ICONV(3) Library Functions Manual ICONV(3)

iconv_open, iconv_open_into, iconv_close, iconv — codeset conversion functions

Standard C Library (libc, -lc)

#include <iconv.h>

iconv_t
iconv_open(const char *dstname, const char *srcname);

int
iconv_open_into(const char *dstname, const char *srcname, iconv_allocation_t *ptr);

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);

size_t
__iconv(iconv_t cd, char ** restrict src, size_t * restrict srcleft, char ** restrict dst, size_t * restrict dstleft, uint32_t flags, size_t * invalids);

The () function opens a converter from the codeset srcname to the codeset dstname and returns its descriptor. The arguments srcname and dstname accept "" and "char", which refer to the current locale encoding.

The () creates a conversion descriptor on a preallocated space. The iconv_allocation_t is used as a spaceholder type when allocating such space. The dstname and srcname arguments are the same as in the case of iconv_open(). The ptr argument is a pointer of iconv_allocation_t to the preallocated space.

The () function closes the specified converter cd.

The () 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. () returns the number of such “invalid conversions”.

There are two special cases of ():

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

If both dst and *dst are non-NULL, () 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.

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.

The () function works just like iconv() but if iconv() fails, the invalid character count is lost there. This is a not bug rather a limitation of IEEE Std 1003.1-2008 (“POSIX.1”), so __iconv() is provided as an alternative but non-standard interface. It also has a flags argument, where currently the following flags can be passed:

__ICONV_F_HIDE_INVALID
Skip invalid characters, instead of returning with an error.

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_open_into(), it returns 0. Otherwise, iconv_open_into() returns -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.

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

[]
Memory is exhausted.
[]
There is no converter specified by srcname and dstname.
The iconv_open_into() function may cause an error in the following cases:
[]
There is no converter specified by srcname and dstname.

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

[]
The conversion descriptor specified by cd is invalid.

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

[]
The conversion descriptor specified by cd is invalid.
[]
The string pointed to by *src contains a byte sequence which does not describe a valid character of the source codeset.
[]
The output buffer pointed to by *dst is too small to store the result string.
[]
The string pointed to by *src terminates with an incomplete character or shift sequence.

iconv(1), mkcsmapper(1), mkesdb(1), __iconv_get_list(3), iconv_canonicalize(3), iconvctl(3), iconvlist(3)

The iconv_open(), iconv_close(), and iconv() functions conform to IEEE Std 1003.1-2008 (“POSIX.1”).

The iconv_open_into() function is a GNU-specific extension and it is not part of any standard, thus its use may break portability. The __iconv() function is an own extension and it is not part of any standard, thus its use may break portability.

August 4, 2014 macOS 15.2