dlmalloc.cxx

ecos实时嵌入式操作系统

      /* Get to the next possibly nonempty block */

      if ( (block <<= 1) <= binblocks && (block != 0) ) 
      {
        while ((block & binblocks) == 0)
        {
          idx += BINBLOCKWIDTH;
          block <<= 1;
        }
      }
      else
        break;
    }
  }


  /* Try to use top chunk */

  /* Require that there be a remainder, ensuring top always exists  */
  remainder_size = long_sub_size_t(chunksize(top), nb);
  if (chunksize(top) < nb || remainder_size < (long)MINSIZE)
  {
      //diag_printf("chunksize(top)=%ld, nb=%d, remainder=%ld\n", chunksize(top),
      //            nb, remainder_size);
      MALLOC_UNLOCK;
      return NULL; /* propagate failure */
  }

  victim = top;
  set_head(victim, nb | PREV_INUSE);
  top = chunk_at_offset(victim, nb);
  set_head(top, remainder_size | PREV_INUSE);
  check_malloced_chunk(victim, nb);
  MALLOC_UNLOCK;
  return chunk2mem(victim);

} // Cyg_Mempool_dlmalloc_Implementation::try_alloc()

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

/*
  free() algorithm :

    cases:

       1. free(NULL) has no effect.  

       2. Chunks are consolidated as they arrive, and
          placed in corresponding bins. (This includes the case of
          consolidating with the current `last_remainder').
*/

cyg_bool
Cyg_Mempool_dlmalloc_Implementation::free( cyg_uint8 *mem, cyg_int32 )
{
  mchunkptr p;         /* chunk corresponding to mem */
  INTERNAL_SIZE_T hd;  /* its head field */
  INTERNAL_SIZE_T sz;  /* its size */
  int       idx;       /* its bin index */
  mchunkptr next;      /* next contiguous chunk */
  INTERNAL_SIZE_T nextsz; /* its size */
  INTERNAL_SIZE_T prevsz; /* size of previous contiguous chunk */
  mchunkptr bck;       /* misc temp for linking */
  mchunkptr fwd;       /* misc temp for linking */
  int       islr;      /* track whether merging with last_remainder */

  if (mem == NULL)                              /* free(NULL) has no effect */
    return false;

  MALLOC_LOCK;

  p = mem2chunk(mem);
  hd = p->size;

  check_inuse_chunk(p);
  
  sz = hd & ~PREV_INUSE;
  next = chunk_at_offset(p, sz);
  nextsz = chunksize(next);
  
  if (next == top)                            /* merge with top */
  {
    sz += nextsz;

    if (!(hd & PREV_INUSE))                    /* consolidate backward */
    {
      prevsz = p->prev_size;
      p = chunk_at_offset(p, -((long) prevsz));
      sz += prevsz;
      unlink(p, bck, fwd);
    }

    set_head(p, sz | PREV_INUSE);
    top = p;
    MALLOC_UNLOCK;
    return true;
  }

  set_head(next, nextsz);                    /* clear inuse bit */

  islr = 0;

  if (!(hd & PREV_INUSE))                    /* consolidate backward */
  {
    prevsz = p->prev_size;
    p = chunk_at_offset(p, -((long) prevsz));
    sz += prevsz;
    
    if (p->fd == last_remainder)             /* keep as last_remainder */
      islr = 1;
    else
      unlink(p, bck, fwd);
  }
  
  if (!(inuse_bit_at_offset(next, nextsz)))   /* consolidate forward */
  {
    sz += nextsz;
    
    if (!islr && next->fd == last_remainder)  /* re-insert last_remainder */
    {
      islr = 1;
      link_last_remainder(p);   
    }
    else
      unlink(next, bck, fwd);
  }


  set_head(p, sz | PREV_INUSE);
  set_foot(p, sz);
  if (!islr)
    frontlink(p, sz, idx, bck, fwd);  

  MALLOC_UNLOCK;

  return true;
} // Cyg_Mempool_dlmalloc_Implementation::free()

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

// resize existing allocation, if oldsize is non-NULL, previous
// allocation size is placed into it. If previous size not available,
// it is set to 0. NB previous allocation size may have been rounded up.
// Occasionally the allocation can be adjusted *backwards* as well as,
// or instead of forwards, therefore the address of the resized
// allocation is returned, or NULL if no resizing was possible.
// Note that this differs from ::realloc() in that no attempt is
// made to call malloc() if resizing is not possible - that is left
// to higher layers. The data is copied from old to new though.
// The effects of alloc_ptr==NULL or newsize==0 are undefined


// DOCUMENTATION FROM ORIGINAL FILE:
// (some now irrelevant parts elided)
/*
  Realloc algorithm:

    If the reallocation is for additional space, and the
    chunk can be extended, it is, else a malloc-copy-free sequence is
    taken.  There are several different ways that a chunk could be
    extended. All are tried:

       * Extending forward into following adjacent free chunk.
       * Shifting backwards, joining preceding adjacent space
       * Both shifting backwards and extending forward.

