From 183635ab5614acfa0acc2d93dc1f460d3e443050 Mon Sep 17 00:00:00 2001
From: Sutou Kouhei <kou@clear-code.com>
Date: Mon, 26 Jun 2023 14:29:26 +0900
Subject: [PATCH] Fix a bug that the same line is used multiple times

GitHub: fix GH-279

It's happen when:

* `keep_start`/`keep_{drop,back}` are nested.
  (e.g.: `strip: true, skip_lines: /.../`)
* Row separator is `\r\n`.
* `InputScanner` is used. (Small input doesn't use `InputScanner`)

Reported by Gabriel Nagy. Thanks!!!
---
 lib/csv/parser.rb                 | 3 ++-
 test/csv/parse/test_skip_lines.rb | 8 ++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/csv/parser.rb b/lib/csv/parser.rb
index 3b051320..ed9297fe 100644
--- a/lib/csv/parser.rb
+++ b/lib/csv/parser.rb
@@ -201,7 +201,8 @@ def keep_back
           # trace(__method__, :rescan, start, buffer)
           string = @scanner.string
           if scanner == @scanner
-            keep = string.byteslice(start, string.bytesize - start)
+            keep = string.byteslice(start,
+                                    string.bytesize - @scanner.pos - start)
           else
             keep = string
           end
diff --git a/test/csv/parse/test_skip_lines.rb b/test/csv/parse/test_skip_lines.rb
index d231cc65..2fea02eb 100644
--- a/test/csv/parse/test_skip_lines.rb
+++ b/test/csv/parse/test_skip_lines.rb
@@ -115,4 +115,12 @@ def test_crlf
                  CSV.parse("a,b\r\n,\r\n",
                            :skip_lines => /^,+$/))
   end
+
+  def test_crlf_strip_no_last_crlf
+    assert_equal([["a"], ["b"]],
+                 CSV.parse("a\r\nb",
+                           row_sep: "\r\n",
+                           skip_lines: /^ *$/,
+                           strip: true))
+  end
 end