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Use more StringScanner based API to parse XML #114

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naitoh
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@naitoh naitoh commented Feb 17, 2024

Why?

Improve maintainability by optimizing the process so that the parsing process proceeds using StringScanner#scan.

Changed

  • Change REXML::Parsers::BaseParser from frozen_string_literal: false to frozen_string_literal: true.
  • Added Source#string= method for error message output.
  • Added TestParseDocumentTypeDeclaration#test_no_name test case.
  • Of the intSubset of DOCTYPE, "<!" added consideration for processing Comments that begin with "<!".

[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     11.240      10.569        17.173       18.219 i/s -     100.000 times in 8.896882s 9.461267s 5.823007s 5.488884s
                 sax     31.812      30.716        48.383       52.532 i/s -     100.000 times in 3.143500s 3.255655s 2.066861s 1.903600s
                pull     36.855      36.354        56.718       61.443 i/s -     100.000 times in 2.713300s 2.750693s 1.763099s 1.627523s
              stream     34.176      34.758        49.801       54.622 i/s -     100.000 times in 2.925991s 2.877065s 2.008003s 1.830779s

Comparison:
                              dom
         after(YJIT):        18.2 i/s
        before(YJIT):        17.2 i/s - 1.06x  slower
              before:        11.2 i/s - 1.62x  slower
               after:        10.6 i/s - 1.72x  slower

                              sax
         after(YJIT):        52.5 i/s
        before(YJIT):        48.4 i/s - 1.09x  slower
              before:        31.8 i/s - 1.65x  slower
               after:        30.7 i/s - 1.71x  slower

                             pull
         after(YJIT):        61.4 i/s
        before(YJIT):        56.7 i/s - 1.08x  slower
              before:        36.9 i/s - 1.67x  slower
               after:        36.4 i/s - 1.69x  slower

                           stream
         after(YJIT):        54.6 i/s
        before(YJIT):        49.8 i/s - 1.10x  slower
               after:        34.8 i/s - 1.57x  slower
              before:        34.2 i/s - 1.60x  slower

  • YJIT=ON : 1.06x - 1.10x faster
  • YJIT=OFF : 0.94x - 1.01x faster

@naitoh naitoh marked this pull request as draft February 18, 2024 21:56
@naitoh naitoh force-pushed the use_string_scanner_if_document_status_is_nil_in_pull_event branch 3 times, most recently from c9a3bf2 to 8a24e85 Compare February 23, 2024 10:34
@naitoh naitoh changed the title Changed processing of @document_status == nil in REXML::Parsers::BaseParser#pull_event from regular expression to processing using StringScanner. Changed processing in REXML::Parsers::BaseParser#pull_event from regular expression to processing using StringScanner. Feb 23, 2024
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naitoh commented Feb 23, 2024

@kou

Could you use this style?

I changed to that style and modified the whole REXML::Parsers::BaseParser#pull_event to use StringScanner.

We don't need to use existing regular expression constants such as DOCTYPE_START for it.
Because match unit will be different for the current approach and StringScanner based approach.

$ cat benchmark/stringscan_1.yaml
loop_count: 100000
contexts:
  - name: No YJIT
    prelude: |
      $LOAD_PATH.unshift(File.expand_path("lib"))
      require 'rexml'

prelude: |
  require 'strscan'
  s = StringScanner.new('abcdefg hijklmn opqrstu vwxyz')
  ext = ''
  ptn_ext = /[a-z]*#{ext}/
  ptn_no_ext = /[a-z]*/
benchmark:
  'check(/[a-z]*/)'  : s.check(/[a-z]*/)
  'ptn_no_ext=/[a-z]*/; s.check(ptn_no_ext)'  : |
    ptn_no_ext=/[a-z]*/
    s.check(ptn_no_ext)
  'check(ptn_no_ext)'  : s.check(ptn_no_ext)

  'check(/[a-z]*#{ext}/)'  : s.check(/[a-z]*#{ext}/)
  'ptn_ext=/[a-z]*#{ext}/; s.check(ptn_ext)'  : |
    ptn_ext=/[a-z]*#{ext}/
    s.check(ptn_ext)
  'check(ptn_ext)'  : s.check(ptn_ext)
$ benchmark-driver benchmark/stringscan_1.yaml
Calculating -------------------------------------
                         check(/[a-z]*/)     8.215M i/s -    100.000k times in 0.012173s (121.73ns/i)
ptn_no_ext=/[a-z]*/; s.check(ptn_no_ext)     8.033M i/s -    100.000k times in 0.012448s (124.48ns/i)
                       check(ptn_no_ext)     8.183M i/s -    100.000k times in 0.012221s (122.21ns/i)
                   check(/[a-z]*#{ext}/)   948.623k i/s -    100.000k times in 0.105416s (1.05μs/i)
ptn_ext=/[a-z]*#{ext}/; s.check(ptn_ext)   958.653k i/s -    100.000k times in 0.104313s (1.04μs/i)
                          check(ptn_ext)     8.180M i/s -    100.000k times in 0.012225s (122.25ns/i)

