Replace Date and DateTime classes from C to Ruby.

C implementation has been rewritten as faithfully as possible in pure Ruby.

[Feature #21264]

https://bugs.ruby-lang.org/issues/21264

Author: jinroq

Rakefile

@@ -1,30 +1,47 @@
 require "bundler/gem_tasks"
 require "rake/testtask"
-require "shellwords"
-require "rake/extensiontask"
 
-extask = Rake::ExtensionTask.new("date") do |ext|
-  ext.name = "date_core"
-  ext.lib_dir.sub!(%r[(?=/|\z)], "/#{RUBY_VERSION}/#{ext.platform}")
-end
+if RUBY_VERSION >= "3.3"
+  # Pure Ruby — no compilation needed
+  Rake::TestTask.new(:test) do |t|
+    t.libs << "lib"
+    t.libs << "test/lib"
+    t.ruby_opts << "-rhelper"
+    t.test_files = FileList['test/**/test_*.rb']
+  end
 
-Rake::TestTask.new(:test) do |t|
-  t.libs << extask.lib_dir
-  t.libs << "test/lib"
-  t.ruby_opts << "-rhelper"
-  t.test_files = FileList['test/**/test_*.rb']
-end
+  task :compile  # no-op
+
+else
+  # C extension for Ruby < 3.3
+  require "shellwords"
+  require "rake/extensiontask"
+
+  extask = Rake::ExtensionTask.new("date") do |ext|
+    ext.name = "date_core"
+    ext.lib_dir.sub!(%r[(?=/|\z)], "/#{RUBY_VERSION}/#{ext.platform}")
+  end
+
+  Rake::TestTask.new(:test) do |t|
+    t.libs << extask.lib_dir
+    t.libs << "test/lib"
+    t.ruby_opts << "-rhelper"
+    t.test_files = FileList['test/**/test_*.rb']
+  end
+
+  task test: :compile
 
-task compile: "ext/date/zonetab.h"
-file "ext/date/zonetab.h" => "ext/date/zonetab.list" do |t|
-  dir, hdr = File.split(t.name)
-  make_program_name =
-    ENV['MAKE'] || ENV['make'] ||
-    RbConfig::CONFIG['configure_args'][/with-make-prog\=\K\w+/] ||
-    (/mswin/ =~ RUBY_PLATFORM ? 'nmake' : 'make')
-  make_program = Shellwords.split(make_program_name)
-  sh(*make_program, "-f", "prereq.mk", "top_srcdir=.."+"/.."*dir.count("/"),
-     hdr, chdir: dir)
+  task compile: "ext/date/zonetab.h"
+  file "ext/date/zonetab.h" => "ext/date/zonetab.list" do |t|
+    dir, hdr = File.split(t.name)
+    make_program_name =
+      ENV['MAKE'] || ENV['make'] ||
+      RbConfig::CONFIG['configure_args'][/with-make-prog\=\K\w+/] ||
+      (/mswin/ =~ RUBY_PLATFORM ? 'nmake' : 'make')
+    make_program = Shellwords.split(make_program_name)
+    sh(*make_program, "-f", "prereq.mk", "top_srcdir=.."+"/.."*dir.count("/"),
+       hdr, chdir: dir)
+  end
 end
 
 task :default => [:compile, :test]

date.gemspec

@@ -1,29 +1,19 @@
 # frozen_string_literal: true
 
-version = File.foreach(File.expand_path("../lib/date.rb", __FILE__)).find do |line|
-  /^\s*VERSION\s*=\s*["'](.*)["']/ =~ line and break $1
-end
+require_relative "lib/date/version"
 
 Gem::Specification.new do |s|
   s.name = "date"
-  s.version = version
+  s.version = Date::VERSION
   s.summary = "The official date library for Ruby."
   s.description = "The official date library for Ruby."
 
-  if Gem::Platform === s.platform and s.platform =~ 'java' or RUBY_ENGINE == 'jruby'
-    s.platform = 'java'
-    # No files shipped, no require path, no-op for now on JRuby
-  else
-    s.require_path = %w{lib}
+  s.require_path = %w{lib}
 
