pg_wchar.h

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * pg_wchar.h
 *    multibyte-character support
 *
 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/mb/pg_wchar.h
 *
 *  NOTES
 *      This is used both by the backend and by frontends, but should not be
 *      included by libpq client programs.  In particular, a libpq client
 *      should not assume that the encoding IDs used by the version of libpq
 *      it's linked to match up with the IDs declared here.
 *
 *-------------------------------------------------------------------------
 */
#ifndef PG_WCHAR_H
#define PG_WCHAR_H
 
#include "port/simd.h"
 
/*
 * The pg_wchar type
 */
typedef unsigned int pg_wchar;
 
/*
 * Maximum byte length of multibyte characters in any backend encoding
 */
#define MAX_MULTIBYTE_CHAR_LEN  4
 
/*
 * various definitions for EUC
 */
#define SS2 0x8e                /* single shift 2 (JIS0201) */
#define SS3 0x8f                /* single shift 3 (JIS0212) */
 
/*
 * SJIS validation macros
 */
#define ISSJISHEAD(c) (((c) >= 0x81 && (c) <= 0x9f) || ((c) >= 0xe0 && (c) <= 0xfc))
#define ISSJISTAIL(c) (((c) >= 0x40 && (c) <= 0x7e) || ((c) >= 0x80 && (c) <= 0xfc))
 
/*----------------------------------------------------
 * MULE Internal Encoding (MIC)
 *
 * This encoding follows the design used within XEmacs; it is meant to
 * subsume many externally-defined character sets.  Each character includes
 * identification of the character set it belongs to, so the encoding is
 * general but somewhat bulky.
 *
 * Currently PostgreSQL supports 5 types of MULE character sets:
 *
 * 1) 1-byte ASCII characters.  Each byte is below 0x80.
 *
 * 2) "Official" single byte charsets such as ISO-8859-1 (Latin1).
 *    Each MULE character consists of 2 bytes: LC1 + C1, where LC1 is
 *    an identifier for the charset (in the range 0x81 to 0x8d) and C1
 *    is the character code (in the range 0xa0 to 0xff).
 *
 * 3) "Private" single byte charsets such as SISHENG.  Each MULE
 *    character consists of 3 bytes: LCPRV1 + LC12 + C1, where LCPRV1
 *    is a private-charset flag, LC12 is an identifier for the charset,
 *    and C1 is the character code (in the range 0xa0 to 0xff).
 *    LCPRV1 is either 0x9a (if LC12 is in the range 0xa0 to 0xdf)
 *    or 0x9b (if LC12 is in the range 0xe0 to 0xef).
 *
 * 4) "Official" multibyte charsets such as JIS X0208.  Each MULE
 *    character consists of 3 bytes: LC2 + C1 + C2, where LC2 is
 *    an identifier for the charset (in the range 0x90 to 0x99) and C1
 *    and C2 form the character code (each in the range 0xa0 to 0xff).
 *
 * 5) "Private" multibyte charsets such as CNS 11643-1992 Plane 3.
 *    Each MULE character consists of 4 bytes: LCPRV2 + LC22 + C1 + C2,
 *    where LCPRV2 is a private-charset flag, LC22 is an identifier for
 *    the charset, and C1 and C2 form the character code (each in the range
 *    0xa0 to 0xff).  LCPRV2 is either 0x9c (if LC22 is in the range 0xf0
 *    to 0xf4) or 0x9d (if LC22 is in the range 0xf5 to 0xfe).
 *
 * "Official" encodings are those that have been assigned code numbers by
 * the XEmacs project; "private" encodings have Postgres-specific charset
 * identifiers.
 *
 * See the "XEmacs Internals Manual", available at http://www.xemacs.org,
 * for more details.  Note that for historical reasons, Postgres'
 * private-charset flag values do not match what XEmacs says they should be,
 * so this isn't really exactly MULE (not that private charsets would be
 * interoperable anyway).
 *
 * Note that XEmacs's implementation is different from what emacs does.
 * We follow emacs's implementation, rather than XEmacs's.
 *----------------------------------------------------
 */
 
/*
 * Charset identifiers (also called "leading bytes" in the MULE documentation)
 */
 
