fxlibc/src/stdio/scanf/scan.c

#include "../stdio_p.h"
#include "../../stdlib/stdlib_p.h"
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdbool.h>

/* Features of this implementation:
   - Specifiers:
     * Integers (%i, %d, %o, %u, %x, %X)
     * Floating-point numbers (%e, %f, %F, %g, %a)
     * Strings (%c, %s, %[])
     * Pointers (%p)
     * Total number of bytes read so far (%n)
   - Integer size modifiers: hh, h, l, ll, L, j, z, t. Supported for all
     integer conversions, i.e. %i, %d, %u, %o, %x, %X and %n.
   - Floating-point size modifiers: l, L for %a, %e, %f, %g.
   - Assignment suppression character '*'.
   - Maximum field width (but buggy for floating-point, see below).

   NOT SUPPORTED:
   - Wide characters: %lc, %ls.
   - q size modifier.
   - "'" (quote) specifier for locale-specific thousand separators.
   - String allocation: %mc, %ms.
   - Out-of-order assignments "%n$".
   - TODO: Maximum field width for floating-point is mostly untested and likely
     has bugs when the field ends in the middle of the number. */

void __scanf_start(struct __scanf_input *in)
{
    if(in->fp)
        in->buffer = fgetc(in->fp);
    else {
        in->buffer = (*in->str ? *in->str : EOF);
        in->str += (in->buffer != EOF);
    }
}

int __scanf_fetch(struct __scanf_input *in)
{
	if(in->fp)
		return fgetc(in->fp);

	int c = *in->str;
	if(c == 0)
		return EOF;
	in->str++;
	return c;
}

void __scanf_end(struct __scanf_input *in)
{
	if(in->buffer == EOF)
		return;

	if(in->fp)
		ungetc(in->buffer, in->fp);
	else
		in->str--;
}

static void __skip_spaces(struct __scanf_input *in)
{
	while(isspace(__scanf_peek(in)))
		__scanf_in(in);
}

static void __scanf_store_i(int64_t value, int size, va_list *args)
{
	if(size == 1)
		*va_arg(*args, int8_t *) = value;
	else if(size == 2)
		*va_arg(*args, int16_t *) = value;
	else if(size == 4)
		*va_arg(*args, int32_t *) = value;
	else if(size == 8)
		*va_arg(*args, int64_t *) = value;
}

static void __scanf_store_d(long double value, int size, va_list *args)
{
	if(size == sizeof(float))
		*va_arg(*args, float *) = value;
	else if(size == sizeof(double))
		*va_arg(*args, double *) = value;
	else if(size == sizeof(long double))
		*va_arg(*args, long double *) = value;
}

struct scanf_format {
	/* Maximum field width */
	int field_width;
	/* Size of the assigned (integer or floating-point) type, in bytes */
	uint8_t size;
	/* Whether to skip assignment */
	bool skip;
	/* Set of bytes allowed for bracket sets in %[] */
	uint8_t bracket_set[32];
};

/* Allow/disallow the entire set */
static void bracket_set_init(uint8_t *set, bool allow)
{
	memset(set, allow ? 0xff : 0x00, 32);
}

/* Allow/disallow a range of characters. Both ends are included. */
static void bracket_set_range(
	uint8_t *set, uint8_t start, uint8_t end, bool allow)
{
	for(int u = start; u <= end; u++) {
		int byte = u >> 3;
		int bit = 1 << (u & 7);
		if(allow)
			set[byte] |= bit;
		else
			set[byte] &= ~bit;
	}
}

/* Check whether a byte is allowed by the bracket set. */
static bool bracket_set_test(uint8_t *set, int c)
{
	return (c != EOF) && (set[c >> 3] & (1 << (c & 7)));
}

/* Parse a bracket set from a format string. Returns true on success. */
static bool bracket_set_parse(uint8_t *set, char const *format, int *pos)
{
	int last = 0;
	bool allow = true;
	bracket_set_init(set, false);

	/* '^' denotes a negated set */
	if(format[*pos] == '^') {
		allow = false;
		(*pos)++;
		bracket_set_init(set, true);
	}
	/* ']' as the first character adds ']' to the set */
	if(format[*pos] == ']' ) {
		bracket_set_range(set, ']', ']', allow);
		(*pos)++;
	}

	for(; format[*pos] && format[*pos] != ']'; (*pos)++) {
		/* '-' as the last character, thus explicitly in the set */
		if(format[*pos] == '-' && format[*pos + 1] == ']')
			bracket_set_range(set, '-', '-', allow);
		/* '-' as denoting a range */
		else if(format[*pos] == '-') {
			(*pos)++;
			bracket_set_range(set,  last, format[*pos], allow);
		}
		/* Any other character */
		else {
			last = format[*pos];
			bracket_set_range(set, last, last, allow);
		}
	}

	return (format[*pos] == ']');
}

/* Parse a format in the format string. Returns specifier, 0 on error. */
static int parse_fmt(char const *fmt, int *pos, struct scanf_format *opt)
{
	opt->field_width = INT_MAX;
	opt->size = sizeof(int);
	opt->skip = false;

	int width = 0;
	char size_letter = 0;

	for((*pos)++;; (*pos)++) {
		int c = fmt[*pos];