Comparison:
                         check(/[a-z]*/):   8214901.3 i/s 
                       check(ptn_no_ext):   8182636.3 i/s - 1.00x  slower
                          check(ptn_ext):   8179959.0 i/s - 1.00x  slower
ptn_no_ext=/[a-z]*/; s.check(ptn_no_ext):   8033419.2 i/s - 1.02x  slower
ptn_ext=/[a-z]*#{ext}/; s.check(ptn_ext):    958653.3 i/s - 8.57x  slower
                   check(/[a-z]*#{ext}/):    948622.6 i/s - 8.66x  slower

The format check(/[a-z]*#{ext}/) is too slow.

For this reason, I do not use @source.match( /((?>#{QNAME_STR}))/um, true), but @source.match(TAG_MATCH, true).

$ cat benchmark/stringscan_2.yaml
loop_count: 100000
contexts:
  - name: No YJIT
    prelude: |
      $LOAD_PATH.unshift(File.expand_path("lib"))
      require 'rexml'

prelude: |
  require 'strscan'
  s = StringScanner.new('abcdefg hijklmn opqrstu vwxyz')
  ext = ''
  ptn_ext = "a#{ext}"
  ptn_no_ext = "a"
benchmark:
  'check("a")'  : s.check("a")
  'ptn_no_ext="a";s.check(ptn_no_ext)'  : |
    ptn_no_ext="a"
    s.check(ptn_no_ext)
  'check(ptn_no_ext)'  : s.check(ptn_no_ext)

  'check("a#{ext}")'  : s.check("a#{ext}")
  'ptn_ext="a#{ext}"; s.check(ptn_ext)'  : |
    ptn_ext="a#{ext}"
    s.check(ptn_ext)
  'check(ptn_ext)'  : s.check(ptn_ext)
$ benchmark-driver benchmark/stringscan_2.yaml
Calculating -------------------------------------
                         check("a")    10.321M i/s -    100.000k times in 0.009689s (96.89ns/i)
 ptn_no_ext="a";s.check(ptn_no_ext)     9.878M i/s -    100.000k times in 0.010123s (101.23ns/i)
                  check(ptn_no_ext)    13.441M i/s -    100.000k times in 0.007440s (74.40ns/i)
                   check("a#{ext}")     7.657M i/s -    100.000k times in 0.013060s (130.60ns/i)
ptn_ext="a#{ext}"; s.check(ptn_ext)     7.522M i/s -    100.000k times in 0.013295s (132.95ns/i)
                     check(ptn_ext)    13.472M i/s -    100.000k times in 0.007423s (74.23ns/i)

Comparison:
                     check(ptn_ext):  13471642.3 i/s 
                  check(ptn_no_ext):  13440859.7 i/s - 1.00x  slower
                         check("a"):  10320982.6 i/s - 1.31x  slower
 ptn_no_ext="a";s.check(ptn_no_ext):   9878495.0 i/s - 1.36x  slower
                   check("a#{ext}"):   7656967.4 i/s - 1.76x  slower
ptn_ext="a#{ext}"; s.check(ptn_ext):   7521624.7 i/s - 1.79x  slower

check("a") is slower than check(ptn_no_ext).
For this reason I use the form @source.match(TAG_START, true, false).

@naitoh naitoh marked this pull request as ready for review February 23, 2024 11:34
@naitoh naitoh requested a review from kou February 23, 2024 11:34
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kou commented Feb 23, 2024

Comparison:
                         check(/[a-z]*/):   8214901.3 i/s 
                       check(ptn_no_ext):   8182636.3 i/s - 1.00x  slower
                          check(ptn_ext):   8179959.0 i/s - 1.00x  slower
ptn_no_ext=/[a-z]*/; s.check(ptn_no_ext):   8033419.2 i/s - 1.02x  slower
ptn_ext=/[a-z]*#{ext}/; s.check(ptn_ext):    958653.3 i/s - 8.57x  slower
                   check(/[a-z]*#{ext}/):    948622.6 i/s - 8.66x  slower

I think that Regexp creation is the reason. ptn_ext=/[a-z]*#{ext}/; s.check(ptn_ext) and check(/[a-z]*#{ext}/) create a new Regexp because it has string (regular expression?) interpolation. We can avoid it by /.../o (o option).

