src/utils.c

/*
 * (C) 2011 by Harald Welte <laforge@gnumonks.org>
 * (C) 2011 by Sylvain Munaut <tnt@246tNt.com>
 * (C) 2014 by Nils O. Selåsdal <noselasd@fiane.dyndns.org>
 *
 * All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */


#include <stdbool.h>
#include <string.h>
#include <stdint.h>
#include <errno.h>
#include <stdio.h>
#include <inttypes.h>

#include <osmocom/core/utils.h>
#include <osmocom/core/bit64gen.h>


/*! \addtogroup utils
 * @{
 * various utility routines
 *
 * \file utils.c */

static char namebuf[255];

/*! get human-readable string for given value
 *  \param[in] vs Array of value_string tuples
 *  \param[in] val Value to be converted
 *  \returns pointer to human-readable string
 *
 * If val is found in vs, the array's string entry is returned. Otherwise, an
 * "unknown" string containing the actual value is composed in a static buffer
 * that is reused across invocations.
 */
const char *get_value_string(const struct value_string *vs, uint32_t val)
{
	const char *str = get_value_string_or_null(vs, val);
	if (str)
		return str;

	snprintf(namebuf, sizeof(namebuf), "unknown 0x%"PRIx32, val);
	namebuf[sizeof(namebuf) - 1] = '\0';
	return namebuf;
}

/*! get human-readable string or NULL for given value
 *  \param[in] vs Array of value_string tuples
 *  \param[in] val Value to be converted
 *  \returns pointer to human-readable string or NULL if val is not found
 */
const char *get_value_string_or_null(const struct value_string *vs,
				     uint32_t val)
{
	int i;

	for (i = 0;; i++) {
		if (vs[i].value == 0 && vs[i].str == NULL)
			break;
		if (vs[i].value == val)
			return vs[i].str;
	}

	return NULL;
}

/*! get numeric value for given human-readable string
 *  \param[in] vs Array of value_string tuples
 *  \param[in] str human-readable string
 *  \returns numeric value (>0) or negative numer in case of error
 */
int get_string_value(const struct value_string *vs, const char *str)
{
	int i;

	for (i = 0;; i++) {
		if (vs[i].value == 0 && vs[i].str == NULL)
			break;
		if (!strcasecmp(vs[i].str, str))
			return vs[i].value;
	}
	return -EINVAL;
}

/*! Convert BCD-encoded digit into printable character
 *  \param[in] bcd A single BCD-encoded digit
 *  \returns single printable character
 */
char osmo_bcd2char(uint8_t bcd)
{
	if (bcd < 0xa)
		return '0' + bcd;
	else
		return 'A' + (bcd - 0xa);
}

/*! Convert number in ASCII to BCD value
 *  \param[in] c ASCII character
 *  \returns BCD encoded value of character
 */
uint8_t osmo_char2bcd(char c)
{
	return c - 0x30;
}

/*! Parse a string containing hexadecimal digits
 *  \param[in] str string containing ASCII encoded hexadecimal digits
 *  \param[out] b output buffer
 *  \param[in] max_len maximum space in output buffer
 *  \returns number of parsed octets, or -1 on error
 */
int osmo_hexparse(const char *str, uint8_t *b, int max_len)

{
	char c;
	uint8_t v;
	const char *strpos;
	unsigned int nibblepos = 0;

	memset(b, 0x00, max_len);

	for (strpos = str; (c = *strpos); strpos++) {
		/* skip whitespace */
		if (c == ' ' || c == '\t' || c == '\n' || c == '\r')
			continue;

		/* If the buffer is too small, error out */
		if (nibblepos >= (max_len << 1))
			return -1;

		if (c >= '0' && c <= '9')
			v = c - '0';
		else if (c >= 'a' && c <= 'f')
			v = 10 + (c - 'a');
		else if (c >= 'A' && c <= 'F')
			v = 10 + (c - 'A');
		else
			return -1;

		b[nibblepos >> 1] |= v << (nibblepos & 1 ? 0 : 4);
		nibblepos ++;
	}

	/* In case of uneven amount of digits, the last byte is not complete
	 * and that's an error. */
	if (nibblepos & 1)
		return -1;

	return nibblepos >> 1;
}

static char hexd_buff[4096];
static const char hex_chars[] = "0123456789abcdef";

static char *_osmo_hexdump(const unsigned char *buf, int len, char *delim)
{
	int i;
	char *cur = hexd_buff;

	hexd_buff[0] = 0;
	for (i = 0; i < len; i++) {
		const char *delimp = delim;
		int len_remain = sizeof(hexd_buff) - (cur - hexd_buff);
		if (len_remain < 3)
			break;

