wchar.c

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/*
 * conversion functions between pg_wchar and multibyte streams.
 * Tatsuo Ishii
 * src/backend/utils/mb/wchar.c
 *
 */
/* can be used in either frontend or backend */
#ifdef FRONTEND
#include "postgres_fe.h"
#else
#include "postgres.h"
#endif

#include "mb/pg_wchar.h"


/*
 * conversion to pg_wchar is done by "table driven."
 * to add an encoding support, define mb2wchar_with_len(), mblen(), dsplen()
 * for the particular encoding. Note that if the encoding is only
 * supported in the client, you don't need to define
 * mb2wchar_with_len() function (SJIS is the case).
 *
 * These functions generally assume that their input is validly formed.
 * The "verifier" functions, further down in the file, have to be more
 * paranoid.  We expect that mblen() does not need to examine more than
 * the first byte of the character to discover the correct length.
 *
 * Note: for the display output of psql to work properly, the return values
 * of the dsplen functions must conform to the Unicode standard. In particular
 * the NUL character is zero width and control characters are generally
 * width -1. It is recommended that non-ASCII encodings refer their ASCII
 * subset to the ASCII routines to ensure consistency.
 */

/*
 * SQL/ASCII
 */
static int
pg_ascii2wchar_with_len(const unsigned char *from, pg_wchar *to, int len)
{
    int         cnt = 0;

    while (len > 0 && *from)
    {
        *to++ = *from++;
        len--;
        cnt++;
    }
    *to = 0;
    return cnt;
}

static int
pg_ascii_mblen(const unsigned char *s)
{
    return 1;
}

static int
pg_ascii_dsplen(const unsigned char *s)
{
    if (*s == '\0')
        return 0;
    if (*s < 0x20 || *s == 0x7f)
        return -1;

    return 1;
}

/*
 * EUC
 */
static int
pg_euc2wchar_with_len(const unsigned char *from, pg_wchar *to, int len)
{
    int         cnt = 0;

    while (len > 0 && *from)
    {
        if (*from == SS2 && len >= 2)   /* JIS X 0201 (so called "1 byte
                                         * KANA") */
        {
            from++;
            *to = (SS2 << 8) | *from++;
            len -= 2;
        }
        else if (*from == SS3 && len >= 3)      /* JIS X 0212 KANJI */
        {
            from++;
            *to = (SS3 << 16) | (*from++ << 8);
            *to |= *from++;
            len -= 3;
        }
        else if (IS_HIGHBIT_SET(*from) && len >= 2)     /* JIS X 0208 KANJI */
        {
            *to = *from++ << 8;
            *to |= *from++;
            len -= 2;
        }
        else                            /* must be ASCII */
        {
            *to = *from++;
            len--;
        }
        to++;
        cnt++;
    }
    *to = 0;
    return cnt;
}

static inline int
pg_euc_mblen(const unsigned char *s)
{
    int         len;

    if (*s == SS2)
        len = 2;
    else if (*s == SS3)
        len = 3;
    else if (IS_HIGHBIT_SET(*s))
        len = 2;
    else
        len = 1;
    return len;
}

static inline int
pg_euc_dsplen(const unsigned char *s)
{
    int         len;

    if (*s == SS2)
        len = 2;
    else if (*s == SS3)
        len = 2;
    else if (IS_HIGHBIT_SET(*s))
        len = 2;
    else
        len = pg_ascii_dsplen(s);
    return len;
}

/*
 * EUC_JP
 */
static int
pg_eucjp2wchar_with_len(const unsigned char *from, pg_wchar *to, int len)
{
    return pg_euc2wchar_with_len(from, to, len);
}

static int
pg_eucjp_mblen(const unsigned char *s)
{
    return pg_euc_mblen(s);
}

static int
pg_eucjp_dsplen(const unsigned char *s)
{
    int         len;

    if (*s == SS2)
        len = 1;
    else if (*s == SS3)
        len = 2;
    else if (IS_HIGHBIT_SET(*s))
        len = 2;
    else
        len = pg_ascii_dsplen(s);
    return len;
}

/*
 * EUC_KR
 */
static int
pg_euckr2wchar_with_len(const unsigned char *from, pg_wchar *to, int len)
{
    return pg_euc2wchar_with_len(from, to, len);
}

static int
pg_euckr_mblen(const unsigned char *s)
{
    return pg_euc_mblen(s);
}

static int
pg_euckr_dsplen(const unsigned char *s)
{
    return pg_euc_dsplen(s);
}

/*
 * EUC_CN
 *
 */
static int
pg_euccn2wchar_with_len(const unsigned char *from, pg_wchar *to, int len)
{
    int         cnt = 0;

    while (len > 0 && *from)
    {
        if (*from == SS2 && len >= 3)   /* code set 2 (unused?) */
        {
            from++;
            *to = (SS2 << 16) | (*from++ << 8);
            *to |= *from++;
            len -= 3;
        }
        else if (*from == SS3 && len >= 3)      /* code set 3 (unused ?) */
        {
            from++;
            *to = (SS3 << 16) | (*from++ << 8);
            *to |= *from++;
            len -= 3;
        }
        else if (IS_HIGHBIT_SET(*from) && len >= 2)     /* code set 1 */
        {
            *to = *from++ << 8;
            *to |= *from++;
            len -= 2;
        }
        else
        {
            *to = *from++;
            len--;
        }
        to++;
        cnt++;
    }
    *to = 0;
    return cnt;
}

static int
pg_euccn_mblen(const unsigned char *s)
{
    int         len;

    if (IS_HIGHBIT_SET(*s))
        len = 2;
    else
        len = 1;
    return len;
}

static int
pg_euccn_dsplen(const unsigned char *s)
{
    int         len;

    if (IS_HIGHBIT_SET(*s))
        len = 2;
    else
        len = pg_ascii_dsplen(s);
    return len;
}

/*
 * EUC_TW
 *
 */
static int
pg_euctw2wchar_with_len(const unsigned char *from, pg_wchar *to, int len)
{
    int         cnt = 0;

    while (len > 0 && *from)
    {
        if (*from == SS2 && len >= 4)   /* code set 2 */
        {
            from++;
            *to = (((uint32) SS2) << 24) | (*from++ << 16);
            *to |= *from++ << 8;
            *to |= *from++;
            len -= 4;
        }
        else if (*from == SS3 && len >= 3)      /* code set 3 (unused?) */
        {
            from++;
            *to = (SS3 << 16) | (*from++ << 8);
            *to |= *from++;
            len -= 3;
        }
        else if (IS_HIGHBIT_SET(*from) && len >= 2)     /* code set 2 */
        {
            *to = *from++ << 8;
            *to |= *from++;
            len -= 2;
        }
        else
        {
            *to = *from++;
            len--;
        }
        to++;
        cnt++;
    }
    *to = 0;
    return cnt;
}

static int
pg_euctw_mblen(const unsigned char *s)
{
    int         len;

    if (*s == SS2)
        len = 4;
    else if (*s == SS3)
        len = 3;
    else if (IS_HIGHBIT_SET(*s))
        len = 2;
    else
        len = 1;
    return len;
}

static int
pg_euctw_dsplen(const unsigned char *s)
{
    int         len;

    if (*s == SS2)
        len = 2;
    else if (*s == SS3)
        len = 2;
    else if (IS_HIGHBIT_SET(*s))
        len = 2;
    else
        len = pg_ascii_dsplen(s);
    return len;
}

