src/backend/utils/adt/ascii.c

   1 /*-----------------------------------------------------------------------
   2  * ascii.c
   3  *       The PostgreSQL routine for string to ascii conversion.
   4  *
   5  *       Portions Copyright (c) 1999-2025, PostgreSQL Global Development Group
   6  *
   7  * IDENTIFICATION
   8  *        src/backend/utils/adt/ascii.c
   9  *
  10  *-----------------------------------------------------------------------
  11  */
  12 #include "postgres.h"
  13
  14 #include "mb/pg_wchar.h"
  15 #include "utils/ascii.h"
  16 #include "utils/fmgrprotos.h"
  17 #include "varatt.h"
  18
  19 static void pg_to_ascii(unsigned char *src, unsigned char *src_end,
  20                                                 unsigned char *dest, int enc);
  21 static text *encode_to_ascii(text *data, int enc);
  22
  23
  24 /* ----------
  25  * to_ascii
  26  * ----------
  27  */
  28 static void
  29 pg_to_ascii(unsigned char *src, unsigned char *src_end, unsigned char *dest, int enc)
  30 {
  31         unsigned char *x;
  32         const unsigned char *ascii;
  33         int                     range;
  34
  35         /*
  36          * relevant start for an encoding
  37          */
  38 #define RANGE_128       128
  39 #define RANGE_160       160
  40
  41         if (enc == PG_LATIN1)
  42         {
  43                 /*
  44                  * ISO-8859-1 <range: 160 -- 255>
  45                  */
  46                 ascii = (const unsigned char *) "  cL Y  \"Ca  -R     'u .,      ?AAAAAAACEEEEIIII NOOOOOxOUUUUYTBaaaaaaaceeeeiiii nooooo/ouuuuyty";
  47                 range = RANGE_160;
  48         }
  49         else if (enc == PG_LATIN2)
  50         {
  51                 /*
  52                  * ISO-8859-2 <range: 160 -- 255>
  53                  */
  54                 ascii = (const unsigned char *) " A L LS \"SSTZ-ZZ a,l'ls ,sstz\"zzRAAAALCCCEEEEIIDDNNOOOOxRUUUUYTBraaaalccceeeeiiddnnoooo/ruuuuyt.";
  55                 range = RANGE_160;
  56         }
  57         else if (enc == PG_LATIN9)
  58         {
  59                 /*
  60                  * ISO-8859-15 <range: 160 -- 255>
  61                  */
  62                 ascii = (const unsigned char *) "  cL YS sCa  -R     Zu .z   EeY?AAAAAAACEEEEIIII NOOOOOxOUUUUYTBaaaaaaaceeeeiiii nooooo/ouuuuyty";
  63                 range = RANGE_160;
  64         }
  65         else if (enc == PG_WIN1250)
  66         {
  67                 /*
  68                  * Window CP1250 <range: 128 -- 255>
  69                  */
  70                 ascii = (const unsigned char *) "  ' \"    %S<STZZ `'\"\".--  s>stzz   L A  \"CS  -RZ  ,l'u .,as L\"lzRAAAALCCCEEEEIIDDNNOOOOxRUUUUYTBraaaalccceeeeiiddnnoooo/ruuuuyt ";
  71                 range = RANGE_128;
  72         }
  73         else
  74         {
  75                 ereport(ERROR,
  76                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  77                                  errmsg("encoding conversion from %s to ASCII not supported",
  78                                                 pg_encoding_to_char(enc))));
  79                 return;                                 /* keep compiler quiet */
  80         }
  81
  82         /*
  83          * Encode
  84          */
  85         for (x = src; x < src_end; x++)
  86         {
  87                 if (*x < 128)
  88                         *dest++ = *x;
  89                 else if (*x < range)
  90                         *dest++ = ' ';          /* bogus 128 to 'range' */
  91                 else
  92                         *dest++ = ascii[*x - range];
  93         }
  94 }
  95
  96 /* ----------
  97  * encode text
  98  *
  99  * The text datum is overwritten in-place, therefore this coding method
 100  * cannot support conversions that change the string length!
 101  * ----------
 102  */
 103 static text *
 104 encode_to_ascii(text *data, int enc)
 105 {
 106         pg_to_ascii((unsigned char *) VARDATA(data),    /* src */
 107                                 (unsigned char *) (data) + VARSIZE(data),       /* src end */
 108                                 (unsigned char *) VARDATA(data),        /* dest */
 109                                 enc);                   /* encoding */
 110
 111         return data;
 112 }
 113
 114 /* ----------
 115  * convert to ASCII - enc is set as 'name' arg.
 116  * ----------
 117  */
 118 Datum
 119 to_ascii_encname(PG_FUNCTION_ARGS)
 120 {
 121         text       *data = PG_GETARG_TEXT_P_COPY(0);
 122         char       *encname = NameStr(*PG_GETARG_NAME(1));
 123         int                     enc = pg_char_to_encoding(encname);
 124
 125         if (enc < 0)
 126                 ereport(ERROR,
 127                                 (errcode(ERRCODE_UNDEFINED_OBJECT),
 128                                  errmsg("%s is not a valid encoding name", encname)));
 129
 130         PG_RETURN_TEXT_P(encode_to_ascii(data, enc));
 131 }
 132
 133 /* ----------
 134  * convert to ASCII - enc is set as int4
 135  * ----------
 136  */
 137 Datum
 138 to_ascii_enc(PG_FUNCTION_ARGS)
 139 {
 140         text       *data = PG_GETARG_TEXT_P_COPY(0);
 141         int                     enc = PG_GETARG_INT32(1);
 142
 143         if (!PG_VALID_ENCODING(enc))
 144                 ereport(ERROR,
 145                                 (errcode(ERRCODE_UNDEFINED_OBJECT),
 146                                  errmsg("%d is not a valid encoding code", enc)));
 147
 148         PG_RETURN_TEXT_P(encode_to_ascii(data, enc));
 149 }
 150
 151 /* ----------
 152  * convert to ASCII - current enc is DatabaseEncoding
 153  * ----------
 154  */
 155 Datum
 156 to_ascii_default(PG_FUNCTION_ARGS)
 157 {
 158         text       *data = PG_GETARG_TEXT_P_COPY(0);
 159         int                     enc = GetDatabaseEncoding();
 160
 161         PG_RETURN_TEXT_P(encode_to_ascii(data, enc));
 162 }
 163
 164 /* ----------
 165  * Copy a string in an arbitrary backend-safe encoding, converting it to a
 166  * valid ASCII string by replacing non-ASCII bytes with '?'.  Otherwise the
 167  * behavior is identical to strlcpy(), except that we don't bother with a
 168  * return value.
 169  *
 170  * This must not trigger ereport(ERROR), as it is called in postmaster.
 171  * ----------
 172  */
 173 void
 174 ascii_safe_strlcpy(char *dest, const char *src, size_t destsiz)
 175 {
 176         if (destsiz == 0)                       /* corner case: no room for trailing nul */
 177                 return;
 178
 179         while (--destsiz > 0)
 180         {
 181                 /* use unsigned char here to avoid compiler warning */
 182                 unsigned char ch = *src++;
 183
 184                 if (ch == '\0')
 185                         break;
 186                 /* Keep printable ASCII characters */
 187                 if (32 <= ch && ch <= 127)
 188                         *dest = ch;
 189                 /* White-space is also OK */
 190                 else if (ch == '\n' || ch == '\r' || ch == '\t')
 191                         *dest = ch;
 192                 /* Everything else is replaced with '?' */
 193                 else
 194                         *dest = '?';
 195                 dest++;
 196         }
 197
 198         *dest = '\0';
 199 }