2 files changed, 57 insertions, 7 deletions
diff --git a/ext/strscan/lib/strscan.rb b/ext/strscan/lib/strscan.rb
new file mode 100644
index 0000000000..4e8910d141
--- /dev/null
+++ b/ext/strscan/lib/strscan.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+case RUBY_ENGINE
+when 'ruby'
+  require 'strscan.so'
+  require_relative 'strscan/strscan'
+when 'jruby'
+  require 'strscan.jar'
+  JRuby::Util.load_ext('org.jruby.ext.strscan.StringScannerLibrary')
+  require_relative 'strscan/strscan'
+when 'truffleruby'
+  if RUBY_ENGINE_VERSION.to_i >= 34
+    require 'strscan/truffleruby'
+  else
+    $LOAD_PATH.delete __dir__
+    require 'strscan'
+  end
+else
+  raise NotImplementedError, "Unknown Ruby: #{RUBY_ENGINE}"
+end
diff --git a/ext/strscan/lib/strscan/strscan.rb b/ext/strscan/lib/strscan/strscan.rb
index 46acc7ea82..5e262f4007 100644
--- a/ext/strscan/lib/strscan/strscan.rb
+++ b/ext/strscan/lib/strscan/strscan.rb
@@ -1,17 +1,47 @@
 # frozen_string_literal: true
 
 class StringScanner
+  unless method_defined?(:integer_at) # For JRuby
+    def integer_at(specifier, *to_i_args)
+      self[specifier]&.to_i(*to_i_args)
+    end
+  end
+
+  # :markup: markdown
+  #
   # call-seq:
-  #   scan_integer(base: 10)
+  #   scan_integer(base: 10) -> integer or nil
+  #
+  # Returns an integer scanned from `self`,
+  # beginning at the current position;
+  # returns `nil` if no such integer was available.
+  #
+  # When `base` is `10` (the default),
+  # equivalent to calling #scan with argument +pattern+
+  # as `'[+-]?\d+'`:
+  #
+  # ```ruby
+  # scanner = StringScanner.new('Form 27B/6')
+  # scanner.scan_integer # => nil # No integer at position 0.
+  # scanner.pos = 5
+  # scanner.scan_integer # => 27
+  # scanner.matched      # => "27"
+  # scanner.pos          # => 7
+  # ```
   #
-  # If `base` isn't provided or is `10`, then it is equivalent to calling `#scan` with a `[+-]?\d+` pattern,
-  # and returns an Integer or nil.
+  # When `base` is `16` (the only other value allowed),
+  # equivalent to calling #scan with argument `pattern`
+  # as `'[+-]?(0x)?[0-9a-fA-F]+'`:
   #
-  # If `base` is `16`, then it is equivalent to calling `#scan` with a `[+-]?(0x)?[0-9a-fA-F]+` pattern,
-  # and returns an Integer or nil.
+  # ```ruby
+  # scanner.pos = 5
+  # scanner.scan_integer(base: 16) # => 635
+  # scanner.matched                # => "27B"
+  # scanner.pos                    # => 8
+  # ```
   #
-  # The scanned string must be encoded with an ASCII compatible encoding, otherwise
-  # Encoding::CompatibilityError will be raised.
+  # Raises Encoding::CompatibilityError if `self` does not have
+  # an ASCII compatible encoding.
   def scan_integer(base: 10)
     case base
     when 10