-    s.files = [
-      "README.md", "COPYING", "BSDL",
-      "lib/date.rb", "ext/date/date_core.c", "ext/date/date_parse.c", "ext/date/date_strftime.c",
-      "ext/date/date_strptime.c", "ext/date/date_tmx.h", "ext/date/extconf.rb", "ext/date/prereq.mk",
-      "ext/date/zonetab.h", "ext/date/zonetab.list"
-    ]
-    s.extensions = "ext/date/extconf.rb"
-  end
+  s.files = Dir["README.md", "COPYING", "BSDL", "lib/**/*.rb",
+                "ext/date/*.c", "ext/date/*.h", "ext/date/extconf.rb",
+                "ext/date/prereq.mk", "ext/date/zonetab.list"]
+  s.extensions = ["ext/date/extconf.rb"]
 
   s.required_ruby_version = ">= 2.6.0"
 

ext/date/extconf.rb

@@ -1,13 +1,16 @@
 # frozen_string_literal: true
 require 'mkmf'
 
-config_string("strict_warnflags") {|w| $warnflags += " #{w}"}
-
-append_cflags("-Wno-compound-token-split-by-macro") if RUBY_VERSION < "2.7."
-have_func("rb_category_warn")
-with_werror("", {:werror => true}) do |opt, |
-  have_var("timezone", "time.h", opt)
-  have_var("altzone", "time.h", opt)
+if RUBY_VERSION >= "3.3"
+  # Pure Ruby implementation; skip C extension build
+  File.write("Makefile", dummy_makefile($srcdir).join(""))
+else
+  config_string("strict_warnflags") {|w| $warnflags += " #{w}"}
+  append_cflags("-Wno-compound-token-split-by-macro") if RUBY_VERSION < "2.7."
+  have_func("rb_category_warn")
+  with_werror("", {:werror => true}) do |opt, |
+    have_var("timezone", "time.h", opt)
+    have_var("altzone", "time.h", opt)
+  end
+  create_makefile('date_core')
 end
-
-create_makefile('date_core')

lib/date.rb

@@ -1,11 +1,20 @@
 # frozen_string_literal: true
 # date.rb: Written by Tadayoshi Funaba 1998-2011
 
-require 'date_core'
+if RUBY_VERSION >= "3.3"
+  require_relative "date/version"
+  require_relative "date/constants"
+  require_relative "date/core"
+  require_relative "date/strftime"
+  require_relative "date/parse"
+  require_relative "date/strptime"
+  require_relative "date/time"
+  require_relative "date/datetime"
+else
+  require 'date_core'
+end
 
 class Date
-  VERSION = "3.5.1" # :nodoc:
-
   # call-seq:
   #   infinite? -> false
   #
@@ -64,7 +73,5 @@ def to_f
         -Float::INFINITY
       end
     end
-
   end
-
 end

