Map props = response["result"];
   assert(props["name"] != null);
   int libId = props["libraryId"];
   assert(libId != null);
   print("  class ${props["name"]} (library id: $libId)");
   List fields = props["fields"];
   if (fields.length > 0) {
     print("  static fields:");
     for (int i = 0; i < fields.length; i++) {
       printNamedObject(fields[i]);
     }
   }
 }


 handleGetLibraryPropsResponse(response) {
   Map props = response["result"];
   assert(props["url"] != null);
   print("  library url: ${props["url"]}");
   assert(props["debuggingEnabled"] != null);
   print("  debugging enabled: ${props["debuggingEnabled"]}");
   List imports = props["imports"];
   assert(imports != null);
   if (imports.length > 0) {
     print("  imports:");
     for (int i = 0; i < imports.length; i++) {
       print("    id ${imports[i]["libraryId"]} prefix ${imports[i]["prefix"]}");
     }
   }
   List globals = props["globals"];
   assert(globals != null);
   if (globals.length > 0) {
     print("  global variables:");
     for (int i = 0; i < globals.length; i++) {
       printNamedObject(globals[i]);
     }
   }
 }


 handleSetLibraryPropsResponse(response) {
   Map props = response["result"];
   assert(props["debuggingEnabled"] != null);
   print("  debugging enabled: ${props["debuggingEnabled"]}");
 }


 handleGetGlobalVarsResponse(response) {
   List globals = response["result"]["globals"];
   for (int i = 0; i < globals.length; i++) {
     printNamedObject(globals[i]);
   }
 }


 handleGetSourceResponse(response) {
   Map result = response["result"];
   String source = result["text"];
   print("Source text:\n$source\n--------");
 }


 void handleGetLibraryResponse(response) {
   Map result = response["result"];
   List libs = result["libraries"];
   print("Loaded libraries:");
   print(libs);
   for (int i = 0; i < libs.length; i++) {
     print("  ${libs[i]["id"]} ${libs[i]["url"]}");
   }
 }


 void handleGetScriptsResponse(response) {
   Map result = response["result"];
   List urls = result["urls"];
   print("Loaded scripts:");
   for (int i = 0; i < urls.length; i++) {
     print("  $i ${urls[i]}");
   }
 }


 void handleSetBpResponse(response) {
   Map result = response["result"];
   var id = result["breakpointId"];
   assert(id != null);
   print("Set BP $id");
 }


 void handleGenericResponse(response) {
   if (response["error"] != null) {
     print("Error: ${response["error"]}");
   }
 }


 void handleStackTraceResponse(response) {
   Map result = response["result"];
   List callFrames = result["callFrames"];
   assert(callFrames != null);
   printStackTrace(callFrames);
 }


 void printStackFrame(frame_num, Map frame) {
   var fname = frame["functionName"];
   var libId = frame["libraryId"];
   var url = frame["location"]["url"];
   var line = frame["location"]["lineNumber"];
   print("$frame_num  $fname ($url:$line) (lib $libId)");
   List locals = frame["locals"];
   for (int i = 0; i < locals.length; i++) {
     printNamedObject(locals[i]);
   }
 }


 void printStackTrace(List frames) {
   for (int i = 0; i < frames.length; i++) {
     printStackFrame(i, frames[i]);
   }
 }


 void handlePausedEvent(msg) {
   assert(msg["params"] != null);
   var reason = msg["params"]["reason"];
   isolate_id = msg["params"]["id"];
   stackTrace = msg["params"]["callFrames"];
   assert(stackTrace != null);
   assert(stackTrace.length >= 1);
   curFrame = stackTrace[0];
   if (reason == "breakpoint") {
     print("Isolate $isolate_id paused on breakpoint");
   } else if (reason == "interrupted") {
     print("Isolate $isolate_id paused due to an interrupt");
   } else {
     assert(reason == "exception");
     var excObj = msg["params"]["exception"];
     print("Isolate $isolate_id paused on exception");
     print(remoteObject(excObj));
   }
   print("Stack trace:");
   printStackTrace(stackTrace);
 }


