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