/*
 * Convert pg_wchar to EUC_* encoding.
 * caller must allocate enough space for "to", including a trailing zero!
 * len: length of from.
 * "from" not necessarily null terminated.
 */
static int
pg_wchar2euc_with_len(const pg_wchar *from, unsigned char *to, int len)
{
    int         cnt = 0;

    while (len > 0 && *from)
    {
        unsigned char c;

        if ((c = (*from >> 24)))
        {
            *to++ = c;
            *to++ = (*from >> 16) & 0xff;
            *to++ = (*from >> 8) & 0xff;
            *to++ = *from & 0xff;
            cnt += 4;
        }
        else if ((c = (*from >> 16)))
        {
            *to++ = c;
            *to++ = (*from >> 8) & 0xff;
            *to++ = *from & 0xff;
            cnt += 3;
        }
        else if ((c = (*from >> 8)))
        {
            *to++ = c;
            *to++ = *from & 0xff;
            cnt += 2;
        }
        else
        {
            *to++ = *from;
            cnt++;
        }
        from++;
        len--;
    }
    *to = 0;
    return cnt;
}


/*
 * JOHAB
 */
static int
pg_johab_mblen(const unsigned char *s)
{
    return pg_euc_mblen(s);
}

static int
pg_johab_dsplen(const unsigned char *s)
{
    return pg_euc_dsplen(s);
}

/*
 * convert UTF8 string to pg_wchar (UCS-4)
 * caller must allocate enough space for "to", including a trailing zero!
 * len: length of from.
 * "from" not necessarily null terminated.
 */
static int
pg_utf2wchar_with_len(const unsigned char *from, pg_wchar *to, int len)
{
    int         cnt = 0;
    uint32      c1,
                c2,
                c3,
                c4;

    while (len > 0 && *from)
    {
        if ((*from & 0x80) == 0)
        {
            *to = *from++;
            len--;
        }
        else if ((*from & 0xe0) == 0xc0)
        {
            if (len < 2)
                break;          /* drop trailing incomplete char */
            c1 = *from++ & 0x1f;
            c2 = *from++ & 0x3f;
            *to = (c1 << 6) | c2;
            len -= 2;
        }
        else if ((*from & 0xf0) == 0xe0)
        {
            if (len < 3)
                break;          /* drop trailing incomplete char */
            c1 = *from++ & 0x0f;
            c2 = *from++ & 0x3f;
            c3 = *from++ & 0x3f;
            *to = (c1 << 12) | (c2 << 6) | c3;
            len -= 3;
        }
        else if ((*from & 0xf8) == 0xf0)
        {
            if (len < 4)
                break;          /* drop trailing incomplete char */
            c1 = *from++ & 0x07;
            c2 = *from++ & 0x3f;
            c3 = *from++ & 0x3f;
            c4 = *from++ & 0x3f;
            *to = (c1 << 18) | (c2 << 12) | (c3 << 6) | c4;
            len -= 4;
        }
        else
        {
            /* treat a bogus char as length 1; not ours to raise error */
            *to = *from++;
            len--;
        }
        to++;
        cnt++;
    }
    *to = 0;
    return cnt;
}


/*
 * Map a Unicode code point to UTF-8.  utf8string must have 4 bytes of
 * space allocated.
 */
unsigned char *
unicode_to_utf8(pg_wchar c, unsigned char *utf8string)
{
    if (c <= 0x7F)
    {
        utf8string[0] = c;
    }
    else if (c <= 0x7FF)
    {
        utf8string[0] = 0xC0 | ((c >> 6) & 0x1F);
        utf8string[1] = 0x80 | (c & 0x3F);
    }
    else if (c <= 0xFFFF)
    {
        utf8string[0] = 0xE0 | ((c >> 12) & 0x0F);
        utf8string[1] = 0x80 | ((c >> 6) & 0x3F);
        utf8string[2] = 0x80 | (c & 0x3F);
    }
    else
    {
        utf8string[0] = 0xF0 | ((c >> 18) & 0x07);
        utf8string[1] = 0x80 | ((c >> 12) & 0x3F);
        utf8string[2] = 0x80 | ((c >> 6) & 0x3F);
        utf8string[3] = 0x80 | (c & 0x3F);
    }

    return utf8string;
}

/*
 * Trivial conversion from pg_wchar to UTF-8.
 * caller should allocate enough space for "to"
 * len: length of from.
 * "from" not necessarily null terminated.
 */
static int
pg_wchar2utf_with_len(const pg_wchar *from, unsigned char *to, int len)
{
    int         cnt = 0;

    while (len > 0 && *from)
    {
        int char_len;

        unicode_to_utf8(*from, to);
        char_len = pg_utf_mblen(to);
        cnt += char_len;
        to += char_len;
        from++;
        len--;
    }
    *to = 0;
    return cnt;
}

/*
 * Return the byte length of a UTF8 character pointed to by s
 *
 * Note: in the current implementation we do not support UTF8 sequences
 * of more than 4 bytes; hence do NOT return a value larger than 4.
 * We return "1" for any leading byte that is either flat-out illegal or
 * indicates a length larger than we support.
 *
 * pg_utf2wchar_with_len(), utf8_to_unicode(), pg_utf8_islegal(), and perhaps
 * other places would need to be fixed to change this.
 */
int
pg_utf_mblen(const unsigned char *s)
{
    int         len;

    if ((*s & 0x80) == 0)
        len = 1;
    else if ((*s & 0xe0) == 0xc0)
        len = 2;
    else if ((*s & 0xf0) == 0xe0)
        len = 3;
    else if ((*s & 0xf8) == 0xf0)
        len = 4;
#ifdef NOT_USED
    else if ((*s & 0xfc) == 0xf8)
        len = 5;
    else if ((*s & 0xfe) == 0xfc)
        len = 6;
#endif
    else
        len = 1;
    return len;
}

/*
 * This is an implementation of wcwidth() and wcswidth() as defined in
 * "The Single UNIX Specification, Version 2, The Open Group, 1997"
 * <http://www.UNIX-systems.org/online.html>
 *
 * Markus Kuhn -- 2001-09-08 -- public domain
 *
 * customised for PostgreSQL
 *
 * original available at : http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
 */

struct mbinterval
{
    unsigned short first;
    unsigned short last;
};

