Import CSV 3.1.2 (#2547)

7 files changed, 511 insertions, 428 deletions

diff --git a/lib/csv.rb b/lib/csv.rb
index 60dbbcc230..8aa65868b7 100644
--- a/lib/csv.rb
+++ b/lib/csv.rb
@@ -10,18 +10,18 @@
 #
 # Welcome to the new and improved CSV.
 #
-# This version of the CSV library began its life as FasterCSV.  FasterCSV was
-# intended as a replacement to Ruby's then standard CSV library.  It was
+# This version of the CSV library began its life as FasterCSV. FasterCSV was
+# intended as a replacement to Ruby's then standard CSV library. It was
 # designed to address concerns users of that library had and it had three
 # primary goals:
 #
 # 1.  Be significantly faster than CSV while remaining a pure Ruby library.
-# 2.  Use a smaller and easier to maintain code base.  (FasterCSV eventually
-#     grew larger, was also but considerably richer in features.  The parsing
+# 2.  Use a smaller and easier to maintain code base. (FasterCSV eventually
+#     grew larger, was also but considerably richer in features. The parsing
 #     core remains quite small.)
 # 3.  Improve on the CSV interface.
 #
-# Obviously, the last one is subjective.  I did try to defer to the original
+# Obviously, the last one is subjective. I did try to defer to the original
 # interface whenever I didn't have a compelling reason to change it though, so
 # hopefully this won't be too radically different.
 #
@@ -29,20 +29,20 @@
 # the original library as of Ruby 1.9. If you are migrating code from 1.8 or
 # earlier, you may have to change your code to comply with the new interface.
 #
-# == What's Different From the Old CSV?
+# == What's the Different From the Old CSV?
 #
 # I'm sure I'll miss something, but I'll try to mention most of the major
 # differences I am aware of, to help others quickly get up to speed:
 #
 # === CSV Parsing
 #
-# * This parser is m17n aware.  See CSV for full details.
+# * This parser is m17n aware. See CSV for full details.
 # * This library has a stricter parser and will throw MalformedCSVErrors on
 #   problematic data.
-# * This library has a less liberal idea of a line ending than CSV.  What you
-#   set as the <tt>:row_sep</tt> is law.  It can auto-detect your line endings
+# * This library has a less liberal idea of a line ending than CSV. What you
+#   set as the <tt>:row_sep</tt> is law. It can auto-detect your line endings
 #   though.
-# * The old library returned empty lines as <tt>[nil]</tt>.  This library calls
+# * The old library returned empty lines as <tt>[nil]</tt>. This library calls
 #   them <tt>[]</tt>.
 # * This library has a much faster parser.
 #
@@ -56,9 +56,9 @@
 # * CSV now has a new() method used to wrap objects like String and IO for
 #   reading and writing.
 # * CSV::generate() is different from the old method.
-# * CSV no longer supports partial reads.  It works line-by-line.
+# * CSV no longer supports partial reads. It works line-by-line.
 # * CSV no longer allows the instance methods to override the separators for
-#   performance reasons.  They must be set in the constructor.
+#   performance reasons. They must be set in the constructor.
 #
 # If you use this library and find yourself missing any functionality I have
 # trimmed, please {let me know}[mailto:james@grayproductions.net].
@@ -70,16 +70,16 @@
 # == What is CSV, really?
 #
 # CSV maintains a pretty strict definition of CSV taken directly from
-# {the RFC}[http://www.ietf.org/rfc/rfc4180.txt].  I relax the rules in only one
-# place and that is to make using this library easier.  CSV will parse all valid
+# {the RFC}[http://www.ietf.org/rfc/rfc4180.txt]. I relax the rules in only one
+# place and that is to make using this library easier. CSV will parse all valid
 # CSV.
 #
-# What you don't want to do is feed CSV invalid data.  Because of the way the
+# What you don't want to do is to feed CSV invalid data. Because of the way the
 # CSV format works, it's common for a parser to need to read until the end of
-# the file to be sure a field is invalid.  This eats a lot of time and memory.
+# the file to be sure a field is invalid. This consumes a lot of time and memory.
 #
 # Luckily, when working with invalid CSV, Ruby's built-in methods will almost
-# always be superior in every way.  For example, parsing non-quoted fields is as
+# always be superior in every way. For example, parsing non-quoted fields is as
 # easy as:
 #
 #   data.split(",")
@@ -104,7 +104,7 @@ require_relative "csv/writer"
 using CSV::MatchP if CSV.const_defined?(:MatchP)
 
 #
-# This class provides a complete interface to CSV files and data.  It offers
+# This class provides a complete interface to CSV files and data. It offers
 # tools to enable you to read and write to and from Strings or IO objects, as
 # needed.
 #
@@ -184,7 +184,7 @@ using CSV::MatchP if CSV.const_defined?(:MatchP)
 # === CSV with headers
 #
 # CSV allows to specify column names of CSV file, whether they are in data, or
-# provided separately. If headers specified, reading methods return an instance
+# provided separately. If headers are specified, reading methods return an instance
 # of CSV::Table, consisting of CSV::Row.
 #
 #   # Headers are part of data
@@ -223,42 +223,42 @@ using CSV::MatchP if CSV.const_defined?(:MatchP)
 # == CSV and Character Encodings (M17n or Multilingualization)
 #
 # This new CSV parser is m17n savvy.  The parser works in the Encoding of the IO
-# or String object being read from or written to.  Your data is never transcoded
+# or String object being read from or written to. Your data is never transcoded
 # (unless you ask Ruby to transcode it for you) and will literally be parsed in
-# the Encoding it is in.  Thus CSV will return Arrays or Rows of Strings in the
-# Encoding of your data.  This is accomplished by transcoding the parser itself
+# the Encoding it is in. Thus CSV will return Arrays or Rows of Strings in the
+# Encoding of your data. This is accomplished by transcoding the parser itself
 # into your Encoding.
 #
 # Some transcoding must take place, of course, to accomplish this multiencoding
-# support.  For example, <tt>:col_sep</tt>, <tt>:row_sep</tt>, and
+# support. For example, <tt>:col_sep</tt>, <tt>:row_sep</tt>, and
 # <tt>:quote_char</tt> must be transcoded to match your data.  Hopefully this
 # makes the entire process feel transparent, since CSV's defaults should just
-# magically work for your data.  However, you can set these values manually in
+# magically work for your data. However, you can set these values manually in
 # the target Encoding to avoid the translation.
 #
 # It's also important to note that while all of CSV's core parser is now
-# Encoding agnostic, some features are not.  For example, the built-in
+# Encoding agnostic, some features are not. For example, the built-in
 # converters will try to transcode data to UTF-8 before making conversions.
 # Again, you can provide custom converters that are aware of your Encodings to
-# avoid this translation.  It's just too hard for me to support native
+# avoid this translation. It's just too hard for me to support native
 # conversions in all of Ruby's Encodings.
 #
-# Anyway, the practical side of this is simple:  make sure IO and String objects
+# Anyway, the practical side of this is simple: make sure IO and String objects
 # passed into CSV have the proper Encoding set and everything should just work.
 # CSV methods that allow you to open IO objects (CSV::foreach(), CSV::open(),
 # CSV::read(), and CSV::readlines()) do allow you to specify the Encoding.
 #
 # One minor exception comes when generating CSV into a String with an Encoding
-# that is not ASCII compatible.  There's no existing data for CSV to use to
+# that is not ASCII compatible. There's no existing data for CSV to use to
 # prepare itself and thus you will probably need to manually specify the desired
-# Encoding for most of those cases.  It will try to guess using the fields in a
+# Encoding for most of those cases. It will try to guess using the fields in a
 # row of output though, when using CSV::generate_line() or Array#to_csv().
 #
 # I try to point out any other Encoding issues in the documentation of methods
 # as they come up.
 #
 # This has been tested to the best of my ability with all non-"dummy" Encodings
-# Ruby ships with.  However, it is brave new code and may have some bugs.
+# Ruby ships with. However, it is brave new code and may have some bugs.
 # Please feel free to {report}[mailto:james@grayproductions.net] any issues you
 # find with it.
 #
@@ -354,7 +354,7 @@ class CSV
 
