Creates a BattOrConnection for communicating with the BattOr

tools/battor_agent/battor_connection.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "tools/battor_agent/battor_connection.h"
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "device/serial/buffer.h"
+#include "device/serial/serial_io_handler.h"
+#include "net/base/io_buffer.h"
+
+using std::vector;
+
+namespace battor {
+
+namespace {
+
+// Serial configuration parameters for the BattOr.
+const uint32_t kBattOrBitrate = 2000000;
+const device::serial::DataBits kBattOrDataBits =
+    device::serial::DATA_BITS_EIGHT;
+const device::serial::ParityBit kBattOrParityBit =
+    device::serial::PARITY_BIT_NONE;
+const device::serial::StopBits kBattOrStopBit = device::serial::STOP_BITS_ONE;
+const bool kBattOrCtsFlowControl = true;
+const bool kBattOrHasCtsFlowControl = true;
+const uint32_t kMaxMessageSize = 50000;
+
+// MessageHealth describes the possible healthiness states that a partially
+// received message could be in.
+enum class MessageHealth {
+  INVALID,
+  INCOMPLETE,
+  COMPLETE,
+};
+
+// Parses the specified message.
+//   - message: The incoming message that needs to be parsed.
+//   - parsed_content: Output argument for the message content after removal of
+//     any start, end, type, and escape bytes.
+//   - health: Output argument for the health of the message.
+//   - type: Output argument for the type of message being parsed.
+//   - escape_byte_count: Output argument for the number of escape bytes
+//     removed from the parsed content.
+void ParseMessage(const vector<char>& message,
+                  vector<char>* parsed_content,
+                  MessageHealth* health,
+                  BattOrMessageType* type,
+                  size_t* escape_byte_count) {
+  *health = MessageHealth::INCOMPLETE;
+  *type = BATTOR_MESSAGE_TYPE_CONTROL;
+  *escape_byte_count = 0;
+  parsed_content->reserve(message.size());
+
+  if (message.size() == 0)
+    return;
+
+  // The first byte is the start byte.
+  if (message[0] != BATTOR_CONTROL_BYTE_START) {
+    *health = MessageHealth::INVALID;
+    return;
+  }
+
+  if (message.size() == 1)
+    return;
+
+  // The second byte specifies the message type.
+  *type = static_cast<BattOrMessageType>(message[1]);
+
+  if (*type < static_cast<uint8_t>(BATTOR_MESSAGE_TYPE_CONTROL) ||
+      *type > static_cast<uint8_t>(BATTOR_MESSAGE_TYPE_PRINT)) {
+    *health = MessageHealth::INVALID;
+    return;
+  }
+
+  // After that comes the message data.
+  bool escape_next_byte = false;
+  for (size_t i = 2; i < message.size(); i++) {
+    if (i >= kMaxMessageSize) {
+      *health = MessageHealth::INVALID;
+      return;
+    }
+
+    char next_byte = message[i];
+
+    if (escape_next_byte) {
+      parsed_content->push_back(next_byte);
+      escape_next_byte = false;
+      continue;
+    }
+
+    switch (next_byte) {
+      case BATTOR_CONTROL_BYTE_START:
+        // Two start bytes in a message is invalid.
+        *health = MessageHealth::INVALID;
+        return;
+
+      case BATTOR_CONTROL_BYTE_END:
+        if (i != message.size() - 1) {
+          // We're only parsing a single message here. If we received more bytes
+          // after the end byte, what we've received so far is *not* valid.
+          *health = MessageHealth::INVALID;
+          return;
+        }
+
+        *health = MessageHealth::COMPLETE;
+        return;
+
+      case BATTOR_CONTROL_BYTE_ESCAPE:
+        escape_next_byte = true;
+        (*escape_byte_count)++;
+        continue;
+
+      default:
+        parsed_content->push_back(next_byte);
+    }
+  }
+}
+
+}  // namespace
+
+BattOrConnection::BattOrConnection(
+    const std::string& path,
+    Listener* listener,
+    scoped_refptr<base::SingleThreadTaskRunner> file_thread_task_runner,
+    scoped_refptr<base::SingleThreadTaskRunner> ui_thread_task_runner)
+    : path_(path),
+      listener_(listener),
+      file_thread_task_runner_(file_thread_task_runner),
+      ui_thread_task_runner_(ui_thread_task_runner) {}
+
+BattOrConnection::~BattOrConnection() {}
+
+void BattOrConnection::Open() {
+  io_handler_ = CreateIoHandler();
+
+  device::serial::ConnectionOptions options;
+  options.bitrate = kBattOrBitrate;
+  options.data_bits = kBattOrDataBits;
+  options.parity_bit = kBattOrParityBit;
+  options.stop_bits = kBattOrStopBit;
+  options.cts_flow_control = kBattOrCtsFlowControl;
+  options.has_cts_flow_control = kBattOrHasCtsFlowControl;
+
+  io_handler_->Open(path_, options,
+                    base::Bind(&BattOrConnection::OnOpened, AsWeakPtr()));
+}
+
+void BattOrConnection::OnOpened(bool success) {
+  if (!success)
+    Close();
+
+  listener_->OnConnectionOpened(success);
+}
+
+bool BattOrConnection::IsOpen() {
+  return io_handler_;
+}
+
+void BattOrConnection::Close() {
+  io_handler_ = nullptr;
+}
+
+void BattOrConnection::SendBytes(BattOrMessageType type,
+                                 const void* buffer,
+                                 size_t bytes_to_send) {
+  const char* bytes = reinterpret_cast<const char*>(buffer);
+
+  // Reserve a send buffer with 3 extra bytes (start, type, and end byte) and
+  // twice as many bytes as we're actually sending, because each raw data byte
+  // might need to be escaped.
