NAME
ipsec ttoul, ultot - convert unsigned-long numbers to and from text
SYNOPSIS
#include <freeswan.h>
const char *ttoul(const char * src, size_t srclen, int base,
unsigned long * n);
size_t ultot(unsigned long n, int format, char * dst, size_t dstlen);
DESCRIPTION
Ttoul converts a text-string number into a binary unsigned long value.
Ultot does the reverse conversion, back to a text version.
Numbers are specified in text as decimal (e.g. 123), octal with a
leading zero (e.g. 012, which has value 10), or hexadecimal with a
leading 0x (e.g. 0x1f, which has value 31) in either upper or lower
case.
The srclen parameter of ttoul specifies the length of the string
pointed to by src; it is an error for there to be anything else (e.g.,
a terminating NUL) within that length. As a convenience for cases where
an entire NUL-terminated string is to be converted, a srclen value of 0
is taken to mean strlen(src).
The base parameter of ttoul can be 8, 10, or 16, in which case the
number supplied is assumed to be of that form (and in the case of 16,
to lack any 0x prefix). It can also be 0, in which case the number is
examined for a leading zero or a leading 0x to determine its base.
The dstlen parameter of ultot specifies the size of the dst parameter;
under no circumstances are more than dstlen bytes written to dst. A
result which will not fit is truncated. Dstlen can be zero, in which
case dst need not be valid and no result is written, but the return
value is unaffected; in all other cases, the (possibly truncated)
result is NUL-terminated. The freeswan.h header file defines a
constant, ULTOT_BUF, which is the size of a buffer just large enough
for worst-case results.
The format parameter of ultot must be one of:
´o´
octal conversion with leading 0
8
octal conversion with no leading 0
´d´
decimal conversion
10
same as d
´x´
hexadecimal conversion, including leading 0x
16
hexadecimal conversion with no leading 0x
17
like 16 except padded on left with 0s to eight digits (full width
of a 32-bit number)
Ttoul returns NULL for success and a pointer to a string-literal error
message for failure; see DIAGNOSTICS. Ultot returns 0 for a failure,
and otherwise returns the size of buffer which would be needed to
accommodate the full conversion result, including terminating NUL (it
is the caller´s responsibility to check this against the size of the
provided buffer to determine whether truncation has occurred).
SEE ALSO
atol(3), strtoul(3)
DIAGNOSTICS
Fatal errors in ttoul are: empty input; unknown base; non-digit
character found; number too large for an unsigned long.
Fatal errors in ultot are: unknown format.
HISTORY
Written for the FreeS/WAN project by Henry Spencer.
BUGS
Conversion of 0 with format o yields 00.
Ultot format 17 is a bit of a kludge.
The restriction of error reports to literal strings (so that callers
don´t need to worry about freeing them or copying them) does limit the
precision of error reporting.
The error-reporting convention lends itself to slightly obscure code,
because many readers will not think of NULL as signifying success. A
good way to make it clearer is to write something like:
const char *error;
error = ttoul( /* ... */ );
if (error != NULL) {
/* something went wrong */