/*
 * Charset IDs for official single byte encodings (0x81-0x8e)
 */
#define LC_ISO8859_1        0x81    /* ISO8859 Latin 1 */
#define LC_ISO8859_2        0x82    /* ISO8859 Latin 2 */
#define LC_ISO8859_3        0x83    /* ISO8859 Latin 3 */
#define LC_ISO8859_4        0x84    /* ISO8859 Latin 4 */
#define LC_TIS620           0x85    /* Thai (not supported yet) */
#define LC_ISO8859_7        0x86    /* Greek (not supported yet) */
#define LC_ISO8859_6        0x87    /* Arabic (not supported yet) */
#define LC_ISO8859_8        0x88    /* Hebrew (not supported yet) */
#define LC_JISX0201K        0x89    /* Japanese 1 byte kana */
#define LC_JISX0201R        0x8a    /* Japanese 1 byte Roman */
/* Note that 0x8b seems to be unused as of Emacs 20.7.
 * However, there might be a chance that 0x8b could be used
 * in later versions of Emacs.
 */
#define LC_KOI8_R           0x8b    /* Cyrillic KOI8-R */
#define LC_ISO8859_5        0x8c    /* ISO8859 Cyrillic */
#define LC_ISO8859_9        0x8d    /* ISO8859 Latin 5 (not supported yet) */
#define LC_ISO8859_15       0x8e    /* ISO8859 Latin 15 (not supported yet) */
/* #define CONTROL_1        0x8f    control characters (unused) */
 
/* Is a leading byte for "official" single byte encodings? */
#define IS_LC1(c)   ((unsigned char)(c) >= 0x81 && (unsigned char)(c) <= 0x8d)
 
/*
 * Charset IDs for official multibyte encodings (0x90-0x99)
 * 0x9a-0x9d are free. 0x9e and 0x9f are reserved.
 */
#define LC_JISX0208_1978    0x90    /* Japanese Kanji, old JIS (not supported) */
#define LC_GB2312_80        0x91    /* Chinese */
#define LC_JISX0208         0x92    /* Japanese Kanji (JIS X 0208) */
#define LC_KS5601           0x93    /* Korean */
#define LC_JISX0212         0x94    /* Japanese Kanji (JIS X 0212) */
#define LC_CNS11643_1       0x95    /* CNS 11643-1992 Plane 1 */
#define LC_CNS11643_2       0x96    /* CNS 11643-1992 Plane 2 */
#define LC_JISX0213_1       0x97    /* Japanese Kanji (JIS X 0213 Plane 1)
                                     * (not supported) */
#define LC_BIG5_1           0x98    /* Plane 1 Chinese traditional (not
                                     * supported) */
#define LC_BIG5_2           0x99    /* Plane 1 Chinese traditional (not
                                     * supported) */
 
/* Is a leading byte for "official" multibyte encodings? */
#define IS_LC2(c)   ((unsigned char)(c) >= 0x90 && (unsigned char)(c) <= 0x99)
 
/*
 * Postgres-specific prefix bytes for "private" single byte encodings
 * (According to the MULE docs, we should be using 0x9e for this)
 */
#define LCPRV1_A        0x9a
#define LCPRV1_B        0x9b
#define IS_LCPRV1(c)    ((unsigned char)(c) == LCPRV1_A || (unsigned char)(c) == LCPRV1_B)
#define IS_LCPRV1_A_RANGE(c)    \
    ((unsigned char)(c) >= 0xa0 && (unsigned char)(c) <= 0xdf)
#define IS_LCPRV1_B_RANGE(c)    \
    ((unsigned char)(c) >= 0xe0 && (unsigned char)(c) <= 0xef)
 
/*
 * Postgres-specific prefix bytes for "private" multibyte encodings
 * (According to the MULE docs, we should be using 0x9f for this)
 */
#define LCPRV2_A        0x9c
#define LCPRV2_B        0x9d
#define IS_LCPRV2(c)    ((unsigned char)(c) == LCPRV2_A || (unsigned char)(c) == LCPRV2_B)
#define IS_LCPRV2_A_RANGE(c)    \
    ((unsigned char)(c) >= 0xf0 && (unsigned char)(c) <= 0xf4)
#define IS_LCPRV2_B_RANGE(c)    \
    ((unsigned char)(c) >= 0xf5 && (unsigned char)(c) <= 0xfe)
 
