Optimize Time.xmlschema by ~4x

[byroot]

It is currentyl fairly slow as it rely on a Regexp match, which isn't very fast an allocates a lot.

Since Ruby 3.2, Time.new(iso_string) is supported, and over 8x faster than Time.xmlschema.

So if we use the regexp with match? to avoid the allocations, and then delegate to .new, we can make Time.xmlschema around 4 times faster:

ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +YJIT +PRISM [arm64-darwin25]
Warming up --------------------------------------
           xmlschema    67.645k i/100ms
            Time.new   531.202k i/100ms
                 opt   263.541k i/100ms
Calculating -------------------------------------
           xmlschema    680.426k (± 0.7%) i/s    (1.47 μs/i) -      3.450M in   5.070197s
            Time.new      5.736M (± 0.9%) i/s  (174.34 ns/i) -     28.685M in   5.000832s
                 opt      2.779M (± 1.1%) i/s  (359.78 ns/i) -     13.968M in   5.025252s

Comparison:
xmlschema:   680426.2 i/s
 Time.new:  5736027.1 i/s - 8.43x  faster
      opt:  2779497.0 i/s - 4.08x  faster

benchmark

require 'time'
require 'benchmark/ips'

class Time
  class << self
    def baseline(time)
      if /\A\s*
          (-?\d+)-(\d\d)-(\d\d)
          T
          (\d\d):(\d\d):(\d\d)
          (\.\d+)?
          (Z|[+-]\d\d(?::?\d\d)?)?
          \s*\z/ix =~ time
        year = $1.to_i
        mon = $2.to_i
        day = $3.to_i
        hour = $4.to_i
        min = $5.to_i
        sec = $6.to_i
        usec = 0
        if $7
          usec = Rational($7) * 1000000
        end
        if $8
          zone = $8
          off = zone_offset(zone)
          year, mon, day, hour, min, sec =
            apply_offset(year, mon, day, hour, min, sec, off)
          t = self.utc(year, mon, day, hour, min, sec, usec)
          force_zone!(t, zone, off)
          t
        else
          self.local(year, mon, day, hour, min, sec, usec)
        end
      else
        raise ArgumentError.new("invalid xmlschema format: #{time.inspect}")
      end
    end

    def match_new(time)
      if /\A\s*
          (-?\d+)-(\d\d)-(\d\d)
          T
          (\d\d):(\d\d):(\d\d)
          (\.\d+)?
          (Z|[+-]\d\d(?::?\d\d)?)?
          \s*\z/ix.match?(time)
        new(time)
      else
        raise ArgumentError.new("invalid xmlschema format: #{time.inspect}")
      end
    end
  end
end

now = Time.now
iso = now.iso8601(6).freeze
p now
p Time.match_new(iso)

Benchmark.ips do |x|
  x.report('xmlschema') { Time.baseline(iso) }
  x.report('Time.new') { Time.new(iso) }
  x.report('opt') { Time.match_new(iso) }

  x.compare!(order: :baseline)
end

Details

Of course, if we were to reimplement .xmlschema in C, we'd likely could be even faster than .new, but that would mean moving that method from the time gem into Ruby core, etc.

[nobu]

Time.new does not allow leading/trailing spaces.

$ ruby3.1 -I./lib -rtime -e 'p Time.xmlschema(" 2011-10-05T22:26:12-04:00 ")'
2011-10-05 22:26:12 -0400

$ ruby3.2 -I./lib -rtime -e 'p Time.xmlschema(" 2011-10-05T22:26:12-04:00 ")'
<internal:timev>:398:in `initialize': can't parse: " 2011-10-05T22:26:12-04:00 " (ArgumentError)
	from /Users/nobu/src/ruby/ruby/time/lib/time.rb:673:in `new'
	from /Users/nobu/src/ruby/ruby/time/lib/time.rb:673:in `_xmlschema'
	from /Users/nobu/src/ruby/ruby/time/lib/time.rb:637:in `xmlschema'
	from -e:1:in `<main>'

[byroot]

Indeed. I'll either add a .strip or revert.