+  vector<char> data;
+  data.reserve(2 * bytes_to_send + 3);
+
+  data.push_back(BATTOR_CONTROL_BYTE_START);
+  data.push_back(type);
+
+  for (size_t i = 0; i < bytes_to_send; i++) {
+    if (bytes[i] == BATTOR_CONTROL_BYTE_START ||
+        bytes[i] == BATTOR_CONTROL_BYTE_END) {
+      data.push_back(BATTOR_CONTROL_BYTE_ESCAPE);
+    }
+
+    data.push_back(bytes[i]);
+  }
+
+  data.push_back(BATTOR_CONTROL_BYTE_END);
+
+  pending_write_length_ = data.size();
+  io_handler_->Write(make_scoped_ptr(new device::SendBuffer(
+      data, base::Bind(&BattOrConnection::OnBytesSent, AsWeakPtr()))));
+}
+
+void BattOrConnection::ReadBytes(size_t bytes_to_read) {
+  // Allocate a read buffer and reserve enough space in it to account for the
+  // start, type, end, and escape bytes.
+  pending_read_buffer_.reset(new vector<char>());
+  pending_read_buffer_->reserve(2 * bytes_to_read + 3);
+  pending_read_escape_byte_count_ = 0;
+
+  // Add 3 bytes to however many bytes the caller requested because we know
+  // we'll have to read the start, type, and end bytes.
+  bytes_to_read += 3;
+
+  ReadMoreBytes(bytes_to_read);
+}
+
+void BattOrConnection::Flush() {
+  io_handler_->Flush();
+}
+
+scoped_refptr<device::SerialIoHandler> BattOrConnection::CreateIoHandler() {
+  return device::SerialIoHandler::Create(file_thread_task_runner_,
+                                         ui_thread_task_runner_);
+}
+
+void BattOrConnection::ReadMoreBytes(size_t bytes_to_read) {
+  last_read_buffer_ = make_scoped_refptr(new net::IOBuffer(bytes_to_read));
+  auto on_receive_buffer_filled =
+      base::Bind(&BattOrConnection::OnBytesRead, AsWeakPtr());
+
+  pending_read_length_ = bytes_to_read;
+  io_handler_->Read(make_scoped_ptr(new device::ReceiveBuffer(
+      last_read_buffer_, bytes_to_read, on_receive_buffer_filled)));
+}
+
+void BattOrConnection::OnBytesRead(int bytes_read,
+                                   device::serial::ReceiveError error) {
+  if ((static_cast<size_t>(bytes_read) < pending_read_length_) ||
+      (error != device::serial::RECEIVE_ERROR_NONE)) {
+    listener_->OnBytesRead(false, BATTOR_MESSAGE_TYPE_CONTROL, nullptr);
+    return;
+  }
+
+  pending_read_buffer_->insert(pending_read_buffer_->end(),
+                               last_read_buffer_->data(),
+                               last_read_buffer_->data() + bytes_read);
+
+  scoped_ptr<vector<char>> parsed_content(new vector<char>());
+  MessageHealth health;
+  BattOrMessageType type;
+  size_t escape_byte_count;
+
+  ParseMessage(*pending_read_buffer_, parsed_content.get(), &health, &type,
+               &escape_byte_count);
+
+  if (health == MessageHealth::INVALID) {
+    // If we already have an invalid message, there's no sense in continuing to
+    // process it.
+    listener_->OnBytesRead(false, BATTOR_MESSAGE_TYPE_CONTROL, nullptr);
+    return;
+  }
+
+  size_t new_escape_bytes = escape_byte_count - pending_read_escape_byte_count_;
+  pending_read_escape_byte_count_ = escape_byte_count;
+
+  if (new_escape_bytes > 0) {
+    // When the caller requested that we read X additional bytes, they weren't
+    // taking into account any escape bytes that we received. Because we got
+    // some escape bytes, we need to fire off another read to get the rest of
+    // the data.
+    ReadMoreBytes(new_escape_bytes);
+    return;
+  }
+
+  if (health == MessageHealth::INCOMPLETE)
+    // If everything is valid and we didn't see any escape bytes, then we should
+    // have the whole message. If we don't, the message was malformed.
+    listener_->OnBytesRead(false, BATTOR_MESSAGE_TYPE_CONTROL, nullptr);
+
+  // If we've gotten this far, we've received the whole, well-formed message.
+  listener_->OnBytesRead(true, type, parsed_content.Pass());
+}
+
+void BattOrConnection::OnBytesSent(int bytes_sent,
+                                   device::serial::SendError error) {
+  bool success = (error == device::serial::SEND_ERROR_NONE) &&
+                 (pending_write_length_ == static_cast<size_t>(bytes_sent));
+  listener_->OnBytesSent(success);
+}
+
+}  // namespace battor