source: rtems/cpukit/score/src/coremsg.c @ 7e66865e

/**
 *  @file
 *
 *  @brief Initialize a Message Queue
 *  @ingroup ScoreMessageQueue
 */

/*
 *  COPYRIGHT (c) 1989-2009.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.org/license/LICENSE.
 */

#if HAVE_CONFIG_H
#include "config.h"
#endif

#include <rtems/score/coremsgimpl.h>
#include <rtems/score/wkspace.h>

/*
 *  size_t_mult32_with_overflow
 *
 *  This method multiplies two size_t 32-bit numbers and checks
 *  for overflow.  It returns false if an overflow occurred and
 *  the result is bad.
 */
static inline bool size_t_mult32_with_overflow(
  size_t  a,
  size_t  b,
  size_t *c
)
{
  long long x = (long long)a*b;

  if ( x > SIZE_MAX )
    return false;
  *c = (size_t) x;
  return true;
}

bool _CORE_message_queue_Initialize(
  CORE_message_queue_Control     *the_message_queue,
  CORE_message_queue_Disciplines  discipline,
  uint32_t                        maximum_pending_messages,
  size_t                          maximum_message_size
)
{
  size_t message_buffering_required = 0;
  size_t allocated_message_size;

  the_message_queue->maximum_pending_messages   = maximum_pending_messages;
  the_message_queue->number_of_pending_messages = 0;
  the_message_queue->maximum_message_size       = maximum_message_size;
  _CORE_message_queue_Set_notify( the_message_queue, NULL );

  allocated_message_size = maximum_message_size;

  /* 
   * Check if allocated_message_size is aligned to uintptr-size boundary. 
   * If not, it will increase allocated_message_size to multiplicity of pointer
   * size.
   */
  if (allocated_message_size & (sizeof(uintptr_t) - 1)) {
    allocated_message_size += sizeof(uintptr_t);
    allocated_message_size &= ~(sizeof(uintptr_t) - 1);
  }

  /* 
   * Check for an overflow. It can occur while increasing allocated_message_size
   * to multiplicity of uintptr_t above.
   */
  if (allocated_message_size < maximum_message_size)
    return false;

  /*
   *  Calculate how much total memory is required for message buffering and
   *  check for overflow on the multiplication.
   */
  if ( !size_t_mult32_with_overflow(
        (size_t) maximum_pending_messages,
        allocated_message_size + sizeof(CORE_message_queue_Buffer_control),
        &message_buffering_required ) ) 
    return false;

  /*
   *  Attempt to allocate the message memory
   */
  the_message_queue->message_buffers = (CORE_message_queue_Buffer *)
     _Workspace_Allocate( message_buffering_required );

  if (the_message_queue->message_buffers == 0)
    return false;

  /*
   *  Initialize the pool of inactive messages, pending messages,
   *  and set of waiting threads.
   */
  _Chain_Initialize (
    &the_message_queue->Inactive_messages,
    the_message_queue->message_buffers,
    (size_t) maximum_pending_messages,
    allocated_message_size + sizeof( CORE_message_queue_Buffer_control )
  );

  _Chain_Initialize_empty( &the_message_queue->Pending_messages );

  _Thread_queue_Initialize( &the_message_queue->Wait_queue );

  if ( discipline == CORE_MESSAGE_QUEUE_DISCIPLINES_PRIORITY ) {
    the_message_queue->operations = &_Thread_queue_Operations_priority;
  } else {
    the_message_queue->operations = &_Thread_queue_Operations_FIFO;
  }

  return true;
}