   #
   # This Hash holds the built-in header converters of CSV that can be accessed
-  # by name.  You can select HeaderConverters with CSV.header_convert() or
+  # by name. You can select HeaderConverters with CSV.header_convert() or
   # through the +options+ Hash passed to CSV::new().
   #
   # <b><tt>:downcase</tt></b>::  Calls downcase() on the header String.
@@ -364,13 +364,13 @@ class CSV
   #                              and finally to_sym() is called.
   #
   # All built-in header converters transcode header data to UTF-8 before
-  # attempting a conversion.  If your data cannot be transcoded to UTF-8 the
+  # attempting a conversion. If your data cannot be transcoded to UTF-8 the
   # conversion will fail and the header will remain unchanged.
   #
   # This Hash is intentionally left unfrozen and users should feel free to add
   # values to it that can be accessed by all CSV objects.
   #
-  # To add a combo field, the value should be an Array of names.  Combo fields
+  # To add a combo field, the value should be an Array of names. Combo fields
   # can be nested with other combo fields.
   #
   HeaderConverters = {
@@ -382,7 +382,7 @@ class CSV
   }
 
   #
-  # The options used when no overrides are given by calling code.  They are:
+  # The options used when no overrides are given by calling code. They are:
   #
   # <b><tt>:col_sep</tt></b>::            <tt>","</tt>
   # <b><tt>:row_sep</tt></b>::            <tt>:auto</tt>
@@ -416,331 +416,337 @@ class CSV
     quote_empty:        true,
   }.freeze
 
-  #
-  # This method will return a CSV instance, just like CSV::new(), but the
-  # instance will be cached and returned for all future calls to this method for
-  # the same +data+ object (tested by Object#object_id()) with the same
-  # +options+.
-  #
-  # If a block is given, the instance is passed to the block and the return
-  # value becomes the return value of the block.
-  #
-  def self.instance(data = $stdout, **options)
-    # create a _signature_ for this method call, data object and options
-    sig = [data.object_id] +
-          options.values_at(*DEFAULT_OPTIONS.keys.sort_by { |sym| sym.to_s })
-
-    # fetch or create the instance for this signature
-    @@instances ||= Hash.new
-    instance = (@@instances[sig] ||= new(data, **options))
-
-    if block_given?
-      yield instance  # run block, if given, returning result
-    else
-      instance        # or return the instance
+  class << self
+    #
+    # This method will return a CSV instance, just like CSV::new(), but the
+    # instance will be cached and returned for all future calls to this method for
+    # the same +data+ object (tested by Object#object_id()) with the same
+    # +options+.
+    #
+    # If a block is given, the instance is passed to the block and the return
+    # value becomes the return value of the block.
+    #
+    def instance(data = $stdout, **options)
+      # create a _signature_ for this method call, data object and options
+      sig = [data.object_id] +
+            options.values_at(*DEFAULT_OPTIONS.keys.sort_by { |sym| sym.to_s })
+
+      # fetch or create the instance for this signature
+      @@instances ||= Hash.new
+      instance = (@@instances[sig] ||= new(data, **options))
+
+      if block_given?
+        yield instance  # run block, if given, returning result
+      else
+        instance        # or return the instance
+      end
     end
-  end
 
-  #
-  # :call-seq:
-  #   filter( **options ) { |row| ... }
-  #   filter( input, **options ) { |row| ... }
-  #   filter( input, output, **options ) { |row| ... }
-  #
-  # This method is a convenience for building Unix-like filters for CSV data.
-  # Each row is yielded to the provided block which can alter it as needed.
-  # After the block returns, the row is appended to +output+ altered or not.
-  #
-  # The +input+ and +output+ arguments can be anything CSV::new() accepts
-  # (generally String or IO objects).  If not given, they default to
-  # <tt>ARGF</tt> and <tt>$stdout</tt>.
-  #
-  # The +options+ parameter is also filtered down to CSV::new() after some
-  # clever key parsing.  Any key beginning with <tt>:in_</tt> or
-  # <tt>:input_</tt> will have that leading identifier stripped and will only
-  # be used in the +options+ Hash for the +input+ object.  Keys starting with
-  # <tt>:out_</tt> or <tt>:output_</tt> affect only +output+.  All other keys
-  # are assigned to both objects.
-  #
-  # The <tt>:output_row_sep</tt> +option+ defaults to
-  # <tt>$INPUT_RECORD_SEPARATOR</tt> (<tt>$/</tt>).
-  #
-  def self.filter(input=nil, output=nil, **options)
-    # parse options for input, output, or both
-    in_options, out_options = Hash.new, {row_sep: $INPUT_RECORD_SEPARATOR}
-    options.each do |key, value|
-      case key.to_s
-      when /\Ain(?:put)?_(.+)\Z/
-        in_options[$1.to_sym] = value
-      when /\Aout(?:put)?_(.+)\Z/
-        out_options[$1.to_sym] = value
-      else
-        in_options[key]  = value
-        out_options[key] = value
+    #
+    # :call-seq:
+    #   filter( **options ) { |row| ... }
+    #   filter( input, **options ) { |row| ... }
+    #   filter( input, output, **options ) { |row| ... }
+    #
+    # This method is a convenience for building Unix-like filters for CSV data.
+    # Each row is yielded to the provided block which can alter it as needed.
+    # After the block returns, the row is appended to +output+ altered or not.
+    #
+    # The +input+ and +output+ arguments can be anything CSV::new() accepts
+    # (generally String or IO objects). If not given, they default to
+    # <tt>ARGF</tt> and <tt>$stdout</tt>.
+    #
+    # The +options+ parameter is also filtered down to CSV::new() after some
+    # clever key parsing. Any key beginning with <tt>:in_</tt> or
+    # <tt>:input_</tt> will have that leading identifier stripped and will only
+    # be used in the +options+ Hash for the +input+ object. Keys starting with
+    # <tt>:out_</tt> or <tt>:output_</tt> affect only +output+. All other keys
+    # are assigned to both objects.
+    #
+    # The <tt>:output_row_sep</tt> +option+ defaults to
+    # <tt>$INPUT_RECORD_SEPARATOR</tt> (<tt>$/</tt>).
+    #
+    def filter(input=nil, output=nil, **options)
+      # parse options for input, output, or both
+      in_options, out_options = Hash.new, {row_sep: $INPUT_RECORD_SEPARATOR}
+      options.each do |key, value|
+        case key.to_s
+        when /\Ain(?:put)?_(.+)\Z/
+          in_options[$1.to_sym] = value
+        when /\Aout(?:put)?_(.+)\Z/
+          out_options[$1.to_sym] = value
+        else
+          in_options[key]  = value
+          out_options[key] = value
+        end
+      end
+      # build input and output wrappers
+      input  = new(input  || ARGF,    **in_options)
+      output = new(output || $stdout, **out_options)
+
+      # read, yield, write
+      input.each do |row|
+        yield row
+        output << row
       end
     end
-    # build input and output wrappers
-    input  = new(input  || ARGF,    **in_options)
-    output = new(output || $stdout, **out_options)
-
-    # read, yield, write
-    input.each do |row|
-      yield row
-      output << row
+
+    #
+    # This method is intended as the primary interface for reading CSV files. You
+    # pass a +path+ and any +options+ you wish to set for the read. Each row of
+    # file will be passed to the provided +block+ in turn.
+    #
+    # The +options+ parameter can be anything CSV::new() understands. This method
+    # also understands an additional <tt>:encoding</tt> parameter that you can use
+    # to specify the Encoding of the data in the file to be read. You must provide
+    # this unless your data is in Encoding::default_external(). CSV will use this
+    # to determine how to parse the data. You may provide a second Encoding to
+    # have the data transcoded as it is read. For example,
+    # <tt>encoding: "UTF-32BE:UTF-8"</tt> would read UTF-32BE data from the file
+    # but transcode it to UTF-8 before CSV parses it.
+    #
+    def foreach(path, mode="r", **options, &block)
+      return to_enum(__method__, path, mode, **options) unless block_given?
+      open(path, mode, **options) do |csv|
+        csv.each(&block)
+      end
     end
-  end
 
