Encoding conversion class.

Constants

INVALID_MASK

Mask for invalid byte sequences

INVALID_REPLACE

Replace invalid byte sequences

UNDEF_MASK

Mask for a valid character in the source encoding but no related character(s) in destination encoding.

UNDEF_REPLACE

Replace byte sequences that are undefined in the destination encoding.

UNDEF_HEX_CHARREF

Replace byte sequences that are undefined in the destination encoding with an XML hexadecimal character reference. This is valid for XML conversion.

PARTIAL_INPUT

Indicates the source may be part of a larger string. See primitive_convert for an example.

AFTER_OUTPUT

Stop converting after some output is complete but before all of the input was consumed. See primitive_convert for an example.

UNIVERSAL_NEWLINE_DECORATOR

Decorator for converting CRLF and CR to LF

CRLF_NEWLINE_DECORATOR

Decorator for converting LF to CRLF

CR_NEWLINE_DECORATOR

Decorator for converting LF to CR

Class Methods

Returns the corresponding ASCII compatible encoding.

Returns nil if the argument is an ASCII compatible encoding.

“corresponding ASCII compatible encoding” is an ASCII compatible encoding which can represents exactly the same characters as the given ASCII incompatible encoding. So, no conversion undefined error occurs when converting between the two encodings.

Encoding::Converter.asciicompat_encoding("ISO-2022-JP") #=> #<Encoding:stateless-ISO-2022-JP>
Encoding::Converter.asciicompat_encoding("UTF-16BE") #=> #<Encoding:UTF-8>
Encoding::Converter.asciicompat_encoding("UTF-8") #=> nil

possible options elements:

hash form:
  :invalid => nil            # raise error on invalid byte sequence (default)
  :invalid => :replace       # replace invalid byte sequence
  :undef => nil              # raise error on undefined conversion (default)
  :undef => :replace         # replace undefined conversion
  :replace => string         # replacement string ("?" or "\uFFFD" if not specified)
  :newline => :universal     # decorator for converting CRLF and CR to LF
  :newline => :crlf          # decorator for converting LF to CRLF
  :newline => :cr            # decorator for converting LF to CR
  :universal_newline => true # decorator for converting CRLF and CR to LF
  :crlf_newline => true      # decorator for converting LF to CRLF
  :cr_newline => true        # decorator for converting LF to CR
  :xml => :text              # escape as XML CharData.
  :xml => :attr              # escape as XML AttValue
integer form:
  Encoding::Converter::INVALID_REPLACE
  Encoding::Converter::UNDEF_REPLACE
  Encoding::Converter::UNDEF_HEX_CHARREF
  Encoding::Converter::UNIVERSAL_NEWLINE_DECORATOR
  Encoding::Converter::CRLF_NEWLINE_DECORATOR
  Encoding::Converter::CR_NEWLINE_DECORATOR
  Encoding::Converter::XML_TEXT_DECORATOR
  Encoding::Converter::XML_ATTR_CONTENT_DECORATOR
  Encoding::Converter::XML_ATTR_QUOTE_DECORATOR

Encoding::Converter.new creates an instance of Encoding::Converter.

Source_encoding and destination_encoding should be a string or Encoding object.

opt should be nil, a hash or an integer.

convpath should be an array. convpath may contain

  • two-element arrays which contain encodings or encoding names, or

  • strings representing decorator names.

Encoding::Converter.new optionally takes an option. The option should be a hash or an integer. The option hash can contain :invalid => nil, etc. The option integer should be logical-or of constants such as Encoding::Converter::INVALID_REPLACE, etc.

:invalid => nil

Raise error on invalid byte sequence. This is a default behavior.

:invalid => :replace

Replace invalid byte sequence by replacement string.

:undef => nil

Raise an error if a character in source_encoding is not defined in destination_encoding. This is a default behavior.

:undef => :replace

Replace undefined character in destination_encoding with replacement string.

:replace => string

Specify the replacement string. If not specified, “uFFFD” is used for Unicode encodings and “?” for others.

