class Encoding::Converter - Documentation for Ruby 4.0
Description: class Encoding::Converter: Encoding conversion class.
Keywords: ruby,class,Encoding::Converter

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# class Encoding::Converter

`Encoding` conversion class.

### Constants

AFTER_OUTPUT

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

CRLF_NEWLINE_DECORATOR

  Decorator for converting LF to CRLF

CR_NEWLINE_DECORATOR

  Decorator for converting LF to CR

INVALID_MASK

  Mask for invalid byte sequences

INVALID_REPLACE

  Replace invalid byte sequences

LF_NEWLINE_DECORATOR

  Decorator for converting CRLF and CR to LF when writing

PARTIAL_INPUT

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

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.

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.

UNIVERSAL_NEWLINE_DECORATOR

  Decorator for converting CRLF and CR to LF

XML_ATTR_CONTENT_DECORATOR

  Escape as XML AttValue

XML_ATTR_QUOTE_DECORATOR

  Escape as XML AttValue

XML_TEXT_DECORATOR

  Escape as XML CharData

### Public Class Methods

Encoding::Converter.asciicompat_encoding(string) → encoding or nil
Encoding::Converter.asciicompat_encoding(encoding) → encoding or nil
Source

    static VALUE
    econv_s_asciicompat_encoding(VALUE klass, VALUE arg)
    {
        const char *arg_name, *result_name;
        rb_encoding *arg_enc, *result_enc;
        VALUE enc = Qnil;

        enc_arg(&arg, &arg_name, &arg_enc);
        result_name = rb_econv_asciicompat_encoding(arg_name);
        if (result_name) {
            result_enc = make_encoding(result_name);
            enc = rb_enc_from_encoding(result_enc);
        }
        return enc;
    }

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

Encoding::Converter.new(source_encoding, destination_encoding)
Encoding::Converter.new(source_encoding, destination_encoding, opt)
Encoding::Converter.new(convpath)
Source

    static VALUE
    econv_init(int argc, VALUE *argv, VALUE self)
    {
        VALUE ecopts;
        VALUE snamev, dnamev;
        const char *sname, *dname;
        rb_encoding *senc, *denc;
        rb_econv_t *ec;
        int ecflags;
        VALUE convpath;

        if (rb_check_typeddata(self, &econv_data_type)) {
            rb_raise(rb_eTypeError, "already initialized");
        }

        if (argc == 1 && !NIL_P(convpath = rb_check_array_type(argv[0]))) {
            ec = rb_econv_init_by_convpath(self, convpath, &sname, &dname, &senc, &denc);
            ecflags = 0;
            ecopts = Qnil;
        }
        else {
            econv_args(argc, argv, &snamev, &dnamev, &sname, &dname, &senc, &denc, &ecflags, &ecopts);
            ec = rb_econv_open_opts(sname, dname, ecflags, ecopts);
        }

        if (!ec) {
            VALUE exc = rb_econv_open_exc(sname, dname, ecflags);
            RB_GC_GUARD(snamev);
            RB_GC_GUARD(dnamev);
            rb_exc_raise(exc);
        }

        if (!DECORATOR_P(sname, dname)) {
            if (!senc)
                senc = make_dummy_encoding(sname);
            if (!denc)
                denc = make_dummy_encoding(dname);
            RB_GC_GUARD(snamev);
            RB_GC_GUARD(dnamev);
        }

        ec->source_encoding = senc;
        ec->destination_encoding = denc;

        DATA_PTR(self) = ec;

        return self;
    }

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 => :lf            # decorator for converting CRLF and CR to LF when writing
      :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
      :lf_newline => true        # decorator for converting CRLF and CR to LF when writing
      :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::LF_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.

:lf_newline => true

  Convert CRLF and CR to LF (when writing).

: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>]]

Encoding::Converter.search_convpath(source_encoding, destination_encoding) → ary
Encoding::Converter.search_convpath(source_encoding, destination_encoding, opt) → ary
Source

    static VALUE
    econv_s_search_convpath(int argc, VALUE *argv, VALUE klass)
    {
        VALUE snamev, dnamev;
        const char *sname, *dname;
        rb_encoding *senc, *denc;
        int ecflags;
        VALUE ecopts;
        VALUE convpath;

        econv_args(argc, argv, &snamev, &dnamev, &sname, &dname, &senc, &denc, &ecflags, &ecopts);

        convpath = Qnil;
        transcode_search_path(sname, dname, search_convpath_i, &convpath);

        if (NIL_P(convpath)) {
            VALUE exc = rb_econv_open_exc(sname, dname, ecflags);
            RB_GC_GUARD(snamev);
            RB_GC_GUARD(dnamev);
            rb_exc_raise(exc);
        }

        if (decorate_convpath(convpath, ecflags) == -1) {
            VALUE exc = rb_econv_open_exc(sname, dname, ecflags);
            RB_GC_GUARD(snamev);
            RB_GC_GUARD(dnamev);
            rb_exc_raise(exc);
        }

        return convpath;
    }

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>]]