/*
 * Charset IDs for private single byte encodings (0xa0-0xef)
 */
#define LC_SISHENG          0xa0    /* Chinese SiSheng characters for
                                     * PinYin/ZhuYin (not supported) */
#define LC_IPA              0xa1    /* IPA (International Phonetic
                                     * Association) (not supported) */
#define LC_VISCII_LOWER     0xa2    /* Vietnamese VISCII1.1 lower-case (not
                                     * supported) */
#define LC_VISCII_UPPER     0xa3    /* Vietnamese VISCII1.1 upper-case (not
                                     * supported) */
#define LC_ARABIC_DIGIT     0xa4    /* Arabic digit (not supported) */
#define LC_ARABIC_1_COLUMN  0xa5    /* Arabic 1-column (not supported) */
#define LC_ASCII_RIGHT_TO_LEFT  0xa6    /* ASCII (left half of ISO8859-1) with
                                         * right-to-left direction (not
                                         * supported) */
#define LC_LAO              0xa7    /* Lao characters (ISO10646 0E80..0EDF)
                                     * (not supported) */
#define LC_ARABIC_2_COLUMN  0xa8    /* Arabic 1-column (not supported) */
 
/*
 * Charset IDs for private multibyte encodings (0xf0-0xff)
 */
#define LC_INDIAN_1_COLUMN  0xf0    /* Indian charset for 1-column width
                                     * glyphs (not supported) */
#define LC_TIBETAN_1_COLUMN 0xf1    /* Tibetan 1-column width glyphs (not
                                     * supported) */
#define LC_UNICODE_SUBSET_2 0xf2    /* Unicode characters of the range
                                     * U+2500..U+33FF. (not supported) */
#define LC_UNICODE_SUBSET_3 0xf3    /* Unicode characters of the range
                                     * U+E000..U+FFFF. (not supported) */
#define LC_UNICODE_SUBSET   0xf4    /* Unicode characters of the range
                                     * U+0100..U+24FF. (not supported) */
#define LC_ETHIOPIC         0xf5    /* Ethiopic characters (not supported) */
#define LC_CNS11643_3       0xf6    /* CNS 11643-1992 Plane 3 */
#define LC_CNS11643_4       0xf7    /* CNS 11643-1992 Plane 4 */
#define LC_CNS11643_5       0xf8    /* CNS 11643-1992 Plane 5 */
#define LC_CNS11643_6       0xf9    /* CNS 11643-1992 Plane 6 */
#define LC_CNS11643_7       0xfa    /* CNS 11643-1992 Plane 7 */
#define LC_INDIAN_2_COLUMN  0xfb    /* Indian charset for 2-column width
                                     * glyphs (not supported) */
#define LC_TIBETAN          0xfc    /* Tibetan (not supported) */
/* #define FREE             0xfd    free (unused) */
/* #define FREE             0xfe    free (unused) */
/* #define FREE             0xff    free (unused) */
 
/*----------------------------------------------------
 * end of MULE stuff
 *----------------------------------------------------
 */
 
/*
 * PostgreSQL encoding identifiers
 *
 * WARNING: the order of this enum must be same as order of entries
 *          in the pg_enc2name_tbl[] array (in src/common/encnames.c), and
 *          in the pg_wchar_table[] array (in src/common/wchar.c)!
 *
 *          If you add some encoding don't forget to check
 *          PG_ENCODING_BE_LAST macro.
 *
 * PG_SQL_ASCII is default encoding and must be = 0.
 *
 * XXX  We must avoid renumbering any backend encoding until libpq's major
 * version number is increased beyond 5; it turns out that the backend
 * encoding IDs are effectively part of libpq's ABI as far as 8.2 initdb and
 * psql are concerned.
 */
typedef enum pg_enc
{
    PG_SQL_ASCII = 0,           /* SQL/ASCII */
    PG_EUC_JP,                  /* EUC for Japanese */
    PG_EUC_CN,                  /* EUC for Chinese */
    PG_EUC_KR,                  /* EUC for Korean */
    PG_EUC_TW,                  /* EUC for Taiwan */
    PG_EUC_JIS_2004,            /* EUC-JIS-2004 */
    PG_UTF8,                    /* Unicode UTF8 */
    PG_MULE_INTERNAL,           /* Mule internal code */
    PG_LATIN1,                  /* ISO-8859-1 Latin 1 */
    PG_LATIN2,                  /* ISO-8859-2 Latin 2 */
    PG_LATIN3,                  /* ISO-8859-3 Latin 3 */
    PG_LATIN4,                  /* ISO-8859-4 Latin 4 */
    PG_LATIN5,                  /* ISO-8859-9 Latin 5 */
    PG_LATIN6,                  /* ISO-8859-10 Latin6 */
    PG_LATIN7,                  /* ISO-8859-13 Latin7 */
    PG_LATIN8,                  /* ISO-8859-14 Latin8 */
    PG_LATIN9,                  /* ISO-8859-15 Latin9 */
    PG_LATIN10,                 /* ISO-8859-16 Latin10 */
    PG_WIN1256,                 /* windows-1256 */
    PG_WIN1258,                 /* Windows-1258 */
    PG_WIN866,                  /* (MS-DOS CP866) */
    PG_WIN874,                  /* windows-874 */
    PG_KOI8R,                   /* KOI8-R */
    PG_WIN1251,                 /* windows-1251 */
    PG_WIN1252,                 /* windows-1252 */
    PG_ISO_8859_5,              /* ISO-8859-5 */
    PG_ISO_8859_6,              /* ISO-8859-6 */
    PG_ISO_8859_7,              /* ISO-8859-7 */
    PG_ISO_8859_8,              /* ISO-8859-8 */
    PG_WIN1250,                 /* windows-1250 */
    PG_WIN1253,                 /* windows-1253 */
    PG_WIN1254,                 /* windows-1254 */
    PG_WIN1255,                 /* windows-1255 */
    PG_WIN1257,                 /* windows-1257 */
    PG_KOI8U,                   /* KOI8-U */
    /* PG_ENCODING_BE_LAST points to the above entry */
 