:universal_newline => true

Convert CRLF and CR to LF.

:crlf_newline => true

Convert LF to CRLF.

:cr_newline => true

Convert LF to CR.

:xml => :text

Escape as XML CharData. This form can be used as an HTML 4.0 PCDATA.

  • ‘&’ -> ‘&amp;’

  • ‘<’ -> ‘&lt;’

  • ‘>’ -> ‘&gt;’

  • undefined characters in destination_encoding -> hexadecimal CharRef such as &#xHH;

:xml => :attr

Escape as XML AttValue. The converted result is quoted as “…”. This form can be used as an HTML 4.0 attribute value.

  • ‘&’ -> ‘&amp;’

  • ‘<’ -> ‘&lt;’

  • ‘>’ -> ‘&gt;’

  • ‘“’ -> ‘&quot;’

  • undefined characters in destination_encoding -> hexadecimal CharRef such as &#xHH;

Examples:

# UTF-16BE to UTF-8
ec = Encoding::Converter.new("UTF-16BE", "UTF-8")

# Usually, decorators such as newline conversion are inserted last.
ec = Encoding::Converter.new("UTF-16BE", "UTF-8", :universal_newline => true)
p ec.convpath #=> [[#<Encoding:UTF-16BE>, #<Encoding:UTF-8>],
              #    "universal_newline"]

# But, if the last encoding is ASCII incompatible,
# decorators are inserted before the last conversion.
ec = Encoding::Converter.new("UTF-8", "UTF-16BE", :crlf_newline => true)
p ec.convpath #=> ["crlf_newline",
              #    [#<Encoding:UTF-8>, #<Encoding:UTF-16BE>]]

# Conversion path can be specified directly.
ec = Encoding::Converter.new(["universal_newline", ["EUC-JP", "UTF-8"], ["UTF-8", "UTF-16BE"]])
p ec.convpath #=> ["universal_newline",
              #    [#<Encoding:EUC-JP>, #<Encoding:UTF-8>],
              #    [#<Encoding:UTF-8>, #<Encoding:UTF-16BE>]]

Returns a conversion path.

p Encoding::Converter.search_convpath("ISO-8859-1", "EUC-JP")
#=> [[#<Encoding:ISO-8859-1>, #<Encoding:UTF-8>],
#    [#<Encoding:UTF-8>, #<Encoding:EUC-JP>]]

p Encoding::Converter.search_convpath("ISO-8859-1", "EUC-JP", universal_newline: true)
or
p Encoding::Converter.search_convpath("ISO-8859-1", "EUC-JP", newline: :universal)
#=> [[#<Encoding:ISO-8859-1>, #<Encoding:UTF-8>],
#    [#<Encoding:UTF-8>, #<Encoding:EUC-JP>],
#    "universal_newline"]

p Encoding::Converter.search_convpath("ISO-8859-1", "UTF-32BE", universal_newline: true)
or
p Encoding::Converter.search_convpath("ISO-8859-1", "UTF-32BE", newline: :universal)
#=> [[#<Encoding:ISO-8859-1>, #<Encoding:UTF-8>],
#    "universal_newline",
#    [#<Encoding:UTF-8>, #<Encoding:UTF-32BE>]]
Instance Methods
No documentation available

Convert source_string and return destination_string.

source_string is assumed as a part of source. i.e. :partial_input=>true is specified internally. finish method should be used last.

ec = Encoding::Converter.new("utf-8", "euc-jp")
puts ec.convert("\u3042").dump     #=> "\xA4\xA2"
puts ec.finish.dump                #=> ""

ec = Encoding::Converter.new("euc-jp", "utf-8")
puts ec.convert("\xA4").dump       #=> ""
puts ec.convert("\xA2").dump       #=> "\xE3\x81\x82"
puts ec.finish.dump                #=> ""

ec = Encoding::Converter.new("utf-8", "iso-2022-jp")
puts ec.convert("\xE3").dump       #=> "".force_encoding("ISO-2022-JP")
puts ec.convert("\x81").dump       #=> "".force_encoding("ISO-2022-JP")
puts ec.convert("\x82").dump       #=> "\e$B$\"".force_encoding("ISO-2022-JP")
puts ec.finish.dump                #=> "\e(B".force_encoding("ISO-2022-JP")

If a conversion error occur, Encoding::UndefinedConversionError or Encoding::InvalidByteSequenceError is raised. Encoding::Converter#convert doesn’t supply methods to recover or restart from these exceptions. When you want to handle these conversion errors, use Encoding::Converter#primitive_convert.

