/*
   *   fs/cifs/cifs_unicode.c
   *

   *   Copyright (c) International Business Machines  Corp., 2000,2009

   *   Modified by Steve French (sfrench@us.ibm.com)
   *
   *   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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
   */
  #include <linux/fs.h>

  #include <linux/slab.h>

  #include "cifs_unicode.h"
  #include "cifs_uniupr.h"
  #include "cifspdu.h"

  #include "cifsglob.h"

  #include "cifs_debug.h"
  
  /*

   * cifs_ucs2_bytes - how long will a string be after conversion?
   * @ucs - pointer to input string
   * @maxbytes - don't go past this many bytes of input string
   * @codepage - destination codepage
   *
   * Walk a ucs2le string and return the number of bytes that the string will
   * be after being converted to the given charset, not including any null
   * termination required. Don't walk past maxbytes in the source buffer.
   */
  int
  cifs_ucs2_bytes(const __le16 *from, int maxbytes,
  		const struct nls_table *codepage)
  {
  	int i;
  	int charlen, outlen = 0;
  	int maxwords = maxbytes / 2;
  	char tmp[NLS_MAX_CHARSET_SIZE];

  	__u16 ftmp;

  	for (i = 0; i < maxwords; i++) {
  		ftmp = get_unaligned_le16(&from[i]);
  		if (ftmp == 0)
  			break;
  
  		charlen = codepage->uni2char(ftmp, tmp, NLS_MAX_CHARSET_SIZE);

  		if (charlen > 0)
  			outlen += charlen;
  		else
  			outlen++;
  	}
  
  	return outlen;
  }
  
  /*

   * cifs_mapchar - convert a host-endian char to proper char in codepage

   * @target - where converted character should be copied

   * @src_char - 2 byte host-endian source character

   * @cp - codepage to which character should be converted
   * @mapchar - should character be mapped according to mapchars mount option?
   *
   * This function handles the conversion of a single character. It is the
   * responsibility of the caller to ensure that the target buffer is large
   * enough to hold the result of the conversion (at least NLS_MAX_CHARSET_SIZE).
   */
  static int

  cifs_mapchar(char *target, const __u16 src_char, const struct nls_table *cp,

  	     bool mapchar)
  {
  	int len = 1;
  
  	if (!mapchar)
  		goto cp_convert;
  
  	/*
  	 * BB: Cannot handle remapping UNI_SLASH until all the calls to
  	 *     build_path_from_dentry are modified, as they use slash as
  	 *     separator.
  	 */

  	switch (src_char) {

  	case UNI_COLON:
  		*target = ':';
  		break;

  	case UNI_ASTERISK:

  		*target = '*';
  		break;
  	case UNI_QUESTION:
  		*target = '?';
  		break;
  	case UNI_PIPE:
  		*target = '|';
  		break;
  	case UNI_GRTRTHAN:
  		*target = '>';
  		break;
  	case UNI_LESSTHAN:
  		*target = '<';
  		break;
  	default:
  		goto cp_convert;
  	}
  
  out:
  	return len;
  
  cp_convert:

  	len = cp->uni2char(src_char, target, NLS_MAX_CHARSET_SIZE);

  	if (len <= 0) {
  		*target = '?';
  		len = 1;
  	}
  	goto out;
  }
  
  /*
   * cifs_from_ucs2 - convert utf16le string to local charset
   * @to - destination buffer
   * @from - source buffer
   * @tolen - destination buffer size (in bytes)
   * @fromlen - source buffer size (in bytes)
   * @codepage - codepage to which characters should be converted
   * @mapchar - should characters be remapped according to the mapchars option?
   *
   * Convert a little-endian ucs2le string (as sent by the server) to a string
   * in the provided codepage. The tolen and fromlen parameters are to ensure
   * that the code doesn't walk off of the end of the buffer (which is always
   * a danger if the alignment of the source buffer is off). The destination
   * string is always properly null terminated and fits in the destination
   * buffer. Returns the length of the destination string in bytes (including
   * null terminator).
   *
   * Note that some windows versions actually send multiword UTF-16 characters
   * instead of straight UCS-2. The linux nls routines however aren't able to
   * deal with those characters properly. In the event that we get some of
   * those characters, they won't be translated properly.
   */
  int
  cifs_from_ucs2(char *to, const __le16 *from, int tolen, int fromlen,
  		 const struct nls_table *codepage, bool mapchar)
  {
  	int i, charlen, safelen;
  	int outlen = 0;
  	int nullsize = nls_nullsize(codepage);
  	int fromwords = fromlen / 2;
  	char tmp[NLS_MAX_CHARSET_SIZE];

  	__u16 ftmp;

  
  	/*
  	 * because the chars can be of varying widths, we need to take care
  	 * not to overflow the destination buffer when we get close to the
  	 * end of it. Until we get to this offset, we don't need to check
  	 * for overflow however.
  	 */
  	safelen = tolen - (NLS_MAX_CHARSET_SIZE + nullsize);

  	for (i = 0; i < fromwords; i++) {
  		ftmp = get_unaligned_le16(&from[i]);
  		if (ftmp == 0)
  			break;

