From f7337084adc225216610a71288e48816b276c9bb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kornel=20Lesi=C5=84ski?= <kornel@geekhood.net>
Date: Thu, 17 Jan 2019 16:04:37 +0000
Subject: [PATCH] Assert

---
 src/png/scan_lines.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/png/scan_lines.rs b/src/png/scan_lines.rs
index 460fd0a0..0b1a6f30 100644
--- a/src/png/scan_lines.rs
+++ b/src/png/scan_lines.rs
@@ -153,6 +153,7 @@ impl Iterator for ScanLineRanges {
         let bits_per_line = pixels_per_line * u32::from(self.bits_per_pixel);
         let bytes_per_line = ((bits_per_line + 7) / 8) as usize;
         let len = bytes_per_line + 1;
+        assert!(self.left >= len);
         self.left -= len;
         Some((len, current_pass))
     }