 void processVmMessage(String json) {
   var msg = JSON.parse(json);
   if (msg == null) {
     return;
   }
   var event = msg["event"];
   if (event == "paused") {
     handlePausedEvent(msg);
     return;
   }
   if (event == "breakpointResolved") {
     Map params = msg["params"];
     assert(params != null);
     print("BP ${params["breakpointId"]} resolved and "
           "set at line ${params["line"]}.");
     return;
   }
   if (event == "isolate") {
     Map params = msg["params"];
     assert(params != null);
     print("Isolate ${params["id"]} has been ${params["reason"]}.");
     return;
   }
   if (msg["id"] != null) {
     var id = msg["id"];
     if (outstandingCommands.containsKey(id)) {
       if (msg["error"] != null) {
         print("VM says: ${msg["error"]}");
       } else {
         var completer = outstandingCommands[id];
         completer.complete(msg);
       }
       outstandingCommands.remove(id);
     }
   }
 }


 void processVmData(String data) {
   final printMessages = false;
   if (vmData == null || vmData.length == 0) {
     vmData = data;
   } else {
     vmData = vmData.concat(data);
   }
   int msg_len = jsonObjectLength(vmData);
   if (printMessages && msg_len == 0) {
     print("have partial or illegal json message"
           " of ${vmData.length} chars:\n'$vmData'");
     return;
   }
   while (msg_len > 0 && msg_len <= vmData.length) {
     if (msg_len == vmData.length) {
       if (printMessages) { print("have one full message:\n$vmData"); }
       processVmMessage(vmData);
       vmData = null;
       return;
     }
     if (printMessages) { print("at least one message: '$vmData'"); }
     var msg = vmData.substring(0, msg_len);
     if (printMessages) { print("first message: $msg"); }
     processVmMessage(msg);
     vmData = vmData.substring(msg_len);
     msg_len = jsonObjectLength(vmData);
   }
   if (printMessages) { print("leftover vm data '$vmData'"); }
 }

 /**
  * Skip past a JSON object value.
  * The object value must start with '{' and continues to the
  * matching '}'. No attempt is made to otherwise validate the contents
  * as JSON. If it is invalid, a later [JSON.parse] will fail.
  */
 int jsonObjectLength(String string) {
   int skipWhitespace(int index) {
     while (index < string.length) {
       String char = string[index];
       if (char != " " && char != "\n" && char != "\r" && char != "\t") break;
       index++;
     }
     return index;
   }
   int skipString(int index) {
     assert(string[index - 1] == '"');
     while (index < string.length) {
       String char = string[index];
       if (char == '"') return index + 1;
       if (char == r'\') index++;
       if (index == string.length) return index;
       index++;
     }
     return index;
   }
   int index = 0;
   index = skipWhitespace(index);
   // Bail out if the first non-whitespace character isn't '{'.
   if (index == string.length || string[index] != '{') return 0;
   int nexting = 0;
   while (index < string.length) {
     String char = string[index++];
     if (char == '{') {
       nexting++;
     } else if (char == '}') {
       nexting--;
       if (nexting == 0) return index;
     } else if (char == '"') {
       // Strings can contain braces. Skip their content.
       index = skipString(index);
     }
   }
   return 0;
 }


 void main() {
   outstandingCommands = new Map<int, Completer>();
   vmSock = new Socket("127.0.0.1", 5858);
   vmStream = vmSock.outputStream;
   var stdinStream = new StringInputStream(stdin);
   stdinStream.onLine = () {
     processCommand(stdinStream.readLine());
   };
   var vmInStream = vmSock.inputStream;
   vmInStream.onData = () {
     String s = decodeUtf8(vmInStream.read());
     processVmData(s);
   };
   vmInStream.onError = (err) {
     print("Error in debug connection: $err");
     quitShell();
   };
   vmInStream.onClosed = () {
     print("VM debugger connection closed");
     quitShell();
   };
 }
	// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	// Simple interactive debugger shell that connects to the Dart VM's debugger
	// connection port.