/* auxiliary function for binary search in interval table */
static int
mbbisearch(pg_wchar ucs, const struct mbinterval * table, int max)
{
    int         min = 0;
    int         mid;

    if (ucs < table[0].first || ucs > table[max].last)
        return 0;
    while (max >= min)
    {
        mid = (min + max) / 2;
        if (ucs > table[mid].last)
            min = mid + 1;
        else if (ucs < table[mid].first)
            max = mid - 1;
        else
            return 1;
    }

    return 0;
}


/* The following functions define the column width of an ISO 10646
 * character as follows:
 *
 *    - The null character (U+0000) has a column width of 0.
 *
 *    - Other C0/C1 control characters and DEL will lead to a return
 *      value of -1.
 *
 *    - Non-spacing and enclosing combining characters (general
 *      category code Mn or Me in the Unicode database) have a
 *      column width of 0.
 *
 *    - Other format characters (general category code Cf in the Unicode
 *      database) and ZERO WIDTH SPACE (U+200B) have a column width of 0.
 *
 *    - Hangul Jamo medial vowels and final consonants (U+1160-U+11FF)
 *      have a column width of 0.
 *
 *    - Spacing characters in the East Asian Wide (W) or East Asian
 *      FullWidth (F) category as defined in Unicode Technical
 *      Report #11 have a column width of 2.
 *
 *    - All remaining characters (including all printable
 *      ISO 8859-1 and WGL4 characters, Unicode control characters,
 *      etc.) have a column width of 1.
 *
 * This implementation assumes that wchar_t characters are encoded
 * in ISO 10646.
 */

static int
ucs_wcwidth(pg_wchar ucs)
{
    /* sorted list of non-overlapping intervals of non-spacing characters */
    static const struct mbinterval combining[] = {
        {0x0300, 0x034E}, {0x0360, 0x0362}, {0x0483, 0x0486},
        {0x0488, 0x0489}, {0x0591, 0x05A1}, {0x05A3, 0x05B9},
        {0x05BB, 0x05BD}, {0x05BF, 0x05BF}, {0x05C1, 0x05C2},
        {0x05C4, 0x05C4}, {0x064B, 0x0655}, {0x0670, 0x0670},
        {0x06D6, 0x06E4}, {0x06E7, 0x06E8}, {0x06EA, 0x06ED},
        {0x070F, 0x070F}, {0x0711, 0x0711}, {0x0730, 0x074A},
        {0x07A6, 0x07B0}, {0x0901, 0x0902}, {0x093C, 0x093C},
        {0x0941, 0x0948}, {0x094D, 0x094D}, {0x0951, 0x0954},
        {0x0962, 0x0963}, {0x0981, 0x0981}, {0x09BC, 0x09BC},
        {0x09C1, 0x09C4}, {0x09CD, 0x09CD}, {0x09E2, 0x09E3},
        {0x0A02, 0x0A02}, {0x0A3C, 0x0A3C}, {0x0A41, 0x0A42},
        {0x0A47, 0x0A48}, {0x0A4B, 0x0A4D}, {0x0A70, 0x0A71},
        {0x0A81, 0x0A82}, {0x0ABC, 0x0ABC}, {0x0AC1, 0x0AC5},
        {0x0AC7, 0x0AC8}, {0x0ACD, 0x0ACD}, {0x0B01, 0x0B01},
        {0x0B3C, 0x0B3C}, {0x0B3F, 0x0B3F}, {0x0B41, 0x0B43},
        {0x0B4D, 0x0B4D}, {0x0B56, 0x0B56}, {0x0B82, 0x0B82},
        {0x0BC0, 0x0BC0}, {0x0BCD, 0x0BCD}, {0x0C3E, 0x0C40},
        {0x0C46, 0x0C48}, {0x0C4A, 0x0C4D}, {0x0C55, 0x0C56},
        {0x0CBF, 0x0CBF}, {0x0CC6, 0x0CC6}, {0x0CCC, 0x0CCD},
        {0x0D41, 0x0D43}, {0x0D4D, 0x0D4D}, {0x0DCA, 0x0DCA},
        {0x0DD2, 0x0DD4}, {0x0DD6, 0x0DD6}, {0x0E31, 0x0E31},
        {0x0E34, 0x0E3A}, {0x0E47, 0x0E4E}, {0x0EB1, 0x0EB1},
        {0x0EB4, 0x0EB9}, {0x0EBB, 0x0EBC}, {0x0EC8, 0x0ECD},
        {0x0F18, 0x0F19}, {0x0F35, 0x0F35}, {0x0F37, 0x0F37},
        {0x0F39, 0x0F39}, {0x0F71, 0x0F7E}, {0x0F80, 0x0F84},
        {0x0F86, 0x0F87}, {0x0F90, 0x0F97}, {0x0F99, 0x0FBC},
        {0x0FC6, 0x0FC6}, {0x102D, 0x1030}, {0x1032, 0x1032},
        {0x1036, 0x1037}, {0x1039, 0x1039}, {0x1058, 0x1059},
        {0x1160, 0x11FF}, {0x17B7, 0x17BD}, {0x17C6, 0x17C6},
        {0x17C9, 0x17D3}, {0x180B, 0x180E}, {0x18A9, 0x18A9},
        {0x200B, 0x200F}, {0x202A, 0x202E}, {0x206A, 0x206F},
        {0x20D0, 0x20E3}, {0x302A, 0x302F}, {0x3099, 0x309A},
        {0xFB1E, 0xFB1E}, {0xFE20, 0xFE23}, {0xFEFF, 0xFEFF},
        {0xFFF9, 0xFFFB}
    };

    /* test for 8-bit control characters */
    if (ucs == 0)
        return 0;

    if (ucs < 0x20 || (ucs >= 0x7f && ucs < 0xa0) || ucs > 0x0010ffff)
        return -1;

    /* binary search in table of non-spacing characters */
    if (mbbisearch(ucs, combining,
                   sizeof(combining) / sizeof(struct mbinterval) - 1))
        return 0;

    /*
     * if we arrive here, ucs is not a combining or C0/C1 control character
     */

    return 1 +
        (ucs >= 0x1100 &&
         (ucs <= 0x115f ||      /* Hangul Jamo init. consonants */
          (ucs >= 0x2e80 && ucs <= 0xa4cf && (ucs & ~0x0011) != 0x300a &&
           ucs != 0x303f) ||    /* CJK ... Yi */
          (ucs >= 0xac00 && ucs <= 0xd7a3) ||   /* Hangul Syllables */
          (ucs >= 0xf900 && ucs <= 0xfaff) ||   /* CJK Compatibility
                                                 * Ideographs */
          (ucs >= 0xfe30 && ucs <= 0xfe6f) ||   /* CJK Compatibility Forms */
          (ucs >= 0xff00 && ucs <= 0xff5f) ||   /* Fullwidth Forms */
          (ucs >= 0xffe0 && ucs <= 0xffe6) ||
          (ucs >= 0x20000 && ucs <= 0x2ffff)));
}