### Public Instance Methods

ec == other → true or false
Source

    static VALUE
    econv_equal(VALUE self, VALUE other)
    {
        rb_econv_t *ec1 = check_econv(self);
        rb_econv_t *ec2;
        int i;

        if (!rb_typeddata_is_kind_of(other, &econv_data_type)) {
            return Qnil;
        }
        ec2 = DATA_PTR(other);
        if (!ec2) return Qfalse;
        if (ec1->source_encoding_name != ec2->source_encoding_name &&
            strcmp(ec1->source_encoding_name, ec2->source_encoding_name))
            return Qfalse;
        if (ec1->destination_encoding_name != ec2->destination_encoding_name &&
            strcmp(ec1->destination_encoding_name, ec2->destination_encoding_name))
            return Qfalse;
        if (ec1->flags != ec2->flags) return Qfalse;
        if (ec1->replacement_enc != ec2->replacement_enc &&
            strcmp(ec1->replacement_enc, ec2->replacement_enc))
            return Qfalse;
        if (ec1->replacement_len != ec2->replacement_len) return Qfalse;
        if (ec1->replacement_str != ec2->replacement_str &&
            memcmp(ec1->replacement_str, ec2->replacement_str, ec2->replacement_len))
            return Qfalse;

        if (ec1->num_trans != ec2->num_trans) return Qfalse;
        for (i = 0; i < ec1->num_trans; i++) {
            if (ec1->elems[i].tc->transcoder != ec2->elems[i].tc->transcoder)
                return Qfalse;
        }
        return Qtrue;
    }

convert(source_string) → destination_string
Source

    static VALUE
    econv_convert(VALUE self, VALUE source_string)
    {
        VALUE ret, dst;
        VALUE av[5];
        int ac;
        rb_econv_t *ec = check_econv(self);

        StringValue(source_string);

        dst = rb_str_new(NULL, 0);

        av[0] = rb_str_dup(source_string);
        av[1] = dst;
        av[2] = Qnil;
        av[3] = Qnil;
        av[4] = INT2NUM(ECONV_PARTIAL_INPUT);
        ac = 5;

        ret = econv_primitive_convert(ac, av, self);

        if (ret == sym_invalid_byte_sequence ||
            ret == sym_undefined_conversion ||
            ret == sym_incomplete_input) {
            VALUE exc = make_econv_exception(ec);
            rb_exc_raise(exc);
        }

        if (ret == sym_finished) {
            rb_raise(rb_eArgError, "converter already finished");
        }

        if (ret != sym_source_buffer_empty) {
            rb_bug("unexpected result of econv_primitive_convert");
        }

        return dst;
    }

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`.

convpath → ary
Source

    static VALUE
    econv_convpath(VALUE self)
    {
        rb_econv_t *ec = check_econv(self);
        VALUE result;
        int i;

        result = rb_ary_new();
        for (i = 0; i < ec->num_trans; i++) {
            const rb_transcoder *tr = ec->elems[i].tc->transcoder;
            VALUE v;
            if (DECORATOR_P(tr->src_encoding, tr->dst_encoding))
                v = rb_str_new_cstr(tr->dst_encoding);
            else
                v = rb_assoc_new(make_encobj(tr->src_encoding), make_encobj(tr->dst_encoding));
            rb_ary_push(result, v);
        }
        return result;
    }

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>,

destination_encoding → encoding
Source

    static VALUE
    econv_destination_encoding(VALUE self)
    {
        rb_econv_t *ec = check_econv(self);
        return econv_get_encoding(ec->destination_encoding);
    }

Returns the destination encoding as an `Encoding` object.

finish → string
Source

    static VALUE
    econv_finish(VALUE self)
    {
        VALUE ret, dst;
        VALUE av[5];
        int ac;
        rb_econv_t *ec = check_econv(self);

        dst = rb_str_new(NULL, 0);

        av[0] = Qnil;
        av[1] = dst;
        av[2] = Qnil;
        av[3] = Qnil;
        av[4] = INT2FIX(0);
        ac = 5;

        ret = econv_primitive_convert(ac, av, self);

        if (ret == sym_invalid_byte_sequence ||
            ret == sym_undefined_conversion ||
            ret == sym_incomplete_input) {
            VALUE exc = make_econv_exception(ec);
            rb_exc_raise(exc);
        }

        if (ret != sym_finished) {
            rb_bug("unexpected result of econv_primitive_convert");
        }

        return dst;
    }

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"

insert_output(string) → nil
Source

    static VALUE
    econv_insert_output(VALUE self, VALUE string)
    {
        const char *insert_enc;

        int ret;

        rb_econv_t *ec = check_econv(self);