    If the reallocation is for less space, and the new request is for
    a `small' (<512 bytes) size, then the newly unused space is lopped
    off and freed.

    The old unix realloc convention of allowing the last-free'd chunk
    to be used as an argument to realloc is no longer supported.
    I don't know of any programs still relying on this feature,
    and allowing it would also allow too many other incorrect 
    usages of realloc to be sensible.
*/

cyg_uint8 *
Cyg_Mempool_dlmalloc_Implementation::resize_alloc( cyg_uint8 *oldmem,
                                                   cyg_int32 bytes,
                                                   cyg_int32 *poldsize )
{

  INTERNAL_SIZE_T nb;             /* padded request size */

  mchunkptr oldp;                 /* chunk corresponding to oldmem */
  INTERNAL_SIZE_T oldsize;        /* its size */

  mchunkptr newp;                 /* chunk to return */
  INTERNAL_SIZE_T newsize;        /* its size */
  cyg_uint8*   newmem;            /* corresponding user mem */

  mchunkptr next;                 /* next contiguous chunk after oldp */
  INTERNAL_SIZE_T nextsize;       /* its size */

  mchunkptr prev;                 /* previous contiguous chunk before oldp */
  INTERNAL_SIZE_T prevsize;       /* its size */

  mchunkptr remainder;            /* holds split off extra space from newp */
  INTERNAL_SIZE_T remainder_size; /* its size */

  mchunkptr bck;                  /* misc temp for linking */
  mchunkptr fwd;                  /* misc temp for linking */

  MALLOC_LOCK;

  newp    = oldp    = mem2chunk(oldmem);
  newsize = oldsize = chunksize(oldp);

  if (NULL != poldsize)
      *poldsize = oldsize - SIZE_SZ;

  nb = request2size(bytes);

  check_inuse_chunk(oldp);

  if ((long)(oldsize) < (long)(nb))  
  {

    /* Try expanding forward */

    next = chunk_at_offset(oldp, oldsize);
    if (next == top || !inuse(next)) 
    {
      nextsize = chunksize(next);

      /* Forward into top only if a remainder */
      if (next == top)
      {
        if ((long)(nextsize + newsize) >= (long)(nb + MINSIZE))
        {
          newsize += nextsize;
          top = chunk_at_offset(oldp, nb);
          set_head(top, (newsize - nb) | PREV_INUSE);
          set_head_size(oldp, nb);
	  MALLOC_UNLOCK;
          return chunk2mem(oldp);
        }
      }

      /* Forward into next chunk */
      else if (((long)(nextsize + newsize) >= (long)(nb)))
      { 
        unlink(next, bck, fwd);
        newsize  += nextsize;
        goto split;
      }
    }
    else
    {
      next = 0;
      nextsize = 0;
    }

    /* Try shifting backwards. */

    if (!prev_inuse(oldp))
    {
      prev = prev_chunk(oldp);
      prevsize = chunksize(prev);

      /* try forward + backward first to save a later consolidation */

      if (next != 0)
      {
        /* into top */
        if (next == top)
        {
          if ((long)(nextsize + prevsize + newsize) >= (long)(nb + MINSIZE))
          {
            unlink(prev, bck, fwd);
            newp = prev;
            newsize += prevsize + nextsize;
            newmem = chunk2mem(newp);
            MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
            top = chunk_at_offset(newp, nb);
            set_head(top, (newsize - nb) | PREV_INUSE);
            set_head_size(newp, nb);
	    MALLOC_UNLOCK;
            return newmem;
          }
        }

        /* into next chunk */
        else if (((long)(nextsize + prevsize + newsize) >= (long)(nb)))
        {
          unlink(next, bck, fwd);
          unlink(prev, bck, fwd);
          newp = prev;
          newsize += nextsize + prevsize;
          newmem = chunk2mem(newp);
          MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
          goto split;
        }
      }
      
