ccan/ccan/ccan_tokenizer/documentation

readui - Flexible function for reading a 64-bit unsigned integer
@sp: Pointer to scanning pointer
@e:  Pointer to end of string
@base:  Typically one of READUI_DEC, READUI_HEX, READUI_OCT, or READUI_BIN.

readui() converts the string of digits from *sp to e to a number, setting *sp to the first invalid character or e if the entire string is valid or empty.  It does not look at prefixes or suffixes, only digits.  It skips preceding whitespace.

readui() uses errno to indicate success or failure.  It will set errno to one of the following:

0:  Input is valid and non-empty
EINVAL:  Input is empty, does not start with any valid digits, or base is 0
ERANGE:  Number given is greater than ULLONG_MAX

Example (UNTESTED):

uint64_t read_number(const char *str) {
	const char *s = str, *e = strchr(str, 0);
	readui_base base = READUI_DEC;
	uint64_t result;
	
	//See if the number has a 0x (for hex) or 0 (for octal) prefix
	if (s+2<=e && *s=='0') {
		s++;
		if (*s=='x' || *s=='X') {
			base = READUI_HEX;
			s++;
		} else
			base = READUI_OCT;
	}
	
	result = readui(&s, e, base);
	
	if (errno)
		perror("read_number");
	
	return result;
}

Rules for a token list:

It always has and starts with a TOK_STARTLINE


Misc.:

If the world were intuitive, the tokenizer would never report warnings or bugs on a source file that compiles successfully.  However, one case where it does is when erroneous tokens appear within an #if 0 block.  Example:

#if 0
0b101.0p0
#endif