	#import("dart:io");
	#import("dart:json");
	#import("dart:math", prefix: "Math");
	#import("dart:utf");


	Map<int, Completer> outstandingCommands;

	Socket vmSock;
	String vmData;
	OutputStream vmStream;
	int seqNum = 0;
	int isolate_id = -1;

	bool verbose = false;

	// The current stack trace, while the VM is paused. It's a list
	// of activation frames.
	List stackTrace;

	// The current activation frame, while the VM is paused.
	Map curFrame;


	void printHelp() {
	print("""
	q Quit debugger shell
	bt Show backtrace
	r Resume execution
	s Single step
	so Step over
	si Step into
	sbp [<file>] <line> Set breakpoint
	rbp <id> Remove breakpoint with given id
	po <id> Print object info for given id
	pl <id> <idx> [<len>] Print list element/slice
	pc <id> Print class info for given id
	ll List loaded libraries
	plib <id> Print library info for given library id
	slib <id> <true\|false> Set library id debuggable
	pg <id> Print all global variables visible within given library id
	ls <lib_id> List loaded scripts in library
	gs <lib_id> <script_url> Get source text of script in library
	epi <none\|all\|unhandled> Set exception pause info
	i <id> Interrupt execution of given isolate id
	h Print help
	""");
	}


	void quitShell() {
	vmStream.close();
	vmSock.close();
	stdin.close();
	}


	Future sendCmd(Map<String, dynamic> cmd) {
	var completer = new Completer();
	int id = cmd["id"];
	outstandingCommands[id] = completer;
	if (verbose) {
	print("sending: '${JSON.stringify(cmd)}'");
	}
	vmStream.writeString(JSON.stringify(cmd));
	return completer.future;
	}


