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/* heap.cc: Cygwin heap manager.
Copyright 1996, 1997, 1998, 1999, 2000, 2001 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 <errno.h>
#include "cygerrno.h"
#include "sync.h"
#include "sigproc.h"
#include "pinfo.h"
#include "heap.h"
#include "shared_info.h"
#define assert(x)
static unsigned page_const = 0;
extern "C" size_t getpagesize ();
/* 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 (brkbase)
{
DWORD chunk = brkchunk; /* allocation chunk */
/* total size commited in parent */
DWORD allocsize = (char *) brktop - (char *) brkbase;
/* 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 (brkbase, reserve_size,
MEM_RESERVE, PAGE_READWRITE);
if (p)
break;
if ((reserve_size -= page_const) <= allocsize)
break;
}
if (p == NULL)
api_fatal ("1. unable to allocate heap %p, heap_chunk_size %d, pid %d, %E",
brkbase, brkchunk, myself->pid);
if (p != brkbase)
api_fatal ("heap allocated but not at %p", brkbase);
if (! VirtualAlloc (brkbase, allocsize, MEM_COMMIT, PAGE_READWRITE))
api_fatal ("MEM_COMMIT failed, %E");
}
else
{
/* Initialize page mask and default heap size. Preallocate a heap
* to assure contiguous memory. */
brk = brktop = brkbase = VirtualAlloc(NULL, brkchunk, MEM_RESERVE, PAGE_NOACCESS);
if (brkbase == NULL)
api_fatal ("2. unable to allocate heap, heap_chunk_size %d, %E",
brkchunk);
}
debug_printf ("heap base %p, heap top %p", brkbase, brktop);
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)
{
sigframe thisframe (mainthread);
char *newtop, *newbrk;
unsigned commitbytes, newbrksize;
if (n == 0)
return brk; /* Just wanted to find current brk address */
newbrk = (char *) brk + n; /* Where new brk will be */
newtop = (char *) pround (newbrk); /* Actual top of allocated memory -
on page boundary */
if (newtop == brktop)
goto good;
if (n < 0)
{ /* Freeing memory */
assert(newtop < brktop);
n = (char *) brktop - newtop;
if (VirtualFree(newtop, n, MEM_DECOMMIT)) /* Give it back to OS */
goto good; /* Didn't take */
else
goto err;
}
assert(newtop > brktop);
/* 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. */
commitbytes = pround (newtop - (char *) brktop);
if (VirtualAlloc(brktop, 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 brkchunk or the requested
amount. Then attempt to actually allocate it. */
if ((newbrksize = brkchunk) < commitbytes)
newbrksize = commitbytes;
if ((VirtualAlloc(brktop, newbrksize, MEM_RESERVE, PAGE_NOACCESS) != NULL) &&
(VirtualAlloc(brktop, commitbytes, MEM_COMMIT, PAGE_READWRITE) != NULL))
goto good;
err:
set_errno (ENOMEM);
return (void *) -1;
good:
void *oldbrk = brk;
brk = newbrk;
brktop = newtop;
return oldbrk;
}
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