-  #
-  # This method is intended as the primary interface for reading CSV files.  You
-  # pass a +path+ and any +options+ you wish to set for the read.  Each row of
-  # file will be passed to the provided +block+ in turn.
-  #
-  # The +options+ parameter can be anything CSV::new() understands.  This method
-  # also understands an additional <tt>:encoding</tt> parameter that you can use
-  # to specify the Encoding of the data in the file to be read. You must provide
-  # this unless your data is in Encoding::default_external().  CSV will use this
-  # to determine how to parse the data.  You may provide a second Encoding to
-  # have the data transcoded as it is read.  For example,
-  # <tt>encoding: "UTF-32BE:UTF-8"</tt> would read UTF-32BE data from the file
-  # but transcode it to UTF-8 before CSV parses it.
-  #
-  def self.foreach(path, mode="r", **options, &block)
-    return to_enum(__method__, path, mode, **options) unless block_given?
-    open(path, mode, **options) do |csv|
-      csv.each(&block)
+    #
+    # :call-seq:
+    #   generate( str, **options ) { |csv| ... }
+    #   generate( **options ) { |csv| ... }
+    #
+    # This method wraps a String you provide, or an empty default String, in a
+    # CSV object which is passed to the provided block. You can use the block to
+    # append CSV rows to the String and when the block exits, the final String
+    # will be returned.
+    #
+    # Note that a passed String *is* modified by this method. Call dup() before
+    # passing if you need a new String.
+    #
+    # The +options+ parameter can be anything CSV::new() understands.  This method
+    # understands an additional <tt>:encoding</tt> parameter when not passed a
+    # String to set the base Encoding for the output.  CSV needs this hint if you
+    # plan to output non-ASCII compatible data.
+    #
+    def generate(str=nil, **options)
+      # add a default empty String, if none was given
+      if str
+        str = StringIO.new(str)
+        str.seek(0, IO::SEEK_END)
+      else
+        encoding = options[:encoding]
+        str = +""
+        str.force_encoding(encoding) if encoding
+      end
+      csv = new(str, **options) # wrap
+      yield csv         # yield for appending
+      csv.string        # return final String
     end
-  end
 
-  #
-  # :call-seq:
-  #   generate( str, **options ) { |csv| ... }
-  #   generate( **options ) { |csv| ... }
-  #
-  # This method wraps a String you provide, or an empty default String, in a
-  # CSV object which is passed to the provided block.  You can use the block to
-  # append CSV rows to the String and when the block exits, the final String
-  # will be returned.
-  #
-  # Note that a passed String *is* modified by this method.  Call dup() before
-  # passing if you need a new String.
-  #
-  # The +options+ parameter can be anything CSV::new() understands.  This method
-  # understands an additional <tt>:encoding</tt> parameter when not passed a
-  # String to set the base Encoding for the output.  CSV needs this hint if you
-  # plan to output non-ASCII compatible data.
-  #
-  def self.generate(str=nil, **options)
-    # add a default empty String, if none was given
-    if str
-      str = StringIO.new(str)
-      str.seek(0, IO::SEEK_END)
-    else
-      encoding = options[:encoding]
+    #
+    # This method is a shortcut for converting a single row (Array) into a CSV
+    # String.
+    #
+    # The +options+ parameter can be anything CSV::new() understands. This method
+    # understands an additional <tt>:encoding</tt> parameter to set the base
+    # Encoding for the output. This method will try to guess your Encoding from
+    # the first non-+nil+ field in +row+, if possible, but you may need to use
+    # this parameter as a backup plan.
+    #
+    # The <tt>:row_sep</tt> +option+ defaults to <tt>$INPUT_RECORD_SEPARATOR</tt>
+    # (<tt>$/</tt>) when calling this method.
+    #
+    def generate_line(row, **options)
+      options = {row_sep: $INPUT_RECORD_SEPARATOR}.merge(options)
       str = +""
-      str.force_encoding(encoding) if encoding
+      if options[:encoding]
+        str.force_encoding(options[:encoding])
+      elsif field = row.find {|f| f.is_a?(String)}
+        str.force_encoding(field.encoding)
+      end
+      (new(str, **options) << row).string
     end
-    csv = new(str, **options) # wrap
-    yield csv         # yield for appending
-    csv.string        # return final String
-  end
 
-  #
-  # This method is a shortcut for converting a single row (Array) into a CSV
-  # String.
-  #
-  # The +options+ parameter can be anything CSV::new() understands.  This method
-  # understands an additional <tt>:encoding</tt> parameter to set the base
-  # Encoding for the output.  This method will try to guess your Encoding from
-  # the first non-+nil+ field in +row+, if possible, but you may need to use
-  # this parameter as a backup plan.
-  #
-  # The <tt>:row_sep</tt> +option+ defaults to <tt>$INPUT_RECORD_SEPARATOR</tt>
-  # (<tt>$/</tt>) when calling this method.
-  #
-  def self.generate_line(row, **options)
-    options = {row_sep: $INPUT_RECORD_SEPARATOR}.merge(options)
-    str = +""
-    if options[:encoding]
-      str.force_encoding(options[:encoding])
-    elsif field = row.find {|f| f.is_a?(String)}
-      str.force_encoding(field.encoding)
-    end
-    (new(str, **options) << row).string
-  end
+    #
+    # :call-seq:
+    #   open( filename, mode = "rb", **options ) { |faster_csv| ... }
+    #   open( filename, **options ) { |faster_csv| ... }
+    #   open( filename, mode = "rb", **options )
+    #   open( filename, **options )
+    #
+    # This method opens an IO object, and wraps that with CSV. This is intended
+    # as the primary interface for writing a CSV file.
+    #
+    # You must pass a +filename+ and may optionally add a +mode+ for Ruby's
+    # open(). You may also pass an optional Hash containing any +options+
+    # CSV::new() understands as the final argument.
+    #
+    # This method works like Ruby's open() call, in that it will pass a CSV object
+    # to a provided block and close it when the block terminates, or it will
+    # return the CSV object when no block is provided. (*Note*: This is different
+    # from the Ruby 1.8 CSV library which passed rows to the block. Use
+    # CSV::foreach() for that behavior.)
+    #
+    # You must provide a +mode+ with an embedded Encoding designator unless your
+    # data is in Encoding::default_external(). CSV will check the Encoding of the
+    # underlying IO object (set by the +mode+ you pass) to determine how to parse
+    # the data. You may provide a second Encoding to have the data transcoded as
+    # it is read just as you can with a normal call to IO::open(). For example,
+    # <tt>"rb:UTF-32BE:UTF-8"</tt> would read UTF-32BE data from the file but
+    # transcode it to UTF-8 before CSV parses it.
+    #
+    # An opened CSV object will delegate to many IO methods for convenience. You
+    # may call:
+    #
+    # * binmode()
+    # * binmode?()
+    # * close()
+    # * close_read()
+    # * close_write()
+    # * closed?()
+    # * eof()
+    # * eof?()
+    # * external_encoding()
+    # * fcntl()
+    # * fileno()
+    # * flock()
+    # * flush()
+    # * fsync()
+    # * internal_encoding()
+    # * ioctl()
+    # * isatty()
+    # * path()
+    # * pid()
+    # * pos()
+    # * pos=()
+    # * reopen()
+    # * seek()
+    # * stat()
+    # * sync()
+    # * sync=()
+    # * tell()
+    # * to_i()
+    # * to_io()
+    # * truncate()
+    # * tty?()
+    #
+    def open(filename, mode="r", **options)
+      # wrap a File opened with the remaining +args+ with no newline
+      # decorator
+      file_opts = {universal_newline: false}.merge(options)
 
