danielfone · August 29, 2015 14:06 · Sep 16, 2014
diff --git a/unindent.rb b/unindent.rb
@@ -0,0 +1,183 @@
+TEXT = <<EOF
+   See, the interesting thing about this text
+     is that while it seems like the first line defines an indent
+       it's actually the last line which has the smallest indent
+
+    there are also some blank lines
+
+    both with and without extra spaces in them
+
+    and it just goes on and on
+
+       this text
+
+    and starts to repeat itself
+   See, the interesting thing about this text
+     is that while it seems like the first line defines an indent
+       it's actually the last line which has the smallest indent
+
+    there are also some blank lines
+
+    both with and without extra spaces in them
+
+    and it just goes on and on
+
+       this text
+
+    and starts to repeat itself
+   See, the interesting thing about this text
+     is that while it seems like the first line defines an indent
+       it's actually the last line which has the smallest indent
+
+    there are also some blank lines
+
+    both with and without extra spaces in them
+
+    and it just goes on and on
+
+       this text
+
+    and starts to repeat itself
+
+  The End.
+EOF
+
+EXPECTED_TEXT = <<EOF
+ See, the interesting thing about this text
+   is that while it seems like the first line defines an indent
+     it's actually the last line which has the smallest indent
+
+  there are also some blank lines
+
+  both with and without extra spaces in them
+
+  and it just goes on and on
+
+     this text
+
+  and starts to repeat itself
+ See, the interesting thing about this text
+   is that while it seems like the first line defines an indent
+     it's actually the last line which has the smallest indent
+
+  there are also some blank lines
+
+  both with and without extra spaces in them
+
+  and it just goes on and on
+
+     this text
+
+  and starts to repeat itself
+ See, the interesting thing about this text
+   is that while it seems like the first line defines an indent
+     it's actually the last line which has the smallest indent
+
+  there are also some blank lines
+
+  both with and without extra spaces in them
+
+  and it just goes on and on
+
+     this text
+
+  and starts to repeat itself
+
+The End.
+EOF
+
+require "minitest/autorun"
+require "minitest"
+require "active_support/core_ext/string"
+require "unindent"
+
+class String
+
+  # Try to optimize by avoiding splitting into an array
+  def unindent_scan
+    indent_str = nil
+    scan(/^[\t ]*(?=\S)/) do |s|
+      indent_str ||= s
+      indent_str = (s.size < indent_str.size) ? s : indent_str
+    end
+    if indent_str
+      gsub(/^#{indent_str}/, "")
+    end
+  end
+
+  # This version tries to avoid a second traversal of the string by
+  # saving a list of offsets. However, it winds up being
+  # slower. Perhaps this is a sign of how well-optimized #gsub is?
+  def unindent_offsets
+    min_indent = nil
+    offsets    = []
+    scan(/^[\t ]*(?=\S)/) do |s|
+      offsets << $~.offset(0).first
+      min_indent ||= s.size
+      min_indent = (s.size < min_indent.size) ? s.size : min_indent
+    end
+    if min_indent
+      result = dup
+      shift  = 0
+      offsets.each do |offset|
+        result[offset - shift, min_indent] = ""
+        shift += min_indent
+      end
+      result
+    else
+      self
+    end
+  end
+end
+
+class TestUnindent < MiniTest::Unit::TestCase
+  def test_unindent_gem
+    assert_equal EXPECTED_TEXT, TEXT.unindent
+  end
+
+  def test_activesupport
+    assert_equal EXPECTED_TEXT, TEXT.strip_heredoc
+  end
+
+  def test_scan
+    assert_equal EXPECTED_TEXT, TEXT.unindent_scan
+  end
+
+  def test_offsets
+    assert_equal EXPECTED_TEXT, TEXT.unindent_offsets
+  end
+end
+
+require "benchmark"
+
+n = 10_000
+
+Benchmark.bmbm(15) do |x|
+  x.report("unindent gem") { n.times { result = TEXT.unindent } }
+  x.report("activesupport") { n.times { result = TEXT.strip_heredoc } }
+  x.report("scan") { n.times { result = TEXT.unindent_scan } }
+  x.report("offsets") { n.times { result = TEXT.unindent_offsets } }
+end
+
+# ~> MiniTest::Unit::TestCase is now Minitest::Test. From -:130:in `<main>'
+# >> Rehearsal ---------------------------------------------------
+# >> unindent gem      0.850000   0.000000   0.850000 (  0.859678)
+# >> activesupport     0.630000   0.000000   0.630000 (  0.638381)
+# >> scan              0.510000   0.000000   0.510000 (  0.502865)
+# >> offsets           0.710000   0.010000   0.720000 (  0.721911)
+# >> ------------------------------------------ total: 2.710000sec
+# >>
+# >>                       user     system      total        real
+# >> unindent gem      0.770000   0.000000   0.770000 (  0.773135)
+# >> activesupport     0.620000   0.000000   0.620000 (  0.627442)
+# >> scan              0.490000   0.000000   0.490000 (  0.497729)
+# >> offsets           0.700000   0.000000   0.700000 (  0.704367)
+# >> Run options: --seed 50148
+# >>
+# >> # Running:
+# >>
+# >> ....
+# >>
+# >> Finished in 0.001476s, 2710.3833 runs/s, 2710.3833 assertions/s.
+# >>
+# >> 4 runs, 4 assertions, 0 failures, 0 errors, 0 skips
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