      /* backward only */
      if (prev != 0 && (long)(prevsize + newsize) >= (long)nb)  
      {
        unlink(prev, bck, fwd);
        newp = prev;
        newsize += prevsize;
        newmem = chunk2mem(newp);
        MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
        goto split;
      }
    }

    // couldn't resize the allocation any direction, so return failure
    MALLOC_UNLOCK;
    return NULL;
  }


 split:  /* split off extra room in old or expanded chunk */

  remainder_size = long_sub_size_t(newsize, nb);

  if (remainder_size >= (long)MINSIZE) /* split off remainder */
  {
    remainder = chunk_at_offset(newp, nb);
    set_head_size(newp, nb);
    set_head(remainder, remainder_size | PREV_INUSE);
    set_inuse_bit_at_offset(remainder, remainder_size);
    /* let free() deal with it */
    Cyg_Mempool_dlmalloc_Implementation::free( chunk2mem(remainder) );
  }
  else
  {
    set_head_size(newp, newsize);
    set_inuse_bit_at_offset(newp, newsize);
  }

  check_inuse_chunk(newp);
  MALLOC_UNLOCK;
  return chunk2mem(newp);

} // Cyg_Mempool_dlmalloc_Implementation::resize_alloc()

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

// Get memory pool status
// flags is a bitmask of requested fields to fill in. The flags are
// defined in common.hxx
void
Cyg_Mempool_dlmalloc_Implementation::get_status( 
                                  cyg_mempool_status_flag_t flags,
                                  Cyg_Mempool_Status &status )
{
    if (0 != (flags&(CYG_MEMPOOL_STAT_FREEBLOCKS|CYG_MEMPOOL_STAT_TOTALFREE|
                     CYG_MEMPOOL_STAT_TOTALALLOCATED|CYG_MEMPOOL_STAT_MAXFREE)))
    {
        int i;
        mbinptr b;
        mchunkptr p;
        cyg_int32 chunksizep;
        cyg_int32 maxfree;
#ifdef CYGDBG_MEMALLOC_ALLOCATOR_DLMALLOC_DEBUG
        mchunkptr q;
#endif
        
        INTERNAL_SIZE_T avail = chunksize(top);
        int   navail = ((long)(avail) >= (long)MINSIZE)? 1 : 0; 
        maxfree = avail;
        
        for (i = 1; i < CYGPRI_MEMALLOC_ALLOCATOR_DLMALLOC_NAV; ++i) {
            b = bin_at(i);
            for (p = last(b); p != b; p = p->bk) {
#ifdef CYGDBG_MEMALLOC_ALLOCATOR_DLMALLOC_DEBUG
                check_free_chunk(p);
                for (q = next_chunk(p); 
                     (q < top) && inuse(q) && 
                         (long)(chunksize(q)) >= (long)MINSIZE; 
                     q = next_chunk(q))
                    check_inuse_chunk(q);
#endif
                chunksizep = chunksize(p);
                avail += chunksizep;
                if ( chunksizep > maxfree )
                    maxfree = chunksizep;
                navail++;
            }
        }
    
        if ( 0 != (flags & CYG_MEMPOOL_STAT_TOTALALLOCATED) )
            status.totalallocated = arenasize - avail;
        // as quick or quicker to just set most of these, rather than
        // test flag first
        status.totalfree = (avail & ~(MALLOC_ALIGN_MASK)) - SIZE_SZ - MINSIZE;
        CYG_ASSERT( ((avail + SIZE_SZ + MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK)
                    >= MINSIZE, "free mem negative!" );
        status.freeblocks = navail;
        status.maxfree = (maxfree & ~(MALLOC_ALIGN_MASK)) - SIZE_SZ - MINSIZE;
        //diag_printf("raw mf: %d, ret mf: %d\n", maxfree, status.maxfree);
        CYG_ASSERT( ((maxfree + SIZE_SZ + MALLOC_ALIGN_MASK) & 
                    ~MALLOC_ALIGN_MASK) >= MINSIZE, 
                    "max free block size negative!" );
    } // if

    // as quick or quicker to just set most of these, rather than
    // test flag first
    status.arenabase = status.origbase = arenabase;
    status.arenasize = status.origsize = arenasize;
    status.maxoverhead = MINSIZE + MALLOC_ALIGNMENT;

} // Cyg_Mempool_dlmalloc_Implementation::get_status()


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

// EOF dlmalloc.cxx