-  #
-  # :call-seq:
-  #   open( filename, mode = "rb", **options ) { |faster_csv| ... }
-  #   open( filename, **options ) { |faster_csv| ... }
-  #   open( filename, mode = "rb", **options )
-  #   open( filename, **options )
-  #
-  # This method opens an IO object, and wraps that with CSV.  This is intended
-  # as the primary interface for writing a CSV file.
-  #
-  # You must pass a +filename+ and may optionally add a +mode+ for Ruby's
-  # open().  You may also pass an optional Hash containing any +options+
-  # CSV::new() understands as the final argument.
-  #
-  # This method works like Ruby's open() call, in that it will pass a CSV object
-  # to a provided block and close it when the block terminates, or it will
-  # return the CSV object when no block is provided.  (*Note*: This is different
-  # from the Ruby 1.8 CSV library which passed rows to the block.  Use
-  # CSV::foreach() for that behavior.)
-  #
-  # You must provide a +mode+ with an embedded Encoding designator unless your
-  # data is in Encoding::default_external().  CSV will check the Encoding of the
-  # underlying IO object (set by the +mode+ you pass) to determine how to parse
-  # the data.   You may provide a second Encoding to have the data transcoded as
-  # it is read just as you can with a normal call to IO::open().  For example,
-  # <tt>"rb:UTF-32BE:UTF-8"</tt> would read UTF-32BE data from the file but
-  # transcode it to UTF-8 before CSV parses it.
-  #
-  # An opened CSV object will delegate to many IO methods for convenience.  You
-  # may call:
-  #
-  # * binmode()
-  # * binmode?()
-  # * close()
-  # * close_read()
-  # * close_write()
-  # * closed?()
-  # * eof()
-  # * eof?()
-  # * external_encoding()
-  # * fcntl()
-  # * fileno()
-  # * flock()
-  # * flush()
-  # * fsync()
-  # * internal_encoding()
-  # * ioctl()
-  # * isatty()
-  # * path()
-  # * pid()
-  # * pos()
-  # * pos=()
-  # * reopen()
-  # * seek()
-  # * stat()
-  # * sync()
-  # * sync=()
-  # * tell()
-  # * to_i()
-  # * to_io()
-  # * truncate()
-  # * tty?()
-  #
-  def self.open(filename, mode="r", **options)
-    # wrap a File opened with the remaining +args+ with no newline
-    # decorator
-    file_opts = {universal_newline: false}.merge(options)
+      begin
+        f = File.open(filename, mode, **file_opts)
+      rescue ArgumentError => e
+        raise unless /needs binmode/.match?(e.message) and mode == "r"
+        mode = "rb"
+        file_opts = {encoding: Encoding.default_external}.merge(file_opts)
+        retry
+      end
+      begin
+        csv = new(f, **options)
+      rescue Exception
+        f.close
+        raise
+      end
 
-    begin
-      f = File.open(filename, mode, **file_opts)
-    rescue ArgumentError => e
-      raise unless /needs binmode/.match?(e.message) and mode == "r"
-      mode = "rb"
-      file_opts = {encoding: Encoding.default_external}.merge(file_opts)
-      retry
-    end
-    begin
-      csv = new(f, **options)
-    rescue Exception
-      f.close
-      raise
+      # handle blocks like Ruby's open(), not like the CSV library
+      if block_given?
+        begin
+          yield csv
+        ensure
+          csv.close
+        end
+      else
+        csv
+      end
     end
 
-    # handle blocks like Ruby's open(), not like the CSV library
-    if block_given?
+    #
+    # :call-seq:
+    #   parse( str, **options ) { |row| ... }
+    #   parse( str, **options )
+    #
+    # This method can be used to easily parse CSV out of a String. You may either
+    # provide a +block+ which will be called with each row of the String in turn,
+    # or just use the returned Array of Arrays (when no +block+ is given).
+    #
+    # You pass your +str+ to read from, and an optional +options+ containing
+    # anything CSV::new() understands.
+    #
+    def parse(str, **options, &block)
+      csv = new(str, **options)
+
+      return csv.each(&block) if block_given?
+
+      # slurp contents, if no block is given
       begin
-        yield csv
+        csv.read
       ensure
         csv.close
       end
-    else
-      csv
     end
-  end
-
-  #
-  # :call-seq:
-  #   parse( str, **options ) { |row| ... }
-  #   parse( str, **options )
-  #
-  # This method can be used to easily parse CSV out of a String.  You may either
-  # provide a +block+ which will be called with each row of the String in turn,
-  # or just use the returned Array of Arrays (when no +block+ is given).
-  #
-  # You pass your +str+ to read from, and an optional +options+ containing
-  # anything CSV::new() understands.
-  #
-  def self.parse(*args, **options, &block)
-    csv = new(*args, **options)
-
-    return csv.each(&block) if block_given?
 
-    # slurp contents, if no block is given
-    begin
-      csv.read
-    ensure
-      csv.close
+    #
+    # This method is a shortcut for converting a single line of a CSV String into
+    # an Array. Note that if +line+ contains multiple rows, anything beyond the
+    # first row is ignored.
+    #
+    # The +options+ parameter can be anything CSV::new() understands.
+    #
+    def parse_line(line, **options)
+      new(line, **options).shift
     end
-  end
 
-  #
-  # This method is a shortcut for converting a single line of a CSV String into
-  # an Array.  Note that if +line+ contains multiple rows, anything beyond the
-  # first row is ignored.
-  #
-  # The +options+ parameter can be anything CSV::new() understands.
-  #
-  def self.parse_line(line, **options)
-    new(line, **options).shift
-  end
-
-  #
-  # Use to slurp a CSV file into an Array of Arrays.  Pass the +path+ to the
-  # file and any +options+ CSV::new() understands.  This method also understands
-  # an additional <tt>:encoding</tt> parameter that you can use to specify the
-  # Encoding of the data in the file to be read. You must provide this unless
-  # your data is in Encoding::default_external().  CSV will use this to determine
-  # how to parse the data.  You may provide a second Encoding to have the data
-  # transcoded as it is read.  For example,
-  # <tt>encoding: "UTF-32BE:UTF-8"</tt> would read UTF-32BE data from the file
-  # but transcode it to UTF-8 before CSV parses it.
-  #
-  def self.read(*args, **options)
-    open(*args, **options) { |csv| csv.read }
-  end
+    #
+    # Use to slurp a CSV file into an Array of Arrays. Pass the +path+ to the
+    # file and any +options+ CSV::new() understands. This method also understands
+    # an additional <tt>:encoding</tt> parameter that you can use to specify the
+    # Encoding of the data in the file to be read. You must provide this unless
+    # your data is in Encoding::default_external(). CSV will use this to determine
+    # how to parse the data. You may provide a second Encoding to have the data
+    # transcoded as it is read. For example,
+    # <tt>encoding: "UTF-32BE:UTF-8"</tt> would read UTF-32BE data from the file
+    # but transcode it to UTF-8 before CSV parses it.
+    #
+    def read(path, **options)
+      open(path, **options) { |csv| csv.read }
+    end
 
-  # Alias for CSV::read().
-  def self.readlines(*args, **options)
-    read(*args, **options)
-  end
+    # Alias for CSV::read().
+    def readlines(path, **options)
+      read(path, **options)
+    end
 
-  #
-  # A shortcut for:
-  #
-  #   CSV.read( path, { headers:           true,
-  #                     converters:        :numeric,
-  #                     header_converters: :symbol }.merge(options) )
-  #
-  def self.table(path, **options)
-    read( path, **{ headers:           true,
-                    converters:        :numeric,
-                    header_converters: :symbol }.merge(options) )
+    #
+    # A shortcut for:
+    #
+    #   CSV.read( path, { headers:           true,
+    #                     converters:        :numeric,
+    #                     header_converters: :symbol }.merge(options) )
+    #
+    def table(path, **options)
+      default_options = {
+        headers:           true,
+        converters:        :numeric,
+        header_converters: :symbol,
+      }
+      options = default_options.merge(options)
+      read(path, **options)
+    end
   end
 