	void processCommand(String cmdLine) {
	seqNum++;
	var args = cmdLine.split(' ');
	if (args.length == 0) {
	return;
	}
	var command = args[0];
	var simple_commands =
	{ 'r':'resume', 's':'stepOver', 'si':'stepInto', 'so':'stepOut'};
	if (simple_commands[command] != null) {
	var cmd = { "id": seqNum,
	"command": simple_commands[command],
	"params": { "isolateId" : isolate_id } };
	sendCmd(cmd).then((result) => handleGenericResponse(result));
	stackTrace = curFrame = null;
	} else if (command == "bt") {
	var cmd = { "id": seqNum,
	"command": "getStackTrace",
	"params": { "isolateId" : isolate_id } };
	sendCmd(cmd).then((result) => handleStackTraceResponse(result));
	} else if (command == "ll") {
	var cmd = { "id": seqNum,
	"command": "getLibraries",
	"params": { "isolateId" : isolate_id } };
	sendCmd(cmd).then((result) => handleGetLibraryResponse(result));
	} else if (command == "sbp" && args.length >= 2) {
	var url, line;
	if (args.length == 2) {
	url = stackTrace[0]["location"]["url"];
	line = Math.parseInt(args[1]);
	} else {
	url = args[1];
	line = Math.parseInt(args[2]);
	}
	var cmd = { "id": seqNum,
	"command": "setBreakpoint",
	"params": { "isolateId" : isolate_id,
	"url": url,
	"line": line }};
	sendCmd(cmd).then((result) => handleSetBpResponse(result));
	} else if (command == "rbp" && args.length == 2) {
	var cmd = { "id": seqNum,
	"command": "removeBreakpoint",
	"params": { "isolateId" : isolate_id,
	"breakpointId": Math.parseInt(args[1]) } };
	sendCmd(cmd).then((result) => handleGenericResponse(result));
	} else if (command == "ls" && args.length == 2) {
	var cmd = { "id": seqNum,
	"command": "getScriptURLs",
	"params": { "isolateId" : isolate_id,
	"libraryId": Math.parseInt(args[1]) } };
	sendCmd(cmd).then((result) => handleGetScriptsResponse(result));
	} else if (command == "po" && args.length == 2) {
	var cmd = { "id": seqNum,
	"command": "getObjectProperties",
	"params": { "isolateId" : isolate_id,
	"objectId": Math.parseInt(args[1]) } };
	sendCmd(cmd).then((result) => handleGetObjPropsResponse(result));
	} else if (command == "pl" && args.length >= 3) {
	var cmd;
	if (args.length == 3) {
	cmd = { "id": seqNum,
	"command": "getListElements",
	"params": { "isolateId" : isolate_id,
	"objectId": Math.parseInt(args[1]),
	"index": Math.parseInt(args[2]) } };
	} else {
	cmd = { "id": seqNum,
	"command": "getListElements",
	"params": { "isolateId" : isolate_id,
	"objectId": Math.parseInt(args[1]),
	"index": Math.parseInt(args[2]),
	"length": Math.parseInt(args[3]) } };
	}
	sendCmd(cmd).then((result) => handleGetListResponse(result));
	} else if (command == "pc" && args.length == 2) {
	var cmd = { "id": seqNum,
	"command": "getClassProperties",
	"params": { "isolateId" : isolate_id,
	"classId": Math.parseInt(args[1]) } };
	sendCmd(cmd).then((result) => handleGetClassPropsResponse(result));
	} else if (command == "plib" && args.length == 2) {
	var cmd = { "id": seqNum,
	"command": "getLibraryProperties",
	"params": {"isolateId" : isolate_id,
	"libraryId": Math.parseInt(args[1]) } };
	sendCmd(cmd).then((result) => handleGetLibraryPropsResponse(result));
	} else if (command == "slib" && args.length == 3) {
	var cmd = { "id": seqNum,
	"command": "setLibraryProperties",
	"params": {"isolateId" : isolate_id,
	"libraryId": Math.parseInt(args[1]),
	"debuggingEnabled": args[2] } };
	sendCmd(cmd).then((result) => handleSetLibraryPropsResponse(result));
	} else if (command == "pg" && args.length == 2) {
	var cmd = { "id": seqNum,
	"command": "getGlobalVariables",
	"params": { "isolateId" : isolate_id,
	"libraryId": Math.parseInt(args[1]) } };
	sendCmd(cmd).then((result) => handleGetGlobalVarsResponse(result));
	} else if (command == "gs" && args.length == 3) {
	var cmd = { "id": seqNum,
	"command": "getScriptSource",
	"params": { "isolateId" : isolate_id,
	"libraryId": Math.parseInt(args[1]),
	"url": args[2] } };
	sendCmd(cmd).then((result) => handleGetSourceResponse(result));
	} else if (command == "epi" && args.length == 2) {
	var cmd = { "id": seqNum,
	"command": "setPauseOnException",
	"params": { "isolateId" : isolate_id,
	"exceptions": args[1] } };
	sendCmd(cmd).then((result) => handleGenericResponse(result));
	} else if (command == "i" && args.length == 2) {
	var cmd = { "id": seqNum,
	"command": "interrupt",
	"params": { "isolateId": Math.parseInt(args[1]) } };
	sendCmd(cmd).then((result) => handleGenericResponse(result));
	} else if (command == "q") {
	quitShell();
	} else if (command == "h") {
	printHelp();
	} else {
	print("command '$command' not understood, try h for help");
	}
	}


	String remoteObject(value) {
	var kind = value["kind"];
	var text = value["text"];
	var id = value["objectId"];
	if (kind == "string") {
	return "(string, id $id) '$text'";
	} else if (kind == "list") {
	var len = value["length"];
	return "(list, id $id, len $len) $text";
	} else if (kind == "object") {
	return "(obj, id $id) $text";
	} else {
	return "$text";
	}
	}


	printNamedObject(obj) {
	var name = obj["name"];
	var value = obj["value"];
	print(" $name = ${remoteObject(value)}");
	}


	handleGetObjPropsResponse(response) {
	Map props = response["result"];
	int class_id = props["classId"];
	if (class_id == -1) {
	print(" null");
	return;
	}
	List fields = props["fields"];
	print(" class id: $class_id");
	for (int i = 0; i < fields.length; i++) {
	printNamedObject(fields[i]);
	}
	}

	handleGetListResponse(response) {
	Map result = response["result"];
	if (result["elements"] != null) {
	// List slice.
	var index = result["index"];
	var length = result["length"];
	List elements = result["elements"];
	assert(length == elements.length);
	for (int i = 0; i < length; i++) {
	var kind = elements[i]["kind"];
	var text = elements[i]["text"];
	print(" ${index + i}: ($kind) $text");
	}
	} else {
	// One element, a remote object.
	print(result);
	print(" ${remoteObject(result)}");
	}
	}


