Move IO#readline to Ruby

This commit moves IO#readline to Ruby.  In order to call C functions,
keyword arguments must be converted to hashes.  Prior to this commit,
code like `io.readline(chomp: true)` would allocate a hash.  This
commits moves the keyword "denaturing" to Ruby, allowing us to send
positional arguments to the C API and avoiding the hash allocation.

Here is an allocation benchmark for the method:

```
x = GC.stat(:total_allocated_objects)
File.open("/usr/share/dict/words") do |f|
  f.readline(chomp: true) until f.eof?
end
p ALLOCATIONS: GC.stat(:total_allocated_objects) - x
```

Before this commit, the output was this:

```
$ make run
./miniruby -I./lib -I. -I.ext/common  -r./arm64-darwin22-fake  ./test.rb
{:ALLOCATIONS=>707939}
```

Now it is this:

```
$ make run
./miniruby -I./lib -I. -I.ext/common  -r./arm64-darwin22-fake  ./test.rb
{:ALLOCATIONS=>471962}
```

[Bug #19890] [ruby-core:114803]

1 files changed, 104 insertions, 0 deletions

diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index 7689b52e23..476d9f882f 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -1898,6 +1898,110 @@ class TestIO < Test::Unit::TestCase
     end)
   end
 
+  def test_readline_bad_param_raises
+    File.open(__FILE__) do |f|
+      assert_raise(TypeError) do
+        f.readline Object.new
+      end
+    end
+
+    File.open(__FILE__) do |f|
+      assert_raise(TypeError) do
+        f.readline 1, 2
+      end
+    end
+  end
+
+  def test_readline_raises
+    File.open(__FILE__) do |f|
+      assert_equal File.read(__FILE__), f.readline(nil)
+      assert_raise(EOFError) do
+        f.readline
+      end
+    end
+  end
+
+  def test_readline_separators
+    File.open(__FILE__) do |f|
+      line = f.readline("def")
+      assert_equal File.read(__FILE__)[/\A.*?def/m], line
+    end
+
+    File.open(__FILE__) do |f|
+      line = f.readline("def", chomp: true)
+      assert_equal File.read(__FILE__)[/\A.*?(?=def)/m], line
+    end
+  end
+
+  def test_readline_separators_limits
+    t = Tempfile.open("readline_limit")
+    str = "#" * 50
+    sep = "def"
+
+    t.write str
+    t.write sep
+    t.write str
+    t.flush
+
+    # over limit
+    File.open(t.path) do |f|
+      line = f.readline sep, str.bytesize
+      assert_equal(str, line)
+    end
+
+    # under limit
+    File.open(t.path) do |f|
+      line = f.readline(sep, str.bytesize + 5)
+      assert_equal(str + sep, line)
+    end
+
+    # under limit + chomp
+    File.open(t.path) do |f|
+      line = f.readline(sep, str.bytesize + 5, chomp: true)
+      assert_equal(str, line)
+    end
+  ensure
+    t&.close!
+  end
+
+  def test_readline_limit_without_separator
+    t = Tempfile.open("readline_limit")
+    str = "#" * 50
+    sep = "\n"
+
+    t.write str
+    t.write sep
+    t.write str
+    t.flush
+
+    # over limit
+    File.open(t.path) do |f|
+      line = f.readline str.bytesize
+      assert_equal(str, line)
+    end
+
+    # under limit
+    File.open(t.path) do |f|
+      line = f.readline(str.bytesize + 5)
+      assert_equal(str + sep, line)
+    end
+
+    # under limit + chomp
+    File.open(t.path) do |f|
+      line = f.readline(str.bytesize + 5, chomp: true)
+      assert_equal(str, line)
+    end
+  ensure
+    t&.close!
+  end
+
+  def test_readline_chomp_true
+    File.open(__FILE__) do |f|
+      line = f.readline(chomp: true)
+      assert_equal File.readlines(__FILE__).first.chomp, line
+    end
+  end
+
   def test_set_lineno_readline
     pipe(proc do |w|
       w.puts "foo"