    /* followings are for client encoding only */
    PG_SJIS,                    /* Shift JIS (Windows-932) */
    PG_BIG5,                    /* Big5 (Windows-950) */
    PG_GBK,                     /* GBK (Windows-936) */
    PG_UHC,                     /* UHC (Windows-949) */
    PG_GB18030,                 /* GB18030 */
    PG_JOHAB,                   /* EUC for Korean JOHAB */
    PG_SHIFT_JIS_2004,          /* Shift-JIS-2004 */
    _PG_LAST_ENCODING_          /* mark only */
 
} pg_enc;
 
#define PG_ENCODING_BE_LAST PG_KOI8U
 
/*
 * Please use these tests before access to pg_enc2name_tbl[]
 * or to other places...
 */
#define PG_VALID_BE_ENCODING(_enc) \
        ((_enc) >= 0 && (_enc) <= PG_ENCODING_BE_LAST)
 
#define PG_ENCODING_IS_CLIENT_ONLY(_enc) \
        ((_enc) > PG_ENCODING_BE_LAST && (_enc) < _PG_LAST_ENCODING_)
 
#define PG_VALID_ENCODING(_enc) \
        ((_enc) >= 0 && (_enc) < _PG_LAST_ENCODING_)
 
/* On FE are possible all encodings */
#define PG_VALID_FE_ENCODING(_enc)  PG_VALID_ENCODING(_enc)
 
/*
 * When converting strings between different encodings, we assume that space
 * for converted result is 4-to-1 growth in the worst case.  The rate for
 * currently supported encoding pairs are within 3 (SJIS JIS X0201 half width
 * kana -> UTF8 is the worst case).  So "4" should be enough for the moment.
 *
 * Note that this is not the same as the maximum character width in any
 * particular encoding.
 */
#define MAX_CONVERSION_GROWTH  4
 
/*
 * Maximum byte length of a string that's required in any encoding to convert
 * at least one character to any other encoding.  In other words, if you feed
 * MAX_CONVERSION_INPUT_LENGTH bytes to any encoding conversion function, it
 * is guaranteed to be able to convert something without needing more input
 * (assuming the input is valid).
 *
 * Currently, the maximum case is the conversion UTF8 -> SJIS JIS X0201 half
 * width kana, where a pair of UTF-8 characters is converted into a single
 * SHIFT_JIS_2004 character (the reverse of the worst case for
 * MAX_CONVERSION_GROWTH).  It needs 6 bytes of input.  In theory, a
 * user-defined conversion function might have more complicated cases, although
 * for the reverse mapping you would probably also need to bump up
 * MAX_CONVERSION_GROWTH.  But there is no need to be stingy here, so make it
 * generous.
 */
#define MAX_CONVERSION_INPUT_LENGTH 16
 