	handleGetClassPropsResponse(response) {
	Map props = response["result"];
	assert(props["name"] != null);
	int libId = props["libraryId"];
	assert(libId != null);
	print(" class ${props["name"]} (library id: $libId)");
	List fields = props["fields"];
	if (fields.length > 0) {
	print(" static fields:");
	for (int i = 0; i < fields.length; i++) {
	printNamedObject(fields[i]);
	}
	}
	}


	handleGetLibraryPropsResponse(response) {
	Map props = response["result"];
	assert(props["url"] != null);
	print(" library url: ${props["url"]}");
	assert(props["debuggingEnabled"] != null);
	print(" debugging enabled: ${props["debuggingEnabled"]}");
	List imports = props["imports"];
	assert(imports != null);
	if (imports.length > 0) {
	print(" imports:");
	for (int i = 0; i < imports.length; i++) {
	print(" id ${imports[i]["libraryId"]} prefix ${imports[i]["prefix"]}");
	}
	}
	List globals = props["globals"];
	assert(globals != null);
	if (globals.length > 0) {
	print(" global variables:");
	for (int i = 0; i < globals.length; i++) {
	printNamedObject(globals[i]);
	}
	}
	}


	handleSetLibraryPropsResponse(response) {
	Map props = response["result"];
	assert(props["debuggingEnabled"] != null);
	print(" debugging enabled: ${props["debuggingEnabled"]}");
	}


	handleGetGlobalVarsResponse(response) {
	List globals = response["result"]["globals"];
	for (int i = 0; i < globals.length; i++) {
	printNamedObject(globals[i]);
	}
	}


	handleGetSourceResponse(response) {
	Map result = response["result"];
	String source = result["text"];
	print("Source text:\n$source\n--------");
	}


	void handleGetLibraryResponse(response) {
	Map result = response["result"];
	List libs = result["libraries"];
	print("Loaded libraries:");
	print(libs);
	for (int i = 0; i < libs.length; i++) {
	print(" ${libs[i]["id"]} ${libs[i]["url"]}");
	}
	}


	void handleGetScriptsResponse(response) {
	Map result = response["result"];
	List urls = result["urls"];
	print("Loaded scripts:");
	for (int i = 0; i < urls.length; i++) {
	print(" $i ${urls[i]}");
	}
	}


	void handleSetBpResponse(response) {
	Map result = response["result"];
	var id = result["breakpointId"];
	assert(id != null);
	print("Set BP $id");
	}


	void handleGenericResponse(response) {
	if (response["error"] != null) {
	print("Error: ${response["error"]}");
	}
	}


	void handleStackTraceResponse(response) {
	Map result = response["result"];
	List callFrames = result["callFrames"];
	assert(callFrames != null);
	printStackTrace(callFrames);
	}


	void printStackFrame(frame_num, Map frame) {
	var fname = frame["functionName"];
	var libId = frame["libraryId"];
	var url = frame["location"]["url"];
	var line = frame["location"]["lineNumber"];
	print("$frame_num $fname ($url:$line) (lib $libId)");
	List locals = frame["locals"];
	for (int i = 0; i < locals.length; i++) {
	printNamedObject(locals[i]);
	}
	}


	void printStackTrace(List frames) {
	for (int i = 0; i < frames.length; i++) {
	printStackFrame(i, frames[i]);
	}
	}


	void handlePausedEvent(msg) {
	assert(msg["params"] != null);
	var reason = msg["params"]["reason"];
	isolate_id = msg["params"]["id"];
	stackTrace = msg["params"]["callFrames"];
	assert(stackTrace != null);
	assert(stackTrace.length >= 1);
	curFrame = stackTrace[0];
	if (reason == "breakpoint") {
	print("Isolate $isolate_id paused on breakpoint");
	} else if (reason == "interrupted") {
	print("Isolate $isolate_id paused due to an interrupt");
	} else {
	assert(reason == "exception");
	var excObj = msg["params"]["exception"];
	print("Isolate $isolate_id paused on exception");
	print(remoteObject(excObj));
	}
	print("Stack trace:");
	printStackTrace(stackTrace);
	}