/*
 * Convert a UTF-8 character to a Unicode code point.
 * This is a one-character version of pg_utf2wchar_with_len.
 *
 * No error checks here, c must point to a long-enough string.
 */
pg_wchar
utf8_to_unicode(const unsigned char *c)
{
    if ((*c & 0x80) == 0)
        return (pg_wchar) c[0];
    else if ((*c & 0xe0) == 0xc0)
        return (pg_wchar) (((c[0] & 0x1f) << 6) |
                           (c[1] & 0x3f));
    else if ((*c & 0xf0) == 0xe0)
        return (pg_wchar) (((c[0] & 0x0f) << 12) |
                           ((c[1] & 0x3f) << 6) |
                           (c[2] & 0x3f));
    else if ((*c & 0xf8) == 0xf0)
        return (pg_wchar) (((c[0] & 0x07) << 18) |
                           ((c[1] & 0x3f) << 12) |
                           ((c[2] & 0x3f) << 6) |
                           (c[3] & 0x3f));
    else
        /* that is an invalid code on purpose */
        return 0xffffffff;
}

static int
pg_utf_dsplen(const unsigned char *s)
{
    return ucs_wcwidth(utf8_to_unicode(s));
}

/*
 * convert mule internal code to pg_wchar
 * caller should allocate enough space for "to"
 * len: length of from.
 * "from" not necessarily null terminated.
 */
static int
pg_mule2wchar_with_len(const unsigned char *from, pg_wchar *to, int len)
{
    int         cnt = 0;

    while (len > 0 && *from)
    {
        if (IS_LC1(*from) && len >= 2)
        {
            *to = *from++ << 16;
            *to |= *from++;
            len -= 2;
        }
        else if (IS_LCPRV1(*from) && len >= 3)
        {
            from++;
            *to = *from++ << 16;
            *to |= *from++;
            len -= 3;
        }
        else if (IS_LC2(*from) && len >= 3)
        {
            *to = *from++ << 16;
            *to |= *from++ << 8;
            *to |= *from++;
            len -= 3;
        }
        else if (IS_LCPRV2(*from) && len >= 4)
        {
            from++;
            *to = *from++ << 16;
            *to |= *from++ << 8;
            *to |= *from++;
            len -= 4;
        }
        else
        {                       /* assume ASCII */
            *to = (unsigned char) *from++;
            len--;
        }
        to++;
        cnt++;
    }
    *to = 0;
    return cnt;
}

/*
 * convert pg_wchar to mule internal code
 * caller should allocate enough space for "to"
 * len: length of from.
 * "from" not necessarily null terminated.
 */
static int
pg_wchar2mule_with_len(const pg_wchar *from, unsigned char *to, int len)
{
    int         cnt = 0;

    while (len > 0 && *from)
    {
        unsigned char lb;

        lb = (*from >> 16) & 0xff;
        if (IS_LC1(lb))
        {
            *to++ = lb;
            *to++ = *from & 0xff;
            cnt += 2;
        }
        else if (IS_LC2(lb))
        {
            *to++ = lb;
            *to++ = (*from >> 8) & 0xff;
            *to++ = *from & 0xff;
            cnt += 3;
        }
        else if (IS_LCPRV1_A_RANGE(lb))
        {
            *to++ = LCPRV1_A;
            *to++ = lb;
            *to++ = *from & 0xff;
            cnt += 3;
        }
        else if (IS_LCPRV1_B_RANGE(lb))
        {
            *to++ = LCPRV1_B;
            *to++ = lb;
            *to++ = *from & 0xff;
            cnt += 3;
        }
        else if (IS_LCPRV2_A_RANGE(lb))
        {
            *to++ = LCPRV2_A;
            *to++ = lb;
            *to++ = (*from >> 8) & 0xff;
            *to++ = *from & 0xff;
            cnt += 4;
        }
        else if (IS_LCPRV2_B_RANGE(lb))
        {
            *to++ = LCPRV2_B;
            *to++ = lb;
            *to++ = (*from >> 8) & 0xff;
            *to++ = *from & 0xff;
            cnt += 4;
        }
        else
        {
            *to++ = *from & 0xff;
            cnt += 1;
        }
        from++;
        len--;
    }
    *to = 0;
    return cnt;
}

int
pg_mule_mblen(const unsigned char *s)
{
    int         len;

    if (IS_LC1(*s))
        len = 2;
    else if (IS_LCPRV1(*s))
        len = 3;
    else if (IS_LC2(*s))
        len = 3;
    else if (IS_LCPRV2(*s))
        len = 4;
    else
        len = 1;                /* assume ASCII */
    return len;
}

static int
pg_mule_dsplen(const unsigned char *s)
{
    int         len;

    /*
     * Note: it's not really appropriate to assume that all multibyte charsets
     * are double-wide on screen.  But this seems an okay approximation for
     * the MULE charsets we currently support.
     */

    if (IS_LC1(*s))
        len = 1;
    else if (IS_LCPRV1(*s))
        len = 1;
    else if (IS_LC2(*s))
        len = 2;
    else if (IS_LCPRV2(*s))
        len = 2;
    else
        len = 1;                /* assume ASCII */

    return len;
}

/*
 * ISO8859-1
 */
static int
pg_latin12wchar_with_len(const unsigned char *from, pg_wchar *to, int len)
{
    int         cnt = 0;

    while (len > 0 && *from)
    {
        *to++ = *from++;
        len--;
        cnt++;
    }
    *to = 0;
    return cnt;
}

/*
 * Trivial conversion from pg_wchar to single byte encoding. Just ignores
 * high bits.
 * caller should allocate enough space for "to"
 * len: length of from.
 * "from" not necessarily null terminated.
 */
static int
pg_wchar2single_with_len(const pg_wchar *from, unsigned char *to, int len)
{
    int         cnt = 0;

    while (len > 0 && *from)
    {
        *to++ = *from++;
        len--;
        cnt++;
    }
    *to = 0;
    return cnt;
}

static int
pg_latin1_mblen(const unsigned char *s)
{
    return 1;
}

static int
pg_latin1_dsplen(const unsigned char *s)
{
    return pg_ascii_dsplen(s);
}

/*
 * SJIS
 */
static int
pg_sjis_mblen(const unsigned char *s)
{
    int         len;

    if (*s >= 0xa1 && *s <= 0xdf)
        len = 1;                /* 1 byte kana? */
    else if (IS_HIGHBIT_SET(*s))
        len = 2;                /* kanji? */
    else
        len = 1;                /* should be ASCII */
    return len;
}

static int
pg_sjis_dsplen(const unsigned char *s)
{
    int         len;

    if (*s >= 0xa1 && *s <= 0xdf)
        len = 1;                /* 1 byte kana? */
    else if (IS_HIGHBIT_SET(*s))
        len = 2;                /* kanji? */
    else
        len = pg_ascii_dsplen(s);       /* should be ASCII */
    return len;
}

/*
 * Big5
 */
static int
pg_big5_mblen(const unsigned char *s)
{
    int         len;

    if (IS_HIGHBIT_SET(*s))
        len = 2;                /* kanji? */
    else
        len = 1;                /* should be ASCII */
    return len;
}

static int
pg_big5_dsplen(const unsigned char *s)
{
    int         len;

    if (IS_HIGHBIT_SET(*s))
        len = 2;                /* kanji? */
    else
        len = pg_ascii_dsplen(s);       /* should be ASCII */
    return len;
}

