ipc/ipc_message.cc

// Copyright (c) 2012 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 "ipc/ipc_message.h"

#include "base/atomicops.h"
#include "base/logging.h"
#include "build/build_config.h"

#if defined(OS_POSIX)
#include "ipc/file_descriptor_set_posix.h"
#endif

namespace {

base::subtle::Atomic32 g_ref_num = 0;

// Create a reference number for identifying IPC messages in traces. The return
// values has the reference number stored in the upper 24 bits, leaving the low
// 8 bits set to 0 for use as flags.
inline uint32 GetRefNumUpper24() {
  base::debug::TraceLog* trace_log = base::debug::TraceLog::GetInstance();
  int32 pid = trace_log ? trace_log->process_id() : 0;
  int32 count = base::subtle::NoBarrier_AtomicIncrement(&g_ref_num, 1);
  // The 24 bit hash is composed of 14 bits of the count and 10 bits of the
  // Process ID. With the current trace event buffer cap, the 14-bit count did
  // not appear to wrap during a trace. Note that it is not a big deal if
  // collisions occur, as this is only used for debugging and trace analysis.
  return ((pid << 14) | (count & 0x3fff)) << 8;
}

}  // namespace

namespace IPC {

//------------------------------------------------------------------------------

Message::~Message() {
}

Message::Message()
    : Pickle(sizeof(Header)) {
  header()->routing = header()->type = 0;
  header()->flags = GetRefNumUpper24();
#if defined(OS_POSIX)
  header()->num_fds = 0;
  header()->pad = 0;
#endif
  InitLoggingVariables();
}

Message::Message(int32 routing_id, uint32 type, PriorityValue priority)
    : Pickle(sizeof(Header)) {
  header()->routing = routing_id;
  header()->type = type;
  DCHECK((priority & 0xffffff00) == 0);
  header()->flags = priority | GetRefNumUpper24();
#if defined(OS_POSIX)
  header()->num_fds = 0;
  header()->pad = 0;
#endif
  InitLoggingVariables();
}

Message::Message(const char* data, int data_len) : Pickle(data, data_len) {
  InitLoggingVariables();
}

Message::Message(const Message& other) : Pickle(other) {
  InitLoggingVariables();
#if defined(OS_POSIX)
  file_descriptor_set_ = other.file_descriptor_set_;
#endif
}

void Message::InitLoggingVariables() {
#ifdef IPC_MESSAGE_LOG_ENABLED
  received_time_ = 0;
  dont_log_ = false;
  log_data_ = NULL;
#endif
}

Message& Message::operator=(const Message& other) {
  *static_cast<Pickle*>(this) = other;
#if defined(OS_POSIX)
  file_descriptor_set_ = other.file_descriptor_set_;
#endif
  return *this;
}

void Message::SetHeaderValues(int32 routing, uint32 type, uint32 flags) {
  // This should only be called when the message is already empty.
  DCHECK(payload_size() == 0);

  header()->routing = routing;
  header()->type = type;
  header()->flags = flags;
}

#ifdef IPC_MESSAGE_LOG_ENABLED
void Message::set_sent_time(int64 time) {
  DCHECK((header()->flags & HAS_SENT_TIME_BIT) == 0);
  header()->flags |= HAS_SENT_TIME_BIT;
  WriteInt64(time);
}

int64 Message::sent_time() const {
  if ((header()->flags & HAS_SENT_TIME_BIT) == 0)
    return 0;

  const char* data = end_of_payload();
  data -= sizeof(int64);
  return *(reinterpret_cast<const int64*>(data));
}

void Message::set_received_time(int64 time) const {
  received_time_ = time;
}
#endif

#if defined(OS_POSIX)
bool Message::WriteFileDescriptor(const base::FileDescriptor& descriptor) {
  // We write the index of the descriptor so that we don't have to
  // keep the current descriptor as extra decoding state when deserialising.
  WriteInt(file_descriptor_set()->size());
  if (descriptor.auto_close) {
    return file_descriptor_set()->AddAndAutoClose(descriptor.fd);
  } else {
    return file_descriptor_set()->Add(descriptor.fd);
  }
}

bool Message::ReadFileDescriptor(PickleIterator* iter,
                                 base::FileDescriptor* descriptor) const {
  int descriptor_index;
  if (!ReadInt(iter, &descriptor_index))
    return false;

  FileDescriptorSet* file_descriptor_set = file_descriptor_set_.get();
  if (!file_descriptor_set)
    return false;

  descriptor->fd = file_descriptor_set->GetDescriptorAt(descriptor_index);
  descriptor->auto_close = true;

  return descriptor->fd >= 0;
}

bool Message::HasFileDescriptors() const {
  return file_descriptor_set_.get() && !file_descriptor_set_->empty();
}

void Message::EnsureFileDescriptorSet() {
  if (file_descriptor_set_.get() == NULL)
    file_descriptor_set_ = new FileDescriptorSet;
}

#endif

}  // namespace IPC