   #
   # This constructor will wrap either a String or IO object passed in +data+ for
-  # reading and/or writing.  In addition to the CSV instance methods, several IO
-  # methods are delegated.  (See CSV::open() for a complete list.)  If you pass
+  # reading and/or writing. In addition to the CSV instance methods, several IO
+  # methods are delegated. (See CSV::open() for a complete list.) If you pass
   # a String for +data+, you can later retrieve it (after writing to it, for
   # example) with CSV.string().
   #
   # Note that a wrapped String will be positioned at the beginning (for
-  # reading).  If you want it at the end (for writing), use CSV::generate().
+  # reading). If you want it at the end (for writing), use CSV::generate().
   # If you want any other positioning, pass a preset StringIO object instead.
   #
   # You may set any reading and/or writing preferences in the +options+ Hash.
@@ -750,25 +756,25 @@ class CSV
   #                                       This String will be transcoded into
   #                                       the data's Encoding before parsing.
   # <b><tt>:row_sep</tt></b>::            The String appended to the end of each
-  #                                       row.  This can be set to the special
+  #                                       row. This can be set to the special
   #                                       <tt>:auto</tt> setting, which requests
   #                                       that CSV automatically discover this
-  #                                       from the data.  Auto-discovery reads
+  #                                       from the data. Auto-discovery reads
   #                                       ahead in the data looking for the next
   #                                       <tt>"\r\n"</tt>, <tt>"\n"</tt>, or
-  #                                       <tt>"\r"</tt> sequence.  A sequence
+  #                                       <tt>"\r"</tt> sequence. A sequence
   #                                       will be selected even if it occurs in
   #                                       a quoted field, assuming that you
   #                                       would have the same line endings
-  #                                       there.  If none of those sequences is
+  #                                       there. If none of those sequences is
   #                                       found, +data+ is <tt>ARGF</tt>,
   #                                       <tt>STDIN</tt>, <tt>STDOUT</tt>, or
   #                                       <tt>STDERR</tt>, or the stream is only
   #                                       available for output, the default
   #                                       <tt>$INPUT_RECORD_SEPARATOR</tt>
-  #                                       (<tt>$/</tt>) is used.  Obviously,
-  #                                       discovery takes a little time.  Set
-  #                                       manually if speed is important.  Also
+  #                                       (<tt>$/</tt>) is used. Obviously,
+  #                                       discovery takes a little time. Set
+  #                                       manually if speed is important. Also
   #                                       note that IO objects should be opened
   #                                       in binary mode on Windows if this
   #                                       feature will be used as the
@@ -780,7 +786,7 @@ class CSV
   #                                       before parsing.
   # <b><tt>:quote_char</tt></b>::         The character used to quote fields.
   #                                       This has to be a single character
-  #                                       String.  This is useful for
+  #                                       String. This is useful for
   #                                       application that incorrectly use
   #                                       <tt>'</tt> as the quote character
   #                                       instead of the correct <tt>"</tt>.
@@ -791,21 +797,21 @@ class CSV
   #                                       before parsing.
   # <b><tt>:field_size_limit</tt></b>::   This is a maximum size CSV will read
   #                                       ahead looking for the closing quote
-  #                                       for a field.  (In truth, it reads to
+  #                                       for a field. (In truth, it reads to
   #                                       the first line ending beyond this
-  #                                       size.)  If a quote cannot be found
+  #                                       size.) If a quote cannot be found
   #                                       within the limit CSV will raise a
   #                                       MalformedCSVError, assuming the data
-  #                                       is faulty.  You can use this limit to
+  #                                       is faulty. You can use this limit to
   #                                       prevent what are effectively DoS
-  #                                       attacks on the parser.  However, this
+  #                                       attacks on the parser. However, this
   #                                       limit can cause a legitimate parse to
   #                                       fail and thus is set to +nil+, or off,
   #                                       by default.
   # <b><tt>:converters</tt></b>::         An Array of names from the Converters
   #                                       Hash and/or lambdas that handle custom
-  #                                       conversion.  A single converter
-  #                                       doesn't have to be in an Array.  All
+  #                                       conversion. A single converter
+  #                                       doesn't have to be in an Array. All
   #                                       built-in converters try to transcode
   #                                       fields to UTF-8 before converting.
   #                                       The conversion will fail if the data
@@ -815,7 +821,7 @@ class CSV
   #                                       unconverted_fields() method will be
   #                                       added to all returned rows (Array or
   #                                       CSV::Row) that will return the fields
-  #                                       as they were before conversion.  Note
+  #                                       as they were before conversion. Note
   #                                       that <tt>:headers</tt> supplied by
   #                                       Array or String were not fields of the
   #                                       document and thus will have an empty
@@ -823,21 +829,21 @@ class CSV
   # <b><tt>:headers</tt></b>::            If set to <tt>:first_row</tt> or
   #                                       +true+, the initial row of the CSV
   #                                       file will be treated as a row of
-  #                                       headers.  If set to an Array, the
+  #                                       headers. If set to an Array, the
   #                                       contents will be used as the headers.
   #                                       If set to a String, the String is run
   #                                       through a call of CSV::parse_line()
   #                                       with the same <tt>:col_sep</tt>,
   #                                       <tt>:row_sep</tt>, and
   #                                       <tt>:quote_char</tt> as this instance
-  #                                       to produce an Array of headers.  This
+  #                                       to produce an Array of headers. This
   #                                       setting causes CSV#shift() to return
   #                                       rows as CSV::Row objects instead of
   #                                       Arrays and CSV#read() to return
   #                                       CSV::Table objects instead of an Array
   #                                       of Arrays.
   # <b><tt>:return_headers</tt></b>::     When +false+, header rows are silently
-  #                                       swallowed.  If set to +true+, header
+  #                                       swallowed. If set to +true+, header
   #                                       rows are returned in a CSV::Row object
   #                                       with identical headers and
   #                                       fields (save that the fields do not go
@@ -848,12 +854,12 @@ class CSV
   # <b><tt>:header_converters</tt></b>::  Identical in functionality to
   #                                       <tt>:converters</tt> save that the
   #                                       conversions are only made to header
-  #                                       rows.  All built-in converters try to
+  #                                       rows. All built-in converters try to
   #                                       transcode headers to UTF-8 before
-  #                                       converting.  The conversion will fail
+  #                                       converting. The conversion will fail
   #                                       if the data cannot be transcoded,
   #                                       leaving the header unchanged.
-  # <b><tt>:skip_blanks</tt></b>::        When set to a +true+ value, CSV will
+  # <b><tt>:skip_blanks</tt></b>::        When setting a +true+ value, CSV will
   #                                       skip over any empty rows. Note that
   #                                       this setting will not skip rows that
   #                                       contain column separators, even if
@@ -863,9 +869,9 @@ class CSV
   #                                       using <tt>:skip_lines</tt>, or
   #                                       inspecting fields.compact.empty? on
   #                                       each row.
-  # <b><tt>:force_quotes</tt></b>::       When set to a +true+ value, CSV will
+  # <b><tt>:force_quotes</tt></b>::       When setting a +true+ value, CSV will
   #                                       quote all CSV fields it creates.
-  # <b><tt>:skip_lines</tt></b>::         When set to an object responding to
+  # <b><tt>:skip_lines</tt></b>::         When setting an object responding to
   #                                       <tt>match</tt>, every line matching
   #                                       it is considered a comment and ignored
   #                                       during parsing. When set to a String,
@@ -874,17 +880,17 @@ class CSV
   #                                       a comment. If the passed object does
   #                                       not respond to <tt>match</tt>,
   #                                       <tt>ArgumentError</tt> is thrown.
-  # <b><tt>:liberal_parsing</tt></b>::    When set to a +true+ value, CSV will
+  # <b><tt>:liberal_parsing</tt></b>::    When setting a +true+ value, CSV will
   #                                       attempt to parse input not conformant
   #                                       with RFC 4180, such as double quotes
   #                                       in unquoted fields.
   # <b><tt>:nil_value</tt></b>::          When set an object, any values of an
-  #                                       empty field are replaced by the set
+  #                                       empty field is replaced by the set
   #                                       object, not nil.
-  # <b><tt>:empty_value</tt></b>::        When set an object, any values of a
+  # <b><tt>:empty_value</tt></b>::        When setting an object, any values of a
   #                                       blank string field is replaced by
   #                                       the set object.
-  # <b><tt>:quote_empty</tt></b>::        When set to a +true+ value, CSV will
+  # <b><tt>:quote_empty</tt></b>::        When setting a +true+ value, CSV will
   #                                       quote empty values with double quotes.
   #                                       When +false+, CSV will emit an
   #                                       empty string for an empty field value.
@@ -901,11 +907,11 @@ class CSV
   # <b><tt>:write_empty_value</tt></b>::  When a <tt>String</tt> or +nil+ value,
   #                                       empty value(s) on each line will be
   #                                       replaced with the specified value.
-  # <b><tt>:strip</tt></b>::              When set to a +true+ value, CSV will
+  # <b><tt>:strip</tt></b>::              When setting a +true+ value, CSV will
   #                                       strip "\t\r\n\f\v" around the values.
   #                                       If you specify a string instead of
   #                                       +true+, CSV will strip string. The
-  #                                       length of string must be 1.
+  #                                       length of the string must be 1.
   #
   # See CSV::DEFAULT_OPTIONS for the default settings.
   #
@@ -939,8 +945,12 @@ class CSV
                  strip: false)
     raise ArgumentError.new("Cannot parse nil as CSV") if data.nil?
 