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kou commented Feb 23, 2024

Comparison:
                     check(ptn_ext):  13471642.3 i/s 
                  check(ptn_no_ext):  13440859.7 i/s - 1.00x  slower
                         check("a"):  10320982.6 i/s - 1.31x  slower
 ptn_no_ext="a";s.check(ptn_no_ext):   9878495.0 i/s - 1.36x  slower
                   check("a#{ext}"):   7656967.4 i/s - 1.76x  slower
ptn_ext="a#{ext}"; s.check(ptn_ext):   7521624.7 i/s - 1.79x  slower

I think that String creation is the reason. Items except check(ptn_ext) and check(ptn_no_ext) creates a new String in each execution.

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kou commented Feb 23, 2024

(I'll review implementation later...)

@naitoh
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naitoh commented Feb 24, 2024

Comparison:
                         check(/[a-z]*/):   8214901.3 i/s 
                       check(ptn_no_ext):   8182636.3 i/s - 1.00x  slower
                          check(ptn_ext):   8179959.0 i/s - 1.00x  slower
ptn_no_ext=/[a-z]*/; s.check(ptn_no_ext):   8033419.2 i/s - 1.02x  slower
ptn_ext=/[a-z]*#{ext}/; s.check(ptn_ext):    958653.3 i/s - 8.57x  slower
                   check(/[a-z]*#{ext}/):    948622.6 i/s - 8.66x  slower

I think that Regexp creation is the reason. ptn_ext=/[a-z]*#{ext}/; s.check(ptn_ext) and check(/[a-z]*#{ext}/) create a new Regexp because it has string (regular expression?) interpolation. We can avoid it by /.../o (o option).

Comparison:
                        check(ptn_no_ext):   8259002.0 i/s 
                           check(ptn_ext):   8211528.9 i/s - 1.01x  slower
                          check(/[a-z]*/):   8206138.1 i/s - 1.01x  slower
                   check(/[a-z]*#{ext}/o):   8198737.4 i/s - 1.01x  slower
 ptn_no_ext=/[a-z]*/; s.check(ptn_no_ext):   8000640.1 i/s - 1.03x  slower
ptn_ext=/[a-z]*#{ext}/o; s.check(ptn_ext):   7968762.5 i/s - 1.04x  slower

I found a workaround with /... /o.
Thanks!

@naitoh
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naitoh commented Feb 24, 2024

Comparison:
                     check(ptn_ext):  13471642.3 i/s 
                  check(ptn_no_ext):  13440859.7 i/s - 1.00x  slower
                         check("a"):  10320982.6 i/s - 1.31x  slower
 ptn_no_ext="a";s.check(ptn_no_ext):   9878495.0 i/s - 1.36x  slower
                   check("a#{ext}"):   7656967.4 i/s - 1.76x  slower
ptn_ext="a#{ext}"; s.check(ptn_ext):   7521624.7 i/s - 1.79x  slower

I think that String creation is the reason. Items except check(ptn_ext) and check(ptn_no_ext) creates a new String in each execution.

Comparison:
                     check(ptn_ext):  13609145.2 i/s 
                  check("a".freeze):  13592498.0 i/s - 1.00x  slower
                  check(ptn_no_ext):  13486176.9 i/s - 1.01x  slower
                         check("a"):  10145074.2 i/s - 1.34x  slower
 ptn_no_ext="a";s.check(ptn_no_ext):  10034116.0 i/s - 1.36x  slower
                   check("a#{ext}"):   7734550.3 i/s - 1.76x  slower
ptn_ext="a#{ext}"; s.check(ptn_ext):   7601094.5 i/s - 1.79x  slower

I found a workaround with "".freeze.
Thanks!

@naitoh naitoh force-pushed the use_string_scanner_if_document_status_is_nil_in_pull_event branch from 8a24e85 to a7c9491 Compare February 24, 2024 06:02
## Why?
Because `s.check("a")` is slower than `s.check("a".freeze)`.

