$//$ HEAP EXPANSION FUNCTIONS

$//$ REQUIRED

$//$ Attempts to append pages of memory to the heap with mmap $().$ npages

$//$ is how many pages are to be appended with total bytes to be

$//$ appended as npages $*$ EL$\_$PAGE BYTES. Calls mmap$()$ with similar

$//$ arguments to those used in el$\_\_$init$()$ however requests the address

$//$ of the pages to be at heap$\_$end so that the heap grows

$//$ contiguously. If this fails, prints the message

$/$l

$//$ ERROR: Unable to mmap$()$ additional $3$ pages

$\frac{1}{?}$

$\frac{\frac{?}{?}}{?}$ and returns $1.$ Note that mmap$()$ returns the constant HAP$\_$FAILED on

$\frac{\frac{?}{?}}{?}$ errors and the returned address will not match the requested

$//$ virtual address on fallures.

$\frac{\frac{?}{?}}{?}$

$//$ Otherwise, adjusts heap size and end for the expanded heap. Creates

$//$ a new block for the freshly allocated pages that is added to the

$//$ ava; able list. Also attempts to merge this block with the block

$//$ below it$.$ Returns $$ on success.

int el$\_$append$\_$pages$\_$to$\_$heap$($int npages$)\{$