* lib/csv.rb: Optimize header hashes by freezing string keys.

  [ruby-core:58510]



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43825 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 2 insertions, 0 deletions

diff --git a/lib/csv.rb b/lib/csv.rb
index d66b84922a..a4d8e3d0a8 100644
--- a/lib/csv.rb
+++ b/lib/csv.rb
@@ -235,6 +235,7 @@ class CSV
     #
     def initialize(headers, fields, header_row = false)
       @header_row = header_row
+      headers.each { |h| h.freeze if h.is_a? String }
 
       # handle extra headers or fields
       @row = if headers.size > fields.size
@@ -2208,6 +2209,7 @@ class CSV
       # prepare converted and unconverted copies
       row      = @headers                       if row.nil?
       @headers = convert_fields(@headers, true)
+      @headers.each { |h| h.freeze if h.is_a? String }
 
       if @return_headers                                     # return headers
         return self.class::Row.new(@headers, row, true)