		*cur++ = hex_chars[buf[i] >> 4];
		*cur++ = hex_chars[buf[i] & 0xf];

		while (len_remain > 1 && *delimp) {
			*cur++ = *delimp++;
			len_remain--;
		}

		*cur = 0;
	}
	hexd_buff[sizeof(hexd_buff)-1] = 0;
	return hexd_buff;
}

/*! Convert a sequence of unpacked bits to ASCII string
 * \param[in] bits A sequence of unpacked bits
 * \param[in] len Length of bits
 */
char *osmo_ubit_dump(const uint8_t *bits, unsigned int len)
{
	int i;

	if (len > sizeof(hexd_buff)-1)
		len = sizeof(hexd_buff)-1;
	memset(hexd_buff, 0, sizeof(hexd_buff));

	for (i = 0; i < len; i++) {
		char outch;
		switch (bits[i]) {
		case 0:
			outch = '0';
			break;
		case 0xff:
			outch = '?';
			break;
		case 1:
			outch = '1';
			break;
		default:
			outch = 'E';
			break;
		}
		hexd_buff[i] = outch;
	}
	hexd_buff[sizeof(hexd_buff)-1] = 0;
	return hexd_buff;
}

/*! Convert binary sequence to hexadecimal ASCII string
 *  \param[in] buf pointer to sequence of bytes
 *  \param[in] len length of buf in number of bytes
 *  \returns pointer to zero-terminated string
 *
 * This function will print a sequence of bytes as hexadecimal numbers,
 * adding one space character between each byte (e.g. "1a ef d9")
 *
 * The maximum size of the output buffer is 4096 bytes, i.e. the maximum
 * number of input bytes that can be printed in one call is 1365!
 */
char *osmo_hexdump(const unsigned char *buf, int len)
{
	return _osmo_hexdump(buf, len, " ");
}

/*! Convert binary sequence to hexadecimal ASCII string
 *  \param[in] buf pointer to sequence of bytes
 *  \param[in] len length of buf in number of bytes
 *  \returns pointer to zero-terminated string
 *
 * This function will print a sequence of bytes as hexadecimal numbers,
 * without any space character between each byte (e.g. "1aefd9")
 *
 * The maximum size of the output buffer is 4096 bytes, i.e. the maximum
 * number of input bytes that can be printed in one call is 2048!
 */
char *osmo_hexdump_nospc(const unsigned char *buf, int len)
{
	return _osmo_hexdump(buf, len, "");
}

/* Compat with previous typo to preserve abi */
char *osmo_osmo_hexdump_nospc(const unsigned char *buf, int len)
#if defined(__MACH__) && defined(__APPLE__)
	;
#else
	__attribute__((weak, alias("osmo_hexdump_nospc")));
#endif

#include "../config.h"
#ifdef HAVE_CTYPE_H
#include <ctype.h>
/*! Convert an entire string to lower case
 *  \param[out] out output string, caller-allocated
 *  \param[in] in input string
 */
void osmo_str2lower(char *out, const char *in)
{
	unsigned int i;

	for (i = 0; i < strlen(in); i++)
		out[i] = tolower((const unsigned char)in[i]);
	out[strlen(in)] = '\0';
}

/*! Convert an entire string to upper case
 *  \param[out] out output string, caller-allocated
 *  \param[in] in input string
 */
void osmo_str2upper(char *out, const char *in)
{
	unsigned int i;

	for (i = 0; i < strlen(in); i++)
		out[i] = toupper((const unsigned char)in[i]);
	out[strlen(in)] = '\0';
}
#endif /* HAVE_CTYPE_H */

/*! Wishful thinking to generate a constant time compare
 *  \param[in] exp Expected data
 *  \param[in] rel Comparison value
 *  \param[in] count Number of bytes to compare
 *  \returns 1 in case \a exp equals \a rel; zero otherwise
 *
 * Compare count bytes of exp to rel. Return 0 if they are identical, 1
 * otherwise. Do not return a mismatch on the first mismatching byte,
 * but always compare all bytes, regardless. The idea is that the amount of
 * matching bytes cannot be inferred from the time the comparison took. */
int osmo_constant_time_cmp(const uint8_t *exp, const uint8_t *rel, const int count)
{
	int x = 0, i;

	for (i = 0; i < count; ++i)
		x |= exp[i] ^ rel[i];