/*
 * Maximum byte length of the string equivalent to any one Unicode code point,
 * in any backend encoding.  The current value assumes that a 4-byte UTF-8
 * character might expand by MAX_CONVERSION_GROWTH, which is a huge
 * overestimate.  But in current usage we don't allocate large multiples of
 * this, so there's little point in being stingy.
 */
#define MAX_UNICODE_EQUIVALENT_STRING   16
 
/*
 * Table for mapping an encoding number to official encoding name and
 * possibly other subsidiary data.  Be careful to check encoding number
 * before accessing a table entry!
 *
 * if (PG_VALID_ENCODING(encoding))
 *      pg_enc2name_tbl[ encoding ];
 */
typedef struct pg_enc2name
{
    const char *name;
    pg_enc      encoding;
#ifdef WIN32
    unsigned    codepage;       /* codepage for WIN32 */
#endif
} pg_enc2name;
 
extern PGDLLIMPORT const pg_enc2name pg_enc2name_tbl[];
 
/*
 * Encoding names for gettext
 */
typedef struct pg_enc2gettext
{
    pg_enc      encoding;
    const char *name;
} pg_enc2gettext;
 
extern PGDLLIMPORT const pg_enc2gettext pg_enc2gettext_tbl[];
 
/*
 * pg_wchar stuff
 */
typedef int (*mb2wchar_with_len_converter) (const unsigned char *from,
                                            pg_wchar *to,
                                            int len);
 
typedef int (*wchar2mb_with_len_converter) (const pg_wchar *from,
                                            unsigned char *to,
                                            int len);
 
typedef int (*mblen_converter) (const unsigned char *mbstr);
 
typedef int (*mbdisplaylen_converter) (const unsigned char *mbstr);
 
typedef bool (*mbcharacter_incrementer) (unsigned char *mbstr, int len);
 
typedef int (*mbchar_verifier) (const unsigned char *mbstr, int len);
 
typedef int (*mbstr_verifier) (const unsigned char *mbstr, int len);
 
typedef struct
{
    mb2wchar_with_len_converter mb2wchar_with_len;  /* convert a multibyte
                                                     * string to a wchar */
    wchar2mb_with_len_converter wchar2mb_with_len;  /* convert a wchar string
                                                     * to a multibyte */
    mblen_converter mblen;      /* get byte length of a char */
    mbdisplaylen_converter dsplen;  /* get display width of a char */
    mbchar_verifier mbverifychar;   /* verify multibyte character */
    mbstr_verifier mbverifystr; /* verify multibyte string */
    int         maxmblen;       /* max bytes for a char in this encoding */
} pg_wchar_tbl;
 
extern PGDLLIMPORT const pg_wchar_tbl pg_wchar_table[];
 
/*
 * Data structures for conversions between UTF-8 and other encodings
 * (UtfToLocal() and LocalToUtf()).  In these data structures, characters of
 * either encoding are represented by uint32 words; hence we can only support
 * characters up to 4 bytes long.  For example, the byte sequence 0xC2 0x89
 * would be represented by 0x0000C289, and 0xE8 0xA2 0xB4 by 0x00E8A2B4.
 *
 * There are three possible ways a character can be mapped:
 *
 * 1. Using a radix tree, from source to destination code.
 * 2. Using a sorted array of source -> destination code pairs. This
 *    method is used for "combining" characters. There are so few of
 *    them that building a radix tree would be wasteful.
 * 3. Using a conversion function.
 */
 
/*
 * Radix tree for character conversion.
 *
 * Logically, this is actually four different radix trees, for 1-byte,
 * 2-byte, 3-byte and 4-byte inputs. The 1-byte tree is a simple lookup
 * table from source to target code. The 2-byte tree consists of two levels:
 * one lookup table for the first byte, where the value in the lookup table
 * points to a lookup table for the second byte. And so on.
 *
 * Physically, all the trees are stored in one big array, in 'chars16' or
 * 'chars32', depending on the maximum value that needs to be represented. For
 * each level in each tree, we also store lower and upper bound of allowed
 * values - values outside those bounds are considered invalid, and are left
 * out of the tables.
 *
 * In the intermediate levels of the trees, the values stored are offsets
 * into the chars[16|32] array.
 *
 * In the beginning of the chars[16|32] array, there is always a number of
 * zeros, so that you safely follow an index from an intermediate table
 * without explicitly checking for a zero. Following a zero any number of
 * times will always bring you to the dummy, all-zeros table in the
 * beginning. This helps to shave some cycles when looking up values.
 */
typedef struct
{
    /*
     * Array containing all the values. Only one of chars16 or chars32 is
     * used, depending on how wide the values we need to represent are.
     */
    const uint16 *chars16;
    const uint32 *chars32;
 
