Beginnings of a debugger wire protocol

runtime/bin/dbg_connection.cc

Index: runtime/bin/dbg_connection.cc
===================================================================
--- runtime/bin/dbg_connection.cc	(revision 0)
+++ runtime/bin/dbg_connection.cc	(revision 0)
@@ -0,0 +1,273 @@
+// 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.
+
+#include "bin/dbg_connection.h"
+#include "bin/dartutils.h"
+#include "bin/fdutils.h"
+#include "bin/socket.h"
+#include "bin/thread.h"
+#include "bin/utils.h"
+
+#include "platform/globals.h"
+#include "platform/json.h"
+#include "platform/thread.h"
+#include "platform/utils.h"
+
+#include "include/dart_api.h"
+
+
+int DebuggerConnectionHandler::listener_fd_ = -1;
+int DebuggerConnectionHandler::debugger_fd_ = -1;
+MessageBuffer* DebuggerConnectionHandler::msgbuf_ = NULL;
+
+bool DebuggerConnectionHandler::handler_started_ = false;
+
+
+// TODO(hausner): Need better error handling.
+#define ASSERT_NOT_ERROR(handle)                                               \
+  ASSERT(!Dart_IsError(handle))
+
+
+class MessageBuffer {
+ public:
+  explicit MessageBuffer(int fd);
+  ~MessageBuffer();
+  void ReadData();
+  bool IsValidMessage() const;
+  void PopMessage();
+  int MessageId() const;
+  char* buf() const { return buf_; }
+  bool Alive() const { return connection_is_alive_; }
+
+ private:
+  static const int kInitialBufferSize = 256;
+  char* buf_;
+  int buf_length_;
+  int fd_;
+  int data_length_;
+  bool connection_is_alive_;
+
+  DISALLOW_COPY_AND_ASSIGN(MessageBuffer);
+};
+
+
+MessageBuffer::MessageBuffer(int fd)
+    :  buf_(NULL),
+        buf_length_(0),
+        fd_(fd),
+        data_length_(0),
+        connection_is_alive_(true) {
+  buf_ = reinterpret_cast<char*>(malloc(kInitialBufferSize));
+  if (buf_ == NULL) {
+    FATAL("Failed to allocate message buffer\n");
+  }
+  buf_length_ = kInitialBufferSize;
+  buf_[0] = '\0';
+  data_length_ = 0;
+}
+
+
+MessageBuffer::~MessageBuffer() {
+  free(buf_);
+  buf_ = NULL;
+  fd_ = -1;
+}
+
+
+bool MessageBuffer::IsValidMessage() const {
+  if (data_length_ == 0) {
+    return false;
+  }
+  dart::JSONReader msg_reader(buf_);
+  return msg_reader.EndOfObject() != NULL;
+}
+
+
+int MessageBuffer::MessageId() const {
+  dart::JSONReader r(buf_);
+  r.Seek("id");
+  if (r.Type() == dart::JSONReader::kInteger) {
+    return atoi(r.ValueChars());
+  } else {
+    return -1;
+  }
+}
+
+
+void MessageBuffer::ReadData() {
+  ASSERT(data_length_ >= 0);
+  ASSERT(data_length_ < buf_length_);
+  int max_read = buf_length_ - data_length_ - 1;
+  if (max_read == 0) {
+    // TODO(hausner):
+    // Buffer is full. What should we do if there is no valid message
+    // in the buffer? This might be possible if the client sends a message
+    // that's larger than the buffer, of if the client sends malformed
+    // messages that keep piling up.
+    ASSERT(IsValidMessage());
+    return;
+  }
+  // TODO(hausner): Handle error conditions returned by Read. We may
+  // want to close the debugger connection if we get any errors.
+  int bytes_read = Socket::Read(fd_, buf_ + data_length_, max_read);
+  if (bytes_read == 0) {
+    connection_is_alive_ = false;
+    return;
+  }
+  ASSERT(bytes_read > 0);
+  data_length_ += bytes_read;
+  ASSERT(data_length_ < buf_length_);
+  buf_[data_length_] = '\0';
+}
+
+
+void MessageBuffer::PopMessage() {
+  dart::JSONReader msg_reader(buf_);
+  const char* end = msg_reader.EndOfObject();
+  if (end != NULL) {
+    ASSERT(*end == '}');
+    end++;
+    data_length_ = 0;
+    while (*end != '\0') {
+      buf_[data_length_] = *end++;
+      data_length_++;
+    }
+    buf_[data_length_] = '\0';
+    ASSERT(data_length_ < buf_length_);
+  }
+}
+
+
+static bool IsValidJSON(const char* msg) {
+  dart::JSONReader r(msg);
+  return r.EndOfObject() != NULL;
+}
+
+
+void DebuggerConnectionHandler::HandleResumeCmd() {
+  int msg_id = msgbuf_->MessageId();
+  dart::TextBuffer msg(64);
+  msg.Printf("{ \"id\": %d }", msg_id);
+  FDUtils::WriteToBlocking(debugger_fd_, msg.buf(), msg.length());
+  // TODO(hausner): Error checking. Probably just shut down the debugger
+  // session if we there is an error while writing.
