Attempt at a zippier HashWithIndifferentAccess for Ruby MRI
  (c) 2009 Lourens Naudé (methodmissing), James Tucker (raggi)

  http://github.com/methodmissing/hwia

This library works with Ruby MRI > 1.8.6 && 1.9.2 and is a more efficient implementation of
ActiveSupport::HashWithIndifferentAccess, which allows interchangeable use of string and symbol
hash keys.

The numbers ?

  methodmissing:hwia lourens$ rake bench
  (in /Users/lourens/projects/hwia)
  /opt/local/bin/ruby extconf.rb
  checking for rb_thread_blocking_region()... no
  checking for rb_trap_immediate in ruby.h,rubysig.h... yes
  creating Makefile
  make
  gcc -I. -I. -I/opt/local/lib/ruby/1.8/i686-darwin9.5.1 -I. -DHAVE_RB_TRAP_IMMEDIATE -DRUBY18    -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE   -fno-common -O2 -pipe -fno-common   -c hwia.c
  cc -dynamic -bundle -undefined suppress -flat_namespace -o hwia.bundle hwia.o -L. -L/opt/local/lib -L.     -ldl -lobjc  
  /opt/local/bin/ruby bench/bench.rb
  Rehearsal ------------------------------------------------------------------------------
  StrHash#[:sym]                               0.000000   0.000000   0.000000 (  0.002999)
  HashWithIndifferentAccess#[:sym]             0.020000   0.000000   0.020000 (  0.021942)
  StrHash#['str']                              0.010000   0.000000   0.010000 (  0.004590)
  HashWithIndifferentAccess#['str]             0.000000   0.000000   0.000000 (  0.003842)
  StrHash#key?(:sym)                           0.010000   0.000000   0.010000 (  0.002902)
  HashWithIndifferentAccess#key?(:sym)         0.010000   0.000000   0.010000 (  0.013906)
  StrHash#key?('str')                          0.000000   0.000000   0.000000 (  0.004245)
  HashWithIndifferentAccess#key?('str')        0.010000   0.000000   0.010000 (  0.010769)
  StrHash#fetch(:sym)                          0.010000   0.000000   0.010000 (  0.003285)
  HashWithIndifferentAccess#fetch(:sym)        0.020000   0.000000   0.020000 (  0.019375)
  StrHash#fetch('str')                         0.000000   0.000000   0.000000 (  0.003811)
  HashWithIndifferentAccess#fetch('str')       0.010000   0.000000   0.010000 (  0.014550)
  StrHash#values_at(:sym)                      0.010000   0.000000   0.010000 (  0.006830)
  HashWithIndifferentAccess#values_at(:sym)    0.020000   0.000000   0.020000 (  0.020391)
  StrHash#values_at('str')                     0.010000   0.000000   0.010000 (  0.007286)
  HashWithIndifferentAccess#values_at('str')   0.020000   0.000000   0.020000 (  0.019495)
  StrHash#['str']=                             0.000000   0.000000   0.000000 (  0.004249)
  HashWithIndifferentAccess#['str]=            0.020000   0.000000   0.020000 (  0.017406)
  StrHash#[:sym]=                              0.000000   0.000000   0.000000 (  0.003898)
  HashWithIndifferentAccess#[:sym]=            0.020000   0.000000   0.020000 (  0.020366)
  StrHash#update                               0.010000   0.000000   0.010000 (  0.005549)
  HashWithIndifferentAccess#update             0.050000   0.000000   0.050000 (  0.058935)
  StrHash#dup                                  0.030000   0.000000   0.030000 (  0.029752)
  HashWithIndifferentAccess#dup                0.120000   0.000000   0.120000 (  0.128600)
  StrHash#merge                                0.030000   0.000000   0.030000 (  0.027572)
  HashWithIndifferentAccess#merge              0.180000   0.000000   0.180000 (  0.179814)
  StrHash#to_hash                              0.030000   0.000000   0.030000 (  0.034352)
  HashWithIndifferentAccess#to_hash            0.040000   0.000000   0.040000 (  0.038520)
  --------------------------------------------------------------------- total: 0.690000sec

                                                   user     system      total        real
  StrHash#[:sym]                               0.010000   0.000000   0.010000 (  0.003005)
  HashWithIndifferentAccess#[:sym]             0.020000   0.000000   0.020000 (  0.020551)
  StrHash#['str']                              0.000000   0.000000   0.000000 (  0.003312)
  HashWithIndifferentAccess#['str]             0.000000   0.000000   0.000000 (  0.003213)
  StrHash#key?(:sym)                           0.000000   0.000000   0.000000 (  0.002851)
  HashWithIndifferentAccess#key?(:sym)         0.010000   0.000000   0.010000 (  0.012139)
  StrHash#key?('str')                          0.010000   0.000000   0.010000 (  0.003496)
  HashWithIndifferentAccess#key?('str')        0.010000   0.000000   0.010000 (  0.009912)
  StrHash#fetch(:sym)                          0.000000   0.000000   0.000000 (  0.003172)
  HashWithIndifferentAccess#fetch(:sym)        0.020000   0.000000   0.020000 (  0.017662)
  StrHash#fetch('str')                         0.000000   0.000000   0.000000 (  0.003850)
  HashWithIndifferentAccess#fetch('str')       0.020000   0.000000   0.020000 (  0.014771)
  StrHash#values_at(:sym)                      0.000000   0.000000   0.000000 (  0.004340)
  HashWithIndifferentAccess#values_at(:sym)    0.030000   0.000000   0.030000 (  0.020821)
  StrHash#values_at('str')                     0.000000   0.000000   0.000000 (  0.004842)
  HashWithIndifferentAccess#values_at('str')   0.020000   0.000000   0.020000 (  0.017479)
  StrHash#['str']=                             0.010000   0.000000   0.010000 (  0.004225)
  HashWithIndifferentAccess#['str]=            0.010000   0.000000   0.010000 (  0.018206)
  StrHash#[:sym]=                              0.010000   0.000000   0.010000 (  0.003825)
  HashWithIndifferentAccess#[:sym]=            0.020000   0.000000   0.020000 (  0.019323)
  StrHash#update                               0.000000   0.000000   0.000000 (  0.005478)
  HashWithIndifferentAccess#update             0.050000   0.000000   0.050000 (  0.048082)
  StrHash#dup                                  0.030000   0.000000   0.030000 (  0.023855)
  HashWithIndifferentAccess#dup                0.110000   0.000000   0.110000 (  0.120992)
  StrHash#merge                                0.030000   0.000000   0.030000 (  0.027412)
  HashWithIndifferentAccess#merge              0.180000   0.000000   0.180000 (  0.173209)
  StrHash#to_hash                              0.030000   0.000000   0.030000 (  0.034561)
  HashWithIndifferentAccess#to_hash            0.030000   0.000000   0.030000 (  0.025392)

Installation

  1. sudo gem install methodmissing-hwia
  2. 'require "hwia_rails"' from within an initializer
  
  There's no step three, however, if the gem hasn't built due to github queue delays today (22/08/2009), clone, 'rake gem' and install.

It's unlikely you'd see these improvements for most apps as at the framework level, especially for Rails 3.0, 
this mostly negates query params access overheads.Any pointers and refactoring suggestions much appreciated.

Have fun, happy hacking!