Bug #6509: String#gsub is too slow if receiver includes a binary

• Status: Closed
• Assignee: naruse (Yui NARUSE)
• Target version: 2.0.0
• ruby -v: ruby 2.0.0dev (2012-05-28 trunk 35830) [x86_64-linux]

[okkez (okkez _)]

=begin

以下のようなコードで String#gsub が遅くなります。

• b = "" の場合(A): 0.2840230464935303
• b = "\xB9" の場合(B): 4.183771848678589

-- coding: utf-8 --

a = ("abcde\n"*50000).force_encoding("binary")
#b = ""
b = "\xB9".force_encoding("binary")
c = ("efghi\n"*50000).force_encoding("binary")

d = "#{a}#{b}#{c}"

start = Time.now.to_f
d.gsub(/\n/) { "" }
puts(Time.now.to_f - start)

それぞれの場合で、プロファイルを取ってみたので添付します。

(B)の場合に、search_nonascii を約20万回呼び出して処理時間の92%を費しています。
(A)の場合は、約10万回しか呼び出しておらず、処理時間も短いです。

=end

[shyouhei (Shyouhei Urabe)]

• Category changed from core to M17N
• Status changed from Open to Assigned
• Assignee set to naruse (Yui NARUSE)

str_gsubの中でdestが一回non asciiになってしまったらそれ以降はsearch_nonasciiしても無駄という気がしますが専門家のご意見をうかがいたいところです。

[naruse (Yui NARUSE)]

• Status changed from Assigned to Closed
• % Done changed from 0 to 100

This issue was solved with changeset r35863.
okkez, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

---

• string.c (rb_enc_cr_str_buf_cat): don't reset coderange as unknown.
  the condition 'ptr_a8 && str_cr != ENC_CODERANGE_7BIT' means not
  unknown, str is also ASCII-8BIT because str_encindex == ptr_encindex,
  and nont (str_cr == ENC_CODERANGE_UNKNOWN) and
  str_cr != ENC_CODERANGE_7BIT means str_cr is valid because ASCII-8BIT
  can't be broken. [ruby-dev:45688] [Bug #6509]