        StringValue(string);
        insert_enc = rb_econv_encoding_to_insert_output(ec);
        string = rb_str_encode(string, rb_enc_from_encoding(rb_enc_find(insert_enc)), 0, Qnil);

        ret = rb_econv_insert_output(ec, (const unsigned char *)RSTRING_PTR(string), RSTRING_LEN(string), insert_enc);
        if (ret == -1) {
            rb_raise(rb_eArgError, "too big string");
        }

        return Qnil;
    }

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"), ""]

inspect → string
Source

    static VALUE
    econv_inspect(VALUE self)
    {
        const char *cname = rb_obj_classname(self);
        rb_econv_t *ec;

        TypedData_Get_Struct(self, rb_econv_t, &econv_data_type, ec);
        if (!ec)
            return rb_sprintf("#<%s: uninitialized>", cname);
        else {
            const char *sname = ec->source_encoding_name;
            const char *dname = ec->destination_encoding_name;
            VALUE str;
            str = rb_sprintf("#<%s: ", cname);
            econv_description(sname, dname, ec->flags, str);
            rb_str_cat2(str, ">");
            return str;
        }
    }

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>

last_error → exception or nil
Source

    static VALUE
    econv_last_error(VALUE self)
    {
        rb_econv_t *ec = check_econv(self);
        VALUE exc;

        exc = make_econv_exception(ec);
        if (NIL_P(exc))
            return Qnil;
        return exc;
    }

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

primitive_convert(source_buffer, destination_buffer) → symbol
primitive_convert(source_buffer, destination_buffer, destination_byteoffset) → symbol
primitive_convert(source_buffer, destination_buffer, destination_byteoffset, destination_bytesize) → symbol
primitive_convert(source_buffer, destination_buffer, destination_byteoffset, destination_bytesize, opt) → symbol
Source

    static VALUE
    econv_primitive_convert(int argc, VALUE *argv, VALUE self)
    {
        VALUE input, output, output_byteoffset_v, output_bytesize_v, opt, flags_v;
        rb_econv_t *ec = check_econv(self);
        rb_econv_result_t res;
        const unsigned char *ip, *is;
        unsigned char *op, *os;
        long output_byteoffset, output_bytesize;
        unsigned long output_byteend;
        int flags;

        argc = rb_scan_args(argc, argv, "23:", &input, &output, &output_byteoffset_v, &output_bytesize_v, &flags_v, &opt);

        if (NIL_P(output_byteoffset_v))
            output_byteoffset = 0; /* dummy */
        else
            output_byteoffset = NUM2LONG(output_byteoffset_v);

        if (NIL_P(output_bytesize_v))
            output_bytesize = 0; /* dummy */
        else
            output_bytesize = NUM2LONG(output_bytesize_v);

        if (!NIL_P(flags_v)) {
            if (!NIL_P(opt)) {
                rb_error_arity(argc + 1, 2, 5);
            }
            flags = NUM2INT(rb_to_int(flags_v));
        }
        else if (!NIL_P(opt)) {
            VALUE v;
            flags = 0;
            v = rb_hash_aref(opt, sym_partial_input);
            if (RTEST(v))
                flags |= ECONV_PARTIAL_INPUT;
            v = rb_hash_aref(opt, sym_after_output);
            if (RTEST(v))
                flags |= ECONV_AFTER_OUTPUT;
        }
        else {
            flags = 0;
        }

        StringValue(output);
        if (!NIL_P(input))
            StringValue(input);
        rb_str_modify(output);

        if (NIL_P(output_bytesize_v)) {
            output_bytesize = rb_str_capacity(output);

            if (!NIL_P(input) && output_bytesize < RSTRING_LEN(input))
                output_bytesize = RSTRING_LEN(input);
        }

      retry:

        if (NIL_P(output_byteoffset_v))
            output_byteoffset = RSTRING_LEN(output);

        if (output_byteoffset < 0)
            rb_raise(rb_eArgError, "negative output_byteoffset");

        if (RSTRING_LEN(output) < output_byteoffset)
            rb_raise(rb_eArgError, "output_byteoffset too big");

        if (output_bytesize < 0)
            rb_raise(rb_eArgError, "negative output_bytesize");

        output_byteend = (unsigned long)output_byteoffset +
                         (unsigned long)output_bytesize;

