Mirror of :pserver:cvs@cvs.fefe.de:/cvs libowfat https://www.fefe.de/libowfat/
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#include "likely.h"
#include <stdlib.h>
#include "iarray.h"
void* iarray_allocate(iarray* ia,size_t pos) {
size_t y;
/* first the easy case without locking */
if (__likely((y=pos/ia->elemperpage) < ia->pagefence && ia->pages[y]))
return ia->pages[y]+(pos%ia->elemperpage)*ia->elemsize;
/* the case where ia->pages == NULL is implicit */
#ifdef __MINGW32__
EnterCriticalSection(&ia->cs);
#else
pthread_mutex_lock(&ia->m);
#endif
if (__unlikely(y >= ia->pagefence)) {
char** np;
/* The data structure is an array of pointer to pages.
* Each page holds at least one element of the array.
* Here we realloc the array of pointers. Each element in this
* array is only 4 or 8 bytes, so we should allocate a few more than
* we need to cut down on future reallocs. */
size_t z=(y+512)&-512; /* round up to multiple of 512 */
/* It may seem as if there can be no integer overflow in the
* indirect index, because then the array would not fit into the
* address space in the first place, but remember that this is a
* sparse array. Someone might just pass in an unreasonable large
* index and have large elements, too */
if (z==0) goto unlockandfail; /* integer overflow */
np=realloc(ia->pages,z*ia->bytesperpage);
if (!np) goto unlockandfail;
ia->pagefence=z;
ia->pages=np;
}
/* at this point we know the slot exists */
/* through a race between the early-out above and the
* pthread_mutex_lock, the page pointer to it could be non-NULL,
* however */
if (__unlikely(ia->pages[y]==0 && (ia->pages[y]=malloc(ia->bytesperpage))==0)) {
unlockandfail:
#ifdef __MINGW32__
LeaveCriticalSection(&ia->cs);
#else
pthread_mutex_unlock(&ia->m);
#endif
return 0;
}
#ifdef __MINGW32__
LeaveCriticalSection(&ia->cs);
#else
pthread_mutex_unlock(&ia->m);
#endif
return ia->pages[y] + (pos%ia->elemperpage)*ia->elemsize;
}