Function get_flow_paths

plugins/renepay/mcf.c:1267–1484

Given a flow in the residual network, build a set of payment flows in the * gossmap that corresponds to this flow. */

/* Given a flow in the residual network, build a set of payment flows in the
 * gossmap that corresponds to this flow. */
static struct flow **
get_flow_paths(const tal_t *ctx, const struct gossmap *gossmap,
	       const bitmap *disabled,

	       // chan_extra_map cannot be const because we use it to keep
	       // track of htlcs and in_flight sats.
	       struct chan_extra_map *chan_extra_map,
	       const struct linear_network *linear_network,
	       const struct residual_network *residual_network,

	       // how many msats in excess we paid for not having msat accuracy
	       // in the MCF solver
	       struct amount_msat excess,
	       const double base_probability,

	       // error message
	       char **fail)
{
	tal_t *this_ctx = tal(ctx,tal_t);
	struct flow **flows = tal_arr(ctx,struct flow*,0);

	assert(amount_msat_less(excess, AMOUNT_MSAT(1000)));

	const size_t max_num_chans = gossmap_max_chan_idx(gossmap);
	struct chan_flow *chan_flow = tal_arrz(this_ctx,struct chan_flow,max_num_chans);

	const size_t max_num_nodes = gossmap_max_node_idx(gossmap);
	s64 *balance = tal_arrz(this_ctx,s64,max_num_nodes);

	const struct gossmap_chan **prev_chan
		= tal_arr(this_ctx,const struct gossmap_chan *,max_num_nodes);


	int *prev_dir = tal_arr(this_ctx,int,max_num_nodes);
	u32 *prev_idx = tal_arr(this_ctx,u32,max_num_nodes);

	if (!chan_flow || !balance || !prev_chan || !prev_idx || !prev_dir) {
		if (fail)
		*fail = tal_fmt(ctx, "bad allocation");
		goto function_fail;
	}

	// Convert the arc based residual network flow into a flow in the
	// directed channel network.
	// Compute balance on the nodes.
	for(u32 n = 0;n<max_num_nodes;++n)
	{
		for(struct arc arc = node_adjacency_begin(linear_network,n);
		        !node_adjacency_end(arc);
			arc = node_adjacency_next(linear_network,arc))
		{
			if(arc_is_dual(arc))
				continue;
			u32 m = arc_head(linear_network,arc);
			s64 flow = get_arc_flow(residual_network,arc);
			u32 chanidx;
			int chandir;