- benchmark/stringscan_2.yaml
```
loop_count: 100000
contexts:
  - name: No YJIT
    prelude: |
      $LOAD_PATH.unshift(File.expand_path("lib"))
      require 'rexml'

prelude: |
  require 'strscan'
  s = StringScanner.new('abcdefg hijklmn opqrstu vwxyz')
  ptn = "a"
benchmark:
  'check("a")'            : s.check("a")
  'check("a".freeze)'     : s.check("a".freeze)
  'ptn="a";s.check(ptn)'  : |
    ptn="a"
    s.check(ptn)
  'check(ptn)'            : s.check(ptn)
```

```
$benchmark-driver benchmark/stringscan_2.yaml
Comparison:
          check(ptn):  13524479.4 i/s
   check("a".freeze):  13433638.1 i/s - 1.01x  slower
          check("a"):  10231225.8 i/s - 1.32x  slower
ptn="a";s.check(ptn):  10013017.0 i/s - 1.35x  slower
```
@naitoh naitoh force-pushed the use_string_scanner_if_document_status_is_nil_in_pull_event branch from a7c9491 to 9a075bf Compare February 24, 2024 06:27
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naitoh commented Feb 24, 2024

  • "".freeze was handled with frozen_string_literal: true.
  • For reasons unknown, /... /o is degrading performance in a YJIT environment, so I would like it to remain as it is.
--- a/lib/rexml/parsers/baseparser.rb (9a075bf)
+++ b/lib/rexml/parsers/baseparser.rb (after)
@@ -373,7 +373,7 @@ module REXML
               return process_instruction
             else
               # Get the next tag
-              md = @source.match(TAG_MATCH, true)
+              md = @source.match(/((?>#{QNAME_STR}))/umo, true)
               unless md
                 @source.string = "<" + @source.buffer
                 raise REXML::ParseException.new("malformed XML: missing tag start", @source)
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 -------------------------------------
                        9a075bf       after  9a075bf(YJIT)  after(YJIT) 
                 dom     11.391      11.456         17.511       17.488 i/s -     100.000 times in 8.778836s 8.728827s 5.710787s 5.718334s
                 sax     31.562      31.574         50.602       45.577 i/s -     100.000 times in 3.168363s 3.167168s 1.976219s 2.194067s
                pull     37.249      37.164         63.066       57.618 i/s -     100.000 times in 2.684616s 2.690755s 1.585646s 1.735582s
              stream     35.675      35.734         55.543       50.465 i/s -     100.000 times in 2.803056s 2.798452s 1.800413s 1.981582s

Comparison:
                              dom
       9a075bf(YJIT):        17.5 i/s 
         after(YJIT):        17.5 i/s - 1.00x  slower
               after:        11.5 i/s - 1.53x  slower
             9a075bf:        11.4 i/s - 1.54x  slower

                              sax
       9a075bf(YJIT):        50.6 i/s 
         after(YJIT):        45.6 i/s - 1.11x  slower
               after:        31.6 i/s - 1.60x  slower
             9a075bf:        31.6 i/s - 1.60x  slower

                             pull
       9a075bf(YJIT):        63.1 i/s 
         after(YJIT):        57.6 i/s - 1.09x  slower
             9a075bf:        37.2 i/s - 1.69x  slower
               after:        37.2 i/s - 1.70x  slower

                           stream
       9a075bf(YJIT):        55.5 i/s 
         after(YJIT):        50.5 i/s - 1.10x  slower
               after:        35.7 i/s - 1.55x  slower
             9a075bf:        35.7 i/s - 1.56x  slower

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naitoh commented Feb 25, 2024

In 8d7fc13, updated handling of document_status == :in_doctype to StringScanner style.

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@naitoh naitoh force-pushed the use_string_scanner_if_document_status_is_nil_in_pull_event branch from 8d7fc13 to bc05d26 Compare February 25, 2024 23:34
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naitoh commented Feb 25, 2024

Fixed what was pointed out.
And optimizations were made.

@naitoh naitoh requested a review from kou February 25, 2024 23:44
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lib/rexml/parsers/baseparser.rb Outdated Show resolved Hide resolved
…lar expression to processing using StringScanner.

## Why
Improve maintainability by optimizing the process so that the parsing process proceeds using StringScanner#scan.

# Changed
- Added Source#string= method for error message output.
- Added TestParseDocumentTypeDeclaration#test_no_name test case.
- Of the `intSubset` of DOCTYPE, "<!" added consideration for processing `Comments` that begin with "<!".