Returns the conversion path of ec.

The result is an array of conversions.

ec = Encoding::Converter.new("ISO-8859-1", "EUC-JP", crlf_newline: true)
p ec.convpath
#=> [[#<Encoding:ISO-8859-1>, #<Encoding:UTF-8>],
#    [#<Encoding:UTF-8>, #<Encoding:EUC-JP>],
#    "crlf_newline"]

Each element of the array is a pair of encodings or a string. A pair means an encoding conversion. A string means a decorator.

In the above example, [#<Encoding:ISO-8859-1>,

Returns the destination encoding as an Encoding object.

Finishes the converter. It returns the last part of the converted string.

ec = Encoding::Converter.new("utf-8", "iso-2022-jp")
p ec.convert("\u3042")     #=> "\e$B$\""
p ec.finish                #=> "\e(B"

Inserts string into the encoding converter. The string will be converted to the destination encoding and output on later conversions.

If the destination encoding is stateful, string is converted according to the state and the state is updated.

This method should be used only when a conversion error occurs.

ec = Encoding::Converter.new("utf-8", "iso-8859-1")
src = "HIRAGANA LETTER A is \u{3042}."
dst = ""
p ec.primitive_convert(src, dst)    #=> :undefined_conversion
puts "[#{dst.dump}, #{src.dump}]"   #=> ["HIRAGANA LETTER A is ", "."]
ec.insert_output("<err>")
p ec.primitive_convert(src, dst)    #=> :finished
puts "[#{dst.dump}, #{src.dump}]"   #=> ["HIRAGANA LETTER A is <err>.", ""]

ec = Encoding::Converter.new("utf-8", "iso-2022-jp")
src = "\u{306F 3041 3068 2661 3002}" # U+2661 is not representable in iso-2022-jp
dst = ""
p ec.primitive_convert(src, dst)    #=> :undefined_conversion
puts "[#{dst.dump}, #{src.dump}]"   #=> ["\e$B$O$!$H".force_encoding("ISO-2022-JP"), "\xE3\x80\x82"]
ec.insert_output "?"                # state change required to output "?".
p ec.primitive_convert(src, dst)    #=> :finished
puts "[#{dst.dump}, #{src.dump}]"   #=> ["\e$B$O$!$H\e(B?\e$B!#\e(B".force_encoding("ISO-2022-JP"), ""]

Returns a printable version of ec

ec = Encoding::Converter.new("iso-8859-1", "utf-8")
puts ec.inspect    #=> #<Encoding::Converter: ISO-8859-1 to UTF-8>

Returns an exception object for the last conversion. Returns nil if the last conversion did not produce an error.

“error” means that Encoding::InvalidByteSequenceError and Encoding::UndefinedConversionError for Encoding::Converter#convert and :invalid_byte_sequence, :incomplete_input and :undefined_conversion for Encoding::Converter#primitive_convert.

ec = Encoding::Converter.new("utf-8", "iso-8859-1")
p ec.primitive_convert(src="\xf1abcd", dst="")       #=> :invalid_byte_sequence
p ec.last_error      #=> #<Encoding::InvalidByteSequenceError: "\xF1" followed by "a" on UTF-8>
p ec.primitive_convert(src, dst, nil, 1)             #=> :destination_buffer_full
p ec.last_error      #=> nil

possible opt elements:

hash form:
  :partial_input => true           # source buffer may be part of larger source
  :after_output => true            # stop conversion after output before input
integer form:
  Encoding::Converter::PARTIAL_INPUT
  Encoding::Converter::AFTER_OUTPUT

possible results:

