/*
 *   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_ASTERIK:
                *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 maxlen,
                 const struct nls_table *cp, int mapChars)
{
        int i, j, charlen;
        int len_remaining = maxlen;
        char src_char;
        __u16 temp;

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

        for (i = 0, j = 0; i < maxlen; j++) {
                src_char = source[i];
                switch (src_char) {
                case 0:
                        put_unaligned_le16(0, &target[j]);
                        goto ctoUCS_out;
                case ':':
                        temp = UNI_COLON;
                        break;
                case '*':
                        temp = UNI_ASTERIK;
                        break;
                case '?':
                        temp = UNI_QUESTION;
                        break;
                case '<':
                        temp = UNI_LESSTHAN;
                        break;
                case '>':
                        temp = UNI_GRTRTHAN;
                        break;
                case '|':
                        temp = 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, len_remaining,
                                                &temp);
                        /*
                         * if no match, use question mark, which at least in
                         * some cases serves as wild card
                         */
                        if (charlen < 1) {
                                temp = 0x003f;
                                charlen = 1;
                        }
                        len_remaining -= charlen;
                        /*
                         * character may take more than one byte in the source
                         * string, but will take exactly two bytes in the
                         * target string
                         */
                        i += charlen;
                        continue;
                }
                put_unaligned_le16(temp, &target[j]);
                i++; /* move to next char in source string */
                len_remaining--;
        }

ctoUCS_out:
        return i;
}