[intSubset Spec]
https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-doctypedecl
> [28] 	doctypedecl   ::= '<!DOCTYPE' S Name (S ExternalID)? S? ('[' intSubset ']' S?)? '>'

https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-intSubset
> [28b] intSubset   ::=  (markupdecl | DeclSep)*

https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-markupdecl
> [29]  markupdecl   ::= elementdecl | AttlistDecl | EntityDecl | NotationDecl | PI | Comment

https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-elementdecl
> [45]  elementdecl   ::=   '<!ELEMENT' S Name S contentspec S? '>'

https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-AttlistDecl
> [52] 	AttlistDecl   ::=   '<!ATTLIST' S Name AttDef* S? '>'

https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EntityDecl
> [70] 	EntityDecl   ::=   GEDecl | PEDecl
> [71] 	GEDecl	   ::=   '<!ENTITY' S Name S EntityDef S? '>'
> [72] 	PEDecl	   ::=   '<!ENTITY' S '%' S Name S PEDef S? '>'

https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-NotationDecl
> [82] 	NotationDecl   ::=   '<!NOTATION' S Name S (ExternalID | PublicID) S? '>'

https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-PI
> [16] 	PI	   ::=   '<?' PITarget (S (Char* - (Char* '?>' Char*)))? '?>'

https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-Comment
> [15] 	Comment	   ::=   '<!--' ((Char - '-') | ('-' (Char - '-')))* '-->'

https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-DeclSep
> [28a] DeclSep	   ::=   PEReference | S

https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-PEReference
> [69]  PEReference   ::=   '%' Name ';'

[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     11.240      10.569        17.173       18.219 i/s -     100.000 times in 8.896882s 9.461267s 5.823007s 5.488884s
                 sax     31.812      30.716        48.383       52.532 i/s -     100.000 times in 3.143500s 3.255655s 2.066861s 1.903600s
                pull     36.855      36.354        56.718       61.443 i/s -     100.000 times in 2.713300s 2.750693s 1.763099s 1.627523s
              stream     34.176      34.758        49.801       54.622 i/s -     100.000 times in 2.925991s 2.877065s 2.008003s 1.830779s

Comparison:
                              dom
         after(YJIT):        18.2 i/s
        before(YJIT):        17.2 i/s - 1.06x  slower
              before:        11.2 i/s - 1.62x  slower
               after:        10.6 i/s - 1.72x  slower

                              sax
         after(YJIT):        52.5 i/s
        before(YJIT):        48.4 i/s - 1.09x  slower
              before:        31.8 i/s - 1.65x  slower
               after:        30.7 i/s - 1.71x  slower

                             pull
         after(YJIT):        61.4 i/s
        before(YJIT):        56.7 i/s - 1.08x  slower
              before:        36.9 i/s - 1.67x  slower
               after:        36.4 i/s - 1.69x  slower

                           stream
         after(YJIT):        54.6 i/s
        before(YJIT):        49.8 i/s - 1.10x  slower
               after:        34.8 i/s - 1.57x  slower
              before:        34.2 i/s - 1.60x  slower

```

- YJIT=ON : 1.06x - 1.10x faster
- YJIT=OFF : 0.94x - 1.01x faster

Co-authored-by: Sutou Kouhei <kou@clear-code.com>
@naitoh naitoh force-pushed the use_string_scanner_if_document_status_is_nil_in_pull_event branch from bc05d26 to 54b0298 Compare February 26, 2024 14:33
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naitoh commented Feb 26, 2024

Fixed what was pointed out.

@naitoh naitoh requested a review from kou February 26, 2024 14:35
@kou kou changed the title Changed processing in REXML::Parsers::BaseParser#pull_event from regular expression to processing using StringScanner. Use more StringScanner based API to parse XML Feb 27, 2024
@kou kou merged commit 370666e into ruby:master Feb 27, 2024
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kou commented Feb 27, 2024

Thanks!

@naitoh naitoh deleted the use_string_scanner_if_document_status_is_nil_in_pull_event branch February 27, 2024 01:28
naitoh added a commit to naitoh/rexml that referenced this pull request Mar 2, 2024
## Why?

ruby#114 (comment)
> I want to just change scan pointer (StringScanner#pos=) instead of changing @scanner.string.
naitoh added a commit to naitoh/rexml that referenced this pull request Mar 3, 2024
## Why?

ruby#114 (comment)
> I want to just change scan pointer (StringScanner#pos=) instead of changing @scanner.string.
naitoh added a commit to naitoh/rexml that referenced this pull request Mar 3, 2024
## Why?

We want to just change scan pointer.

ruby#114 (comment)
> I want to just change scan pointer (StringScanner#pos=) instead of changing @scanner.string.
kou pushed a commit that referenced this pull request Mar 3, 2024
## Why?

We want to just change scan pointer.

#114 (comment)
> I want to just change scan pointer (`StringScanner#pos=`) instead of
changing `@scanner.string`.
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2 participants