	void processVmMessage(String json) {
	var msg = JSON.parse(json);
	if (msg == null) {
	return;
	}
	var event = msg["event"];
	if (event == "paused") {
	handlePausedEvent(msg);
	return;
	}
	if (event == "breakpointResolved") {
	Map params = msg["params"];
	assert(params != null);
	print("BP ${params["breakpointId"]} resolved and "
	"set at line ${params["line"]}.");
	return;
	}
	if (event == "isolate") {
	Map params = msg["params"];
	assert(params != null);
	print("Isolate ${params["id"]} has been ${params["reason"]}.");
	return;
	}
	if (msg["id"] != null) {
	var id = msg["id"];
	if (outstandingCommands.containsKey(id)) {
	if (msg["error"] != null) {
	print("VM says: ${msg["error"]}");
	} else {
	var completer = outstandingCommands[id];
	completer.complete(msg);
	}
	outstandingCommands.remove(id);
	}
	}
	}


	void processVmData(String data) {
	final printMessages = false;
	if (vmData == null \|\| vmData.length == 0) {
	vmData = data;
	} else {
	vmData = vmData.concat(data);
	}
	int msg_len = jsonObjectLength(vmData);
	if (printMessages && msg_len == 0) {
	print("have partial or illegal json message"
	" of ${vmData.length} chars:\n'$vmData'");
	return;
	}
	while (msg_len > 0 && msg_len <= vmData.length) {
	if (msg_len == vmData.length) {
	if (printMessages) { print("have one full message:\n$vmData"); }
	processVmMessage(vmData);
	vmData = null;
	return;
	}
	if (printMessages) { print("at least one message: '$vmData'"); }
	var msg = vmData.substring(0, msg_len);
	if (printMessages) { print("first message: $msg"); }
	processVmMessage(msg);
	vmData = vmData.substring(msg_len);
	msg_len = jsonObjectLength(vmData);
	}
	if (printMessages) { print("leftover vm data '$vmData'"); }
	}

	/**
	* Skip past a JSON object value.
	* The object value must start with '{' and continues to the
	* matching '}'. No attempt is made to otherwise validate the contents
	* as JSON. If it is invalid, a later [JSON.parse] will fail.
	*/
	int jsonObjectLength(String string) {
	int skipWhitespace(int index) {
	while (index < string.length) {
	String char = string[index];
	if (char != " " && char != "\n" && char != "\r" && char != "\t") break;
	index++;
	}
	return index;
	}
	int skipString(int index) {
	assert(string[index - 1] == '"');
	while (index < string.length) {
	String char = string[index];
	if (char == '"') return index + 1;
	if (char == r'\') index++;
	if (index == string.length) return index;
	index++;
	}
	return index;
	}
	int index = 0;
	index = skipWhitespace(index);
	// Bail out if the first non-whitespace character isn't '{'.
	if (index == string.length \|\| string[index] != '{') return 0;
	int nexting = 0;
	while (index < string.length) {
	String char = string[index++];
	if (char == '{') {
	nexting++;
	} else if (char == '}') {
	nexting--;
	if (nexting == 0) return index;
	} else if (char == '"') {
	// Strings can contain braces. Skip their content.
	index = skipString(index);
	}
	}
	return 0;
	}


	void main() {
	outstandingCommands = new Map<int, Completer>();
	vmSock = new Socket("127.0.0.1", 5858);
	vmStream = vmSock.outputStream;
	var stdinStream = new StringInputStream(stdin);
	stdinStream.onLine = () {
	processCommand(stdinStream.readLine());
	};
	var vmInStream = vmSock.inputStream;
	vmInStream.onData = () {
	String s = decodeUtf8(vmInStream.read());
	processVmData(s);
	};
	vmInStream.onError = (err) {
	print("Error in debug connection: $err");
	quitShell();
	};
	vmInStream.onClosed = () {
	print("VM debugger connection closed");
	quitShell();
	};
	}