The iconv_open() function shall return a conversion descriptor that
describes a conversion from the codeset specified by the string pointed to by
the fromcode argument to the codeset specified by the string pointed to
by the tocode argument. For state-dependent encodings, the conversion
descriptor shall be in a codeset-dependent initial shift state, ready for
immediate use with iconv().
Settings of fromcode and tocode and their permitted combinations
A conversion descriptor shall remain valid until it is closed by
iconv_close() or an implicit close.
If a file descriptor is used to implement conversion descriptors, the FD_CLOEXEC
flag shall be set; see <fcntl.h>.
Upon successful completion, iconv_open() shall return a conversion
descriptor for use on subsequent calls to iconv(). Otherwise,
iconv_open() shall return ( iconv_t)-1 and set errno to
indicate the error.
Some implementations of iconv_open() use malloc() to allocate
space for internal buffer areas. The iconv_open() function may fail if
there is insufficient storage space to accommodate these buffers.
Conforming applications must assume that conversion descriptors are not valid
after a call to one of the exec functions.
Application developers should consult the system documentation to determine the
supported codesets and their naming schemes.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html