source: Remove unnecessary string length comparisons in the case of string comparisons

[naitoh]

Why

rexml/lib/rexml/source.rb

Lines 208 to 234 in 370666e

	def readline
	str = @source.readline(@line_break)
	if @pending_buffer
	if str.nil?
	str = @pending_buffer
	else
	str = @pending_buffer + str
	end
	@pending_buffer = nil
	end
	return nil if str.nil?
	if @to_utf
	decode(str)
	else
	str.force_encoding(::Encoding::UTF_8) if @force_utf8
	str
	end
	end
	def encoding_updated
	case @encoding
	when "UTF-16BE", "UTF-16LE"
	@source.binmode
	@source.set_encoding(@encoding, @encoding)
	end
	@line_break = encode(">")

Because @line_break = encode(">"), the end of @scanner << readline is one of the following.

1. ">"
2. "X>"
3. "X" (eof)

This will not be matched by additional reads in the following cases.

• @source.match("<?")
• @source.match("--")
• @source.match("DOCTYPE")

In the following cases, additional reads may result in a match, but explicitly prohibiting such a specification with a comment makes the string length check unnecessary.

• @source.match(">>")
• @source.match(">X")

Benchmark

RUBYLIB= BUNDLER_ORIG_RUBYLIB= /Users/naitoh/.rbenv/versions/3.3.0/bin/ruby -v -S benchmark-driver /Users/naitoh/ghq/github.com/naitoh/rexml/benchmark/parse.yaml
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin22]
Calculating -------------------------------------
                         before       after  before(YJIT)  after(YJIT)
                 dom     10.689      10.736        18.484       18.108 i/s -     100.000 times in 9.355754s 9.314792s 5.409984s 5.522527s
                 sax     30.793      31.583        52.965       52.641 i/s -     100.000 times in 3.247486s 3.166258s 1.888036s 1.899660s
                pull     36.308      37.182        63.773       64.669 i/s -     100.000 times in 2.754203s 2.689440s 1.568069s 1.546325s
              stream     34.936      35.991        56.830       57.729 i/s -     100.000 times in 2.862361s 2.778467s 1.759632s 1.732238s

Comparison:
                              dom
        before(YJIT):        18.5 i/s
         after(YJIT):        18.1 i/s - 1.02x  slower
               after:        10.7 i/s - 1.72x  slower
              before:        10.7 i/s - 1.73x  slower

                              sax
        before(YJIT):        53.0 i/s
         after(YJIT):        52.6 i/s - 1.01x  slower
               after:        31.6 i/s - 1.68x  slower
              before:        30.8 i/s - 1.72x  slower

                             pull
         after(YJIT):        64.7 i/s
        before(YJIT):        63.8 i/s - 1.01x  slower
               after:        37.2 i/s - 1.74x  slower
              before:        36.3 i/s - 1.78x  slower

                           stream
         after(YJIT):        57.7 i/s
        before(YJIT):        56.8 i/s - 1.02x  slower
               after:        36.0 i/s - 1.60x  slower
              before:        34.9 i/s - 1.65x  slower

• YJIT=ON : 0.98x - 1.02x faster
• YJIT=OFF : 1.00x - 1.03x faster

[kou]

+1

[kou]

Suggested change

	# Note: "When specifying a string for 'pattern', it must not include '>' except in the following format."
	# Note: When specifying a string for 'pattern', it must not include '>' except in the following formats: