how to understand those assembly code well.

i find some assembly code, but i can not unstandard it well, could someone convert it into c++ code?
****************code begin****************
procedure _FillLongwordRect(Src: Pointer; W, H, X1, Y1, X2, Y2: Integer; Value: Longword);
asm
PUSH EDI
PUSH EAX
PUSH EBX
PUSH ECX
PUSH EDX

MOV EDI, EAX
XOR EBX, EBX
XOR EAX, EAX
MOV EBX, W
MOV EAX, Y1
MUL EBX
ADD EAX, X1
ADD EDI, EAX
ADD EDI, EAX
ADD EDI, EAX
ADD EDI, EAX

MOV EBX, X2
SUB EBX, X1
INC EBX
TEST EBX,EBX
JS @exit

MOV EDX, Y2
SUB EDX, Y1
INC EDX
TEST EDX,EDX
JS @exit
MOV EAX, VALUE

@1:
PUSH EDI
MOV ECX, EBX
CLD
REP STOSD
POP EDI
POP ECX
ADD EDI, ECX
ADD EDI, ECX
ADD EDI, ECX
ADD EDI, ECX
PUSH ECX
DEC EDX
CMP EDX, 0
JNE @1

@exit:
POP EDX
POP ECX
POP EBX
POP EAX
POP EDI
end;
****************code end****************

unsigned int VideoMemory[800*600]; unsigned int Y,i,k,r,n,c,W = 800,H = 600, X1 = 0,Y1 = 0,X2 =10,Y2 = 10,Value = 0x00ffffff; if (X2 < X1 || Y2 < Y1) return ; Y = (Y1*W) + X1; i = Y*4 ; c = (X2 - X1) ; r = (Y2 - Y1) ; do { for(n=0;n<=c;n++) { VideoMemory[i+ n]= Value ; } i+= W*H*4; r--; } while (r>0);