xref: /external/wpa_supplicant_8/hostapd/src/utils/common.c

/*
 * wpa_supplicant/hostapd / common helper functions, etc.
 * Copyright (c) 2002-2007, Jouni Malinen <j@w1.fi>
 *
 * This software may be distributed under the terms of the BSD license.
 * See README for more details.
 */

#include "includes.h"

#include "common.h"


static int hex2num(char c)
{
	if (c >= '0' && c <= '9')
		return c - '0';
	if (c >= 'a' && c <= 'f')
		return c - 'a' + 10;
	if (c >= 'A' && c <= 'F')
		return c - 'A' + 10;
	return -1;
}


int hex2byte(const char *hex)
{
	int a, b;
	a = hex2num(*hex++);
	if (a < 0)
		return -1;
	b = hex2num(*hex++);
	if (b < 0)
		return -1;
	return (a << 4) | b;
}


static const char * hwaddr_parse(const char *txt, u8 *addr)
{
	size_t i;

	for (i = 0; i < ETH_ALEN; i++) {
		int a;

		a = hex2byte(txt);
		if (a < 0)
			return NULL;
		txt += 2;
		addr[i] = a;
		if (i < ETH_ALEN - 1 && *txt++ != ':')
			return NULL;
	}
	return txt;
}


/**
 * hwaddr_aton - Convert ASCII string to MAC address (colon-delimited format)
 * @txt: MAC address as a string (e.g., "00:11:22:33:44:55")
 * @addr: Buffer for the MAC address (ETH_ALEN = 6 bytes)
 * Returns: 0 on success, -1 on failure (e.g., string not a MAC address)
 */
int hwaddr_aton(const char *txt, u8 *addr)
{
	return hwaddr_parse(txt, addr) ? 0 : -1;
}


/**
 * hwaddr_masked_aton - Convert ASCII string with optional mask to MAC address (colon-delimited format)
 * @txt: MAC address with optional mask as a string (e.g., "00:11:22:33:44:55/ff:ff:ff:ff:00:00")
 * @addr: Buffer for the MAC address (ETH_ALEN = 6 bytes)
 * @mask: Buffer for the MAC address mask (ETH_ALEN = 6 bytes)
 * @maskable: Flag to indicate whether a mask is allowed
 * Returns: 0 on success, -1 on failure (e.g., string not a MAC address)
 */
int hwaddr_masked_aton(const char *txt, u8 *addr, u8 *mask, u8 maskable)
{
	const char *r;

	/* parse address part */
	r = hwaddr_parse(txt, addr);
	if (!r)
		return -1;

	/* check for optional mask */
	if (*r == '\0' || isspace(*r)) {
		/* no mask specified, assume default */
		os_memset(mask, 0xff, ETH_ALEN);
	} else if (maskable && *r == '/') {
		/* mask specified and allowed */
		r = hwaddr_parse(r + 1, mask);
		/* parser error? */
		if (!r)
			return -1;
	} else {
		/* mask specified but not allowed or trailing garbage */
		return -1;
	}

	return 0;
}


/**
 * hwaddr_compact_aton - Convert ASCII string to MAC address (no colon delimitors format)
 * @txt: MAC address as a string (e.g., "001122334455")
 * @addr: Buffer for the MAC address (ETH_ALEN = 6 bytes)
 * Returns: 0 on success, -1 on failure (e.g., string not a MAC address)
 */
int hwaddr_compact_aton(const char *txt, u8 *addr)
{
	int i;

	for (i = 0; i < 6; i++) {
		int a, b;

		a = hex2num(*txt++);
		if (a < 0)
			return -1;
		b = hex2num(*txt++);
		if (b < 0)
			return -1;
		*addr++ = (a << 4) | b;
	}

	return 0;
}

/**
 * hwaddr_aton2 - Convert ASCII string to MAC address (in any known format)
 * @txt: MAC address as a string (e.g., 00:11:22:33:44:55 or 0011.2233.4455)
 * @addr: Buffer for the MAC address (ETH_ALEN = 6 bytes)
 * Returns: Characters used (> 0) on success, -1 on failure
 */
int hwaddr_aton2(const char *txt, u8 *addr)
{
	int i;
	const char *pos = txt;

	for (i = 0; i < 6; i++) {
		int a, b;

		while (*pos == ':' || *pos == '.' || *pos == '-')
			pos++;

