ChibiOS/os/kernel/src/chheap.c

/*
    ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,
                 2011,2012,2013 Giovanni Di Sirio.

    This file is part of ChibiOS/RT.

    ChibiOS/RT is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    ChibiOS/RT is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/**
 * @file    chheap.c
 * @brief   Heaps code.
 *
 * @addtogroup heaps
 * @details Heap Allocator related APIs.
 *          <h2>Operation mode</h2>
 *          The heap allocator implements a first-fit strategy and its APIs
 *          are functionally equivalent to the usual @p malloc() and @p free()
 *          library functions. The main difference is that the OS heap APIs
 *          are guaranteed to be thread safe.<br>
 *          By enabling the @p CH_USE_MALLOC_HEAP option the heap manager
 *          will use the runtime-provided @p malloc() and @p free() as
 *          back end for the heap APIs instead of the system provided
 *          allocator.
 * @pre     In order to use the heap APIs the @p CH_USE_HEAP option must
 *          be enabled in @p chconf.h.
 * @{
 */

#include "ch.h"

#if CH_USE_HEAP || defined(__DOXYGEN__)

#if !CH_USE_MALLOC_HEAP || defined(__DOXYGEN__)

/*
 * Defaults on the best synchronization mechanism available.
 */
#if CH_USE_MUTEXES || defined(__DOXYGEN__)
#define H_LOCK(h)       chMtxLock(&(h)->h_mtx)
#define H_UNLOCK(h)     chMtxUnlock()
#else
#define H_LOCK(h)       chSemWait(&(h)->h_sem)
#define H_UNLOCK(h)     chSemSignal(&(h)->h_sem)
#endif

/**
 * @brief   Default heap descriptor.
 */
static MemoryHeap default_heap;

/**
 * @brief   Initializes the default heap.
 *
 * @notapi
 */
void _heap_init(void) {
  default_heap.h_provider = chCoreAlloc;
  default_heap.h_free.h.u.next = (union heap_header *)NULL;
  default_heap.h_free.h.size = 0;
#if CH_USE_MUTEXES || defined(__DOXYGEN__)
  chMtxInit(&default_heap.h_mtx);
#else
  chSemInit(&default_heap.h_sem, 1);
#endif
}

/**
 * @brief   Initializes a memory heap from a static memory area.
 * @pre     Both the heap buffer base and the heap size must be aligned to
 *          the @p stkalign_t type size.
 * @pre     In order to use this function the option @p CH_USE_MALLOC_HEAP
 *          must be disabled.
 *
 * @param[out] heapp    pointer to the memory heap descriptor to be initialized
 * @param[in] buf       heap buffer base
 * @param[in] size      heap size
 *
 * @init
 */
void chHeapInit(MemoryHeap *heapp, void *buf, size_t size) {
  union heap_header *hp;

  chDbgCheck(MEM_IS_ALIGNED(buf) && MEM_IS_ALIGNED(size), "chHeapInit");

  heapp->h_provider = (memgetfunc_t)NULL;
  heapp->h_free.h.u.next = hp = buf;
  heapp->h_free.h.size = 0;
  hp->h.u.next = NULL;
  hp->h.size = size - sizeof(union heap_header);
#if CH_USE_MUTEXES || defined(__DOXYGEN__)
  chMtxInit(&heapp->h_mtx);
#else
  chSemInit(&heapp->h_sem, 1);
#endif
}

/**
 * @brief   Allocates a block of memory from the heap by using the first-fit
 *          algorithm.
 * @details The allocated block is guaranteed to be properly aligned for a
 *          pointer data type (@p stkalign_t).
 *
 * @param[in] heapp     pointer to a heap descriptor or @p NULL in order to
 *                      access the default heap.
 * @param[in] size      the size of the block to be allocated. Note that the
 *                      allocated block may be a bit bigger than the requested
 *                      size for alignment and fragmentation reasons.
 * @return              A pointer to the allocated block.
 * @retval NULL         if the block cannot be allocated.
 *
 * @api
 */
void *chHeapAlloc(MemoryHeap *heapp, size_t size) {
  union heap_header *qp, *hp, *fp;

  if (heapp == NULL)
    heapp = &default_heap;

  size = MEM_ALIGN_NEXT(size);
  qp = &heapp->h_free;
  H_LOCK(heapp);

  while (qp->h.u.next != NULL) {
    hp = qp->h.u.next;
    if (hp->h.size >= size) {
      if (hp->h.size < size + sizeof(union heap_header)) {
        /* Gets the whole block even if it is slightly bigger than the
           requested size because the fragment would be too small to be
           useful.*/
        qp->h.u.next = hp->h.u.next;
      }
      else {
        /* Block bigger enough, must split it.*/
        fp = (void *)((uint8_t *)(hp) + sizeof(union heap_header) + size);
        fp->h.u.next = hp->h.u.next;
        fp->h.size = hp->h.size - sizeof(union heap_header) - size;
        qp->h.u.next = fp;
        hp->h.size = size;
      }
      hp->h.u.heap = heapp;

