From fc9fc1a04858998d3c6e96cbe473f2dbd62b6eb3 Mon Sep 17 00:00:00 2001
From: ddidderr <ddidderr@paul.network>
Date: Fri, 16 Jun 2023 16:57:25 +0200
Subject: [PATCH] (fix) unsafe array access in skipf and skipb

skipf was accessed at index 81 (len only 81)
skipb was accessed at index -1 (u64::MAX)

I still don't know, why the skipb case didn't crash.
---
 src/main.rs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index ab091b4..0208f17 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -51,7 +51,7 @@ impl SField {
             fixed_count
         }
 
-        let mut skipf = vec![0; NUM_FIELDS];
+        let mut skipf = vec![0; NUM_FIELDS + 1];
         for (idx, nr) in field.iter().enumerate() {
             match nr {
                 0 => skipf[idx] = *nr,
@@ -59,11 +59,11 @@ impl SField {
             }
         }
 
-        let mut skipb = vec![0; NUM_FIELDS];
+        let mut skipb = vec![0; NUM_FIELDS + 1];
         for (idx, nr) in field.iter().enumerate().rev() {
             match nr {
-                0 => skipb[idx] = *nr,
-                _ => skipb[idx] = find_fixed_streak_backward(idx, &field),
+                0 => skipb[idx + 1] = *nr,
+                _ => skipb[idx + 1] = find_fixed_streak_backward(idx, &field),
             }
         }
 
@@ -257,7 +257,7 @@ impl SField {
     }
 
     fn prev(&mut self) -> bool {
-        let new_pos = self.pos - 1 - unsafe { *self.skipb.get_unchecked(self.pos - 1) as usize };
+        let new_pos = self.pos - 1 - unsafe { *self.skipb.get_unchecked(self.pos) as usize };
 
         if new_pos >= NUM_FIELDS {
             return false;