+}
+
+
+void DebuggerConnectionHandler::HandleMessages() {
+  for (;;) {
+    while (!msgbuf_->IsValidMessage() && msgbuf_->Alive()) {
+      msgbuf_->ReadData();
+    }
+    if (!msgbuf_->Alive()) {
+      return;
+    }
+    dart::JSONReader r(msgbuf_->buf());
+    bool found = r.Seek("command");
+    if (r.Error()) {
+      FATAL("Illegal JSON message received");
+    }
+    if (!found) {
+      printf("'command' not found in JSON message: '%s'\n", msgbuf_->buf());
+      msgbuf_->PopMessage();
+    } else if (r.IsStringLiteral("resume")) {
+      HandleResumeCmd();
+      msgbuf_->PopMessage();
+      return;
+    } else {
+      printf("unrecognized command received: '%s'\n", msgbuf_->buf());
+      msgbuf_->PopMessage();
+    }
+  }
+}
+
+
+void DebuggerConnectionHandler::SendBreakpointEvent(Dart_Breakpoint bpt,
+                                                    Dart_StackTrace trace) {
+  dart::TextBuffer msg(128);
+  intptr_t trace_len = 0;
+  Dart_Handle res = Dart_StackTraceLength(trace, &trace_len);
+  ASSERT_NOT_ERROR(res);
+  msg.Printf("{ \"command\" : \"paused\", \"params\" : ");
+  msg.Printf("{ \"callFrames\" : [ ");
+  for (int i = 0; i < trace_len; i++) {
+    Dart_ActivationFrame frame;
+    res = Dart_GetActivationFrame(trace, i, &frame);
+    ASSERT_NOT_ERROR(res);
+    Dart_Handle func_name;
+    Dart_Handle script_url;
+    intptr_t line_number = 0;
+    res = Dart_ActivationFrameInfo(
+              frame, &func_name, &script_url, &line_number);
+    ASSERT_NOT_ERROR(res);
+    ASSERT(Dart_IsString(func_name));
+    const char* func_name_chars;
+    Dart_StringToCString(func_name, &func_name_chars);
+    msg.Printf("%s { \"functionName\" : \"%s\" , ",
+              i > 0 ? "," : "",
+              func_name_chars);
+    ASSERT(Dart_IsString(script_url));
+    const char* script_url_chars;
+    Dart_StringToCString(script_url, &script_url_chars);
+    msg.Printf("\"location\": { \"scriptId\": \"%s\", \"lineNumber\": %d }}",
+               script_url_chars, line_number);
+  }
+  msg.Printf("]}}");
+  Socket::Write(debugger_fd_, msg.buf(), msg.length());
+  ASSERT(IsValidJSON(msg.buf()));
+}
+
+
+void DebuggerConnectionHandler::BreakpointHandler(Dart_Breakpoint bpt,
+                                                  Dart_StackTrace trace) {
+  // TODO(hausner): rather than busy-waiting, block on the pipe to the
+  // debugger thread and wait until a debugger connection has been
+  // established.
+  while (!IsConnected()) {
+    printf("Waiting for debugger connection\n");
+    sleep(1);
+  }
+  SendBreakpointEvent(bpt, trace);
+  HandleMessages();
+  if (!msgbuf_->Alive()) {
+    CloseDbgConnection();
+  }
+}
+
+
+void DebuggerConnectionHandler::AcceptDbgConnection(int debugger_fd) {
+  debugger_fd_ = debugger_fd;
+  ASSERT(msgbuf_ == NULL);
+  msgbuf_ = new MessageBuffer(debugger_fd_);
+}
+
+void DebuggerConnectionHandler::CloseDbgConnection() {
+  if (debugger_fd_ >= 0) {
+    // TODO(hausner): need a Socket::Close() function.
+  }
+  if (msgbuf_ != NULL) {
+    delete msgbuf_;
+    msgbuf_ = NULL;
+  }
+  // TODO(hausner): Need to tell the VM debugger object to remove all
+  // breakpoints.
+}
+
+void DebuggerConnectionHandler::StartHandler(const char* address,
+                                             int port_number) {
+  if (handler_started_) {
+    return;
+  }
+  ASSERT(listener_fd_ == -1);
+  listener_fd_ = ServerSocket::CreateBindListen(address, port_number, 1);
+
+  handler_started_ = true;
+  DebuggerConnectionImpl::StartHandler(port_number);
+  Dart_SetBreakpointHandler(BreakpointHandler);
+}
+
+
+DebuggerConnectionHandler::~DebuggerConnectionHandler() {
+  CloseDbgConnection();
+}