lib/date/constants.rb

@@ -0,0 +1,182 @@
+# frozen_string_literal: true
+
+# Constants
+class Date
+  HAVE_JD     = 0b00000001  # 1
+  HAVE_DF     = 0b00000010  # 2
+  HAVE_CIVIL  = 0b00000100  # 4
+  HAVE_TIME   = 0b00001000  # 8
+  COMPLEX_DAT = 0b10000000  # 128
+  private_constant :HAVE_JD, :HAVE_DF, :HAVE_CIVIL, :HAVE_TIME, :COMPLEX_DAT
+
+  MONTHNAMES = [nil, "January", "February", "March", "April", "May", "June",
+                "July", "August", "September", "October", "November", "December"]
+                 .map { |s| s&.encode(Encoding::US_ASCII)&.freeze }.freeze
+  ABBR_MONTHNAMES = [nil, "Jan", "Feb", "Mar", "Apr", "May", "Jun",
+                     "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
+                      .map { |s| s&.encode(Encoding::US_ASCII)&.freeze }.freeze
+  DAYNAMES = %w[Sunday Monday Tuesday Wednesday Thursday Friday Saturday]
+               .map { |s| s.encode(Encoding::US_ASCII).freeze }.freeze
+  ABBR_DAYNAMES = %w[Sun Mon Tue Wed Thu Fri Sat]
+                    .map { |s| s.encode(Encoding::US_ASCII).freeze }.freeze
+
+  # Pattern constants for regex
+  ABBR_DAYS_PATTERN = 'sun|mon|tue|wed|thu|fri|sat'
+  DAYS_PATTERN = 'sunday|monday|tuesday|wednesday|thursday|friday|saturday'
+  ABBR_MONTHS_PATTERN = 'jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec'
+  private_constant :ABBR_DAYS_PATTERN, :DAYS_PATTERN, :ABBR_MONTHS_PATTERN
+
+  ITALY     = 2299161 # 1582-10-15
+  ENGLAND   = 2361222 # 1752-09-14
+  JULIAN    = Float::INFINITY
+  GREGORIAN = -Float::INFINITY
+
+  DEFAULT_SG = ITALY
+  private_constant :DEFAULT_SG
+
+  MINUTE_IN_SECONDS      = 60
+  HOUR_IN_SECONDS        = 3600
+  DAY_IN_SECONDS         = 86400
+  HALF_DAYS_IN_SECONDS   = DAY_IN_SECONDS / 2
+  SECOND_IN_MILLISECONDS = 1000
+  SECOND_IN_NANOSECONDS  = 1_000_000_000
+  private_constant :MINUTE_IN_SECONDS, :HOUR_IN_SECONDS, :DAY_IN_SECONDS, :SECOND_IN_MILLISECONDS, :SECOND_IN_NANOSECONDS, :HALF_DAYS_IN_SECONDS
+
+  JC_PERIOD0 = 1461     # 365.25 * 4
+  GC_PERIOD0 = 146097   # 365.2425 * 400
+  CM_PERIOD0 = 71149239 # (lcm 7 1461 146097)
+  CM_PERIOD = (0xfffffff / CM_PERIOD0) * CM_PERIOD0
+  CM_PERIOD_JCY = (CM_PERIOD / JC_PERIOD0) * 4
+  CM_PERIOD_GCY = (CM_PERIOD / GC_PERIOD0) * 400
+  private_constant :JC_PERIOD0, :GC_PERIOD0, :CM_PERIOD0, :CM_PERIOD, :CM_PERIOD_JCY, :CM_PERIOD_GCY
+
+  REFORM_BEGIN_YEAR = 1582
+  REFORM_END_YEAR   = 1930
+  REFORM_BEGIN_JD = 2298874  # ns 1582-01-01
+  REFORM_END_JD = 2426355    # os 1930-12-31
+  private_constant :REFORM_BEGIN_YEAR, :REFORM_END_YEAR, :REFORM_BEGIN_JD, :REFORM_END_JD
+
+  SEC_WIDTH  = 6
+  MIN_WIDTH  = 6
+  HOUR_WIDTH = 5
+  MDAY_WIDTH = 5
+  MON_WIDTH  = 4
+  private_constant :SEC_WIDTH, :MIN_WIDTH, :HOUR_WIDTH, :MDAY_WIDTH, :MON_WIDTH
+
+  SEC_SHIFT  = 0
+  MIN_SHIFT  = SEC_WIDTH
+  HOUR_SHIFT = MIN_WIDTH + SEC_WIDTH
+  MDAY_SHIFT = HOUR_WIDTH + MIN_WIDTH + SEC_WIDTH
+  MON_SHIFT  = MDAY_WIDTH + HOUR_WIDTH + MIN_WIDTH + SEC_WIDTH
+  private_constant :SEC_SHIFT, :MIN_SHIFT, :HOUR_SHIFT, :MDAY_SHIFT, :MON_SHIFT
+
+  PK_MASK = ->(x) { (1 << x) - 1 }
+  private_constant :PK_MASK
+
+  # Days in each month (non-leap and leap year)
+  MONTH_DAYS = [
+    [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31],  # non-leap
+    [0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]   # leap
+  ].freeze
+  private_constant :MONTH_DAYS
+
+  YEARTAB = [
+    [0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334],  # non-leap
+    [0, 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335]   # leap
+  ].freeze
+  private_constant :YEARTAB
+
+  # Neri-Schneider algorithm constants
+  # JDN of March 1, Year 0 in proleptic Gregorian calendar
+  NS_EPOCH = 1721120
+  private_constant :NS_EPOCH
+
+  # Days in a 4-year cycle (3 normal years + 1 leap year)
