path: root/wtf8.c

#include "wtf8.h"

/*
 * Check if first two bits of the character are "10", meaning it'str a UTF-8
 * continuation character
 */
int is_utf8_cont(unsigned char chr) {
	return (chr & 0xC0) == 0x80;
}

/*
 * Print each octet of a string of characters as lowercase hex followed by a
 * trailing space, ending with a newline
 */
void print_octets(FILE *stream, char *str) {
	unsigned char chr;

	/*
	 * Iterate through the string, printing each octet, ending with a newline
	 */
	while ((chr = *str++)) {
		char sep;
		sep = is_utf8_cont(chr)
			? BYTE_SEP
			: CHAR_SEP;
		fprintf(stream, "%c%02x", sep, chr);
	}
	fputc('\n', stream);

	return;
}

/*
 * Print each of the UTF-8 characters to align with the output of
 * print_octets(), with each character in line with the end of the octet that
 * terminates it, ending with a newline
 */
void print_characters(FILE *stream, char *str) {

	/*
	 * Iterate through the string
	 */
	while (*str) {

		/*
		 * We need a short counter to find how long each character is
		 */
		unsigned char chr;

		/*
		 * Print blanks and increment a counter until we find how long this
		 * character is
		 */
		for (chr = 1; is_utf8_cont(str[chr]); chr++) {

			/*
			 * Print blanks
			 */
			fprintf(stream, "   ");

			/*
			 * If we've hit UCHAR_MAX, this is probably a perverse
			 * string of bytes for fuzzing or exploitation; bail
			 * out
			 */
			if (chr == UCHAR_MAX) {
				fprintf(stderr, "Perverse byte count, bailing\n");
				exit(1);
			}
		}

		/*
		 * Print two spaces, and then the full character
		 */
		fprintf(stream, "  ");
		while (chr--)
			fputc(*str++, stream);
	}

	/*
	 * End with a newline
	 */
	fputc('\n', stream);
	return;
}

/*
 * Main function
 */
int main(int argc, char **argv) {

	/*
	 * Check we have one and only one argument
	 */
	if (argc != 2) {
		fprintf(stderr, "%s: Need one argument\n", PROGRAM_NAME);
		exit(EXIT_FAILURE);
	}

	/*
	 * Print the sole argument first as hex octets, then as characters, spaced
	 * accordingly
	 */
	print_octets(stdout, argv[1]);
	print_characters(stdout, argv[1]);

	/*
	 * Done!
	 */
	exit(EXIT_SUCCESS);
}