pack.c: add an offset argument to unpack and unpack1

[Feature #18254]

This is useful to avoid repeteadly copying strings when parsing binary formats

1 files changed, 26 insertions, 0 deletions

diff --git a/test/ruby/test_pack.rb b/test/ruby/test_pack.rb
index c9ca9c3dfd..af45adb2b2 100644
--- a/test/ruby/test_pack.rb
+++ b/test/ruby/test_pack.rb
@@ -869,4 +869,30 @@ EXPECTED
     assert_equal "hogefuga", "aG9nZWZ1Z2E=".unpack1("m")
     assert_equal "01000001", "A".unpack1("B*")
   end
+
+  def test_unpack1_offset
+    assert_equal 65, "ZA".unpack1("C", offset: 1)
+    assert_equal "01000001", "YZA".unpack1("B*", offset: 2)
+    assert_nil "abc".unpack1("C", offset: 3)
+    assert_raise_with_message(ArgumentError, /offset can't be negative/) {
+      "a".unpack1("C", offset: -1)
+    }
+    assert_raise_with_message(ArgumentError, /offset outside of string/) {
+      "a".unpack1("C", offset: 2)
+    }
+    assert_nil "a".unpack1("C", offset: 1)
+  end
+
+  def test_unpack_offset
+    assert_equal [65], "ZA".unpack("C", offset: 1)
+    assert_equal ["01000001"], "YZA".unpack("B*", offset: 2)
+    assert_equal [nil, nil, nil], "abc".unpack("CCC", offset: 3)
+    assert_raise_with_message(ArgumentError, /offset can't be negative/) {
+      "a".unpack("C", offset: -1)
+    }
+    assert_raise_with_message(ArgumentError, /offset outside of string/) {
+      "a".unpack("C", offset: 2)
+    }
+    assert_equal [nil], "a".unpack("C", offset: 1)
+  end
 end