帮我看看这段汇编代码

[shiove]

__thiscall ABinaryStream::pastEndWith(unsigned long) {

arg_0 = dowrd ptr 4

mov edx, [ecx]
mov eax, [esp + arg_0]
add eax, edx
cmp byte ptr [ecx + 0ah], 0
jnz l1

cmp eax, [ecx + 4]
ja l1

cmp eax, edx
jb l1

xor al, al
jmp l2

l1:
mov [ecx], eax
mov byte ptr [ecx + 0ah], 1
mov al, 1

l2:
retn 4
}

能告诉我是什么意思吗？能看懂操作，但是我自己说不出这段代码到底要做什么事情，
谢谢了，急啊！

[greatws]

class ABinaryStream
{
int a;
int b;
char c[4];
...
}


bool __thiscall ABinaryStream::pastEndWith(unsigned long arg) 
{
int aa = a + arg;
if(c[1] != 0 || aa > b || aa < a)
{
  a = aa;
  c[1] = 1;
  return true;
}
return false;
}

[greatws]

还请大家指正