/*
 * GBK
 */
static int
pg_gbk_mblen(const unsigned char *s)
{
    int         len;

    if (IS_HIGHBIT_SET(*s))
        len = 2;                /* kanji? */
    else
        len = 1;                /* should be ASCII */
    return len;
}

static int
pg_gbk_dsplen(const unsigned char *s)
{
    int         len;

    if (IS_HIGHBIT_SET(*s))
        len = 2;                /* kanji? */
    else
        len = pg_ascii_dsplen(s);       /* should be ASCII */
    return len;
}

/*
 * UHC
 */
static int
pg_uhc_mblen(const unsigned char *s)
{
    int         len;

    if (IS_HIGHBIT_SET(*s))
        len = 2;                /* 2byte? */
    else
        len = 1;                /* should be ASCII */
    return len;
}

static int
pg_uhc_dsplen(const unsigned char *s)
{
    int         len;

    if (IS_HIGHBIT_SET(*s))
        len = 2;                /* 2byte? */
    else
        len = pg_ascii_dsplen(s);       /* should be ASCII */
    return len;
}

/*
 *  * GB18030
 *   * Added by Bill Huang <[email protected]>,<[email protected]>
 *    */
static int
pg_gb18030_mblen(const unsigned char *s)
{
    int         len;

    if (!IS_HIGHBIT_SET(*s))
        len = 1;                /* ASCII */
    else
    {
        if ((*(s + 1) >= 0x40 && *(s + 1) <= 0x7e) || (*(s + 1) >= 0x80 && *(s + 1) <= 0xfe))
            len = 2;
        else if (*(s + 1) >= 0x30 && *(s + 1) <= 0x39)
            len = 4;
        else
            len = 2;
    }
    return len;
}

static int
pg_gb18030_dsplen(const unsigned char *s)
{
    int         len;

    if (IS_HIGHBIT_SET(*s))
        len = 2;
    else
        len = pg_ascii_dsplen(s);       /* ASCII */
    return len;
}

/*
 *-------------------------------------------------------------------
 * multibyte sequence validators
 *
 * These functions accept "s", a pointer to the first byte of a string,
 * and "len", the remaining length of the string.  If there is a validly
 * encoded character beginning at *s, return its length in bytes; else
 * return -1.
 *
 * The functions can assume that len > 0 and that *s != '\0', but they must
 * test for and reject zeroes in any additional bytes of a multibyte character.
 *
 * Note that this definition allows the function for a single-byte
 * encoding to be just "return 1".
 *-------------------------------------------------------------------
 */

static int
pg_ascii_verifier(const unsigned char *s, int len)
{
    return 1;
}

#define IS_EUC_RANGE_VALID(c)   ((c) >= 0xa1 && (c) <= 0xfe)

static int
pg_eucjp_verifier(const unsigned char *s, int len)
{
    int         l;
    unsigned char c1,
                c2;

    c1 = *s++;

    switch (c1)
    {
        case SS2:               /* JIS X 0201 */
            l = 2;
            if (l > len)
                return -1;
            c2 = *s++;
            if (c2 < 0xa1 || c2 > 0xdf)
                return -1;
            break;

        case SS3:               /* JIS X 0212 */
            l = 3;
            if (l > len)
                return -1;
            c2 = *s++;
            if (!IS_EUC_RANGE_VALID(c2))
                return -1;
            c2 = *s++;
            if (!IS_EUC_RANGE_VALID(c2))
                return -1;
            break;

        default:
            if (IS_HIGHBIT_SET(c1))     /* JIS X 0208? */
            {
                l = 2;
                if (l > len)
                    return -1;
                if (!IS_EUC_RANGE_VALID(c1))
                    return -1;
                c2 = *s++;
                if (!IS_EUC_RANGE_VALID(c2))
                    return -1;
            }
            else
                /* must be ASCII */
            {
                l = 1;
            }
            break;
    }

    return l;
}

static int
pg_euckr_verifier(const unsigned char *s, int len)
{
    int         l;
    unsigned char c1,
                c2;

    c1 = *s++;

    if (IS_HIGHBIT_SET(c1))
    {
        l = 2;
        if (l > len)
            return -1;
        if (!IS_EUC_RANGE_VALID(c1))
            return -1;
        c2 = *s++;
        if (!IS_EUC_RANGE_VALID(c2))
            return -1;
    }
    else
        /* must be ASCII */
    {
        l = 1;
    }

    return l;
}

/* EUC-CN byte sequences are exactly same as EUC-KR */
#define pg_euccn_verifier   pg_euckr_verifier

static int
pg_euctw_verifier(const unsigned char *s, int len)
{
    int         l;
    unsigned char c1,
                c2;

    c1 = *s++;

    switch (c1)
    {
        case SS2:               /* CNS 11643 Plane 1-7 */
            l = 4;
            if (l > len)
                return -1;
            c2 = *s++;
            if (c2 < 0xa1 || c2 > 0xa7)
                return -1;
            c2 = *s++;
            if (!IS_EUC_RANGE_VALID(c2))
                return -1;
            c2 = *s++;
            if (!IS_EUC_RANGE_VALID(c2))
                return -1;
            break;

        case SS3:               /* unused */
            return -1;

        default:
            if (IS_HIGHBIT_SET(c1))     /* CNS 11643 Plane 1 */
            {
                l = 2;
                if (l > len)
                    return -1;
                /* no further range check on c1? */
                c2 = *s++;
                if (!IS_EUC_RANGE_VALID(c2))
                    return -1;
            }
            else
                /* must be ASCII */
            {
                l = 1;
            }
            break;
    }
    return l;
}

static int
pg_johab_verifier(const unsigned char *s, int len)
{
    int         l,
                mbl;
    unsigned char c;

    l = mbl = pg_johab_mblen(s);

    if (len < l)
        return -1;

    if (!IS_HIGHBIT_SET(*s))
        return mbl;

    while (--l > 0)
    {
        c = *++s;
        if (!IS_EUC_RANGE_VALID(c))
            return -1;
    }
    return mbl;
}

static int
pg_mule_verifier(const unsigned char *s, int len)
{
    int         l,
                mbl;
    unsigned char c;

    l = mbl = pg_mule_mblen(s);

    if (len < l)
        return -1;

    while (--l > 0)
    {
        c = *++s;
        if (!IS_HIGHBIT_SET(c))
            return -1;
    }
    return mbl;
}

static int
pg_latin1_verifier(const unsigned char *s, int len)
{
    return 1;
}

static int
pg_sjis_verifier(const unsigned char *s, int len)
{
    int         l,
                mbl;
    unsigned char c1,
                c2;

    l = mbl = pg_sjis_mblen(s);

    if (len < l)
        return -1;

    if (l == 1)                 /* pg_sjis_mblen already verified it */
        return mbl;

    c1 = *s++;
    c2 = *s;
    if (!ISSJISHEAD(c1) || !ISSJISTAIL(c2))
        return -1;
    return mbl;
}

