/* Author : Raj Bandyopadhyay, Rice University (rajb@rice.edu)
 * Date: July 28, 2008
 *
 * This code has been developed and is owned by the
 * Resource Aware Programming (RAP) Group, Rice University.
 * URL: http://www.resource-aware.org
 *
 * This code is offered as is, to the OCaml project without any restrictions
 * or warranties.
 *
 * For further enquiries about the RAP group, please contact 
 * Prof Walid Taha (taha@rice.edu)
 *
 */





CAMLprim value caml_general_array_sub(value source, value ofs, value len)
{
    CAMLparam3 (source,ofs,len);
    CAMLlocal2 (res,elt);
    mlsize_t size, srcsize, wsize, i,offset;
    double d;

    srcsize = Wosize_val(source);
    size = Long_val(len);
    offset = Long_val(ofs);

    //boundary checks

    if (offset < 0 || size < 0 || offset > (srcsize - size))
        caml_invalid_argument("Array.sub");

    //for a source array of size 0, return empty array
    if (size == 0)
    {
        res = Atom(0);
    }
    else
    {
        //Retrieve one element of the source array and check its type
        elt = Field(source,0);

        //specialize for arrays of doubles
        if (Is_block(elt)
           && Is_in_value_area(elt)
           && Tag_val(elt) == Double_tag) 
        {
            wsize = size * Double_wosize;
            if (wsize > Max_wosize) caml_invalid_argument("Array.sub");
            res = caml_alloc(wsize, Double_array_tag);
            for (i = 0; i < size; i++) 
            {
                d = Double_val(Field(source,i+offset));
                Store_double_field(res, i, d);
            }
        }
        else 
        {
	        if (size > Max_wosize) caml_invalid_argument("Array.sub");
            //for small arrays
	        if (size < Max_young_wosize)
	        {
	            res = caml_alloc_small(size, 0);
	            for (i = 0; i < size; i++)
	            {
	                Field(res, i) = Field(source,i+offset);
	            }
	        }//if
	        else
	        {
                if (Is_block(elt) && Is_young(elt)) 
                { 
		            caml_minor_collection();
		            res = caml_alloc_shr(size, 0);
		            for (i = 0; i < size; i++)
		            {
		                Field(res, i) = Field(source,i+offset);
		            }
		            res = caml_check_urgent_gc (res);
                }//if
                else
                { 
		            res = caml_alloc_shr(size, 0);
		            for (i = 0; i < size; i++)
		            {
		                caml_initialize(&Field(res, i), Field(source,i+offset));
		            }
		            res = caml_check_urgent_gc (res);
                }//else

	        }//else
        }//else
    }//else 
    CAMLreturn (res);
}//caml_general_array_sub