    /* Radix tree for 1-byte inputs */
    uint32      b1root;         /* offset of table in the chars[16|32] array */
    uint8       b1_lower;       /* min allowed value for a single byte input */
    uint8       b1_upper;       /* max allowed value for a single byte input */
 
    /* Radix tree for 2-byte inputs */
    uint32      b2root;         /* offset of 1st byte's table */
    uint8       b2_1_lower;     /* min/max allowed value for 1st input byte */
    uint8       b2_1_upper;
    uint8       b2_2_lower;     /* min/max allowed value for 2nd input byte */
    uint8       b2_2_upper;
 
    /* Radix tree for 3-byte inputs */
    uint32      b3root;         /* offset of 1st byte's table */
    uint8       b3_1_lower;     /* min/max allowed value for 1st input byte */
    uint8       b3_1_upper;
    uint8       b3_2_lower;     /* min/max allowed value for 2nd input byte */
    uint8       b3_2_upper;
    uint8       b3_3_lower;     /* min/max allowed value for 3rd input byte */
    uint8       b3_3_upper;
 
    /* Radix tree for 4-byte inputs */
    uint32      b4root;         /* offset of 1st byte's table */
    uint8       b4_1_lower;     /* min/max allowed value for 1st input byte */
    uint8       b4_1_upper;
    uint8       b4_2_lower;     /* min/max allowed value for 2nd input byte */
    uint8       b4_2_upper;
    uint8       b4_3_lower;     /* min/max allowed value for 3rd input byte */
    uint8       b4_3_upper;
    uint8       b4_4_lower;     /* min/max allowed value for 4th input byte */
    uint8       b4_4_upper;
 
} pg_mb_radix_tree;
 
/*
 * UTF-8 to local code conversion map (for combined characters)
 */
typedef struct
{
    uint32      utf1;           /* UTF-8 code 1 */
    uint32      utf2;           /* UTF-8 code 2 */
    uint32      code;           /* local code */
} pg_utf_to_local_combined;
 
/*
 * local code to UTF-8 conversion map (for combined characters)
 */
typedef struct
{
    uint32      code;           /* local code */
    uint32      utf1;           /* UTF-8 code 1 */
    uint32      utf2;           /* UTF-8 code 2 */
} pg_local_to_utf_combined;
 
/*
 * callback function for algorithmic encoding conversions (in either direction)
 *
 * if function returns zero, it does not know how to convert the code
 */
typedef uint32 (*utf_local_conversion_func) (uint32 code);
 
/*
 * Support macro for encoding conversion functions to validate their
 * arguments.  (This could be made more compact if we included fmgr.h
 * here, but we don't want to do that because this header file is also
 * used by frontends.)
 */
#define CHECK_ENCODING_CONVERSION_ARGS(srcencoding,destencoding) \
    check_encoding_conversion_args(PG_GETARG_INT32(0), \
                                   PG_GETARG_INT32(1), \
                                   PG_GETARG_INT32(4), \
                                   (srcencoding), \
                                   (destencoding))
 
 
/*
 * Some handy functions for Unicode-specific tests.
 */
static inline bool
is_valid_unicode_codepoint(pg_wchar c)
{
    return (c > 0 && c <= 0x10FFFF);
}
 
static inline bool
is_utf16_surrogate_first(pg_wchar c)
{
    return (c >= 0xD800 && c <= 0xDBFF);
}
 
static inline bool
is_utf16_surrogate_second(pg_wchar c)
{
    return (c >= 0xDC00 && c <= 0xDFFF);
}
 
static inline pg_wchar
surrogate_pair_to_codepoint(pg_wchar first, pg_wchar second)
{
    return ((first & 0x3FF) << 10) + 0x10000 + (second & 0x3FF);
}
 
 
/*
 * These functions are considered part of libpq's exported API and
 * are also declared in libpq-fe.h.
 */
extern int  pg_char_to_encoding(const char *name);
extern const char *pg_encoding_to_char(int encoding);
extern int  pg_valid_server_encoding_id(int encoding);
 