-    # create the IO object we will read from
-    @io = data.is_a?(String) ? StringIO.new(data) : data
+    if data.is_a?(String)
+      @io = StringIO.new(data)
+      @io.set_encoding(encoding || data.encoding)
+    else
+      @io = data
+    end
     @encoding = determine_encoding(encoding, internal_encoding)
 
     @base_fields_converter_options = {
@@ -992,41 +1002,47 @@ class CSV
   end
 
   #
-  # The encoded <tt>:col_sep</tt> used in parsing and writing.  See CSV::new
-  # for details.
+  # The encoded <tt>:col_sep</tt> used in parsing and writing.
+  # See CSV::new for details.
   #
   def col_sep
     parser.column_separator
   end
 
   #
-  # The encoded <tt>:row_sep</tt> used in parsing and writing.  See CSV::new
-  # for details.
+  # The encoded <tt>:row_sep</tt> used in parsing and writing.
+  # See CSV::new for details.
   #
   def row_sep
     parser.row_separator
   end
 
   #
-  # The encoded <tt>:quote_char</tt> used in parsing and writing.  See CSV::new
-  # for details.
+  # The encoded <tt>:quote_char</tt> used in parsing and writing.
+  # See CSV::new for details.
   #
   def quote_char
     parser.quote_character
   end
 
-  # The limit for field size, if any.  See CSV::new for details.
+  #
+  # The limit for field size, if any.
+  # See CSV::new for details.
+  #
   def field_size_limit
     parser.field_size_limit
   end
 
-  # The regex marking a line as a comment. See CSV::new for details
+  #
+  # The regex marking a line as a comment.
+  # See CSV::new for details.
+  #
   def skip_lines
     parser.skip_lines
   end
 
   #
-  # Returns the current list of converters in effect.  See CSV::new for details.
+  # Returns the current list of converters in effect. See CSV::new for details.
   # Built-in converters will be returned by name, while others will be returned
   # as is.
   #
@@ -1036,9 +1052,10 @@ class CSV
       name ? name.first : converter
     end
   end
+
   #
-  # Returns +true+ if unconverted_fields() to parsed results.  See CSV::new
-  # for details.
+  # Returns +true+ if unconverted_fields() to parsed results.
+  # See CSV::new for details.
   #
   def unconverted_fields?
     parser.unconverted_fields?
@@ -1046,8 +1063,8 @@ class CSV
 
   #
   # Returns +nil+ if headers will not be used, +true+ if they will but have not
-  # yet been read, or the actual headers after they have been read.  See
-  # CSV::new for details.
+  # yet been read, or the actual headers after they have been read.
+  # See CSV::new for details.
   #
   def headers
     if @writer
@@ -1068,14 +1085,17 @@ class CSV
     parser.return_headers?
   end
 
-  # Returns +true+ if headers are written in output. See CSV::new for details.
+  #
+  # Returns +true+ if headers are written in output.
+  # See CSV::new for details.
+  #
   def write_headers?
     @writer_options[:write_headers]
   end
 
   #
-  # Returns the current list of converters in effect for headers.  See CSV::new
-  # for details.  Built-in converters will be returned by name, while others
+  # Returns the current list of converters in effect for headers. See CSV::new
+  # for details. Built-in converters will be returned by name, while others
   # will be returned as is.
   #
   def header_converters
@@ -1201,7 +1221,7 @@ class CSV
 
   #
   # The primary write method for wrapped Strings and IOs, +row+ (an Array or
-  # CSV::Row) is converted to CSV and appended to the data source.  When a
+  # CSV::Row) is converted to CSV and appended to the data source. When a
   # CSV::Row is passed, only the row's fields() are appended to the output.
   #
   # The data source must be open for writing.
@@ -1223,9 +1243,9 @@ class CSV
   # block that handles a custom conversion.
   #
   # If you provide a block that takes one argument, it will be passed the field
-  # and is expected to return the converted value or the field itself.  If your
+  # and is expected to return the converted value or the field itself. If your
   # block takes two arguments, it will also be passed a CSV::FieldInfo Struct,
-  # containing details about the field.  Again, the block should return a
+  # containing details about the field. Again, the block should return a
   # converted field or the field itself.
   #
   def convert(name = nil, &converter)
@@ -1377,9 +1397,9 @@ class CSV
 
   #
   # Processes +fields+ with <tt>@converters</tt>, or <tt>@header_converters</tt>
-  # if +headers+ is passed as +true+, returning the converted field set.  Any
+  # if +headers+ is passed as +true+, returning the converted field set. Any
   # converter that changes the field into something other than a String halts
-  # the pipeline of conversion for that field.  This is primarily an efficiency
+  # the pipeline of conversion for that field. This is primarily an efficiency
   # shortcut.
   #
   def convert_fields(fields, headers = false)
diff --git a/lib/csv/fields_converter.rb b/lib/csv/fields_converter.rb
index c2fa5798ff..a751c9ea1d 100644
--- a/lib/csv/fields_converter.rb
+++ b/lib/csv/fields_converter.rb
@@ -1,8 +1,14 @@
 # frozen_string_literal: true
 
 class CSV
+  # Note: Don't use this class directly. This is an internal class.
   class FieldsConverter
     include Enumerable
+    #
+    # A CSV::FieldsConverter is a data structure for storing the
+    # fields converter properties to be passed as a parameter
+    # when parsing a new file (e.g. CSV::Parser.new(@io, parser_options))
+    #
 
     def initialize(options={})
       @converters = []
diff --git a/lib/csv/parser.rb b/lib/csv/parser.rb
index 2ef2a28ff3..42145f8923 100644
--- a/lib/csv/parser.rb
+++ b/lib/csv/parser.rb
@@ -11,10 +11,31 @@ using CSV::DeleteSuffix if CSV.const_defined?(:DeleteSuffix)
 using CSV::MatchP if CSV.const_defined?(:MatchP)
 
 class CSV
+  # Note: Don't use this class directly. This is an internal class.
   class Parser
+    #
+    # A CSV::Parser is m17n aware. The parser works in the Encoding of the IO
+    # or String object being read from or written to. Your data is never transcoded
+    # (unless you ask Ruby to transcode it for you) and will literally be parsed in
+    # the Encoding it is in. Thus CSV will return Arrays or Rows of Strings in the
+    # Encoding of your data. This is accomplished by transcoding the parser itself
+    # into your Encoding.
+    #
+
+    # Raised when encoding is invalid.
     class InvalidEncoding < StandardError
     end
 
+    #
+    # CSV::Scanner receives a CSV output, scans it and return the content.
+    # It also controls the life cycle of the object with its methods +keep_start+,
+    # +keep_end+, +keep_back+, +keep_drop+.
+    #
+    # Uses StringScanner (the official strscan gem). Strscan provides lexical
+    # scanning operations on a String. We inherit its object and take advantage
+    # on the methods. For more information, please visit:
+    # https://ruby-doc.org/stdlib-2.6.1/libdoc/strscan/rdoc/StringScanner.html
+    #
     class Scanner < StringScanner
       alias_method :scan_all, :scan
 
