If it will not use special variables (like $1, $&, $`...),
it can improve the performance by using Regexp#match? or String#match? instead of Regexp#=~ or String#=~.
This patch is same idea as https://github.com/ruby/ruby/pull/1836
[Fix GH-1842]
## Environment
* OS : Ubuntu 17.10
* Compiler : gcc version 7.2.0
* CPU : Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
* Memory : 16 GB
## TL;DR
Methods | Before | After | Speed up
----------- | ------ | ------ | --------
CSV.foreach | 44.825 | 48.201 | 7.5%
CSV#shift | 45.200 | 49.584 | 9.7%
CSV.read | 42.968 | 46.853 | 9.0%
CSV.table | 10.933 | 11.277 | 3.1%
## Before
```
Calculating -------------------------------------
CSV.foreach 44.825 (± 0.0%) i/s - 228.000 in 5.086576s
CSV#shift 45.200 (± 0.0%) i/s - 228.000 in 5.044297s
CSV.read 42.968 (± 0.0%) i/s - 216.000 in 5.027504s
CSV.table 10.933 (± 0.0%) i/s - 55.000 in 5.031098s
```
## After
```
Calculating -------------------------------------
CSV.foreach 48.201 (± 0.0%) i/s - 244.000 in 5.062256s
CSV#shift 49.584 (± 0.0%) i/s - 248.000 in 5.001652s
CSV.read 46.853 (± 0.0%) i/s - 236.000 in 5.037044s
CSV.table 11.277 (± 0.0%) i/s - 57.000 in 5.054694s
```
## Benchmark code
```ruby
require 'csv'
require 'benchmark/ips'
CSV.open("/tmp/file.csv", "w") do |csv|
csv << ["player", "gameA", "gameB"]
1000.times do
csv << ['"Alice"', "84.0", "79.5"]
csv << ['"Bob"', "20.0", "56.5"]
end
end
Benchmark.ips do |x|
x.report "CSV.foreach" do
CSV.foreach("/tmp/file.csv") do |row|
end
end
x.report "CSV#shift" do
CSV.open("/tmp/file.csv") do |csv|
while line = csv.shift
end
end
end
x.report "CSV.read" do
CSV.read("/tmp/file.csv")
end
x.report "CSV.table" do
CSV.table("/tmp/file.csv")
end
end
```
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62806 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
dce4a3f58c