reallocarray.c


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#include "malloc.h"
#include <assert.h>
#include <string.h>

void*
__reallocarray_impl(heap_cache_t *cache, void *ptr, size_t nmemb, size_t w)
{
    /* Free if w == nmemb == 0*/
    if(w == 0 || nmemb == 0) {
        __free_impl(cache, ptr);
        return NULL;
    }
    
    if(ptr == NULL)
        return __calloc_impl(cache, nmemb, w);

    size_t allocw = w * nmemb;
    w = REALW(w);
    
    bucket_obj_t *obj = OBJ_FROM_PTR(ptr);
    assert(OBJ_VALID(obj));
    size_t oldw = OBJ_WIDTH(obj);
    if(allocw < oldw) return ptr;

    ptr = __realloc_impl(cache, ptr, allocw);
    size_t wdiff = allocw - oldw;
    void *zeroat = (void*)(((uintptr_t)ptr) + oldw);
    memset(zeroat, 0, wdiff);
    return ptr;
}