@@ -38,7 +59,7 @@ class CSV
 
       def keep_end
         start = @keeps.pop
-        string[start, pos - start]
+        string.byteslice(start, pos - start)
       end
 
       def keep_back
@@ -50,6 +71,18 @@ class CSV
       end
     end
 
+    #
+    # CSV::InputsScanner receives IO inputs, encoding and the chunk_size.
+    # It also controls the life cycle of the object with its methods +keep_start+,
+    # +keep_end+, +keep_back+, +keep_drop+.
+    #
+    # CSV::InputsScanner.scan() tries to match with pattern at the current position.
+    # If there's a match, the scanner advances the “scan pointer” and returns the matched string.
+    # Otherwise, the scanner returns nil.
+    #
+    # CSV::InputsScanner.rest() returns the “rest” of the string (i.e. everything after the scan pointer).
+    # If there is no more data (eos? = true), it returns "".
+    #
     class InputsScanner
       def initialize(inputs, encoding, chunk_size: 8192)
         @inputs = inputs.dup
@@ -137,7 +170,7 @@ class CSV
 
       def keep_end
         start, buffer = @keeps.pop
-        keep = @scanner.string[start, @scanner.pos - start]
+        keep = @scanner.string.byteslice(start, @scanner.pos - start)
         if buffer
           buffer << keep
           keep = buffer
@@ -192,7 +225,7 @@ class CSV
         input = @inputs.first
         case input
         when StringIO
-          string = input.string
+          string = input.read
           raise InvalidEncoding unless string.valid_encoding?
           @scanner = StringScanner.new(string)
           @inputs.shift
@@ -319,6 +352,7 @@ class CSV
     end
 
     private
+    # A set of tasks to prepare the file in order to parse it
     def prepare
       prepare_variable
       prepare_quote_character
@@ -447,7 +481,13 @@ class CSV
     end
 
     def prepare_separators
-      @column_separator = @options[:column_separator].to_s.encode(@encoding)
+      column_separator = @options[:column_separator]
+      @column_separator = column_separator.to_s.encode(@encoding)
+      if @column_separator.size < 1
+        message = ":col_sep must be 1 or more characters: "
+        message += column_separator.inspect
+        raise ArgumentError, message
+      end
       @row_separator =
         resolve_row_separator(@options[:row_separator]).encode(@encoding)
 
@@ -534,7 +574,9 @@ class CSV
         cr = "\r".encode(@encoding)
         lf = "\n".encode(@encoding)
         if @input.is_a?(StringIO)
-          separator = detect_row_separator(@input.string, cr, lf)
+          pos = @input.pos
+          separator = detect_row_separator(@input.read, cr, lf)
+          @input.seek(pos)
         elsif @input.respond_to?(:gets)
           if @input.is_a?(File)
             chunk_size = 32 * 1024
@@ -651,7 +693,9 @@ class CSV
       return false if @quote_character.nil?
 
       if @input.is_a?(StringIO)
-        sample = @input.string
+        pos = @input.pos
+        sample = @input.read
+        @input.seek(pos)
       else
         return false if @samples.empty?
         sample = @samples.first
@@ -684,7 +728,7 @@ class CSV
           UnoptimizedStringIO.new(sample)
         end
         if @input.is_a?(StringIO)
-          inputs << UnoptimizedStringIO.new(@input.string)
+          inputs << UnoptimizedStringIO.new(@input.read)
         else
           inputs << @input
         end
@@ -697,7 +741,7 @@ class CSV
       def build_scanner
         string = nil
         if @samples.empty? and @input.is_a?(StringIO)
-          string = @input.string
+          string = @input.read
         elsif @samples.size == 1 and @input.respond_to?(:eof?) and @input.eof?
           string = @samples[0]
         end
diff --git a/lib/csv/row.rb b/lib/csv/row.rb
index 1e1f27587b..4aa0f30911 100644
--- a/lib/csv/row.rb
+++ b/lib/csv/row.rb
@@ -4,7 +4,7 @@ require "forwardable"
 
 class CSV
   #
-  # A CSV::Row is part Array and part Hash.  It retains an order for the fields
+  # A CSV::Row is part Array and part Hash. It retains an order for the fields
   # and allows duplicates just as an Array would, but also allows you to access
   # fields by name just as you could if they were in a Hash.
   #
@@ -13,13 +13,13 @@ class CSV
   #
   class Row
     #
-    # Construct a new CSV::Row from +headers+ and +fields+, which are expected
-    # to be Arrays.  If one Array is shorter than the other, it will be padded
+    # Constructs a new CSV::Row from +headers+ and +fields+, which are expected
+    # to be Arrays. If one Array is shorter than the other, it will be padded
     # with +nil+ objects.
     #
     # The optional +header_row+ parameter can be set to +true+ to indicate, via
     # CSV::Row.header_row?() and CSV::Row.field_row?(), that this is a header
-    # row.  Otherwise, the row is assumes to be a field row.
+    # row. Otherwise, the row assumes to be a field row.
     #
     # A CSV::Row object supports the following Array methods through delegation:
     #
@@ -74,11 +74,11 @@ class CSV
     #   field( header, offset )
     #   field( index )
     #
-    # This method will return the field value by +header+ or +index+.  If a field
+    # This method will return the field value by +header+ or +index+. If a field
     # is not found, +nil+ is returned.
     #
     # When provided, +offset+ ensures that a header match occurs on or later
-    # than the +offset+ index.  You can use this to find duplicate headers,
+    # than the +offset+ index. You can use this to find duplicate headers,
     # without resorting to hard-coding exact indices.
     #
     def field(header_or_index, minimum_index = 0)
@@ -142,7 +142,7 @@ class CSV
     # assigns the +value+.
     #
     # Assigning past the end of the row with an index will set all pairs between
-    # to <tt>[nil, nil]</tt>.  Assigning to an unused header appends the new
+    # to <tt>[nil, nil]</tt>. Assigning to an unused header appends the new
     # pair.
     #
     def []=(*args)
@@ -172,8 +172,8 @@ class CSV
     #   <<( header_and_field_hash )
     #
     # If a two-element Array is provided, it is assumed to be a header and field
-    # and the pair is appended.  A Hash works the same way with the key being
-    # the header and the value being the field.  Anything else is assumed to be
+    # and the pair is appended. A Hash works the same way with the key being
+    # the header and the value being the field. Anything else is assumed to be
     # a lone field which is appended with a +nil+ header.
     #
     # This method returns the row for chaining.
@@ -191,7 +191,7 @@ class CSV
     end
 
     #
-    # A shortcut for appending multiple fields.  Equivalent to:
+    # A shortcut for appending multiple fields. Equivalent to:
     #
     #   args.each { |arg| csv_row << arg }
     #
@@ -209,8 +209,8 @@ class CSV
     #   delete( header, offset )
     #   delete( index )
     #
-    # Used to remove a pair from the row by +header+ or +index+.  The pair is
-    # located as described in CSV::Row.field().  The deleted pair is returned,
+    # Removes a pair from the row by +header+ or +index+. The pair is
+    # located as described in CSV::Row.field(). The deleted pair is returned,
     # or +nil+ if a pair could not be found.
     #
     def delete(header_or_index, minimum_index = 0)
@@ -325,7 +325,7 @@ class CSV
     end
 
     #
-    # Collapses the row into a simple Hash.  Be warned that this discards field
+    # Collapses the row into a simple Hash. Be warned that this discards field
     # order and clobbers duplicate fields.
     #
     def to_h
@@ -340,7 +340,7 @@ class CSV
     alias_method :to_ary, :to_a
 
     #
-    # Returns the row as a CSV String.  Headers are not used.  Equivalent to:
+    # Returns the row as a CSV String. Headers are not used. Equivalent to:
     #
     #   csv_row.fields.to_csv( options )
     #
@@ -367,7 +367,9 @@ class CSV
       end
     end
 
+    #
     # A summary of fields, by header, in an ASCII compatible String.
+    #
     def inspect
       str = ["#<", self.class.to_s]
       each do |header, field|
diff --git a/lib/csv/table.rb b/lib/csv/table.rb
index 29b188a6d7..e6c1ee11fa 100644
--- a/lib/csv/table.rb
+++ b/lib/csv/table.rb
@@ -5,7 +5,7 @@ require "forwardable"
 class CSV
   #
   # A CSV::Table is a two-dimensional data structure for representing CSV
-  # documents.  Tables allow you to work with the data by row or column,
+  # documents. Tables allow you to work with the data by row or column,
   # manipulate the data, and even convert the results back to CSV, if needed.
   #
   # All tables returned by CSV will be constructed from this class, if header
@@ -13,8 +13,8 @@ class CSV
   #
   class Table
     #
-    # Construct a new CSV::Table from +array_of_rows+, which are expected
-    # to be CSV::Row objects.  All rows are assumed to have the same headers.
+    # Constructs a new CSV::Table from +array_of_rows+, which are expected
+    # to be CSV::Row objects. All rows are assumed to have the same headers.
     #
     # The optional +headers+ parameter can be set to Array of headers.
     # If headers aren't set, headers are fetched from CSV::Row objects.
@@ -55,11 +55,11 @@ class CSV
     def_delegators :@table, :empty?, :length, :size
 
