ICONV(3)                   POSIX Programmer's Manual                  ICONV(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       iconv -- codeset conversion function

SYNOPSIS
       #include <iconv.h>

       size_t iconv(iconv_t cd, char **restrict inbuf,
           size_t *restrict inbytesleft, char **restrict outbuf,
           size_t *restrict outbytesleft);

DESCRIPTION
       The iconv() function shall convert the sequence of characters from one
       codeset, in the array specified by inbuf, into a sequence of
       corresponding characters in another codeset, in the array specified by
       outbuf.  The codesets are those specified in the iconv__open() call that
       returned the conversion descriptor, cd.  The inbuf argument points to a
       variable that points to the first character in the input buffer and
       inbytesleft indicates the number of bytes to the end of the buffer to
       be converted. The outbuf argument points to a variable that points to
       the first available byte in the output buffer and outbytesleft
       indicates the number of the available bytes to the end of the buffer.

       For state-dependent encodings, the conversion descriptor cd is placed
       into its initial shift state by a call for which inbuf is a null
       pointer, or for which inbuf points to a null pointer. When iconv() is
       called in this way, and if outbuf is not a null pointer or a pointer to
       a null pointer, and outbytesleft points to a positive value, iconv()
       shall place, into the output buffer, the byte sequence to change the
       output buffer to its initial shift state. If the output buffer is not
       large enough to hold the entire reset sequence, iconv() shall fail and
       set errno to [E2BIG].  Subsequent calls with inbuf as other than a null
       pointer or a pointer to a null pointer cause the conversion to take
       place from the current state of the conversion descriptor.

       If a sequence of input bytes does not form a valid character in the
       specified codeset, conversion shall stop after the previous
       successfully converted character. If the input buffer ends with an
       incomplete character or shift sequence, conversion shall stop after the
       previous successfully converted bytes. If the output buffer is not
       large enough to hold the entire converted input, conversion shall stop
       just prior to the input bytes that would cause the output buffer to
       overflow. The variable pointed to by inbuf shall be updated to point to
       the byte following the last byte successfully used in the conversion.
       The value pointed to by inbytesleft shall be decremented to reflect the
       number of bytes still not converted in the input buffer. The variable
       pointed to by outbuf shall be updated to point to the byte following
       the last byte of converted output data. The value pointed to by
       outbytesleft shall be decremented to reflect the number of bytes still
       available in the output buffer. For state-dependent encodings, the
       conversion descriptor shall be updated to reflect the shift state in
       effect at the end of the last successfully converted byte sequence.

       If iconv() encounters a character in the input buffer that is valid,
       but for which an identical character does not exist in the target
       codeset, iconv() shall perform an implementation-defined conversion on
       this character.

RETURN VALUE
       The iconv() function shall update the variables pointed to by the
       arguments to reflect the extent of the conversion and return the number
       of non-identical conversions performed. If the entire string in the
       input buffer is converted, the value pointed to by inbytesleft shall be
       0. If the input conversion is stopped due to any conditions mentioned
       above, the value pointed to by inbytesleft shall be non-zero and errno
       shall be set to indicate the condition. If an error occurs, iconv()
       shall return (size_t)-1 and set errno to indicate the error.

ERRORS
       The iconv() function shall fail if:

       EILSEQ Input conversion stopped due to an input byte that does not
              belong to the input codeset.

       E2BIG  Input conversion stopped due to lack of space in the output
              buffer.

       EINVAL Input conversion stopped due to an incomplete character or shift
              sequence at the end of the input buffer.

       The iconv() function may fail if:

       EBADF  The cd argument is not a valid open conversion descriptor.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       The inbuf argument indirectly points to the memory area which contains
       the conversion input data. The outbuf argument indirectly points to the
       memory area which is to contain the result of the conversion. The
       objects indirectly pointed to by inbuf and outbuf are not restricted to
       containing data that is directly representable in the ISO C standard
       language char data type. The type of inbuf and outbuf, char ****, does
       not imply that the objects pointed to are interpreted as null-
       terminated C strings or arrays of characters. Any interpretation of a
       byte sequence that represents a character in a given character set
       encoding scheme is done internally within the codeset converters. For
       example, the area pointed to indirectly by inbuf and/or outbuf can
       contain all zero octets that are not interpreted as string terminators
       but as coded character data according to the respective codeset
       encoding scheme. The type of the data (char, short, long, and so on)
       read or stored in the objects is not specified, but may be inferred for
       both the input and output data by the converters determined by the
       fromcode and tocode arguments of iconv__open().

       Regardless of the data type inferred by the converter, the size of the
       remaining space in both input and output objects (the intbytesleft and
       outbytesleft arguments) is always measured in bytes.

       For implementations that support the conversion of state-dependent
       encodings, the conversion descriptor must be able to accurately reflect
       the shift-state in effect at the end of the last successful conversion.
       It is not required that the conversion descriptor itself be updated,
       which would require it to be a pointer type. Thus, implementations are
       free to implement the descriptor as a handle (other than a pointer
       type) by which the conversion information can be accessed and updated.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       iconv__open(), iconv__close(), mbsrtowcs()

       The Base Definitions volume of POSIX.1-2017, <iconv.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                             ICONV(3)
