pipewire/src/modules/module-avb/strings.c

/* SPDX-FileCopyrightText: Copyright © 2026 Nils Tonnaett
 * Nils Tonnaett <ntonnatt@ccrma.stanford.edu> */
/* SPDX-License-Identifier: MIT */

#include "strings.h"

typedef enum {
	ST_START,
	ST_A,
	ST_B,
	ST_C,
	ST_D,
	ST_E,
	ST_F,
	ST_G,
	ST_ERROR,
} UTF8_STATE;

int validate_utf8 (uint8_t *str, size_t len)
{
	UTF8_STATE state = ST_START;

	for (int i = 0; i < len; ++i)
	{
		switch (state)
		{
		case ST_START:
			if (str[i] <= 0x7F)
			{
				continue;
			}
			else if (str[i] >= 0xC2 && str[i] <= 0xDF)
			{
				state = ST_A;
			}
			else if (str[i] >= 0xE1 && str[i] <= 0xEC)
			{
				state = ST_B;
			}
			else if (str[i] >= 0xEE && str[i] <= 0xEF)
			{
				state = ST_B;
			}
			else if (str[i] == 0xE0)
			{
				state = ST_C;
			}
			else if (str[i] == 0xED)
			{
				state = ST_D;
			}
			else if (str[i] >= 0xF1 && str[i] <= 0xF3)
			{
				state = ST_E;
			}
			else if (str[i] == 0xF0)
			{
				state = ST_F;
			}
			else if (str[i] >= 0xF4)
			{
				state = ST_G;
			}
			else
			{
				state = ST_ERROR;
			}
			break;
		case ST_A:
			state = (str[i] >= 0x80 && str[i] <= 0xBF) ? ST_START : ST_ERROR;
			break;
		case ST_B:
			state = (str[i] >= 0x80 && str[i] <= 0xBF) ? ST_A : ST_ERROR;
			break;
		case ST_C:
			state = (str[i] >= 0xA0 && str[i] <= 0xBF) ? ST_A : ST_ERROR;
			break;
		case ST_D:
			state = (str[i] >= 0x80 && str[i] <= 0x9F) ? ST_A : ST_ERROR;
			break;
		case ST_E:
			state = (str[i] >= 0x80 && str[i] <= 0xBF) ? ST_B : ST_ERROR;
			break;
		case ST_F:
			state = (str[i] >= 0x90 && str[i] <= 0xBF) ? ST_B : ST_ERROR;
			break;
		case ST_G:
			state = (str[i] >= 0x80 && str[i] <= 0x8F) ? ST_B : ST_ERROR;
			break;
		}
		if (state == ST_ERROR)
		{
			return -1;
		}
	}
	if (state != ST_START)
	{
		return -1;
	}
	else
	{
		return 0;
	}
}

int check_zero_padding (uint8_t const *str, size_t len)
{
	size_t str_len = strnlen ((char *)str, len);
	/* String doesn't need to be null-terminated. Return success if there is no
	* null in str */
	if (str_len == len)
	{
		return 0;
	}

	for (int i = str_len; i < len; ++i)
	{
		if (str[i] != 0x00)
		{
			return -1;
		}
	}

	return 0;
}