iconv Interface

In a network environment, the code sets of the communicating systems and the protocols of communication determine the transformation of user-specified data so that it can be sent to the remote system in a meaningful way. The user data (not user names) may need to be transformed from the sender's code set to the receiver's code set, or 8-bit data may need to be transformed into a 7-bit form to conform to protocols. A uniform interface is needed to accomplish this.

In the following examples, using the iconv() interface is illustrated by explaining how to use iconv_open(), iconv(), and iconv_close(). To do the conversion, iconv_open() must be followed by iconv(). The terms 7-bit interchange and 8-bit interchange are used to refer to any interchange encoding used for 7-bit and 8-bit data, respectively.

Sender and Receiver Use the Same Code Sets:

• If the protocol allows 8-bit data, use 8-bit data because the same code set is being used. No conversion is needed.

• If the protocol allows only 7-bit data, use iconv():

  • Sender

    cd =iconv_open(locale_codeset, uuencoded ); 

  • Receiver

    cd = iconv_open("uucode", locale_codeset ); 

Sender and Receiver Use Different Code Sets:

• If the protocol allows 8-bit data:

• Sender

  cd = iconv_open(locale_codeset, 8-bitinterchange );

• Receiver

  cd = iconv_open(8-bitinterchange, locale_codeset );

• If the protocol allows only 7-bit data, do the following:

  • Sender

    cd = iconv_open(locale_codeset, 7-bitinterchange );

  • Receiver

    cd = iconv_open(7-bitinterchange, locale_codeset );

  The locale_codeset() refers to the code set used locally by the application. It is implementation-dependent whether any conversion names match the return from the nl_langinfo()(CODESET) function. Table 3-1 outlines how the use of iconv() to perform conversions for various conditions. Specific protocols may dictate other conversions needed.

  Table 3-1 Using iconv to Perform Conversions

  	Communication with system using the same code set (for example, XYZ)		Communication with system using different code sets or receiver's code set is unknown
  Conversion to Use	7-bit Protocol	8-bit Protocol	7-bit Protocol	8-bit Protocol
  code XYZ	Invalid	Best Choice	Invalid	Invalid if remote code set is unknown
  7-bit Interchange ISO2022	OK	OK	Best Choice	OK
  8-bit Interchange ISO2022 ISO 10646	Invalid [Invalid means the interchange encoding should not be used for the choice of code set and type of protocol.]	OK	Invalid	Best Choice
  7-bit Untagged quoted-printable uucode	OK	OK	Requires code set identification	Requires code set identification
  8-bit Untagged base64	Invalid	OK	Requires code set identification	Requires code set identification