base/mach_ipc_mac.mm

// Copyright (c) 2011 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 "base/mach_ipc_mac.h"

#import <Foundation/Foundation.h>

#include <stdio.h>
#include "base/logging.h"

namespace base {

// static
const size_t MachMessage::kEmptyMessageSize = sizeof(mach_msg_header_t) +
    sizeof(mach_msg_body_t) + sizeof(MessageDataPacket);

//==============================================================================
MachSendMessage::MachSendMessage(int32_t message_id) : MachMessage() {
  Initialize(message_id);
}

MachSendMessage::MachSendMessage(void *storage, size_t storage_length,
                                 int32_t message_id)
    : MachMessage(storage, storage_length) {
  Initialize(message_id);
}

void MachSendMessage::Initialize(int32_t message_id) {
  Head()->msgh_bits = MACH_MSGH_BITS(MACH_MSG_TYPE_COPY_SEND, 0);

  // head.msgh_remote_port = ...; // filled out in MachPortSender::SendMessage()
  Head()->msgh_local_port = MACH_PORT_NULL;
  Head()->msgh_reserved = 0;
  Head()->msgh_id = 0;

  SetDescriptorCount(0);  // start out with no descriptors

  SetMessageID(message_id);
  SetData(NULL, 0);       // client may add data later
}

//==============================================================================
MachMessage::MachMessage()
    : storage_(new MachMessageData),  // Allocate storage_ ourselves
      storage_length_bytes_(sizeof(MachMessageData)),
      own_storage_(true) {
  memset(storage_, 0, storage_length_bytes_);
}

//==============================================================================
MachMessage::MachMessage(void *storage, size_t storage_length)
    : storage_(static_cast<MachMessageData*>(storage)),
      storage_length_bytes_(storage_length),
      own_storage_(false) {
  DCHECK(storage);
  DCHECK_GE(storage_length, kEmptyMessageSize);
}

//==============================================================================
MachMessage::~MachMessage() {
  if (own_storage_) {
    delete storage_;
    storage_ = NULL;
  }
}

//==============================================================================
// returns true if successful
bool MachMessage::SetData(const void* data,
                          int32_t data_length) {
  // Enforce the fact that it's only safe to call this method once on a
  // message.
  DCHECK(GetDataPacket()->data_length == 0);

  // first check to make sure we have enough space
  int size = CalculateSize();
  int new_size = size + data_length;

  if ((unsigned)new_size > storage_length_bytes_) {
    return false;  // not enough space
  }

  GetDataPacket()->data_length = EndianU32_NtoL(data_length);
  if (data) memcpy(GetDataPacket()->data, data, data_length);

  // Update the Mach header with the new aligned size of the message.
  CalculateSize();

  return true;
}

//==============================================================================
// calculates and returns the total size of the message
// Currently, the entire message MUST fit inside of the MachMessage
//    messsage size <= EmptyMessageSize()
int MachMessage::CalculateSize() {
  int size = sizeof(mach_msg_header_t) + sizeof(mach_msg_body_t);

  // add space for MessageDataPacket
  int32_t alignedDataLength = (GetDataLength() + 3) & ~0x3;
  size += 2*sizeof(int32_t) + alignedDataLength;

  // add space for descriptors
  size += GetDescriptorCount() * sizeof(MachMsgPortDescriptor);

  Head()->msgh_size = size;

  return size;
}

//==============================================================================
MachMessage::MessageDataPacket *MachMessage::GetDataPacket() {
  int desc_size = sizeof(MachMsgPortDescriptor)*GetDescriptorCount();
  MessageDataPacket *packet =
    reinterpret_cast<MessageDataPacket*>(storage_->padding + desc_size);

  return packet;
}

//==============================================================================
void MachMessage::SetDescriptor(int n,
                                const MachMsgPortDescriptor &desc) {
  MachMsgPortDescriptor *desc_array =
    reinterpret_cast<MachMsgPortDescriptor*>(storage_->padding);
  desc_array[n] = desc;
}

//==============================================================================
// returns true if successful otherwise there was not enough space
bool MachMessage::AddDescriptor(const MachMsgPortDescriptor &desc) {
  // first check to make sure we have enough space
  int size = CalculateSize();
  int new_size = size + sizeof(MachMsgPortDescriptor);

  if ((unsigned)new_size > storage_length_bytes_) {
    return false;  // not enough space
  }

  // unfortunately, we need to move the data to allow space for the
  // new descriptor
  u_int8_t *p = reinterpret_cast<u_int8_t*>(GetDataPacket());
  bcopy(p, p+sizeof(MachMsgPortDescriptor), GetDataLength()+2*sizeof(int32_t));

  SetDescriptor(GetDescriptorCount(), desc);
  SetDescriptorCount(GetDescriptorCount() + 1);

  CalculateSize();

  return true;
}

//==============================================================================
void MachMessage::SetDescriptorCount(int n) {
  storage_->body.msgh_descriptor_count = n;

  if (n > 0) {
    Head()->msgh_bits |= MACH_MSGH_BITS_COMPLEX;
  } else {
    Head()->msgh_bits &= ~MACH_MSGH_BITS_COMPLEX;
  }
}