		a = hex2num(*pos++);
		if (a < 0)
			return -1;
		b = hex2num(*pos++);
		if (b < 0)
			return -1;
		*addr++ = (a << 4) | b;
	}

	return pos - txt;
}


/**
 * hexstr2bin - Convert ASCII hex string into binary data
 * @hex: ASCII hex string (e.g., "01ab")
 * @buf: Buffer for the binary data
 * @len: Length of the text to convert in bytes (of buf); hex will be double
 * this size
 * Returns: 0 on success, -1 on failure (invalid hex string)
 */
int hexstr2bin(const char *hex, u8 *buf, size_t len)
{
	size_t i;
	int a;
	const char *ipos = hex;
	u8 *opos = buf;

	for (i = 0; i < len; i++) {
		a = hex2byte(ipos);
		if (a < 0)
			return -1;
		*opos++ = a;
		ipos += 2;
	}
	return 0;
}


int hwaddr_mask_txt(char *buf, size_t len, const u8 *addr, const u8 *mask)
{
	size_t i;
	int print_mask = 0;
	int res;

	for (i = 0; i < ETH_ALEN; i++) {
		if (mask[i] != 0xff) {
			print_mask = 1;
			break;
		}
	}

	if (print_mask)
		res = os_snprintf(buf, len, MACSTR "/" MACSTR,
				  MAC2STR(addr), MAC2STR(mask));
	else
		res = os_snprintf(buf, len, MACSTR, MAC2STR(addr));
	if (os_snprintf_error(len, res))
		return -1;
	return res;
}


/**
 * inc_byte_array - Increment arbitrary length byte array by one
 * @counter: Pointer to byte array
 * @len: Length of the counter in bytes
 *
 * This function increments the last byte of the counter by one and continues
 * rolling over to more significant bytes if the byte was incremented from
 * 0xff to 0x00.
 */
void inc_byte_array(u8 *counter, size_t len)
{
	int pos = len - 1;
	while (pos >= 0) {
		counter[pos]++;
		if (counter[pos] != 0)
			break;
		pos--;
	}
}


void wpa_get_ntp_timestamp(u8 *buf)
{
	struct os_time now;
	u32 sec, usec;
	be32 tmp;

	/* 64-bit NTP timestamp (time from 1900-01-01 00:00:00) */
	os_get_time(&now);
	sec = now.sec + 2208988800U; /* Epoch to 1900 */
	/* Estimate 2^32/10^6 = 4295 - 1/32 - 1/512 */
	usec = now.usec;
	usec = 4295 * usec - (usec >> 5) - (usec >> 9);
	tmp = host_to_be32(sec);
	os_memcpy(buf, (u8 *) &tmp, 4);
	tmp = host_to_be32(usec);
	os_memcpy(buf + 4, (u8 *) &tmp, 4);
}

/**
 * wpa_scnprintf - Simpler-to-use snprintf function
 * @buf: Output buffer
 * @size: Buffer size
 * @fmt: format
 *
 * Simpler snprintf version that doesn't require further error checks - the
 * return value only indicates how many bytes were actually written, excluding
 * the NULL byte (i.e., 0 on error, size-1 if buffer is not big enough).
 */
int wpa_scnprintf(char *buf, size_t size, const char *fmt, ...)
{
	va_list ap;
	int ret;

	if (!size)
		return 0;

	va_start(ap, fmt);
	ret = vsnprintf(buf, size, fmt, ap);
	va_end(ap);

	if (ret < 0)
		return 0;
	if ((size_t) ret >= size)
		return size - 1;

	return ret;
}


int wpa_snprintf_hex_sep(char *buf, size_t buf_size, const u8 *data, size_t len,
			 char sep)
{
	size_t i;
	char *pos = buf, *end = buf + buf_size;
	int ret;

	if (buf_size == 0)
		return 0;

	for (i = 0; i < len; i++) {
		ret = os_snprintf(pos, end - pos, "%02x%c",
				  data[i], sep);
		if (os_snprintf_error(end - pos, ret)) {
			end[-1] = '\0';
			return pos - buf;
		}
		pos += ret;
	}
	pos[-1] = '\0';
	return pos - buf;
}


static inline int _wpa_snprintf_hex(char *buf, size_t buf_size, const u8 *data,
				    size_t len, int uppercase)
{
	size_t i;
	char *pos = buf, *end = buf + buf_size;
	int ret;
	if (buf_size == 0)
		return 0;
	for (i = 0; i < len; i++) {
		ret = os_snprintf(pos, end - pos, uppercase ? "%02X" : "%02x",
				  data[i]);
		if (os_snprintf_error(end - pos, ret)) {
			end[-1] = '\0';
			return pos - buf;
		}
		pos += ret;
	}
	end[-1] = '\0';
	return pos - buf;
}