+  NS_DAYS_IN_4_YEARS = 1461
+  private_constant :NS_DAYS_IN_4_YEARS
+
+  # Days in a 400-year Gregorian cycle (97 leap years in 400 years)
+  NS_DAYS_IN_400_YEARS = 146097
+  private_constant :NS_DAYS_IN_400_YEARS
+
+  # Years per century
+  NS_YEARS_PER_CENTURY = 100
+  private_constant :NS_YEARS_PER_CENTURY
+
+  # Multiplier for extracting year within century using fixed-point arithmetic.
+  # This is ceil(2^32 / NS_DAYS_IN_4_YEARS) for the Euclidean affine function.
+  NS_YEAR_MULTIPLIER = 2939745
+  private_constant :NS_YEAR_MULTIPLIER
+
+  # Coefficients for month calculation from day-of-year.
+  # Maps day-of-year to month using: month = (NS_MONTH_COEFF * doy + NS_MONTH_OFFSET) >> 16
+  NS_MONTH_COEFF  = 2141
+  NS_MONTH_OFFSET = 197913
+  private_constant :NS_MONTH_COEFF, :NS_MONTH_OFFSET
+
+  # Coefficients for civil date to JDN month contribution.
+  # Maps month to accumulated days: days = (NS_CIVIL_MONTH_COEFF * m - NS_CIVIL_MONTH_OFFSET) / 32
+  NS_CIVIL_MONTH_COEFF   = 979
+  NS_CIVIL_MONTH_OFFSET  = 2919
+  NS_CIVIL_MONTH_DIVISOR = 32
+  private_constant :NS_CIVIL_MONTH_COEFF, :NS_CIVIL_MONTH_OFFSET, :NS_CIVIL_MONTH_DIVISOR
+
+  # Days from March 1 to December 31 (for Jan/Feb year adjustment)
+  NS_DAYS_BEFORE_NEW_YEAR = 306
+  private_constant :NS_DAYS_BEFORE_NEW_YEAR
+
+  # Safe bounds for Neri-Schneider algorithm to avoid integer overflow.
+  # These correspond to approximately years -1,000,000 to +1,000,000.
+  NS_JD_MIN = -364_000_000
+  NS_JD_MAX = 538_000_000
+  private_constant :NS_JD_MIN, :NS_JD_MAX
+
+  JULIAN_EPOCH_DATE              = "-4712-01-01"
+  JULIAN_EPOCH_DATETIME          = "-4712-01-01T00:00:00+00:00"
+  JULIAN_EPOCH_DATETIME_RFC2822  = "Mon, 1 Jan -4712 00:00:00 +0000"
+  JULIAN_EPOCH_DATETIME_HTTPDATE = "Mon, 01 Jan -4712 00:00:00 GMT"
+  private_constant :JULIAN_EPOCH_DATE, :JULIAN_EPOCH_DATETIME, :JULIAN_EPOCH_DATETIME_RFC2822, :JULIAN_EPOCH_DATETIME_HTTPDATE
+
+  JISX0301_ERA_INITIALS = 'mtshr'
+  JISX0301_DEFAULT_ERA = 'H'  # obsolete
+  private_constant :JISX0301_ERA_INITIALS, :JISX0301_DEFAULT_ERA
+
+  HAVE_ALPHA = 1 << 0
+  HAVE_DIGIT = 1 << 1
+  HAVE_DASH  = 1 << 2
+  HAVE_DOT   = 1 << 3
+  HAVE_SLASH = 1 << 4
+  private_constant :HAVE_ALPHA, :HAVE_DIGIT, :HAVE_DASH, :HAVE_DOT, :HAVE_SLASH
+
+  # C: default strftime format is US-ASCII
+  STRFTIME_DEFAULT_FMT = '%F'.encode(Encoding::US_ASCII)
+  private_constant :STRFTIME_DEFAULT_FMT
+
+  # strftime spec categories
+  NUMERIC_SPECS = %w[Y C y m d j H I M S L N G g U W V u w s Q].freeze
+  SPACE_PAD_SPECS = %w[e k l].freeze
+  CHCASE_UPPER_SPECS = %w[A a B b h].freeze
+  CHCASE_LOWER_SPECS = %w[Z p].freeze
+  private_constant :NUMERIC_SPECS, :SPACE_PAD_SPECS,
+                   :CHCASE_UPPER_SPECS, :CHCASE_LOWER_SPECS
+
+  # strptime digit-consuming specs
+  NUM_PATTERN_SPECS = "CDdeFGgHIjkLlMmNQRrSsTUuVvWwXxYy"
+  private_constant :NUM_PATTERN_SPECS
+
+  # Fragment completion table for DateTime parsing
+  COMPLETE_FRAGS_TABLE = [
+    [:time,       [:hour, :min, :sec].freeze],
+    [nil,         [:jd].freeze],
+    [:ordinal,    [:year, :yday, :hour, :min, :sec].freeze],
+    [:civil,      [:year, :mon, :mday, :hour, :min, :sec].freeze],
+    [:commercial, [:cwyear, :cweek, :cwday, :hour, :min, :sec].freeze],
+    [:wday,       [:wday, :hour, :min, :sec].freeze],
+    [:wnum0,      [:year, :wnum0, :wday, :hour, :min, :sec].freeze],
+    [:wnum1,      [:year, :wnum1, :wday, :hour, :min, :sec].freeze],
+    [nil,         [:cwyear, :cweek, :wday, :hour, :min, :sec].freeze],
+    [nil,         [:year, :wnum0, :cwday, :hour, :min, :sec].freeze],
+    [nil,         [:year, :wnum1, :cwday, :hour, :min, :sec].freeze],
+  ].each { |a| a.freeze }.freeze
+  private_constant :COMPLETE_FRAGS_TABLE
+end