/*
   * lib/parser.c - simple parser for mount, etc. options.
   *
   * This source code is licensed under the GNU General Public License,
   * Version 2.  See the file COPYING for more details.
   */
  
  #include <linux/ctype.h>
  #include <linux/module.h>
  #include <linux/parser.h>
  #include <linux/slab.h>
  #include <linux/string.h>
  
  /**
   * match_one: - Determines if a string matches a simple pattern

   * @s: the string to examine for presence of the pattern

   * @p: the string containing the pattern
   * @args: array of %MAX_OPT_ARGS &substring_t elements. Used to return match
   * locations.
   *
   * Description: Determines if the pattern @p is present in string @s. Can only
   * match extremely simple token=arg style patterns. If the pattern is found,
   * the location(s) of the arguments will be returned in the @args array.
   */

  static int match_one(char *s, const char *p, substring_t args[])

  {
  	char *meta;
  	int argc = 0;
  
  	if (!p)
  		return 1;
  
  	while(1) {
  		int len = -1;
  		meta = strchr(p, '%');
  		if (!meta)
  			return strcmp(p, s) == 0;
  
  		if (strncmp(p, s, meta-p))
  			return 0;
  
  		s += meta - p;
  		p = meta + 1;
  
  		if (isdigit(*p))

  			len = simple_strtoul(p, (char **) &p, 10);

  		else if (*p == '%') {
  			if (*s++ != '%')
  				return 0;
  			p++;
  			continue;
  		}
  
  		if (argc >= MAX_OPT_ARGS)
  			return 0;
  
  		args[argc].from = s;
  		switch (*p++) {

  		case 's': {
  			size_t str_len = strlen(s);
  
  			if (str_len == 0)

  				return 0;

  			if (len == -1 || len > str_len)
  				len = str_len;

  			args[argc].to = s + len;
  			break;

  		}

  		case 'd':
  			simple_strtol(s, &args[argc].to, 0);
  			goto num;
  		case 'u':
  			simple_strtoul(s, &args[argc].to, 0);
  			goto num;
  		case 'o':
  			simple_strtoul(s, &args[argc].to, 8);
  			goto num;
  		case 'x':
  			simple_strtoul(s, &args[argc].to, 16);
  		num:
  			if (args[argc].to == args[argc].from)
  				return 0;
  			break;
  		default:
  			return 0;
  		}
  		s = args[argc].to;
  		argc++;
  	}
  }
  
  /**
   * match_token: - Find a token (and optional args) in a string
   * @s: the string to examine for token/argument pairs
   * @table: match_table_t describing the set of allowed option tokens and the
   * arguments that may be associated with them. Must be terminated with a
   * &struct match_token whose pattern is set to the NULL pointer.
   * @args: array of %MAX_OPT_ARGS &substring_t elements. Used to return match
   * locations.
   *
   * Description: Detects which if any of a set of token strings has been passed
   * to it. Tokens can include up to MAX_OPT_ARGS instances of basic c-style
   * format identifiers which will be taken into account when matching the
   * tokens, and whose locations will be returned in the @args array.
   */

  int match_token(char *s, const match_table_t table, substring_t args[])

  {

  	const struct match_token *p;

  
  	for (p = table; !match_one(s, p->pattern, args) ; p++)
  		;
  
  	return p->token;
  }
  
  /**
   * match_number: scan a number in the given base from a substring_t
   * @s: substring to be scanned
   * @result: resulting integer on success
   * @base: base to use when converting string
   *
   * Description: Given a &substring_t and a base, attempts to parse the substring
   * as a number in that base. On success, sets @result to the integer represented
   * by the string and returns 0. Returns either -ENOMEM or -EINVAL on failure.
   */
  static int match_number(substring_t *s, int *result, int base)
  {
  	char *endp;
  	char *buf;
  	int ret;

  	size_t len = s->to - s->from;

  	buf = kmalloc(len + 1, GFP_KERNEL);

  	if (!buf)
  		return -ENOMEM;

  	memcpy(buf, s->from, len);
  	buf[len] = '\0';

  	*result = simple_strtol(buf, &endp, base);
  	ret = 0;
  	if (endp == buf)
  		ret = -EINVAL;
  	kfree(buf);
  	return ret;
  }
  
  /**
   * match_int: - scan a decimal representation of an integer from a substring_t
   * @s: substring_t to be scanned
   * @result: resulting integer on success
   *
   * Description: Attempts to parse the &substring_t @s as a decimal integer. On
   * success, sets @result to the integer represented by the string and returns 0.
   * Returns either -ENOMEM or -EINVAL on failure.
   */
  int match_int(substring_t *s, int *result)
  {
  	return match_number(s, result, 0);
  }
  
  /**
   * match_octal: - scan an octal representation of an integer from a substring_t
   * @s: substring_t to be scanned
   * @result: resulting integer on success
   *
   * Description: Attempts to parse the &substring_t @s as an octal integer. On
   * success, sets @result to the integer represented by the string and returns
   * 0. Returns either -ENOMEM or -EINVAL on failure.
   */
  int match_octal(substring_t *s, int *result)
  {
  	return match_number(s, result, 8);
  }
  
  /**
   * match_hex: - scan a hex representation of an integer from a substring_t
   * @s: substring_t to be scanned
   * @result: resulting integer on success
   *
   * Description: Attempts to parse the &substring_t @s as a hexadecimal integer.
   * On success, sets @result to the integer represented by the string and
   * returns 0. Returns either -ENOMEM or -EINVAL on failure.
   */
  int match_hex(substring_t *s, int *result)
  {
  	return match_number(s, result, 16);
  }
  
  /**

   * match_strlcpy: - Copy the characters from a substring_t to a sized buffer
   * @dest: where to copy to
   * @src: &substring_t to copy
   * @size: size of destination buffer

   *

   * Description: Copy the characters in &substring_t @src to the
   * c-style string @dest.  Copy no more than @size - 1 characters, plus
   * the terminating NUL.  Return length of @src.

   */

  size_t match_strlcpy(char *dest, const substring_t *src, size_t size)

  {

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

  }
  
  /**
   * match_strdup: - allocate a new string with the contents of a substring_t
   * @s: &substring_t to copy
   *
   * Description: Allocates and returns a string filled with the contents of
   * the &substring_t @s. The caller is responsible for freeing the returned
   * string with kfree().
   */

  char *match_strdup(const substring_t *s)

  {

  	size_t sz = s->to - s->from + 1;
  	char *p = kmalloc(sz, GFP_KERNEL);

  	if (p)

  		match_strlcpy(p, s, sz);

  	return p;
  }
  
  EXPORT_SYMBOL(match_token);
  EXPORT_SYMBOL(match_int);
  EXPORT_SYMBOL(match_octal);
  EXPORT_SYMBOL(match_hex);

  EXPORT_SYMBOL(match_strlcpy);

  EXPORT_SYMBOL(match_strdup);