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IPSEC_TTODATA(3) | 16 August 2003 | IPSEC_TTODATA(3) |
NAME¶
ipsec_ttodata, ipsec_datatot - convert binary data bytes from and to text formatsSYNOPSIS¶
#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.11/14/2008 | 16 August 2003 |