/**
 * wpa_snprintf_hex - Print data as a hex string into a buffer
 * @buf: Memory area to use as the output buffer
 * @buf_size: Maximum buffer size in bytes (should be at least 2 * len + 1)
 * @data: Data to be printed
 * @len: Length of data in bytes
 * Returns: Number of bytes written
 */
int wpa_snprintf_hex(char *buf, size_t buf_size, const u8 *data, size_t len)
{
	return _wpa_snprintf_hex(buf, buf_size, data, len, 0);
}


/**
 * wpa_snprintf_hex_uppercase - Print data as a upper case hex string into buf
 * @buf: Memory area to use as the output buffer
 * @buf_size: Maximum buffer size in bytes (should be at least 2 * len + 1)
 * @data: Data to be printed
 * @len: Length of data in bytes
 * Returns: Number of bytes written
 */
int wpa_snprintf_hex_uppercase(char *buf, size_t buf_size, const u8 *data,
			       size_t len)
{
	return _wpa_snprintf_hex(buf, buf_size, data, len, 1);
}


#ifdef CONFIG_ANSI_C_EXTRA

#ifdef _WIN32_WCE
void perror(const char *s)
{
	wpa_printf(MSG_ERROR, "%s: GetLastError: %d",
		   s, (int) GetLastError());
}
#endif /* _WIN32_WCE */


int optind = 1;
int optopt;
char *optarg;

int getopt(int argc, char *const argv[], const char *optstring)
{
	static int optchr = 1;
	char *cp;

	if (optchr == 1) {
		if (optind >= argc) {
			/* all arguments processed */
			return EOF;
		}

		if (argv[optind][0] != '-' || argv[optind][1] == '\0') {
			/* no option characters */
			return EOF;
		}
	}

	if (os_strcmp(argv[optind], "--") == 0) {
		/* no more options */
		optind++;
		return EOF;
	}

	optopt = argv[optind][optchr];
	cp = os_strchr(optstring, optopt);
	if (cp == NULL || optopt == ':') {
		if (argv[optind][++optchr] == '\0') {
			optchr = 1;
			optind++;
		}
		return '?';
	}

	if (cp[1] == ':') {
		/* Argument required */
		optchr = 1;
		if (argv[optind][optchr + 1]) {
			/* No space between option and argument */
			optarg = &argv[optind++][optchr + 1];
		} else if (++optind >= argc) {
			/* option requires an argument */
			return '?';
		} else {
			/* Argument in the next argv */
			optarg = argv[optind++];
		}
	} else {
		/* No argument */
		if (argv[optind][++optchr] == '\0') {
			optchr = 1;
			optind++;
		}
		optarg = NULL;
	}
	return *cp;
}
#endif /* CONFIG_ANSI_C_EXTRA */


#ifdef CONFIG_NATIVE_WINDOWS
/**
 * wpa_unicode2ascii_inplace - Convert unicode string into ASCII
 * @str: Pointer to string to convert
 *
 * This function converts a unicode string to ASCII using the same
 * buffer for output. If UNICODE is not set, the buffer is not
 * modified.
 */
void wpa_unicode2ascii_inplace(TCHAR *str)
{
#ifdef UNICODE
	char *dst = (char *) str;
	while (*str)
		*dst++ = (char) *str++;
	*dst = '\0';
#endif /* UNICODE */
}


TCHAR * wpa_strdup_tchar(const char *str)
{
#ifdef UNICODE
	TCHAR *buf;
	buf = os_malloc((strlen(str) + 1) * sizeof(TCHAR));
	if (buf == NULL)
		return NULL;
	wsprintf(buf, L"%S", str);
	return buf;
#else /* UNICODE */
	return os_strdup(str);
#endif /* UNICODE */
}
#endif /* CONFIG_NATIVE_WINDOWS */


void printf_encode(char *txt, size_t maxlen, const u8 *data, size_t len)
{
	char *end = txt + maxlen;
	size_t i;

	for (i = 0; i < len; i++) {
		if (txt + 4 >= end)
			break;