static int
pg_big5_verifier(const unsigned char *s, int len)
{
    int         l,
                mbl;

    l = mbl = pg_big5_mblen(s);

    if (len < l)
        return -1;

    while (--l > 0)
    {
        if (*++s == '\0')
            return -1;
    }

    return mbl;
}

static int
pg_gbk_verifier(const unsigned char *s, int len)
{
    int         l,
                mbl;

    l = mbl = pg_gbk_mblen(s);

    if (len < l)
        return -1;

    while (--l > 0)
    {
        if (*++s == '\0')
            return -1;
    }

    return mbl;
}

static int
pg_uhc_verifier(const unsigned char *s, int len)
{
    int         l,
                mbl;

    l = mbl = pg_uhc_mblen(s);

    if (len < l)
        return -1;

    while (--l > 0)
    {
        if (*++s == '\0')
            return -1;
    }

    return mbl;
}

static int
pg_gb18030_verifier(const unsigned char *s, int len)
{
    int         l,
                mbl;

    l = mbl = pg_gb18030_mblen(s);

    if (len < l)
        return -1;

    while (--l > 0)
    {
        if (*++s == '\0')
            return -1;
    }

    return mbl;
}

static int
pg_utf8_verifier(const unsigned char *s, int len)
{
    int         l = pg_utf_mblen(s);

    if (len < l)
        return -1;

    if (!pg_utf8_islegal(s, l))
        return -1;

    return l;
}

/*
 * Check for validity of a single UTF-8 encoded character
 *
 * This directly implements the rules in RFC3629.  The bizarre-looking
 * restrictions on the second byte are meant to ensure that there isn't
 * more than one encoding of a given Unicode character point; that is,
 * you may not use a longer-than-necessary byte sequence with high order
 * zero bits to represent a character that would fit in fewer bytes.
 * To do otherwise is to create security hazards (eg, create an apparent
 * non-ASCII character that decodes to plain ASCII).
 *
 * length is assumed to have been obtained by pg_utf_mblen(), and the
 * caller must have checked that that many bytes are present in the buffer.
 */
bool
pg_utf8_islegal(const unsigned char *source, int length)
{
    unsigned char a;

    switch (length)
    {
        default:
            /* reject lengths 5 and 6 for now */
            return false;
        case 4:
            a = source[3];
            if (a < 0x80 || a > 0xBF)
                return false;
            /* FALL THRU */
        case 3:
            a = source[2];
            if (a < 0x80 || a > 0xBF)
                return false;
            /* FALL THRU */
        case 2:
            a = source[1];
            switch (*source)
            {
                case 0xE0:
                    if (a < 0xA0 || a > 0xBF)
                        return false;
                    break;
                case 0xED:
                    if (a < 0x80 || a > 0x9F)
                        return false;
                    break;
                case 0xF0:
                    if (a < 0x90 || a > 0xBF)
                        return false;
                    break;
                case 0xF4:
                    if (a < 0x80 || a > 0x8F)
                        return false;
                    break;
                default:
                    if (a < 0x80 || a > 0xBF)
                        return false;
                    break;
            }
            /* FALL THRU */
        case 1:
            a = *source;
            if (a >= 0x80 && a < 0xC2)
                return false;
            if (a > 0xF4)
                return false;
            break;
    }
    return true;
}

#ifndef FRONTEND

/*
 * Generic character incrementer function.
 *
 * Not knowing anything about the properties of the encoding in use, we just
 * keep incrementing the last byte until we get a validly-encoded result,
 * or we run out of values to try.  We don't bother to try incrementing
 * higher-order bytes, so there's no growth in runtime for wider characters.
 * (If we did try to do that, we'd need to consider the likelihood that 255
 * is not a valid final byte in the encoding.)
 */
static bool
pg_generic_charinc(unsigned char *charptr, int len)
{
    unsigned char *lastbyte = charptr + len - 1;
    mbverifier  mbverify;

    /* We can just invoke the character verifier directly. */
    mbverify = pg_wchar_table[GetDatabaseEncoding()].mbverify;

    while (*lastbyte < (unsigned char) 255)
    {
        (*lastbyte)++;
        if ((*mbverify) (charptr, len) == len)
            return true;
    }

    return false;
}

/*
 * UTF-8 character incrementer function.
 *
 * For a one-byte character less than 0x7F, we just increment the byte.
 *
 * For a multibyte character, every byte but the first must fall between 0x80
 * and 0xBF; and the first byte must be between 0xC0 and 0xF4.  We increment
 * the last byte that's not already at its maximum value.  If we can't find a
 * byte that's less than the maximum allowable value, we simply fail.  We also
 * need some special-case logic to skip regions used for surrogate pair
 * handling, as those should not occur in valid UTF-8.
 *
 * Note that we don't reset lower-order bytes back to their minimums, since
 * we can't afford to make an exhaustive search (see make_greater_string).
 */
static bool
pg_utf8_increment(unsigned char *charptr, int length)
{
    unsigned char a;
    unsigned char limit;

    switch (length)
    {
        default:
            /* reject lengths 5 and 6 for now */
            return false;
        case 4:
            a = charptr[3];
            if (a < 0xBF)
            {
                charptr[3]++;
                break;
            }
            /* FALL THRU */
        case 3:
            a = charptr[2];
            if (a < 0xBF)
            {
                charptr[2]++;
                break;
            }
            /* FALL THRU */
        case 2:
            a = charptr[1];
            switch (*charptr)
            {
                case 0xED:
                    limit = 0x9F;
                    break;
                case 0xF4:
                    limit = 0x8F;
                    break;
                default:
                    limit = 0xBF;
                    break;
            }
            if (a < limit)
            {
                charptr[1]++;
                break;
            }
            /* FALL THRU */
        case 1:
            a = *charptr;
            if (a == 0x7F || a == 0xDF || a == 0xEF || a == 0xF4)
                return false;
            charptr[0]++;
            break;
    }

    return true;
}

/*
 * EUC-JP character incrementer function.
 *
 * If the sequence starts with SS2 (0x8e), it must be a two-byte sequence
 * representing JIS X 0201 characters with the second byte ranging between
 * 0xa1 and 0xdf.  We just increment the last byte if it's less than 0xdf,
 * and otherwise rewrite the whole sequence to 0xa1 0xa1.
 *
 * If the sequence starts with SS3 (0x8f), it must be a three-byte sequence
 * in which the last two bytes range between 0xa1 and 0xfe.  The last byte
 * is incremented if possible, otherwise the second-to-last byte.
 *
 * If the sequence starts with a value other than the above and its MSB
 * is set, it must be a two-byte sequence representing JIS X 0208 characters
 * with both bytes ranging between 0xa1 and 0xfe.  The last byte is
 * incremented if possible, otherwise the second-to-last byte.
 *
 * Otherwise, the sequence is a single-byte ASCII character. It is
 * incremented up to 0x7f.
 */
static bool
pg_eucjp_increment(unsigned char *charptr, int length)
{
    unsigned char c1,
                c2;
    int         i;

    c1 = *charptr;

    switch (c1)
    {
        case SS2:               /* JIS X 0201 */
            if (length != 2)
                return false;

            c2 = charptr[1];

            if (c2 >= 0xdf)
                charptr[0] = charptr[1] = 0xa1;
            else if (c2 < 0xa1)
                charptr[1] = 0xa1;
            else
                charptr[1]++;
            break;

        case SS3:               /* JIS X 0212 */
            if (length != 3)
                return false;

            for (i = 2; i > 0; i--)
            {
                c2 = charptr[i];
                if (c2 < 0xa1)
                {
                    charptr[i] = 0xa1;
                    return true;
                }
                else if (c2 < 0xfe)
                {
                    charptr[i]++;
                    return true;
                }
            }