	/* if x is zero, all data was identical */
	return x? 1 : 0;
}

/*! Generic retrieval of 1..8 bytes as big-endian uint64_t
 *  \param[in] data Input data as byte-array
 *  \param[in] data_len Length of \a data in octets
 *  \returns uint64_t of \a data interpreted as big-endian
 *
 * This is like osmo_load64be_ext, except that if data_len is less than
 * sizeof(uint64_t), the data is interpreted as the least significant bytes
 * (osmo_load64be_ext loads them as the most significant bytes into the
 * returned uint64_t). In this way, any integer size up to 64 bits can be
 * decoded conveniently by using sizeof(), without the need to call specific
 * numbered functions (osmo_load16, 32, ...). */
uint64_t osmo_decode_big_endian(const uint8_t *data, size_t data_len)
{
	uint64_t value = 0;

	while (data_len > 0) {
		value = (value << 8) + *data;
		data += 1;
		data_len -= 1;
	}

	return value;
}

/*! Generic big-endian encoding of big endian number up to 64bit
 *  \param[in] value unsigned integer value to be stored
 *  \param[in] data_len number of octets 
 *  \returns static buffer containing big-endian stored value
 *
 * This is like osmo_store64be_ext, except that this returns a static buffer of
 * the result (for convenience, but not threadsafe). If data_len is less than
 * sizeof(uint64_t), only the least significant bytes of value are encoded. */
uint8_t *osmo_encode_big_endian(uint64_t value, size_t data_len)
{
	static uint8_t buf[sizeof(uint64_t)];
	OSMO_ASSERT(data_len <= ARRAY_SIZE(buf));
	osmo_store64be_ext(value, buf, data_len);
	return buf;
}

/*! Copy a C-string into a sized buffer
 *  \param[in] src source string
 *  \param[out] dst destination string
 *  \param[in] siz size of the \a dst buffer
 *  \returns length of \a src
 *
 * Copy at most \a siz bytes from \a src to \a dst, ensuring that the result is
 * NUL terminated. The NUL character is included in \a siz, i.e. passing the
 * actual sizeof(*dst) is correct.
 */
size_t osmo_strlcpy(char *dst, const char *src, size_t siz)
{
	size_t ret = strlen(src);

	if (siz) {
		size_t len = (ret >= siz) ? siz - 1 : ret;
		memcpy(dst, src, len);
		dst[len] = '\0';
	}
	return ret;
}

/*! Validate that a given string is a hex string within given size limits.
 * Note that each hex digit amounts to a nibble, so if checking for a hex
 * string to result in N bytes, pass amount of digits as 2*N.
 * \param str  A nul-terminated string to validate, or NULL.
 * \param min_digits  least permitted amount of digits.
 * \param max_digits  most permitted amount of digits.
 * \param require_even  if true, require an even amount of digits.
 * \returns true when the hex_str contains only hexadecimal digits (no
 *          whitespace) and matches the requested length; also true
 *          when min_digits <= 0 and str is NULL.
 */
bool osmo_is_hexstr(const char *str, int min_digits, int max_digits,
		    bool require_even)
{
	int len;
	/* Use unsigned char * to avoid a compiler warning of
	 * "error: array subscript has type 'char' [-Werror=char-subscripts]" */
	const unsigned char *pos = (const unsigned char*)str;
	if (!pos)
		return min_digits < 1;
	for (len = 0; *pos && len < max_digits; len++, pos++)
		if (!isxdigit(*pos))
			return false;
	if (len < min_digits)
		return false;
	/* With not too many digits, we should have reached *str == nul */
	if (*pos)
		return false;
	if (require_even && (len & 1))
		return false;

	return true;
}

/*! Determine if a given identifier is valid, i.e. doesn't contain illegal chars
 *  \param[in] str String to validate
 *  \returns true in case string contains valid identifier, false otherwise
 */
bool osmo_identifier_valid(const char *str)
{
	/* characters that are illegal in names */
	static const char illegal_chars[] = "., {}[]()<>|~\\^`'\"?=;/+*&%$#!";
	unsigned int i;

	/* an empty string is not a valid identifier */
	if (!str || strlen(str) == 0)
		return false;

	for (i = 0; i < strlen(str); i++) {
		/* check for 7-bit ASCII */
		if (str[i] & 0x80)
			return false;
		/* check for some explicit reserved control characters */
		if (strchr(illegal_chars, str[i]))
			return false;
	}

	return true;
}

/*! @} */