		switch (data[i]) {
		case '\"':
			*txt++ = '\\';
			*txt++ = '\"';
			break;
		case '\\':
			*txt++ = '\\';
			*txt++ = '\\';
			break;
		case '\033':
			*txt++ = '\\';
			*txt++ = 'e';
			break;
		case '\n':
			*txt++ = '\\';
			*txt++ = 'n';
			break;
		case '\r':
			*txt++ = '\\';
			*txt++ = 'r';
			break;
		case '\t':
			*txt++ = '\\';
			*txt++ = 't';
			break;
		default:
			if (data[i] >= 32 && data[i] <= 127) {
				*txt++ = data[i];
			} else {
				txt += os_snprintf(txt, end - txt, "\\x%02x",
						   data[i]);
			}
			break;
		}
	}

	*txt = '\0';
}


size_t printf_decode(u8 *buf, size_t maxlen, const char *str)
{
	const char *pos = str;
	size_t len = 0;
	int val;

	while (*pos) {
		if (len + 1 >= maxlen)
			break;
		switch (*pos) {
		case '\\':
			pos++;
			switch (*pos) {
			case '\\':
				buf[len++] = '\\';
				pos++;
				break;
			case '"':
				buf[len++] = '"';
				pos++;
				break;
			case 'n':
				buf[len++] = '\n';
				pos++;
				break;
			case 'r':
				buf[len++] = '\r';
				pos++;
				break;
			case 't':
				buf[len++] = '\t';
				pos++;
				break;
			case 'e':
				buf[len++] = '\033';
				pos++;
				break;
			case 'x':
				pos++;
				val = hex2byte(pos);
				if (val < 0) {
					val = hex2num(*pos);
					if (val < 0)
						break;
					buf[len++] = val;
					pos++;
				} else {
					buf[len++] = val;
					pos += 2;
				}
				break;
			case '0':
			case '1':
			case '2':
			case '3':
			case '4':
			case '5':
			case '6':
			case '7':
				val = *pos++ - '0';
				if (*pos >= '0' && *pos <= '7')
					val = val * 8 + (*pos++ - '0');
				if (*pos >= '0' && *pos <= '7')
					val = val * 8 + (*pos++ - '0');
				buf[len++] = val;
				break;
			default:
				break;
			}
			break;
		default:
			buf[len++] = *pos++;
			break;
		}
	}
	if (maxlen > len)
		buf[len] = '\0';

	return len;
}


/**
 * wpa_ssid_txt - Convert SSID to a printable string
 * @ssid: SSID (32-octet string)
 * @ssid_len: Length of ssid in octets
 * Returns: Pointer to a printable string
 *
 * This function can be used to convert SSIDs into printable form. In most
 * cases, SSIDs do not use unprintable characters, but IEEE 802.11 standard
 * does not limit the used character set, so anything could be used in an SSID.
 *
 * This function uses a static buffer, so only one call can be used at the
 * time, i.e., this is not re-entrant and the returned buffer must be used
 * before calling this again.
 */
const char * wpa_ssid_txt(const u8 *ssid, size_t ssid_len)
{
	static char ssid_txt[32 * 4 + 1];

	if (ssid == NULL) {
		ssid_txt[0] = '\0';
		return ssid_txt;
	}

	printf_encode(ssid_txt, sizeof(ssid_txt), ssid, ssid_len);
	return ssid_txt;
}


void * __hide_aliasing_typecast(void *foo)
{
	return foo;
}


char * wpa_config_parse_string(const char *value, size_t *len)
{
	if (*value == '"') {
		const char *pos;
		char *str;
		value++;
		pos = os_strrchr(value, '"');
		if (pos == NULL || pos[1] != '\0')
			return NULL;
		*len = pos - value;
		str = dup_binstr(value, *len);
		if (str == NULL)
			return NULL;
		return str;
	} else if (*value == 'P' && value[1] == '"') {
		const char *pos;
		char *tstr, *str;
		size_t tlen;
		value += 2;
		pos = os_strrchr(value, '"');
		if (pos == NULL || pos[1] != '\0')
			return NULL;
		tlen = pos - value;
		tstr = dup_binstr(value, tlen);
		if (tstr == NULL)
			return NULL;

		str = os_malloc(tlen + 1);
		if (str == NULL) {
			os_free(tstr);
			return NULL;
		}

