libc/winsup/cygwin/heap.cc

/* heap.cc: Cygwin heap manager.

   Copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.

This file is part of Cygwin.

This software is a copyrighted work licensed under the terms of the
Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
details. */

#include "winsup.h"
#include "cygerrno.h"
#include "sigproc.h"
#include "pinfo.h"
#include "heap.h"
#include "shared_info.h"
#include "security.h"
#include "path.h"
#include "fhandler.h"
#include "dtable.h"
#include "cygheap.h"
#include "registry.h"
#include "cygwin_version.h"

#define assert(x)

static unsigned page_const;

extern "C" size_t getpagesize ();

#define MINHEAP_SIZE (4 * 1024 * 1024)

/* Initialize the heap at process start up.  */

void
heap_init ()
{
  /* If we're the forkee, we must allocate the heap at exactly the same place
     as our parent.  If not, we don't care where it ends up.  */

  page_const = system_info.dwPageSize;
  if (!cygheap->user_heap.base)
    {
      cygheap->user_heap.chunk = cygwin_shared->heap_chunk_size ();
      while (cygheap->user_heap.chunk >= MINHEAP_SIZE)
	{
	  /* Initialize page mask and default heap size.  Preallocate a heap
	   * to assure contiguous memory.  */
	  cygheap->user_heap.ptr = cygheap->user_heap.top =
	  cygheap->user_heap.base =
	    VirtualAlloc (NULL, cygheap->user_heap.chunk, MEM_RESERVE, PAGE_NOACCESS);
	  if (cygheap->user_heap.base)
	    break;
	  cygheap->user_heap.chunk -= 1 * 1024 * 1024;
	}
      if (cygheap->user_heap.base == NULL)
	api_fatal ("unable to allocate heap, heap_chunk_size %d, %E",
		   cygheap->user_heap.chunk);
      cygheap->user_heap.max = (char *) cygheap->user_heap.base + cygheap->user_heap.chunk;
    }
  else
    {
      DWORD chunk = cygheap->user_heap.chunk;	/* allocation chunk */
      /* total size commited in parent */
      DWORD allocsize = (char *) cygheap->user_heap.top -
			(char *) cygheap->user_heap.base;
      /* round up by chunk size */
      DWORD reserve_size = chunk * ((allocsize + (chunk - 1)) / chunk);

      /* Loop until we've managed to reserve an adequate amount of memory. */
      char *p;
      for (;;)
	{
	  p = (char *) VirtualAlloc (cygheap->user_heap.base, reserve_size,
				     MEM_RESERVE, PAGE_READWRITE);
	  if (p)
	    break;
	  if ((reserve_size -= page_const) <= allocsize)
	    break;
	}
      if (p != cygheap->user_heap.base)
	api_fatal ("heap allocated but not at %p", cygheap->user_heap.base);
      if (!VirtualAlloc (cygheap->user_heap.base, allocsize, MEM_COMMIT, PAGE_READWRITE))
	api_fatal ("MEM_COMMIT failed, %E");
    }

  debug_printf ("heap base %p, heap top %p", cygheap->user_heap.base,
		cygheap->user_heap.top);
  page_const--;
  malloc_init ();
}

#define pround(n) (((size_t)(n) + page_const) & ~page_const)

/* FIXME: This function no longer handles "split heaps". */

extern "C" void *
sbrk (int n)
{
  char *newtop, *newbrk;
  unsigned commitbytes, newbrksize;

  if (n == 0)
    return cygheap->user_heap.ptr;		/* Just wanted to find current cygheap->user_heap.ptr address */

  newbrk = (char *) cygheap->user_heap.ptr + n;	/* Where new cygheap->user_heap.ptr will be */
  newtop = (char *) pround (newbrk);		/* Actual top of allocated memory -
						   on page boundary */

  if (newtop == cygheap->user_heap.top)
    goto good;

  if (n < 0)
    {						/* Freeing memory */
      assert (newtop < cygheap->user_heap.top);
      n = (char *) cygheap->user_heap.top - newtop;
      if (VirtualFree (newtop, n, MEM_DECOMMIT)) /* Give it back to OS */
	goto good;				/*  Didn't take */
      else
	goto err;
    }

  assert (newtop > cygheap->user_heap.top);

  /* Find the number of bytes to commit, rounded up to the nearest page. */
  commitbytes = pround (newtop - (char *) cygheap->user_heap.top);

  /* Need to grab more pages from the OS.  If this fails it may be because
     we have used up previously reserved memory.  Or, we're just plumb out
     of memory.  Only attempt to commit memory that we know we've previously
     reserved.  */
  if (newtop <= cygheap->user_heap.max)
    {
      if (VirtualAlloc (cygheap->user_heap.top, commitbytes, MEM_COMMIT, PAGE_READWRITE) != NULL)
	goto good;
    }

  /* Couldn't allocate memory.  Maybe we can reserve some more.
     Reserve either the maximum of the standard cygwin_shared->heap_chunk_size ()
     or the requested amount.  Then attempt to actually allocate it.  */
  if ((newbrksize = cygheap->user_heap.chunk) < commitbytes)
    newbrksize = commitbytes;

   if ((VirtualAlloc (cygheap->user_heap.top, newbrksize, MEM_RESERVE, PAGE_NOACCESS)
        || VirtualAlloc (cygheap->user_heap.top, newbrksize = commitbytes, MEM_RESERVE, PAGE_NOACCESS))
       && VirtualAlloc (cygheap->user_heap.top, commitbytes, MEM_COMMIT, PAGE_READWRITE) != NULL)
     {
	cygheap->user_heap.max = (char *) cygheap->user_heap.max + pround (newbrksize);
	goto good;
     }

err:
  set_errno (ENOMEM);
  return (void *) -1;

good:
  void *oldbrk = cygheap->user_heap.ptr;
  cygheap->user_heap.ptr = newbrk;
  cygheap->user_heap.top = newtop;
  return oldbrk;
}