ICONV(3)

NAME
iconv_open, iconv_close, iconv - codeset conversion functions

LIBRARY
libc

SYNOPSIS
#include <iconv.h>
iconv_t
iconv_open(const char *dstname, const char *srcname);
int
iconv_close(iconv_t cd);
size_t
iconv(iconv_t cd, char ** restrict src, size_t * restrict srcleft, char ** restrict dst, size_t * restrict dstleft);

DESCRIPTION
The iconv_open() function opens a converter from the codeset srcname to the codeset dstname and returns its descriptor.

The iconv_close() function closes the specified converter cd.

The iconv() function converts the string in the buffer *src of length *srcleft bytes and stores the converted string in the buffer *dst of size *dstleft bytes. After calling iconv(), the values pointed to by src, srcleft, dst, and dstleft are updated as follows:

*src
    Pointer to the byte just after the last character fetched.

*srcleft
    Number of remaining bytes in the source buffer.

*dst
    Pointer to the byte just after the last character stored.

*dstleft
    Number of remainder bytes in the destination buffer.

If the string pointed to by *src contains a byte sequence which is not a valid character in the source codeset, the conversion stops just after the last successful conversion. If the output buffer is too small to store the converted character, the conversion also stops in the same way. In these cases, the values pointed to by src, srcleft, dst, and dstleft are updated to the state just after the last successful conversion.

If the string pointed to by *src contains a character which is valid under the source codeset but can not be converted to the destination codeset, the character is replaced by an “invalid character” which depends on the destination codeset, e.g., ‘’?, and the conversion is continued. iconv() returns the number of such “invalid conversions”.

If src or *src is NULL and the source and/or destination codesets are stateful, iconv() places these into their initial state.

1.  If both dst and *dst are non-NULL, iconv() stores the shift sequence for the destination switching to the initial state in the buffer pointed to by *dst. The buffer size is specified by the value pointed to by dstleft as above. iconv() will fail if the buffer is too small to store the shift sequence.

2.  On the other hand, dst or *dst may be NULL. In this case, the shift sequence for the destination switching to the initial state is discarded.

RETURN VALUES
Upon successful completion of iconv_open(), it returns a conversion descriptor. Otherwise, iconv_open() returns (iconv_t)-1 and sets errno to indicate the error.

Upon successful completion of iconv_close(), it returns 0. Otherwise, iconv_close() returns -1 and sets errno to indicate the error.

Upon successful completion of iconv(), it returns the number of “invalid” conversions. Otherwise, iconv() returns (size_t)-1 and sets errno to indicate the error.

ERRORS
The iconv_open() function may cause an error in the following cases:

[EINVAL]
    There is no converter specified by srcname and dstname.

[ENOMEM]
    Memory is exhausted.

The iconv_close() function may cause an error in the following case:

[EBADF]
    The conversion descriptor specified by cd is invalid.

The iconv() function may cause an error in the following cases:

[E2BIG]
    The output buffer pointed to by *dst is too small to store the result string.

[EBADF]
    The conversion descriptor specified by cd is invalid.

[EILSEQ]
    The string pointed to by *src contains a byte sequence which does not describe a valid character of the source codeset.

[EINVAL]
    The string pointed to by *src terminates with an incomplete character or shift sequence.

SEE ALSO
iconv(1)

STANDARDS
iconv_open(), iconv_close(), and iconv() conform to p1003.1-2001.

Historically, the definition of iconv has not been consistent across operating systems. This is due to an unfortunate historical mistake, documented in this e-mail: https://www5.opengroup.org/sophocles2/show_mail.tpl?&source=L&listname=austin-group-l&id=7404. The standards page for the header file <iconv.h> defined the second argument of iconv() as char **, but the standards page for the iconv() implementation defined it as const char **. The standards committee later chose to change the function definition to follow the header file definition (without const), even though the version with const is arguably more correct. NetBSD used initially the const form. It was decided to reject the committee's regression and become (technically) incompatible.

This decision was changed in NetBSD 10 and the iconv() prototype was synchronized with the standard.

BUGS
If iconv() is aborted due to the occurrence of some error, the “invalid conversion” count mentioned above is unfortunately lost.