/*
 * These functions are available to frontend code that links with libpgcommon
 * (in addition to the ones just above).  The constant tables declared
 * earlier in this file are also available from libpgcommon.
 */
extern int  pg_encoding_mblen(int encoding, const char *mbstr);
extern int  pg_encoding_mblen_bounded(int encoding, const char *mbstr);
extern int  pg_encoding_dsplen(int encoding, const char *mbstr);
extern int  pg_encoding_verifymbchar(int encoding, const char *mbstr, int len);
extern int  pg_encoding_verifymbstr(int encoding, const char *mbstr, int len);
extern int  pg_encoding_max_length(int encoding);
extern int  pg_valid_client_encoding(const char *name);
extern int  pg_valid_server_encoding(const char *name);
extern bool is_encoding_supported_by_icu(int encoding);
extern const char *get_encoding_name_for_icu(int encoding);
 
extern unsigned char *unicode_to_utf8(pg_wchar c, unsigned char *utf8string);
extern pg_wchar utf8_to_unicode(const unsigned char *c);
extern bool pg_utf8_islegal(const unsigned char *source, int length);
extern int  pg_utf_mblen(const unsigned char *s);
extern int  pg_mule_mblen(const unsigned char *s);
 
/*
 * The remaining functions are backend-only.
 */
extern int  pg_mb2wchar(const char *from, pg_wchar *to);
extern int  pg_mb2wchar_with_len(const char *from, pg_wchar *to, int len);
extern int  pg_encoding_mb2wchar_with_len(int encoding,
                                          const char *from, pg_wchar *to, int len);
extern int  pg_wchar2mb(const pg_wchar *from, char *to);
extern int  pg_wchar2mb_with_len(const pg_wchar *from, char *to, int len);
extern int  pg_encoding_wchar2mb_with_len(int encoding,
                                          const pg_wchar *from, char *to, int len);
extern int  pg_char_and_wchar_strcmp(const char *s1, const pg_wchar *s2);
extern int  pg_wchar_strncmp(const pg_wchar *s1, const pg_wchar *s2, size_t n);
extern int  pg_char_and_wchar_strncmp(const char *s1, const pg_wchar *s2, size_t n);
extern size_t pg_wchar_strlen(const pg_wchar *str);
extern int  pg_mblen(const char *mbstr);
extern int  pg_dsplen(const char *mbstr);
extern int  pg_mbstrlen(const char *mbstr);
extern int  pg_mbstrlen_with_len(const char *mbstr, int limit);
extern int  pg_mbcliplen(const char *mbstr, int len, int limit);
extern int  pg_encoding_mbcliplen(int encoding, const char *mbstr,
                                  int len, int limit);
extern int  pg_mbcharcliplen(const char *mbstr, int len, int limit);
extern int  pg_database_encoding_max_length(void);
extern mbcharacter_incrementer pg_database_encoding_character_incrementer(void);
 
extern int  PrepareClientEncoding(int encoding);
extern int  SetClientEncoding(int encoding);
extern void InitializeClientEncoding(void);
extern int  pg_get_client_encoding(void);
extern const char *pg_get_client_encoding_name(void);
 
extern void SetDatabaseEncoding(int encoding);
extern int  GetDatabaseEncoding(void);
extern const char *GetDatabaseEncodingName(void);
extern void SetMessageEncoding(int encoding);
extern int  GetMessageEncoding(void);
 
#ifdef ENABLE_NLS
extern int  pg_bind_textdomain_codeset(const char *domainname);
#endif
 
extern unsigned char *pg_do_encoding_conversion(unsigned char *src, int len,
                                                int src_encoding,
                                                int dest_encoding);
extern int  pg_do_encoding_conversion_buf(Oid proc,
                                          int src_encoding,
                                          int dest_encoding,
                                          unsigned char *src, int srclen,
                                          unsigned char *dest, int destlen,
                                          bool noError);
 
extern char *pg_client_to_server(const char *s, int len);
extern char *pg_server_to_client(const char *s, int len);
extern char *pg_any_to_server(const char *s, int len, int encoding);
extern char *pg_server_to_any(const char *s, int len, int encoding);
 
extern void pg_unicode_to_server(pg_wchar c, unsigned char *s);
extern bool pg_unicode_to_server_noerror(pg_wchar c, unsigned char *s);
 
extern unsigned short BIG5toCNS(unsigned short big5, unsigned char *lc);
extern unsigned short CNStoBIG5(unsigned short cns, unsigned char lc);
 
