Ruby: Add method KernAux.sprintf1

pkgs/ruby/lib/kernaux.rb

@@ -6,18 +6,28 @@ require_relative 'kernaux/version'
 # Auxiliary library for kernel development.
 #
 module KernAux
-  # Default callback for assertions
-  DEFAULT_ASSERT_CB = lambda { |file, line, str|
+  # Default callback for assertions ({.assert_cb})
+  DEFAULT_ASSERT_CB = @assert_cb = lambda { |file, line, str|
     raise AssertError, "#{file}:#{line}:#{str}"
   }
 
-  @assert_cb = DEFAULT_ASSERT_CB
+  # Buffer size for {.sprintf1}
+  # @todo make it dynamic
+  SPRINTF1_BUFFER_SIZE = 10_000
 
   def self.panic(msg)
     file, line = caller(1..1).first.split(':')[0..1]
     assert_do file, Integer(line), msg
   end
 
+  def self.sprintf1(format, arg = nil)
+    if arg.nil?
+      snprintf1(SPRINTF1_BUFFER_SIZE, format).first
+    else
+      snprintf1(SPRINTF1_BUFFER_SIZE, format, arg).first
+    end
+  end
+
   ##
   # Our base class for runtime errors.
   #

pkgs/ruby/spec/lib/kernaux/sprintf1_spec.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe KernAux, '.sprintf1' do
+  context 'with 1 argument' do
+    subject(:sprintf1) { described_class.sprintf1 format }
+
+    let(:format) { '%%' }
+
+    it { is_expected.to be_instance_of String }
+    it { is_expected.to be_frozen }
+    it { is_expected.to eq described_class.snprintf1(1000, format).first }
+  end
+
+  context 'with 2 argument' do
+    subject(:sprintf1) { described_class.sprintf1 format, arg }
+
+    let(:format) { '%s' }
+    let(:arg) { 'Hello, World!' }
+
+    it { is_expected.to be_instance_of String }
+    it { is_expected.to be_frozen }
+    it { is_expected.to eq described_class.snprintf1(1000, format, arg).first }
+  end
+end