NAME

       ipsec_ttodata, ipsec_datatot - convert binary data bytes from and to text formats

SYNOPSIS

       #include <freeswan.h>

       const char *ttodata(const char * src, size_t srclen, int base, char * dst, size_t dstlen,
                           size_t * lenp);

       const char *ttodatav(const char * src, size_t srclen, int base, char * dst, size_t dstlen,
                            size_t * lenp, char * errp, size_t errlen, int flags);

       size_t datatot(const char * src, size_t srclen, int format, char * dst, size_t dstlen);

DESCRIPTION

       Ttodata, ttodatav, and datatot convert arbitrary binary data (e.g. encryption or
       authentication keys) from and to more-or-less human-readable text formats.

       Currently supported formats are hexadecimal, base64, and characters.

       A hexadecimal text value begins with a 0x (or 0X) prefix and continues with two-digit
       groups of hexadecimal digits (0-9, and a-f or A-F), each group encoding the value of one
       binary byte, high-order digit first. A single _ (underscore) between consecutive groups is
       ignored, permitting punctuation to improve readability; doing this every eight digits
       seems about right.

       A base64 text value begins with a 0s (or 0S) prefix and continues with four-digit groups
       of base64 digits (A-Z, a-z, 0-9, +, and /), each group encoding the value of three binary
       bytes as described in section 6.8 of RFC 2045. If flags has the TTODATAV_IGNORESPACE bit
       on, blanks are ignore (after the prefix). Note that the last one or two digits of a base64
       group can be = to indicate that fewer than three binary bytes are encoded.

       A character text value begins with a 0t (or 0T) prefix and continues with text characters,
       each being the value of one binary byte.

       All these functions basically copy data from src (whose size is specified by srclen) to
       dst (whose size is specified by dstlen), doing the conversion en route. If the result will
       not fit in dst, it is truncated; under no circumstances are more than dstlen bytes of
       result written to dst.  Dstlen can be zero, in which case dst need not be valid and no
       result bytes are written at all.

       The base parameter of ttodata and ttodatav specifies what format the input is in; normally
       it should be 0 to signify that this gets figured out from the prefix. Values of 16, 64,
       and 256 respectively signify hexadecimal, base64, and character-text formats without
       prefixes.

       The format parameter of datatot, a single character used as a type code, specifies which
       text format is wanted. The value 0 (not ASCII ´0´, but a zero value) specifies a
       reasonable default. Other currently-supported values are:

       ´x´
           continuous lower-case hexadecimal with a 0x prefix

       ´h´
           lower-case hexadecimal with a 0x prefix and a _ every eight digits

       ´:´
           lower-case hexadecimal with no prefix and a : (colon) every two digits

       16
           lower-case hexadecimal with no prefix or _

       ´s´
           continuous base64 with a 0s prefix

       64
           continuous base64 with no prefix

       The default format is currently ´h´.

       Ttodata returns NULL for success and a pointer to a string-literal error message for
       failure; see DIAGNOSTICS. On success, if and only if lenp is non-NULL, *lenp is set to the
       number of bytes required to contain the full untruncated result. It is the caller´s
       responsibility to check this against dstlen to determine whether he has obtained a
       complete result. The *lenp value is correct even if dstlen is zero, which offers a way to
       determine how much space would be needed before having to allocate any.

       Ttodatav is just like ttodata except that in certain cases, if errp is non-NULL, the
       buffer pointed to by errp (whose length is given by errlen) is used to hold a more
       detailed error message. The return value is NULL for success, and is either errp or a
       pointer to a string literal for failure. If the size of the error-message buffer is
       inadequate for the desired message, ttodatav will fall back on returning a pointer to a
       literal string instead. The freeswan.h header file defines a constant TTODATAV_BUF which
       is the size of a buffer large enough for worst-case results.

       The normal return value of datatot is the number of bytes required to contain the full
       untruncated result. It is the caller´s responsibility to check this against dstlen to
       determine whether he has obtained a complete result. The return value is correct even if
       dstlen is zero, which offers a way to determine how much space would be needed before
       having to allocate any. A return value of 0 signals a fatal error of some kind (see
       DIAGNOSTICS).

       A zero value for srclen in ttodata (but not datatot!) is synonymous with strlen(src). A
       non-zero srclen in ttodata must not include the terminating NUL.

       Unless dstlen is zero, the result supplied by datatot is always NUL-terminated, and its
       needed-size return value includes space for the terminating NUL.

       Several obsolete variants of these functions (atodata, datatoa, atobytes, and bytestoa)
       are temporarily also supported.

SEE ALSO

       sprintf(3), ipsec_atoaddr(3)

DIAGNOSTICS

       Fatal errors in ttodata and ttodatav are: unknown characters in the input; unknown or
       missing prefix; unknown base; incomplete digit group; non-zero padding in a base64
       less-than-three-bytes digit group; zero-length input.

       Fatal errors in datatot are: unknown format code; zero-length input.

HISTORY

       Written for the FreeS/WAN project by Henry Spencer.

BUGS

       Datatot should have a format code to produce character-text output.

       The 0s and 0t prefixes are the author´s inventions and are not a standard of any kind.
       They have been chosen to avoid collisions with existing practice (some C implementations
       use 0b for binary) and possible confusion with unprefixed hexadecimal.