        if (output_byteend < (unsigned long)output_byteoffset ||
            LONG_MAX < output_byteend)
            rb_raise(rb_eArgError, "output_byteoffset+output_bytesize too big");

        if (rb_str_capacity(output) < output_byteend)
            rb_str_resize(output, output_byteend);

        if (NIL_P(input)) {
            ip = is = NULL;
        }
        else {
            ip = (const unsigned char *)RSTRING_PTR(input);
            is = ip + RSTRING_LEN(input);
        }

        op = (unsigned char *)RSTRING_PTR(output) + output_byteoffset;
        os = op + output_bytesize;

        res = rb_econv_convert(ec, &ip, is, &op, os, flags);
        rb_str_set_len(output, op-(unsigned char *)RSTRING_PTR(output));
        if (!NIL_P(input)) {
            rb_str_drop_bytes(input, ip - (unsigned char *)RSTRING_PTR(input));
        }

        if (NIL_P(output_bytesize_v) && res == econv_destination_buffer_full) {
            if (LONG_MAX / 2 < output_bytesize)
                rb_raise(rb_eArgError, "too long conversion result");
            output_bytesize *= 2;
            output_byteoffset_v = Qnil;
            goto retry;
        }

        if (ec->destination_encoding) {
            rb_enc_associate(output, ec->destination_encoding);
        }

        return econv_result_to_symbol(res);
    }

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 → array
Source

    static VALUE
    econv_primitive_errinfo(VALUE self)
    {
        rb_econv_t *ec = check_econv(self);

        VALUE ary;

        ary = rb_ary_new2(5);

        rb_ary_store(ary, 0, econv_result_to_symbol(ec->last_error.result));
        rb_ary_store(ary, 4, Qnil);

        if (ec->last_error.source_encoding)
            rb_ary_store(ary, 1, rb_str_new2(ec->last_error.source_encoding));

        if (ec->last_error.destination_encoding)
            rb_ary_store(ary, 2, rb_str_new2(ec->last_error.destination_encoding));

        if (ec->last_error.error_bytes_start) {
            rb_ary_store(ary, 3, rb_str_new((const char *)ec->last_error.error_bytes_start, ec->last_error.error_bytes_len));
            rb_ary_store(ary, 4, rb_str_new((const char *)ec->last_error.error_bytes_start + ec->last_error.error_bytes_len, ec->last_error.readagain_len));
        }

        return ary;
    }

`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", "Shift_JIS", "\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
    #=> ""

putback → string
putback(max_numbytes) → string
Source

    static VALUE
    econv_putback(int argc, VALUE *argv, VALUE self)
    {
        rb_econv_t *ec = check_econv(self);
        int n;
        int putbackable;
        VALUE str, max;

        if (!rb_check_arity(argc, 0, 1) || NIL_P(max = argv[0])) {
            n = rb_econv_putbackable(ec);
        }
        else {
            n = NUM2INT(max);
            putbackable = rb_econv_putbackable(ec);
            if (putbackable < n)
                n = putbackable;
        }

        str = rb_str_new(NULL, n);
        rb_econv_putback(ec, (unsigned char *)RSTRING_PTR(str), n);

        if (ec->source_encoding) {
            rb_enc_associate(str, ec->source_encoding);
        }

        return str;
    }

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

replacement → string
Source

    static VALUE
    econv_get_replacement(VALUE self)
    {
        rb_econv_t *ec = check_econv(self);
        int ret;
        rb_encoding *enc;

        ret = make_replacement(ec);
        if (ret == -1) {
            rb_raise(rb_eUndefinedConversionError, "replacement character setup failed");
        }

        enc = rb_enc_find(ec->replacement_enc);
        return rb_enc_str_new((const char *)ec->replacement_str, (long)ec->replacement_len, enc);
    }

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"

replacement = string
Source

    static VALUE
    econv_set_replacement(VALUE self, VALUE arg)
    {
        rb_econv_t *ec = check_econv(self);
        VALUE string = arg;
        int ret;
        rb_encoding *enc;

        StringValue(string);
        enc = rb_enc_get(string);

        ret = rb_econv_set_replacement(ec,
                (const unsigned char *)RSTRING_PTR(string),
                RSTRING_LEN(string),
                rb_enc_name(enc));

        if (ret == -1) {
            /* xxx: rb_eInvalidByteSequenceError? */
            rb_raise(rb_eUndefinedConversionError, "replacement character setup failed");
        }

        return arg;
    }

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"

source_encoding → encoding
Source

    static VALUE
    econv_source_encoding(VALUE self)
    {
        rb_econv_t *ec = check_econv(self);
        return econv_get_encoding(ec->source_encoding);
    }

Returns the source encoding as an `Encoding` object.