  		/*
  		 * check to see if converting this character might make the
  		 * conversion bleed into the null terminator
  		 */
  		if (outlen >= safelen) {

  			charlen = cifs_mapchar(tmp, ftmp, codepage, mapchar);

  			if ((outlen + charlen) > (tolen - nullsize))
  				break;
  		}
  
  		/* put converted char into 'to' buffer */

  		charlen = cifs_mapchar(&to[outlen], ftmp, codepage, mapchar);

  		outlen += charlen;
  	}
  
  	/* properly null-terminate string */
  	for (i = 0; i < nullsize; i++)
  		to[outlen++] = 0;
  
  	return outlen;
  }
  
  /*

   * NAME:	cifs_strtoUCS()
   *
   * FUNCTION:	Convert character string to unicode string
   *
   */
  int

  cifs_strtoUCS(__le16 *to, const char *from, int len,

  	      const struct nls_table *codepage)
  {
  	int charlen;
  	int i;

  	wchar_t wchar_to; /* needed to quiet sparse */

  
  	for (i = 0; len && *from; i++, from += charlen, len -= charlen) {

  		charlen = codepage->char2uni(from, len, &wchar_to);

  		if (charlen < 1) {

  			cERROR(1, "strtoUCS: char2uni of 0x%x returned %d",
  				*from, charlen);

  			/* A question mark */

  			wchar_to = 0x003f;

  			charlen = 1;

  		}
  		put_unaligned_le16(wchar_to, &to[i]);

  	}

  	put_unaligned_le16(0, &to[i]);

  	return i;
  }

  /*

   * cifs_strndup_from_ucs - copy a string from wire format to the local codepage

   * @src - source string
   * @maxlen - don't walk past this many bytes in the source string
   * @is_unicode - is this a unicode string?
   * @codepage - destination codepage
   *
   * Take a string given by the server, convert it to the local codepage and
   * put it in a new buffer. Returns a pointer to the new string or NULL on
   * error.
   */
  char *

  cifs_strndup_from_ucs(const char *src, const int maxlen, const bool is_unicode,

  	     const struct nls_table *codepage)
  {
  	int len;
  	char *dst;
  
  	if (is_unicode) {
  		len = cifs_ucs2_bytes((__le16 *) src, maxlen, codepage);
  		len += nls_nullsize(codepage);
  		dst = kmalloc(len, GFP_KERNEL);
  		if (!dst)
  			return NULL;
  		cifs_from_ucs2(dst, (__le16 *) src, len, maxlen, codepage,
  			       false);
  	} else {
  		len = strnlen(src, maxlen);
  		len++;
  		dst = kmalloc(len, GFP_KERNEL);
  		if (!dst)
  			return NULL;
  		strlcpy(dst, src, len);
  	}
  
  	return dst;
  }

  /*
   * Convert 16 bit Unicode pathname to wire format from string in current code
   * page. Conversion may involve remapping up the six characters that are
   * only legal in POSIX-like OS (if they are present in the string). Path
   * names are little endian 16 bit Unicode on the wire
   */
  int

  cifsConvertToUCS(__le16 *target, const char *source, int srclen,

  		 const struct nls_table *cp, int mapChars)
  {
  	int i, j, charlen;

  	char src_char;

  	__le16 dst_char;
  	wchar_t tmp;

  
  	if (!mapChars)
  		return cifs_strtoUCS(target, source, PATH_MAX, cp);

  	for (i = 0, j = 0; i < srclen; j++) {

  		src_char = source[i];

  		charlen = 1;

  		switch (src_char) {
  		case 0:

  			put_unaligned(0, &target[j]);

  			goto ctoUCS_out;
  		case ':':

  			dst_char = cpu_to_le16(UNI_COLON);

  			break;
  		case '*':

  			dst_char = cpu_to_le16(UNI_ASTERISK);

  			break;
  		case '?':

  			dst_char = cpu_to_le16(UNI_QUESTION);

  			break;
  		case '<':

  			dst_char = cpu_to_le16(UNI_LESSTHAN);

  			break;
  		case '>':

  			dst_char = cpu_to_le16(UNI_GRTRTHAN);

  			break;
  		case '|':

  			dst_char = cpu_to_le16(UNI_PIPE);

  			break;
  		/*
  		 * FIXME: We can not handle remapping backslash (UNI_SLASH)
  		 * until all the calls to build_path_from_dentry are modified,
  		 * as they use backslash as separator.
  		 */
  		default:

  			charlen = cp->char2uni(source + i, srclen - i, &tmp);
  			dst_char = cpu_to_le16(tmp);

  			/*
  			 * if no match, use question mark, which at least in
  			 * some cases serves as wild card
  			 */
  			if (charlen < 1) {

  				dst_char = cpu_to_le16(0x003f);

  				charlen = 1;
  			}

  		}

  		/*
  		 * character may take more than one byte in the source string,
  		 * but will take exactly two bytes in the target string
  		 */
  		i += charlen;

  		put_unaligned(dst_char, &target[j]);

  	}
  
  ctoUCS_out:
  	return i;
  }