extern int  UtfToLocal(const unsigned char *utf, int len,
                       unsigned char *iso,
                       const pg_mb_radix_tree *map,
                       const pg_utf_to_local_combined *cmap, int cmapsize,
                       utf_local_conversion_func conv_func,
                       int encoding, bool noError);
extern int  LocalToUtf(const unsigned char *iso, int len,
                       unsigned char *utf,
                       const pg_mb_radix_tree *map,
                       const pg_local_to_utf_combined *cmap, int cmapsize,
                       utf_local_conversion_func conv_func,
                       int encoding, bool noError);
 
extern bool pg_verifymbstr(const char *mbstr, int len, bool noError);
extern bool pg_verify_mbstr(int encoding, const char *mbstr, int len,
                            bool noError);
extern int  pg_verify_mbstr_len(int encoding, const char *mbstr, int len,
                                bool noError);
 
extern void check_encoding_conversion_args(int src_encoding,
                                           int dest_encoding,
                                           int len,
                                           int expected_src_encoding,
                                           int expected_dest_encoding);
 
extern void report_invalid_encoding(int encoding, const char *mbstr, int len) pg_attribute_noreturn();
extern void report_untranslatable_char(int src_encoding, int dest_encoding,
                                       const char *mbstr, int len) pg_attribute_noreturn();
 
extern int  local2local(const unsigned char *l, unsigned char *p, int len,
                        int src_encoding, int dest_encoding,
                        const unsigned char *tab, bool noError);
extern int  latin2mic(const unsigned char *l, unsigned char *p, int len,
                      int lc, int encoding, bool noError);
extern int  mic2latin(const unsigned char *mic, unsigned char *p, int len,
                      int lc, int encoding, bool noError);
extern int  latin2mic_with_table(const unsigned char *l, unsigned char *p,
                                 int len, int lc, int encoding,
                                 const unsigned char *tab, bool noError);
extern int  mic2latin_with_table(const unsigned char *mic, unsigned char *p,
                                 int len, int lc, int encoding,
                                 const unsigned char *tab, bool noError);
 
#ifdef WIN32
extern WCHAR *pgwin32_message_to_UTF16(const char *str, int len, int *utf16len);
#endif
 
 
/*
 * Verify a chunk of bytes for valid ASCII.
 *
 * Returns false if the input contains any zero bytes or bytes with the
 * high-bit set. Input len must be a multiple of the chunk size (8 or 16).
 */
static inline bool
is_valid_ascii(const unsigned char *s, int len)
{
    const unsigned char *const s_end = s + len;
    Vector8     chunk;
    Vector8     highbit_cum = vector8_broadcast(0);
#ifdef USE_NO_SIMD
    Vector8     zero_cum = vector8_broadcast(0x80);
#endif
 
    Assert(len % sizeof(chunk) == 0);
 
    while (s < s_end)
    {
        vector8_load(&chunk, s);
 
        /* Capture any zero bytes in this chunk. */
#ifdef USE_NO_SIMD
 
        /*
         * First, add 0x7f to each byte. This sets the high bit in each byte,
         * unless it was a zero. If any resulting high bits are zero, the
         * corresponding high bits in the zero accumulator will be cleared.
         *
         * If none of the bytes in the chunk had the high bit set, the max
         * value each byte can have after the addition is 0x7f + 0x7f = 0xfe,
         * and we don't need to worry about carrying over to the next byte. If
         * any input bytes did have the high bit set, it doesn't matter
         * because we check for those separately.
         */
        zero_cum &= (chunk + vector8_broadcast(0x7F));
#else
 
        /*
         * Set all bits in each lane of the highbit accumulator where input
         * bytes are zero.
         */
        highbit_cum = vector8_or(highbit_cum,
                                 vector8_eq(chunk, vector8_broadcast(0)));
#endif
 
        /* Capture all set bits in this chunk. */
        highbit_cum = vector8_or(highbit_cum, chunk);
 
        s += sizeof(chunk);
    }
 
    /* Check if any high bits in the high bit accumulator got set. */
    if (vector8_is_highbit_set(highbit_cum))
        return false;
 
#ifdef USE_NO_SIMD
    /* Check if any high bits in the zero accumulator got cleared. */
    if (zero_cum != vector8_broadcast(0x80))
        return false;
#endif
 
    return true;
}
 
#endif                          /* PG_WCHAR_H */