From 7bfbee136ec19b94359068bbaaa7acf7eb59cfa9 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Mon, 2 May 2016 15:57:56 +0930
Subject: [PATCH] permute_tx: fix map logic (again!)

8a4246cb368d (permute: use BIP69 order) removed the invert_map change
from a25ba452f34f (permute_tx: fix horrible thinko.) but it's still
needed.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 permute_tx.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/permute_tx.c b/permute_tx.c
index 85293e959..7c1a5934a 100644
--- a/permute_tx.c
+++ b/permute_tx.c
@@ -13,6 +13,21 @@ static void init_map(size_t *map, size_t len)
 		map[i] = i;
 }
 
+/* This map says where things ended up, eg. 0 might be in slot 3.  we
+ * want to change it so map[0] = 3. */
+static void invert_map(size_t *map, size_t len)
+{
+	if (map) {
+		size_t i, newmap[len];
+
+		memset(newmap, 0, sizeof(newmap));
+		for (i = 0; i < len; i++) {
+			newmap[map[i]] = i;
+		}
+		memcpy(map, newmap, sizeof(newmap));
+	}
+}
+
 static bool input_better(const struct bitcoin_tx_input *a,
 			 const struct bitcoin_tx_input *b)
 {
@@ -75,6 +90,8 @@ void permute_inputs(struct bitcoin_tx_input *inputs,
 		swap_inputs(inputs, map,
 			    i, i + find_best_in(inputs + i, num_inputs - i));
 	}
+
+	invert_map(map, num_inputs);
 }
 
 static void swap_outputs(struct bitcoin_tx_output *outputs, size_t *map,
@@ -141,4 +158,6 @@ void permute_outputs(struct bitcoin_tx_output *outputs,
 		swap_outputs(outputs, map,
 			     i, i + find_best_out(outputs + i, num_outputs - i));
 	}
+
+	invert_map(map, num_outputs);
 }