		*len = printf_decode((u8 *) str, tlen + 1, tstr);
		os_free(tstr);

		return str;
	} else {
		u8 *str;
		size_t tlen, hlen = os_strlen(value);
		if (hlen & 1)
			return NULL;
		tlen = hlen / 2;
		str = os_malloc(tlen + 1);
		if (str == NULL)
			return NULL;
		if (hexstr2bin(value, str, tlen)) {
			os_free(str);
			return NULL;
		}
		str[tlen] = '\0';
		*len = tlen;
		return (char *) str;
	}
}


int is_hex(const u8 *data, size_t len)
{
	size_t i;

	for (i = 0; i < len; i++) {
		if (data[i] < 32 || data[i] >= 127)
			return 1;
	}
	return 0;
}


size_t merge_byte_arrays(u8 *res, size_t res_len,
			 const u8 *src1, size_t src1_len,
			 const u8 *src2, size_t src2_len)
{
	size_t len = 0;

	os_memset(res, 0, res_len);

	if (src1) {
		if (src1_len >= res_len) {
			os_memcpy(res, src1, res_len);
			return res_len;
		}

		os_memcpy(res, src1, src1_len);
		len += src1_len;
	}

	if (src2) {
		if (len + src2_len >= res_len) {
			os_memcpy(res + len, src2, res_len - len);
			return res_len;
		}

		os_memcpy(res + len, src2, src2_len);
		len += src2_len;
	}

	return len;
}


char * dup_binstr(const void *src, size_t len)
{
	char *res;

	if (src == NULL)
		return NULL;
	res = os_malloc(len + 1);
	if (res == NULL)
		return NULL;
	os_memcpy(res, src, len);
	res[len] = '\0';

	return res;
}


int freq_range_list_parse(struct wpa_freq_range_list *res, const char *value)
{
	struct wpa_freq_range *freq = NULL, *n;
	unsigned int count = 0;
	const char *pos, *pos2, *pos3;

	/*
	 * Comma separated list of frequency ranges.
	 * For example: 2412-2432,2462,5000-6000
	 */
	pos = value;
	while (pos && pos[0]) {
		n = os_realloc_array(freq, count + 1,
				     sizeof(struct wpa_freq_range));
		if (n == NULL) {
			os_free(freq);
			return -1;
		}
		freq = n;
		freq[count].min = atoi(pos);
		pos2 = os_strchr(pos, '-');
		pos3 = os_strchr(pos, ',');
		if (pos2 && (!pos3 || pos2 < pos3)) {
			pos2++;
			freq[count].max = atoi(pos2);
		} else
			freq[count].max = freq[count].min;
		pos = pos3;
		if (pos)
			pos++;
		count++;
	}

	os_free(res->range);
	res->range = freq;
	res->num = count;

	return 0;
}


int freq_range_list_includes(const struct wpa_freq_range_list *list,
			     unsigned int freq)
{
	unsigned int i;

	if (list == NULL)
		return 0;

	for (i = 0; i < list->num; i++) {
		if (freq >= list->range[i].min && freq <= list->range[i].max)
			return 1;
	}

	return 0;
}


char * freq_range_list_str(const struct wpa_freq_range_list *list)
{
	char *buf, *pos, *end;
	size_t maxlen;
	unsigned int i;
	int res;

	if (list->num == 0)
		return NULL;

	maxlen = list->num * 30;
	buf = os_malloc(maxlen);
	if (buf == NULL)
		return NULL;
	pos = buf;
	end = buf + maxlen;

	for (i = 0; i < list->num; i++) {
		struct wpa_freq_range *range = &list->range[i];

		if (range->min == range->max)
			res = os_snprintf(pos, end - pos, "%s%u",
					  i == 0 ? "" : ",", range->min);
		else
			res = os_snprintf(pos, end - pos, "%s%u-%u",
					  i == 0 ? "" : ",",
					  range->min, range->max);
		if (os_snprintf_error(end - pos, res)) {
			os_free(buf);
			return NULL;
		}
		pos += res;
	}

	return buf;
}


int int_array_len(const int *a)
{
	int i;
	for (i = 0; a && a[i]; i++)
		;
	return i;
}


void int_array_concat(int **res, const int *a)
{
	int reslen, alen, i;
	int *n;

	reslen = int_array_len(*res);
	alen = int_array_len(a);

	n = os_realloc_array(*res, reslen + alen + 1, sizeof(int));
	if (n == NULL) {
		os_free(*res);
		*res = NULL;
		return;
	}
	for (i = 0; i <= alen; i++)
		n[reslen + i] = a[i];
	*res = n;
}