:invalid_byte_sequence
:incomplete_input
:undefined_conversion
:after_output
:destination_buffer_full
:source_buffer_empty
:finished

primitive_convert converts source_buffer into destination_buffer.

source_buffer should be a string or nil. nil means an empty string.

destination_buffer should be a string.

destination_byteoffset should be an integer or nil. nil means the end of destination_buffer. If it is omitted, nil is assumed.

destination_bytesize should be an integer or nil. nil means unlimited. If it is omitted, nil is assumed.

opt should be nil, a hash or an integer. nil means no flags. If it is omitted, nil is assumed.

primitive_convert converts the content of source_buffer from beginning and store the result into destination_buffer.

destination_byteoffset and destination_bytesize specify the region which the converted result is stored. destination_byteoffset specifies the start position in destination_buffer in bytes. If destination_byteoffset is nil, destination_buffer.bytesize is used for appending the result. destination_bytesize specifies maximum number of bytes. If destination_bytesize is nil, destination size is unlimited. After conversion, destination_buffer is resized to destination_byteoffset + actually produced number of bytes. Also destination_buffer’s encoding is set to destination_encoding.

primitive_convert drops the converted part of source_buffer. the dropped part is converted in destination_buffer or buffered in Encoding::Converter object.

primitive_convert stops conversion when one of following condition met.

  • invalid byte sequence found in source buffer (:invalid_byte_sequence) primitive_errinfo and last_error methods returns the detail of the error.

  • unexpected end of source buffer (:incomplete_input) this occur only when :partial_input is not specified. primitive_errinfo and last_error methods returns the detail of the error.

  • character not representable in output encoding (:undefined_conversion) primitive_errinfo and last_error methods returns the detail of the error.

  • after some output is generated, before input is done (:after_output) this occur only when :after_output is specified.

  • destination buffer is full (:destination_buffer_full) this occur only when destination_bytesize is non-nil.

  • source buffer is empty (:source_buffer_empty) this occur only when :partial_input is specified.

  • conversion is finished (:finished)

example:

ec = Encoding::Converter.new("UTF-8", "UTF-16BE")
ret = ec.primitive_convert(src="pi", dst="", nil, 100)
p [ret, src, dst] #=> [:finished, "", "\x00p\x00i"]

ec = Encoding::Converter.new("UTF-8", "UTF-16BE")
ret = ec.primitive_convert(src="pi", dst="", nil, 1)
p [ret, src, dst] #=> [:destination_buffer_full, "i", "\x00"]
ret = ec.primitive_convert(src, dst="", nil, 1)
p [ret, src, dst] #=> [:destination_buffer_full, "", "p"]
ret = ec.primitive_convert(src, dst="", nil, 1)
p [ret, src, dst] #=> [:destination_buffer_full, "", "\x00"]
ret = ec.primitive_convert(src, dst="", nil, 1)
p [ret, src, dst] #=> [:finished, "", "i"]

primitive_errinfo returns important information regarding the last error as a 5-element array:

[result, enc1, enc2, error_bytes, readagain_bytes]

result is the last result of primitive_convert.

Other elements are only meaningful when result is :invalid_byte_sequence, :incomplete_input or :undefined_conversion.

enc1 and enc2 indicate a conversion step as a pair of strings. For example, a converter from EUC-JP to ISO-8859-1 converts a string as follows: EUC-JP -> UTF-8 -> ISO-8859-1. So [enc1, enc2] is either [“EUC-JP”, “UTF-8”] or [“UTF-8”, “ISO-8859-1”].

error_bytes and readagain_bytes indicate the byte sequences which caused the error. error_bytes is discarded portion. readagain_bytes is buffered portion which is read again on next conversion.