            /* Out of 3-byte code region */
            return false;

        default:
            if (IS_HIGHBIT_SET(c1))     /* JIS X 0208? */
            {
                if (length != 2)
                    return false;

                for (i = 1; i >= 0; i--)
                {
                    c2 = charptr[i];
                    if (c2 < 0xa1)
                    {
                        charptr[i] = 0xa1;
                        return true;
                    }
                    else if (c2 < 0xfe)
                    {
                        charptr[i]++;
                        return true;
                    }
                }

                /* Out of 2 byte code region */
                return false;
            }
            else
            {                   /* ASCII, single byte */
                if (c1 > 0x7e)
                    return false;
                (*charptr)++;
            }
            break;
    }

    return true;
}
#endif   /* !FRONTEND */


/*
 *-------------------------------------------------------------------
 * encoding info table
 * XXX must be sorted by the same order as enum pg_enc (in mb/pg_wchar.h)
 *-------------------------------------------------------------------
 */
pg_wchar_tbl pg_wchar_table[] = {
    {pg_ascii2wchar_with_len, pg_wchar2single_with_len, pg_ascii_mblen, pg_ascii_dsplen, pg_ascii_verifier, 1}, /* PG_SQL_ASCII */
    {pg_eucjp2wchar_with_len, pg_wchar2euc_with_len, pg_eucjp_mblen, pg_eucjp_dsplen, pg_eucjp_verifier, 3},    /* PG_EUC_JP */
    {pg_euccn2wchar_with_len, pg_wchar2euc_with_len, pg_euccn_mblen, pg_euccn_dsplen, pg_euccn_verifier, 2},    /* PG_EUC_CN */
    {pg_euckr2wchar_with_len, pg_wchar2euc_with_len, pg_euckr_mblen, pg_euckr_dsplen, pg_euckr_verifier, 3},    /* PG_EUC_KR */
    {pg_euctw2wchar_with_len, pg_wchar2euc_with_len, pg_euctw_mblen, pg_euctw_dsplen, pg_euctw_verifier, 4},    /* PG_EUC_TW */
    {pg_eucjp2wchar_with_len, pg_wchar2euc_with_len, pg_eucjp_mblen, pg_eucjp_dsplen, pg_eucjp_verifier, 3},    /* PG_EUC_JIS_2004 */
    {pg_utf2wchar_with_len, pg_wchar2utf_with_len, pg_utf_mblen, pg_utf_dsplen, pg_utf8_verifier, 4},   /* PG_UTF8 */
    {pg_mule2wchar_with_len, pg_wchar2mule_with_len, pg_mule_mblen, pg_mule_dsplen, pg_mule_verifier, 4},       /* PG_MULE_INTERNAL */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_LATIN1 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_LATIN2 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_LATIN3 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_LATIN4 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_LATIN5 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_LATIN6 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_LATIN7 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_LATIN8 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_LATIN9 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_LATIN10 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_WIN1256 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_WIN1258 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_WIN866 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_WIN874 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_KOI8R */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_WIN1251 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_WIN1252 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* ISO-8859-5 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* ISO-8859-6 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* ISO-8859-7 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* ISO-8859-8 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_WIN1250 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_WIN1253 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_WIN1254 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_WIN1255 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_WIN1257 */
    {pg_latin12wchar_with_len, pg_wchar2single_with_len, pg_latin1_mblen, pg_latin1_dsplen, pg_latin1_verifier, 1},     /* PG_KOI8U */
    {0, 0, pg_sjis_mblen, pg_sjis_dsplen, pg_sjis_verifier, 2}, /* PG_SJIS */
    {0, 0, pg_big5_mblen, pg_big5_dsplen, pg_big5_verifier, 2}, /* PG_BIG5 */
    {0, 0, pg_gbk_mblen, pg_gbk_dsplen, pg_gbk_verifier, 2},        /* PG_GBK */
    {0, 0, pg_uhc_mblen, pg_uhc_dsplen, pg_uhc_verifier, 2},        /* PG_UHC */
    {0, 0, pg_gb18030_mblen, pg_gb18030_dsplen, pg_gb18030_verifier, 4},    /* PG_GB18030 */
    {0, 0, pg_johab_mblen, pg_johab_dsplen, pg_johab_verifier, 3}, /* PG_JOHAB */
    {0, 0, pg_sjis_mblen, pg_sjis_dsplen, pg_sjis_verifier, 2}      /* PG_SHIFT_JIS_2004 */
};

/* returns the byte length of a word for mule internal code */
int
pg_mic_mblen(const unsigned char *mbstr)
{
    return pg_mule_mblen(mbstr);
}

/*
 * Returns the byte length of a multibyte character.
 */
int
pg_encoding_mblen(int encoding, const char *mbstr)
{
    Assert(PG_VALID_ENCODING(encoding));

    return ((encoding >= 0 &&
             encoding < sizeof(pg_wchar_table) / sizeof(pg_wchar_tbl)) ?
        ((*pg_wchar_table[encoding].mblen) ((const unsigned char *) mbstr)) :
    ((*pg_wchar_table[PG_SQL_ASCII].mblen) ((const unsigned char *) mbstr)));
}

/*
 * Returns the display length of a multibyte character.
 */
int
pg_encoding_dsplen(int encoding, const char *mbstr)
{
    Assert(PG_VALID_ENCODING(encoding));

    return ((encoding >= 0 &&
             encoding < sizeof(pg_wchar_table) / sizeof(pg_wchar_tbl)) ?
       ((*pg_wchar_table[encoding].dsplen) ((const unsigned char *) mbstr)) :
    ((*pg_wchar_table[PG_SQL_ASCII].dsplen) ((const unsigned char *) mbstr)));
}

/*
 * Verify the first multibyte character of the given string.
 * Return its byte length if good, -1 if bad.  (See comments above for
 * full details of the mbverify API.)
 */
int
pg_encoding_verifymb(int encoding, const char *mbstr, int len)
{
    Assert(PG_VALID_ENCODING(encoding));

    return ((encoding >= 0 &&
             encoding < sizeof(pg_wchar_table) / sizeof(pg_wchar_tbl)) ?
            ((*pg_wchar_table[encoding].mbverify) ((const unsigned char *) mbstr, len)) :
            ((*pg_wchar_table[PG_SQL_ASCII].mbverify) ((const unsigned char *) mbstr, len)));
}

