gpsr core

pseudo-code

note:

C : Current node.
D : Destination node.
set_C : Set of neighbor nodes of C.
M,N：the neighbor of C.
flag : neighbor node is available or not
d_(neighbor→D ): The distance from neighbor to D.
θ_neighbor : The corresponding angle of neighbor.
Q : The allowed communication area.

---

greedy_forward

Caculate min = d_(C->D);
Initialize nexthop;

while(N in set_C)//对当前节点的所有邻居节点
	Caculate d_(N->D)
	if d_(N->D)<min then
		min = d_(N->D);
		nexthop <- N;
	end if
end while

return nexthop;

---

rng_planarize

while(N in set_C)  do //对当前节点的所有邻居节点
	Caculate d_(N->C); 
	
	while(M in set_C) do
		Caculate d_(M->C);
		Caculate d_(M->N);
		if d_(M->C)<d(N->C) && d_(M->N)<d(N->C) then
			N <- unavailable;
			//remove node N from the list
			break; //舍弃节点N
		end if
	end while 
		
	if(N is available) then 
		add the node into newset;
	end if
end while

return newset;

---

gg_planarize

while(N in set_C) do
	Caculate d_(C->middle);

	while(M in set_C) do
		if(N != M) then
			Caculate d_(M->middle);
			if(d(M->caculate) < d(C->middle)) then
				N <- unavailable;
				//remove node N from the list
				break; //舍弃节点N
			end if
		end if
	end while

	if(N is available) then
		add the node into newset;
	end if
end while
return nweset;

---

angle

exist two nodes R1(x1, y1) and R2(x2, y2)
caculate the relative angle of line R1->R2

Caculate d_(R1->R2);
if d_(R1->R2) then
	R1 and R2 are the same;
else
	Caculate sin = (y2-y1) / d_(R1->R2);
	Caculate cos = (x2-x1) / d_(R1->R2);
	Caculate theta = arccos(cos);
	if sin < 0 then
		//R2 在 R1 的负方向
		theta = 2*PI - theta;
	end if
end if
return theta;

---

intersect

在这篇博客中介绍了判断线段是否相交的方法，感觉讲的也比较详细。
current a(x1, y1) nexthop b(x2,y2)
source c(x3, y3) destination d(x4, y4)

if 'the rectangle of ab' and 'the rectangle of cd' have public areas then
	Caculate u = (c.x-a.x)*(b.y-a.y)-(b.x-a.x)*(c.y-a.y);
	Caculate v = (d.x-a.x)*(b.y-a.y)-(b.x-a.x)*(d.y-a.y)
	Caculate w = (a.x-c.x)*(d.y-c.y)-(d.x-c.x)*(a.y-c.y);
	Caculate z = (b.x-c.x)*(d.y-c.y)-(d.x-c.x)*(b.y-c.y);
	if u*v <= 0 && w*z <= 0 then
		is crossed;
	else 
		is uncrossed;
	end if
else
	is uncrossed;
end if

---

perimeter_forward

//平面化
if(choose RNG planarization)
	neighborset = rng_planarize();
else
	neighborset = gg_planarize();
end if

//周边转发
if exist last hop M then
	Caculate alpha = θ_M; //计算当前节点与上一跳节点连线ml的夹角
else
	Caculate alpha = θ_D;  //计算当前节点与目的节点连线md的夹角
end if

while(N in neighborset && N is not equivalent to M) //遍历平面化后的邻居列表
	Caculate delta = θ_N;
	//选取逆时针方向的节点
	//且该节点与当前节点的连线与ml或md的夹角是最小的
	delta = delt-alpha;
	if delta < 0.0 then  //两条线的逆时针夹角
		delt = 2*PI + delta;
	end if
	if delt < minangle then
		minangle = delt;
		choose N as the next hop;
	end if
end while

if the line 'from me to the next hop' and the line 'from source and destination' is intersecting each other then
	repeat perimeter_forward with choosing the next hop as the next hop;
end if

---

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