		if(c == '*')
			opt->skip = true;
		else if(strchr("hlzjtL", c)) {
			if(c == 'h')
				opt->size = (size_letter=='h') ? sizeof(char) : sizeof(short);
			else if(c == 'l')
				opt->size = (size_letter=='l') ? sizeof(long long) :
			                sizeof(long);
			else if(c == 'z')
				opt->size = sizeof(size_t);
			else if(c == 'j')
				opt->size = sizeof(intmax_t);
			else if(c == 't')
				opt->size = sizeof(ptrdiff_t);
			else if(c == 'L')
				opt->size = sizeof(long double);

			size_letter = c;
		}
		else if(isdigit(c)) {
			width = width * 10 + (fmt[*pos] - '0');
			opt->field_width = width;
		}
		else if(c == '[') {
			(*pos)++;
			return bracket_set_parse(opt->bracket_set, fmt, pos) ? '[' : 0;
		}
		else if(strchr("diouxXpsn", c))
			return c;
		else if(strchr("aAeEfFgG", c)) {
			/* Adjust interpretation of no size / 'l' size  */
			if(size_letter == 0)
				opt->size = sizeof(float);
			if(size_letter == 'l')
				opt->size = sizeof(double);
			return c;
		}
		else if(c == 'c') {
			if(opt->field_width == INT_MAX)
				opt->field_width = 1;
			return c;
		}
		else return 0;
	}
	return 0;
}

int __scanf(
	struct __scanf_input * __restrict__ in,
	char const * __restrict__ format,
	va_list *args)
{
	/* Number of successful assignments */
	int validrets = 0;

	__scanf_start( in );

	// TODO: No __scanf_end() in any of the "return validrets"!!

	for(int pos = 0; format[pos]; pos++) {
		if(format[pos] == ' ') {
			__skip_spaces(in);
			continue;
		}
		else if(format[pos] != '%' || format[pos + 1] == '%') {
			/* Expect this specific character */
			if(__scanf_peek(in) != format[pos])
				return validrets;
			__scanf_in(in);
			pos += (format[pos] == '%');
			continue;
		}

		/* Perform a conversion */
		struct scanf_format opt;
		int spec = parse_fmt(format, &pos, &opt);
		if(spec == 0)
			return validrets;

		switch(spec) {
		case '[': {
			char *c = opt.skip ? NULL : va_arg(*args, char *);
			int i;
			for(i = 0; i < opt.field_width; i++) {
				int temp = __scanf_peek(in);
				if(bracket_set_test(opt.bracket_set, temp)) {
					__scanf_in(in);
					if(c) *c++ = temp;
				}
				else if(temp==EOF && !i && !validrets)
					return EOF;
				else break;
			}
			if(!i)
				return validrets;
			*c = '\0';
			validrets += !opt.skip;
			break;
		}

		case 'n':
			__scanf_store_i(in->bytes_read, opt.size, args);
			break;

		case 'd':
		case 'i':
		case 'o':
		case 'u':
		case 'x':
		case 'X': {
			int f = format[pos];
			int base = (f == 'd' || f == 'u') ? 10 :
			           (f == 'o') ? 8:
			           (f == 'x' || f == 'X') ? 16 : 0;
			bool use_unsigned = (f == 'o' || f == 'x' || f == 'X');

			long long int temp;
			int err = __strto_int(in, base, NULL, &temp, use_unsigned,
				opt.field_width);
			if(err == EOF && validrets == 0) return EOF;
			if(err) return validrets;
			if(!opt.skip)
				__scanf_store_i(temp, opt.size, args);
			validrets++;
			break;
		}

		case 'a':
		case 'A':
		case 'e':
		case 'E':
		case 'f':
		case 'F':
		case 'g':
		case 'G': {
			long double temp;
			int err = __strto_fp(in, NULL, NULL, &temp, opt.field_width);
			if(err == EOF && validrets == 0) return EOF;
			if(err) return validrets;
			if(!opt.skip)
				__scanf_store_d(temp, opt.size, args);
			validrets++;
			break;
		}

		case 'p': {
			void *p = opt.skip ? NULL : va_arg(*args, void *);
			_Static_assert(sizeof(p) == sizeof(long));
			int err = __strto_int(in, 0, p, NULL, true, opt.field_width);
			if(err) return validrets;
			validrets += !opt.skip;
			break;
		}

		case 'c': {
			char *c = opt.skip ? NULL : va_arg(*args, char *);

			for(int u = 0; u < opt.field_width; u++) {
				int temp = __scanf_in(in);
				if(temp==EOF) return EOF;
				else if(c) *c++ = temp;
			}
			validrets += !opt.skip;
			break;
		}

		case 's': {
			char *c = opt.skip ? NULL : va_arg(*args, char *);
			__skip_spaces(in);

			for(int i = 0; i < opt.field_width; i++) {
				int temp = __scanf_peek(in);
				if(temp==EOF && !i) return validrets;
				if(isspace(temp) || temp==EOF) {
					if(c) {
						*c = 0;
						validrets++;
					}
					break;
				}
				else {
					int temp = __scanf_in(in);
					if(c) *c++ = temp;
				}
			}
			break;
		}
		}
	}

	__scanf_end( in );
	return validrets;
}