ext/digest: faster code. (merged from CRuby)

ruby/ruby@69f1e595

Test Script:
----
require 'benchmark'

Benchmark.bm(10) do |x|
  x.report "before" do
    10000.times do
      ipad = Array.new(1000).fill(0x36)
      ipad.inject('') { |s, c| s << c.chr }.freeze
    end
  end

  x.report "after" do
    10000.times do
      ipad = Array.new(1000, 0x36)
      ipad.pack('C*').freeze
    end
  end
end
----
                user     system      total        real
before     15.220000   0.320000  15.540000 ( 13.063469)
after       0.460000   0.010000   0.470000 (  0.453947)

ext/digest/lib/digest/hmac.rb

@@ -49,17 +49,17 @@ def initialize(key, digester)
         key = @md.digest(key)
       end
 
-      ipad = Array.new(block_len).fill(0x36)
-      opad = Array.new(block_len).fill(0x5c)
+      ipad = Array.new(block_len, 0x36)
+      opad = Array.new(block_len, 0x5c)
 
       key.bytes.each_with_index { |c, i|
         ipad[i] ^= c
         opad[i] ^= c
       }
 
       @key = key.freeze
-      @ipad = ipad.inject('') { |s, c| s << c.chr }.freeze
-      @opad = opad.inject('') { |s, c| s << c.chr }.freeze
+      @ipad = ipad.pack('C*').freeze
+      @opad = opad.pack('C*').freeze
       @md.update(@ipad)
     end
 
@@ -102,7 +102,7 @@ def inspect
 end
 
 if $0 == __FILE__
-  eval DATA.read, nil, $0, __LINE__+4
+  eval DATA.gets(nil), nil, $0, DATA.lineno
 end
 
 __END__
@@ -142,7 +142,7 @@ def test_reset
       }
     }
   end
-end  
+end
 
 class TC_HMAC_MD5 < Test::Unit::TestCase
   include TM_HMAC