NAME
ipsec ttodata, 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.