//==============================================================================
MachMsgPortDescriptor *MachMessage::GetDescriptor(int n) {
  if (n < GetDescriptorCount()) {
    MachMsgPortDescriptor *desc =
        reinterpret_cast<MachMsgPortDescriptor*>(storage_->padding);
    return desc + n;
  }

  return nil;
}

//==============================================================================
mach_port_t MachMessage::GetTranslatedPort(int n) {
  if (n < GetDescriptorCount()) {
    return GetDescriptor(n)->GetMachPort();
  }
  return MACH_PORT_NULL;
}

#pragma mark -

//==============================================================================
// create a new mach port for receiving messages and register a name for it
ReceivePort::ReceivePort(const char *receive_port_name) {
  mach_port_t current_task = mach_task_self();

  init_result_ = mach_port_allocate(current_task,
                                    MACH_PORT_RIGHT_RECEIVE,
                                    &port_);

  if (init_result_ != KERN_SUCCESS)
    return;

  init_result_ = mach_port_insert_right(current_task,
                                        port_,
                                        port_,
                                        MACH_MSG_TYPE_MAKE_SEND);

  if (init_result_ != KERN_SUCCESS)
    return;

  // Without |NSMachPortDeallocateNone|, the NSMachPort seems to deallocate
  // receive rights on port when it is eventually released.  It is not necessary
  // to deallocate any rights here as |port_| is fully deallocated in the
  // ReceivePort destructor.
  NSPort *ns_port = [NSMachPort portWithMachPort:port_
                                         options:NSMachPortDeallocateNone];
  NSString *port_name = [NSString stringWithUTF8String:receive_port_name];
  [[NSMachBootstrapServer sharedInstance] registerPort:ns_port name:port_name];
}

//==============================================================================
// create a new mach port for receiving messages
ReceivePort::ReceivePort() {
  mach_port_t current_task = mach_task_self();

  init_result_ = mach_port_allocate(current_task,
                                    MACH_PORT_RIGHT_RECEIVE,
                                    &port_);

  if (init_result_ != KERN_SUCCESS)
    return;

  init_result_ = mach_port_insert_right(current_task,
                                        port_,
                                        port_,
                                        MACH_MSG_TYPE_MAKE_SEND);
}

//==============================================================================
// Given an already existing mach port, use it.  We take ownership of the
// port and deallocate it in our destructor.
ReceivePort::ReceivePort(mach_port_t receive_port)
  : port_(receive_port),
    init_result_(KERN_SUCCESS) {
}

//==============================================================================
ReceivePort::~ReceivePort() {
  if (init_result_ == KERN_SUCCESS)
    mach_port_deallocate(mach_task_self(), port_);
}

//==============================================================================
kern_return_t ReceivePort::WaitForMessage(MachReceiveMessage *out_message,
                                          mach_msg_timeout_t timeout) {
  if (!out_message) {
    return KERN_INVALID_ARGUMENT;
  }

  // return any error condition encountered in constructor
  if (init_result_ != KERN_SUCCESS)
    return init_result_;

  out_message->Head()->msgh_bits = 0;
  out_message->Head()->msgh_local_port = port_;
  out_message->Head()->msgh_remote_port = MACH_PORT_NULL;
  out_message->Head()->msgh_reserved = 0;
  out_message->Head()->msgh_id = 0;

  mach_msg_option_t rcv_options = MACH_RCV_MSG;
  if (timeout != MACH_MSG_TIMEOUT_NONE)
    rcv_options |= MACH_RCV_TIMEOUT;

  kern_return_t result = mach_msg(out_message->Head(),
                                  rcv_options,
                                  0,
                                  out_message->MaxSize(),
                                  port_,
                                  timeout,              // timeout in ms
                                  MACH_PORT_NULL);

  return result;
}

#pragma mark -

//==============================================================================
// get a port with send rights corresponding to a named registered service
MachPortSender::MachPortSender(const char *receive_port_name) {
  mach_port_t bootstrap_port = 0;
  init_result_ = task_get_bootstrap_port(mach_task_self(), &bootstrap_port);

  if (init_result_ != KERN_SUCCESS)
    return;

  init_result_ = bootstrap_look_up(bootstrap_port,
                    const_cast<char*>(receive_port_name),
                    &send_port_);
}

//==============================================================================
MachPortSender::MachPortSender(mach_port_t send_port)
  : send_port_(send_port),
    init_result_(KERN_SUCCESS) {
}

//==============================================================================
kern_return_t MachPortSender::SendMessage(MachSendMessage &message,
                                          mach_msg_timeout_t timeout) {
  if (message.Head()->msgh_size == 0) {
    NOTREACHED();
    return KERN_INVALID_VALUE;    // just for safety -- never should occur
  };

  if (init_result_ != KERN_SUCCESS)
    return init_result_;

  message.Head()->msgh_remote_port = send_port_;

  kern_return_t result = mach_msg(message.Head(),
                                  MACH_SEND_MSG | MACH_SEND_TIMEOUT,
                                  message.Head()->msgh_size,
                                  0,
                                  MACH_PORT_NULL,
                                  timeout,              // timeout in ms
                                  MACH_PORT_NULL);

  return result;
}

}  // namespace base