Also unfold and split lazily

This has little effect on the specs, but on my header reading example it
makes about a 10x performance difference, finally bringing it within one
order of magnitude of the "fast hacky solution" at
https://gist.github.com/5901bbd810c08ed3d0b1

lib/mail/field.rb

@@ -115,7 +115,8 @@ def initialize(name, value = nil, charset = 'utf-8')
       case
       when name =~ /:/                  # Field.new("field-name: field data")
         @charset = value.blank? ? charset : value
-        @name, @value = split(name)
+        @name = name[FIELD_PREFIX]
+        @raw_value = name
       when name !~ /:/ && value.blank?  # Field.new("field-name")
         @name = name
         @value = nil
@@ -125,19 +126,20 @@ def initialize(name, value = nil, charset = 'utf-8')
         @value = value
         @charset = charset
       end
-      return self
+      @name = FIELD_NAME_MAP[@name.to_s.downcase] || @name
     end
 
     def field=(value)
       @field = value
     end
 
     def field
+      _, @value = split(@raw_value) if @raw_value && !@value
       @field ||= create_field(@name, @value, @charset)
     end
 
     def name
-      FIELD_NAME_MAP[@name.to_s.downcase] || @name
+      @name
     end
 
     def value
@@ -198,7 +200,21 @@ def split(raw_field)
       STDERR.puts "WARNING: Could not parse (and so ignoring) '#{raw_field}'"
     end
 
+    # 2.2.3. Long Header Fields
+    #
+    #  The process of moving from this folded multiple-line representation
+    #  of a header field to its single line representation is called
+    #  "unfolding". Unfolding is accomplished by simply removing any CRLF
+    #  that is immediately followed by WSP.  Each header field should be
+    #  treated in its unfolded form for further syntactic and semantic
+    #  evaluation.
+    def unfold(string)
+      string.gsub(/[\r\n \t]+/m, ' ')
+    end
+
     def create_field(name, value, charset)
+      value = unfold(value) if value.is_a?(String) || value.is_a?(Mail::Multibyte::Chars)
+
       begin
         new_field(name, value, charset)
       rescue Mail::Field::ParseError => e

lib/mail/header.rb

@@ -244,27 +244,10 @@ def raw_source=(val)
       @raw_source = val
     end
 
-    # 2.2.3. Long Header Fields
-    # 
-    #  The process of moving from this folded multiple-line representation
-    #  of a header field to its single line representation is called
-    #  "unfolding". Unfolding is accomplished by simply removing any CRLF
-    #  that is immediately followed by WSP.  Each header field should be
-    #  treated in its unfolded form for further syntactic and semantic
-    #  evaluation.
-    def unfold(string)
-      string.gsub(/#{CRLF}#{WSP}+/, ' ').gsub(/#{WSP}+/, ' ')
-    end
-
-    # Returns the header with all the folds removed
-    def unfolded_header
-      @unfolded_header ||= unfold(raw_source)
-    end
-
     # Splits an unfolded and line break cleaned header into individual field
     # strings.
     def split_header
-      self.fields = unfolded_header.split(CRLF)
+      self.fields = raw_source.split(HEADER_SPLIT)
     end
 
     def select_field_for(name)

lib/mail/patterns.rb

@@ -20,10 +20,12 @@ module Patterns
     FWS           = /#{CRLF}#{WSP}*/
     TEXT          = /[#{text}]/ # + obs-text
     FIELD_NAME    = /[#{field_name}]+/
-    FIELD_BODY    = /.+/
+    FIELD_PREFIX  = /\A(#{FIELD_NAME})/
+    FIELD_BODY    = /.+/m
     FIELD_LINE    = /^[#{field_name}]+:\s*.+$/
     FIELD_SPLIT   = /^(#{FIELD_NAME})\s*:\s*(#{FIELD_BODY})?$/
     HEADER_LINE   = /^([#{field_name}]+:\s*.+)$/
+    HEADER_SPLIT  = /#{CRLF}(?!#{WSP})/
 
     QP_UNSAFE     = /[^#{qp_safe}]/
     QP_SAFE       = /[#{qp_safe}]/

spec/mail/message_spec.rb

@@ -109,7 +109,7 @@ def basic_email
 
     it "should raise a warning (and keep parsing) on having an incorrectly formatted header" do
       STDERR.should_receive(:puts).with("WARNING: Could not parse (and so ignoring) 'quite Delivered-To: xxx@xxx.xxx'")
-      Mail.read(fixture('emails', 'plain_emails', 'raw_email_incorrect_header.eml'))
+      Mail.read(fixture('emails', 'plain_emails', 'raw_email_incorrect_header.eml')).to_s
     end
 
     it "should read in an email message and basically parse it" do