ascii.c

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/*-----------------------------------------------------------------------
 * ascii.c
 *   The PostgreSQL routine for string to ascii conversion.
 *
 *   Portions Copyright (c) 1999-2025, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/ascii.c
 *
 *-----------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "mb/pg_wchar.h"
#include "utils/ascii.h"
#include "utils/fmgrprotos.h"
#include "varatt.h"
 
static void pg_to_ascii(unsigned char *src, unsigned char *src_end,
                        unsigned char *dest, int enc);
static text *encode_to_ascii(text *data, int enc);
 
 
/* ----------
 * to_ascii
 * ----------
 */
static void
pg_to_ascii(unsigned char *src, unsigned char *src_end, unsigned char *dest, int enc)
{
    unsigned char *x;
    const unsigned char *ascii;
    int         range;
 
    /*
     * relevant start for an encoding
     */
#define RANGE_128   128
#define RANGE_160   160
 
    if (enc == PG_LATIN1)
    {
        /*
         * ISO-8859-1 <range: 160 -- 255>
         */
        ascii = (const unsigned char *) "  cL Y  \"Ca  -R     'u .,      ?AAAAAAACEEEEIIII NOOOOOxOUUUUYTBaaaaaaaceeeeiiii nooooo/ouuuuyty";
        range = RANGE_160;
    }
    else if (enc == PG_LATIN2)
    {
        /*
         * ISO-8859-2 <range: 160 -- 255>
         */
        ascii = (const unsigned char *) " A L LS \"SSTZ-ZZ a,l'ls ,sstz\"zzRAAAALCCCEEEEIIDDNNOOOOxRUUUUYTBraaaalccceeeeiiddnnoooo/ruuuuyt.";
        range = RANGE_160;
    }
    else if (enc == PG_LATIN9)
    {
        /*
         * ISO-8859-15 <range: 160 -- 255>
         */
        ascii = (const unsigned char *) "  cL YS sCa  -R     Zu .z   EeY?AAAAAAACEEEEIIII NOOOOOxOUUUUYTBaaaaaaaceeeeiiii nooooo/ouuuuyty";
        range = RANGE_160;
    }
    else if (enc == PG_WIN1250)
    {
        /*
         * Window CP1250 <range: 128 -- 255>
         */
        ascii = (const unsigned char *) "  ' \"    %S<STZZ `'\"\".--  s>stzz   L A  \"CS  -RZ  ,l'u .,as L\"lzRAAAALCCCEEEEIIDDNNOOOOxRUUUUYTBraaaalccceeeeiiddnnoooo/ruuuuyt ";
        range = RANGE_128;
    }
    else
    {
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("encoding conversion from %s to ASCII not supported",
                        pg_encoding_to_char(enc))));
        return;                 /* keep compiler quiet */
    }
 
    /*
     * Encode
     */
    for (x = src; x < src_end; x++)
    {
        if (*x < 128)
            *dest++ = *x;
        else if (*x < range)
            *dest++ = ' ';      /* bogus 128 to 'range' */
        else
            *dest++ = ascii[*x - range];
    }
}
 
/* ----------
 * encode text
 *
 * The text datum is overwritten in-place, therefore this coding method
 * cannot support conversions that change the string length!
 * ----------
 */
static text *
encode_to_ascii(text *data, int enc)
{
    pg_to_ascii((unsigned char *) VARDATA(data),    /* src */
                (unsigned char *) (data) + VARSIZE(data),   /* src end */
                (unsigned char *) VARDATA(data),    /* dest */
                enc);           /* encoding */
 
    return data;
}
 
/* ----------
 * convert to ASCII - enc is set as 'name' arg.
 * ----------
 */
Datum
to_ascii_encname(PG_FUNCTION_ARGS)
{
    text       *data = PG_GETARG_TEXT_P_COPY(0);
    char       *encname = NameStr(*PG_GETARG_NAME(1));
    int         enc = pg_char_to_encoding(encname);
 
    if (enc < 0)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("%s is not a valid encoding name", encname)));
 
    PG_RETURN_TEXT_P(encode_to_ascii(data, enc));
}
 
/* ----------
 * convert to ASCII - enc is set as int4
 * ----------
 */
Datum
to_ascii_enc(PG_FUNCTION_ARGS)
{
    text       *data = PG_GETARG_TEXT_P_COPY(0);
    int         enc = PG_GETARG_INT32(1);
 
    if (!PG_VALID_ENCODING(enc))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("%d is not a valid encoding code", enc)));
 
    PG_RETURN_TEXT_P(encode_to_ascii(data, enc));
}
 
/* ----------
 * convert to ASCII - current enc is DatabaseEncoding
 * ----------
 */
Datum
to_ascii_default(PG_FUNCTION_ARGS)
{
    text       *data = PG_GETARG_TEXT_P_COPY(0);
    int         enc = GetDatabaseEncoding();
 
    PG_RETURN_TEXT_P(encode_to_ascii(data, enc));
}
 
/* ----------
 * Copy a string in an arbitrary backend-safe encoding, converting it to a
 * valid ASCII string by replacing non-ASCII bytes with '?'.  Otherwise the
 * behavior is identical to strlcpy(), except that we don't bother with a
 * return value.
 *
 * This must not trigger ereport(ERROR), as it is called in postmaster.
 * ----------
 */
void
ascii_safe_strlcpy(char *dest, const char *src, size_t destsiz)
{
    if (destsiz == 0)           /* corner case: no room for trailing nul */
        return;
 
    while (--destsiz > 0)
    {
        /* use unsigned char here to avoid compiler warning */
        unsigned char ch = *src++;
 
        if (ch == '\0')
            break;
        /* Keep printable ASCII characters */
        if (32 <= ch && ch <= 127)
            *dest = ch;
        /* White-space is also OK */
        else if (ch == '\n' || ch == '\r' || ch == '\t')
            *dest = ch;
        /* Everything else is replaced with '?' */
        else
            *dest = '?';
        dest++;
    }
 
    *dest = '\0';
}