     #
-    # Returns a duplicate table object, in column mode.  This is handy for
+    # Returns a duplicate table object, in column mode. This is handy for
     # chaining in a single call without changing the table mode, but be aware
     # that this method can consume a fair amount of memory for bigger data sets.
     #
-    # This method returns the duplicate table for chaining.  Don't chain
+    # This method returns the duplicate table for chaining. Don't chain
     # destructive methods (like []=()) this way though, since you are working
     # with a duplicate.
     #
@@ -68,7 +68,7 @@ class CSV
     end
 
     #
-    # Switches the mode of this table to column mode.  All calls to indexing and
+    # Switches the mode of this table to column mode. All calls to indexing and
     # iteration methods will work with columns until the mode is changed again.
     #
     # This method returns the table and is safe to chain.
@@ -80,7 +80,7 @@ class CSV
     end
 
     #
-    # Returns a duplicate table object, in mixed mode.  This is handy for
+    # Returns a duplicate table object, in mixed mode. This is handy for
     # chaining in a single call without changing the table mode, but be aware
     # that this method can consume a fair amount of memory for bigger data sets.
     #
@@ -93,9 +93,9 @@ class CSV
     end
 
     #
-    # Switches the mode of this table to mixed mode.  All calls to indexing and
+    # Switches the mode of this table to mixed mode. All calls to indexing and
     # iteration methods will use the default intelligent indexing system until
-    # the mode is changed again.  In mixed mode an index is assumed to be a row
+    # the mode is changed again. In mixed mode an index is assumed to be a row
     # reference while anything else is assumed to be column access by headers.
     #
     # This method returns the table and is safe to chain.
@@ -120,7 +120,7 @@ class CSV
     end
 
     #
-    # Switches the mode of this table to row mode.  All calls to indexing and
+    # Switches the mode of this table to row mode. All calls to indexing and
     # iteration methods will work with rows until the mode is changed again.
     #
     # This method returns the table and is safe to chain.
@@ -146,7 +146,7 @@ class CSV
 
     #
     # In the default mixed mode, this method returns rows for index access and
-    # columns for header access.  You can force the index association by first
+    # columns for header access. You can force the index association by first
     # calling by_col!() or by_row!().
     #
     # Columns are returned as an Array of values.  Altering that Array has no
@@ -163,18 +163,18 @@ class CSV
 
     #
     # In the default mixed mode, this method assigns rows for index access and
-    # columns for header access.  You can force the index association by first
+    # columns for header access. You can force the index association by first
     # calling by_col!() or by_row!().
     #
     # Rows may be set to an Array of values (which will inherit the table's
     # headers()) or a CSV::Row.
     #
     # Columns may be set to a single value, which is copied to each row of the
-    # column, or an Array of values.  Arrays of values are assigned to rows top
-    # to bottom in row major order.  Excess values are ignored and if the Array
+    # column, or an Array of values. Arrays of values are assigned to rows top
+    # to bottom in row major order. Excess values are ignored and if the Array
     # does not have a value for each row the extra rows will receive a +nil+.
     #
-    # Assigning to an existing column or row clobbers the data.  Assigning to
+    # Assigning to an existing column or row clobbers the data. Assigning to
     # new columns creates them at the right end of the table.
     #
     def []=(index_or_header, value)
@@ -212,9 +212,9 @@ class CSV
 
     #
     # The mixed mode default is to treat a list of indices as row access,
-    # returning the rows indicated.  Anything else is considered columnar
-    # access.  For columnar access, the return set has an Array for each row
-    # with the values indicated by the headers in each Array.  You can force
+    # returning the rows indicated. Anything else is considered columnar
+    # access. For columnar access, the return set has an Array for each row
+    # with the values indicated by the headers in each Array. You can force
     # column or row mode using by_col!() or by_row!().
     #
     # You cannot mix column and row access.
@@ -234,7 +234,7 @@ class CSV
     end
 
     #
-    # Adds a new row to the bottom end of this table.  You can provide an Array,
+    # Adds a new row to the bottom end of this table. You can provide an Array,
     # which will be converted to a CSV::Row (inheriting the table's headers()),
     # or a CSV::Row.
     #
@@ -251,7 +251,7 @@ class CSV
     end
 
     #
-    # A shortcut for appending multiple rows.  Equivalent to:
+    # A shortcut for appending multiple rows. Equivalent to:
     #
     #   rows.each { |row| self << row }
     #
@@ -264,9 +264,9 @@ class CSV
     end
 
     #
-    # Removes and returns the indicated columns or rows.  In the default mixed
+    # Removes and returns the indicated columns or rows. In the default mixed
     # mode indices refer to rows and everything else is assumed to be a column
-    # headers.  Use by_col!() or by_row!() to force the lookup.
+    # headers. Use by_col!() or by_row!() to force the lookup.
     #
     def delete(*indexes_or_headers)
       if indexes_or_headers.empty?
@@ -293,9 +293,9 @@ class CSV
     end
 
     #
-    # Removes any column or row for which the block returns +true+.  In the
+    # Removes any column or row for which the block returns +true+. In the
     # default mixed mode or row mode, iteration is the standard row major
-    # walking of rows.  In column mode, iteration will +yield+ two element
+    # walking of rows. In column mode, iteration will +yield+ two element
     # tuples containing the column name and an Array of values for that column.
     #
     # This method returns the table for chaining.
@@ -321,7 +321,7 @@ class CSV
 
     #
     # In the default mixed mode or row mode, iteration is the standard row major
-    # walking of rows.  In column mode, iteration will +yield+ two element
+    # walking of rows. In column mode, iteration will +yield+ two element
     # tuples containing the column name and an Array of values for that column.
     #
     # This method returns the table for chaining.
@@ -347,7 +347,7 @@ class CSV
     end
 
     #
-    # Returns the table as an Array of Arrays.  Headers will be the first row,
+    # Returns the table as an Array of Arrays. Headers will be the first row,
     # then all of the field rows will follow.
     #
     def to_a
@@ -360,7 +360,7 @@ class CSV
     end
 
     #
-    # Returns the table as a complete CSV String.  Headers will be listed first,
+    # Returns the table as a complete CSV String. Headers will be listed first,
     # then all of the field rows.
     #
     # This method assumes you want the Table.headers(), unless you explicitly
diff --git a/lib/csv/version.rb b/lib/csv/version.rb
index ce55373f02..072400fe01 100644
--- a/lib/csv/version.rb
+++ b/lib/csv/version.rb
@@ -2,5 +2,5 @@
 
 class CSV
   # The version of the installed library.
-  VERSION = "3.1.1"
+  VERSION = "3.1.2"
 end
diff --git a/lib/csv/writer.rb b/lib/csv/writer.rb
index 1682ac03ea..9243d23641 100644
--- a/lib/csv/writer.rb
+++ b/lib/csv/writer.rb
@@ -6,7 +6,12 @@ require_relative "row"
 using CSV::MatchP if CSV.const_defined?(:MatchP)
 
 class CSV
+  # Note: Don't use this class directly. This is an internal class.
   class Writer
+    #
+    # A CSV::Writer receives an output, prepares the header, format and output.
+    # It allows us to write new rows in the object and rewind it.
+    #
     attr_reader :lineno
     attr_reader :headers
 
@@ -22,6 +27,9 @@ class CSV
       @fields_converter = @options[:fields_converter]
     end
 
+    #
+    # Adds a new row
+    #
     def <<(row)
       case row
       when Row
@@ -47,6 +55,9 @@ class CSV
       self
     end
 
+    #
+    # Winds back to the beginning
+    #
     def rewind
       @lineno = 0
       @headers = nil if @options[:headers].nil?