      H_UNLOCK(heapp);
      return (void *)(hp + 1);
    }
    qp = hp;
  }

  H_UNLOCK(heapp);

  /* More memory is required, tries to get it from the associated provider
     else fails.*/
  if (heapp->h_provider) {
    hp = heapp->h_provider(size + sizeof(union heap_header));
    if (hp != NULL) {
      hp->h.u.heap = heapp;
      hp->h.size = size;
      hp++;
      return (void *)hp;
    }
  }
  return NULL;
}

#define LIMIT(p) (union heap_header *)((uint8_t *)(p) + \
                                        sizeof(union heap_header) + \
                                        (p)->h.size)

/**
 * @brief   Frees a previously allocated memory block.
 *
 * @param[in] p         pointer to the memory block to be freed
 *
 * @api
 */
void chHeapFree(void *p) {
  union heap_header *qp, *hp;
  MemoryHeap *heapp;

  chDbgCheck(p != NULL, "chHeapFree");

  hp = (union heap_header *)p - 1;
  heapp = hp->h.u.heap;
  qp = &heapp->h_free;
  H_LOCK(heapp);

  while (TRUE) {
    chDbgAssert((hp < qp) || (hp >= LIMIT(qp)),
                "chHeapFree(), #1",
                "within free block");

    if (((qp == &heapp->h_free) || (hp > qp)) &&
        ((qp->h.u.next == NULL) || (hp < qp->h.u.next))) {
      /* Insertion after qp.*/
      hp->h.u.next = qp->h.u.next;
      qp->h.u.next = hp;
      /* Verifies if the newly inserted block should be merged.*/
      if (LIMIT(hp) == hp->h.u.next) {
        /* Merge with the next block.*/
        hp->h.size += hp->h.u.next->h.size + sizeof(union heap_header);
        hp->h.u.next = hp->h.u.next->h.u.next;
      }
      if ((LIMIT(qp) == hp)) {
        /* Merge with the previous block.*/
        qp->h.size += hp->h.size + sizeof(union heap_header);
        qp->h.u.next = hp->h.u.next;
      }
      break;
    }
    qp = qp->h.u.next;
  }

  H_UNLOCK(heapp);
  return;
}

/**
 * @brief   Reports the heap status.
 * @note    This function is meant to be used in the test suite, it should
 *          not be really useful for the application code.
 * @note    This function is not implemented when the @p CH_USE_MALLOC_HEAP
 *          configuration option is used (it always returns zero).
 *
 * @param[in] heapp     pointer to a heap descriptor or @p NULL in order to
 *                      access the default heap.
 * @param[in] sizep     pointer to a variable that will receive the total
 *                      fragmented free space
 * @return              The number of fragments in the heap.
 *
 * @api
 */
size_t chHeapStatus(MemoryHeap *heapp, size_t *sizep) {
  union heap_header *qp;
  size_t n, sz;

  if (heapp == NULL)
    heapp = &default_heap;

  H_LOCK(heapp);

  sz = 0;
  for (n = 0, qp = &heapp->h_free; qp->h.u.next; n++, qp = qp->h.u.next)
    sz += qp->h.u.next->h.size;
  if (sizep)
    *sizep = sz;

  H_UNLOCK(heapp);
  return n;
}

#else /* CH_USE_MALLOC_HEAP */

#include <stdlib.h>

#if CH_USE_MUTEXES
#define H_LOCK()        chMtxLock(&hmtx)
#define H_UNLOCK()      chMtxUnlock()
static Mutex            hmtx;
#elif CH_USE_SEMAPHORES
#define H_LOCK()        chSemWait(&hsem)
#define H_UNLOCK()      chSemSignal(&hsem)
static Semaphore        hsem;
#endif

void _heap_init(void) {

#if CH_USE_MUTEXES
  chMtxInit(&hmtx);
#else
  chSemInit(&hsem, 1);
#endif
}

void *chHeapAlloc(MemoryHeap *heapp, size_t size) {
  void *p;

  chDbgCheck(heapp == NULL, "chHeapAlloc");

  H_LOCK();
  p = malloc(size);
  H_UNLOCK();
  return p;
}

void chHeapFree(void *p) {

  chDbgCheck(p != NULL, "chHeapFree");

  H_LOCK();
  free(p);
  H_UNLOCK();
}

size_t chHeapStatus(MemoryHeap *heapp, size_t *sizep) {

  chDbgCheck(heapp == NULL, "chHeapStatus");

  if (sizep)
    *sizep = 0;
  return 0;
}

#endif /* CH_USE_MALLOC_HEAP */

#endif /* CH_USE_HEAP */

/** @} */