Example:

# \xff is invalid as EUC-JP.
ec = Encoding::Converter.new("EUC-JP", "Shift_JIS")
ec.primitive_convert(src="\xff", dst="", nil, 10)
p ec.primitive_errinfo
#=> [:invalid_byte_sequence, "EUC-JP", "UTF-8", "\xFF", ""]

# HIRAGANA LETTER A (\xa4\xa2 in EUC-JP) is not representable in ISO-8859-1.
# Since this error is occur in UTF-8 to ISO-8859-1 conversion,
# error_bytes is HIRAGANA LETTER A in UTF-8 (\xE3\x81\x82).
ec = Encoding::Converter.new("EUC-JP", "ISO-8859-1")
ec.primitive_convert(src="\xa4\xa2", dst="", nil, 10)
p ec.primitive_errinfo
#=> [:undefined_conversion, "UTF-8", "ISO-8859-1", "\xE3\x81\x82", ""]

# partial character is invalid
ec = Encoding::Converter.new("EUC-JP", "ISO-8859-1")
ec.primitive_convert(src="\xa4", dst="", nil, 10)
p ec.primitive_errinfo
#=> [:incomplete_input, "EUC-JP", "UTF-8", "\xA4", ""]

# Encoding::Converter::PARTIAL_INPUT prevents invalid errors by
# partial characters.
ec = Encoding::Converter.new("EUC-JP", "ISO-8859-1")
ec.primitive_convert(src="\xa4", dst="", nil, 10, Encoding::Converter::PARTIAL_INPUT)
p ec.primitive_errinfo
#=> [:source_buffer_empty, nil, nil, nil, nil]

# \xd8\x00\x00@ is invalid as UTF-16BE because
# no low surrogate after high surrogate (\xd8\x00).
# It is detected by 3rd byte (\00) which is part of next character.
# So the high surrogate (\xd8\x00) is discarded and
# the 3rd byte is read again later.
# Since the byte is buffered in ec, it is dropped from src.
ec = Encoding::Converter.new("UTF-16BE", "UTF-8")
ec.primitive_convert(src="\xd8\x00\x00@", dst="", nil, 10)
p ec.primitive_errinfo
#=> [:invalid_byte_sequence, "UTF-16BE", "UTF-8", "\xD8\x00", "\x00"]
p src
#=> "@"

# Similar to UTF-16BE, \x00\xd8@\x00 is invalid as UTF-16LE.
# The problem is detected by 4th byte.
ec = Encoding::Converter.new("UTF-16LE", "UTF-8")
ec.primitive_convert(src="\x00\xd8@\x00", dst="", nil, 10)
p ec.primitive_errinfo
#=> [:invalid_byte_sequence, "UTF-16LE", "UTF-8", "\x00\xD8", "@\x00"]
p src
#=> ""

Put back the bytes which will be converted.

The bytes are caused by invalid_byte_sequence error. When invalid_byte_sequence error, some bytes are discarded and some bytes are buffered to be converted later. The latter bytes can be put back. It can be observed by Encoding::InvalidByteSequenceError#readagain_bytes and Encoding::Converter#primitive_errinfo.

ec = Encoding::Converter.new("utf-16le", "iso-8859-1")
src = "\x00\xd8\x61\x00"
dst = ""
p ec.primitive_convert(src, dst)   #=> :invalid_byte_sequence
p ec.primitive_errinfo     #=> [:invalid_byte_sequence, "UTF-16LE", "UTF-8", "\x00\xD8", "a\x00"]
p ec.putback               #=> "a\x00"
p ec.putback               #=> ""          # no more bytes to put back

Returns the replacement string.

ec = Encoding::Converter.new("euc-jp", "us-ascii")
p ec.replacement    #=> "?"

ec = Encoding::Converter.new("euc-jp", "utf-8")
p ec.replacement    #=> "\uFFFD"

Sets the replacement string.

ec = Encoding::Converter.new("utf-8", "us-ascii", :undef => :replace)
ec.replacement = "<undef>"
p ec.convert("a \u3042 b")      #=> "a <undef> b"

Returns the source encoding as an Encoding object.