static int freq_cmp(const void *a, const void *b)
{
	int _a = *(int *) a;
	int _b = *(int *) b;

	if (_a == 0)
		return 1;
	if (_b == 0)
		return -1;
	return _a - _b;
}


void int_array_sort_unique(int *a)
{
	int alen;
	int i, j;

	if (a == NULL)
		return;

	alen = int_array_len(a);
	qsort(a, alen, sizeof(int), freq_cmp);

	i = 0;
	j = 1;
	while (a[i] && a[j]) {
		if (a[i] == a[j]) {
			j++;
			continue;
		}
		a[++i] = a[j++];
	}
	if (a[i])
		i++;
	a[i] = 0;
}


void int_array_add_unique(int **res, int a)
{
	int reslen;
	int *n;

	for (reslen = 0; *res && (*res)[reslen]; reslen++) {
		if ((*res)[reslen] == a)
			return; /* already in the list */
	}

	n = os_realloc_array(*res, reslen + 2, sizeof(int));
	if (n == NULL) {
		os_free(*res);
		*res = NULL;
		return;
	}

	n[reslen] = a;
	n[reslen + 1] = 0;

	*res = n;
}


void str_clear_free(char *str)
{
	if (str) {
		size_t len = os_strlen(str);
		os_memset(str, 0, len);
		os_free(str);
	}
}


void bin_clear_free(void *bin, size_t len)
{
	if (bin) {
		os_memset(bin, 0, len);
		os_free(bin);
	}
}


int random_mac_addr(u8 *addr)
{
	if (os_get_random(addr, ETH_ALEN) < 0)
		return -1;
	addr[0] &= 0xfe; /* unicast */
	addr[0] |= 0x02; /* locally administered */
	return 0;
}


int random_mac_addr_keep_oui(u8 *addr)
{
	if (os_get_random(addr + 3, 3) < 0)
		return -1;
	addr[0] &= 0xfe; /* unicast */
	addr[0] |= 0x02; /* locally administered */
	return 0;
}


/**
 * str_token - Get next token from a string
 * @buf: String to tokenize. Note that the string might be modified.
 * @delim: String of delimiters
 * @context: Pointer to save our context. Should be initialized with
 *	NULL on the first call, and passed for any further call.
 * Returns: The next token, NULL if there are no more valid tokens.
 */
char * str_token(char *str, const char *delim, char **context)
{
	char *end, *pos = str;

	if (*context)
		pos = *context;

	while (*pos && os_strchr(delim, *pos))
		pos++;
	if (!*pos)
		return NULL;

	end = pos + 1;
	while (*end && !os_strchr(delim, *end))
		end++;

	if (*end)
		*end++ = '\0';

	*context = end;
	return pos;
}


size_t utf8_unescape(const char *inp, size_t in_size,
		     char *outp, size_t out_size)
{
	size_t res_size = 0;

	if (!inp || !outp)
		return 0;

	if (!in_size)
		in_size = os_strlen(inp);

	/* Advance past leading single quote */
	if (*inp == '\'' && in_size) {
		inp++;
		in_size--;
	}

	while (in_size--) {
		if (res_size >= out_size)
			return 0;

		switch (*inp) {
		case '\'':
			/* Terminate on bare single quote */
			*outp = '\0';
			return res_size;

		case '\\':
			if (!in_size--)
				return 0;
			inp++;
			/* fall through */

		default:
			*outp++ = *inp++;
			res_size++;
		}
	}

	/* NUL terminate if space allows */
	if (res_size < out_size)
		*outp = '\0';

	return res_size;
}


size_t utf8_escape(const char *inp, size_t in_size,
		   char *outp, size_t out_size)
{
	size_t res_size = 0;

	if (!inp || !outp)
		return 0;

	/* inp may or may not be NUL terminated, but must be if 0 size
	 * is specified */
	if (!in_size)
		in_size = os_strlen(inp);

	while (in_size--) {
		if (res_size++ >= out_size)
			return 0;

		switch (*inp) {
		case '\\':
		case '\'':
			if (res_size++ >= out_size)
				return 0;
			*outp++ = '\\';
			/* fall through */

		default:
			*outp++ = *inp++;
			break;
		}
	}

	/* NUL terminate if space allows */
	if (res_size < out_size)
		*outp = '\0';

	return res_size;
}