/*
 * fetch maximum length of a given encoding
 */
int
pg_encoding_max_length(int encoding)
{
    Assert(PG_VALID_ENCODING(encoding));

    return pg_wchar_table[encoding].maxmblen;
}

#ifndef FRONTEND

/*
 * fetch maximum length of the encoding for the current database
 */
int
pg_database_encoding_max_length(void)
{
    return pg_wchar_table[GetDatabaseEncoding()].maxmblen;
}

/*
 * get the character incrementer for the encoding for the current database
 */
mbcharacter_incrementer
pg_database_encoding_character_incrementer(void)
{
    /*
     * Eventually it might be best to add a field to pg_wchar_table[], but for
     * now we just use a switch.
     */
    switch (GetDatabaseEncoding())
    {
        case PG_UTF8:
            return pg_utf8_increment;

        case PG_EUC_JP:
            return pg_eucjp_increment;

        default:
            return pg_generic_charinc;
    }
}

/*
 * Verify mbstr to make sure that it is validly encoded in the current
 * database encoding.  Otherwise same as pg_verify_mbstr().
 */
bool
pg_verifymbstr(const char *mbstr, int len, bool noError)
{
    return
        pg_verify_mbstr_len(GetDatabaseEncoding(), mbstr, len, noError) >= 0;
}

/*
 * Verify mbstr to make sure that it is validly encoded in the specified
 * encoding.
 */
bool
pg_verify_mbstr(int encoding, const char *mbstr, int len, bool noError)
{
    return pg_verify_mbstr_len(encoding, mbstr, len, noError) >= 0;
}

/*
 * Verify mbstr to make sure that it is validly encoded in the specified
 * encoding.
 *
 * mbstr is not necessarily zero terminated; length of mbstr is
 * specified by len.
 *
 * If OK, return length of string in the encoding.
 * If a problem is found, return -1 when noError is
 * true; when noError is false, ereport() a descriptive message.
 */
int
pg_verify_mbstr_len(int encoding, const char *mbstr, int len, bool noError)
{
    mbverifier  mbverify;
    int         mb_len;

    Assert(PG_VALID_ENCODING(encoding));

    /*
     * In single-byte encodings, we need only reject nulls (\0).
     */
    if (pg_encoding_max_length(encoding) <= 1)
    {
        const char *nullpos = memchr(mbstr, 0, len);

        if (nullpos == NULL)
            return len;
        if (noError)
            return -1;
        report_invalid_encoding(encoding, nullpos, 1);
    }

    /* fetch function pointer just once */
    mbverify = pg_wchar_table[encoding].mbverify;

    mb_len = 0;

    while (len > 0)
    {
        int         l;

        /* fast path for ASCII-subset characters */
        if (!IS_HIGHBIT_SET(*mbstr))
        {
            if (*mbstr != '\0')
            {
                mb_len++;
                mbstr++;
                len--;
                continue;
            }
            if (noError)
                return -1;
            report_invalid_encoding(encoding, mbstr, len);
        }

        l = (*mbverify) ((const unsigned char *) mbstr, len);

        if (l < 0)
        {
            if (noError)
                return -1;
            report_invalid_encoding(encoding, mbstr, len);
        }

        mbstr += l;
        len -= l;
        mb_len++;
    }
    return mb_len;
}

/*
 * check_encoding_conversion_args: check arguments of a conversion function
 *
 * "expected" arguments can be either an encoding ID or -1 to indicate that
 * the caller will check whether it accepts the ID.
 *
 * Note: the errors here are not really user-facing, so elog instead of
 * ereport seems sufficient.  Also, we trust that the "expected" encoding
 * arguments are valid encoding IDs, but we don't trust the actuals.
 */
void
check_encoding_conversion_args(int src_encoding,
                               int dest_encoding,
                               int len,
                               int expected_src_encoding,
                               int expected_dest_encoding)
{
    if (!PG_VALID_ENCODING(src_encoding))
        elog(ERROR, "invalid source encoding ID: %d", src_encoding);
    if (src_encoding != expected_src_encoding && expected_src_encoding >= 0)
        elog(ERROR, "expected source encoding \"%s\", but got \"%s\"",
             pg_enc2name_tbl[expected_src_encoding].name,
             pg_enc2name_tbl[src_encoding].name);
    if (!PG_VALID_ENCODING(dest_encoding))
        elog(ERROR, "invalid destination encoding ID: %d", dest_encoding);
    if (dest_encoding != expected_dest_encoding && expected_dest_encoding >= 0)
        elog(ERROR, "expected destination encoding \"%s\", but got \"%s\"",
             pg_enc2name_tbl[expected_dest_encoding].name,
             pg_enc2name_tbl[dest_encoding].name);
    if (len < 0)
        elog(ERROR, "encoding conversion length must not be negative");
}

/*
 * report_invalid_encoding: complain about invalid multibyte character
 *
 * note: len is remaining length of string, not length of character;
 * len must be greater than zero, as we always examine the first byte.
 */
void
report_invalid_encoding(int encoding, const char *mbstr, int len)
{
    int         l = pg_encoding_mblen(encoding, mbstr);
    char        buf[8 * 5 + 1];
    char       *p = buf;
    int         j,
                jlimit;

    jlimit = Min(l, len);
    jlimit = Min(jlimit, 8);    /* prevent buffer overrun */

    for (j = 0; j < jlimit; j++)
    {
        p += sprintf(p, "0x%02x", (unsigned char) mbstr[j]);
        if (j < jlimit - 1)
            p += sprintf(p, " ");
    }

    ereport(ERROR,
            (errcode(ERRCODE_CHARACTER_NOT_IN_REPERTOIRE),
             errmsg("invalid byte sequence for encoding \"%s\": %s",
                    pg_enc2name_tbl[encoding].name,
                    buf)));
}

/*
 * report_untranslatable_char: complain about untranslatable character
 *
 * note: len is remaining length of string, not length of character;
 * len must be greater than zero, as we always examine the first byte.
 */
void
report_untranslatable_char(int src_encoding, int dest_encoding,
                           const char *mbstr, int len)
{
    int         l = pg_encoding_mblen(src_encoding, mbstr);
    char        buf[8 * 5 + 1];
    char       *p = buf;
    int         j,
                jlimit;

    jlimit = Min(l, len);
    jlimit = Min(jlimit, 8);    /* prevent buffer overrun */

    for (j = 0; j < jlimit; j++)
    {
        p += sprintf(p, "0x%02x", (unsigned char) mbstr[j]);
        if (j < jlimit - 1)
            p += sprintf(p, " ");
    }

    ereport(ERROR,
            (errcode(ERRCODE_UNTRANSLATABLE_CHARACTER),
             errmsg("character with byte sequence %s in encoding \"%s\" has no equivalent in encoding \"%s\"",
                    buf,
                    pg_enc2name_tbl[src_encoding].name,
                    pg_enc2name_tbl[dest_encoding].name)));
}

#endif   /* !FRONTEND */