Adding MY_CHARSET_HANDLER::native_to_mb().

This is a pre-requisite patch for:
- MDEV-8433 Make field<'broken-string' use indexes
- MDEV-8625 Bad result set with ignorable characters when using a prefix key
- MDEV-8626 Bad result set with contractions when using a prefix key

include/m_ctype.h

@@ -511,6 +511,20 @@ struct my_charset_handler_st
                       char *dst, size_t dst_length,
                       const char *src, size_t src_length,
                       size_t nchars, MY_STRCOPY_STATUS *status);
+  /**
+    Write a character to the target string, using its native code.
+    For Unicode character sets (utf8, ucs2, utf16, utf16le, utf32, filename)
+    native codes are equvalent to Unicode code points.
+    For 8bit character sets the native code is just the byte value.
+    For Asian characters sets:
+    - MB1 native code is just the byte value (e.g. on the ASCII range)
+    - MB2 native code is ((b0 << 8) + b1).
+    - MB3 native code is ((b0 <<16) + (b1 << 8) + b2)
+    Note, CHARSET_INFO::min_sort_char and CHARSET_INFO::max_sort_char
+    are defined in native notation and should be written using
+    cs->cset->native_to_mb() rather than cs->cset->wc_mb().
+  */
+  my_charset_conv_wc_mb native_to_mb;
 };
 
 extern MY_CHARSET_HANDLER my_charset_8bit_handler;
@@ -664,6 +678,7 @@ extern int my_strcasecmp_8bit(CHARSET_INFO * cs, const char *, const char *);
 
 int my_mb_wc_8bit(CHARSET_INFO *cs,my_wc_t *wc, const uchar *s,const uchar *e);
 int my_wc_mb_8bit(CHARSET_INFO *cs,my_wc_t wc, uchar *s, uchar *e);
+int my_wc_mb_bin(CHARSET_INFO *cs,my_wc_t wc, uchar *s, uchar *e);
 
 int my_mb_ctype_8bit(CHARSET_INFO *,int *, const uchar *,const uchar *);
 int my_mb_ctype_mb(CHARSET_INFO *,int *, const uchar *,const uchar *);

strings/ctype-big5.c

@@ -6847,6 +6847,7 @@ static MY_CHARSET_HANDLER my_charset_big5_handler=
   my_charlen_big5,
   my_well_formed_char_length_big5,
   my_copy_fix_mb,
+  my_native_to_mb_big5,
 };
 
 struct charset_info_st my_charset_big5_chinese_ci=

strings/ctype-bin.c

@@ -256,10 +256,8 @@ static int my_mb_wc_bin(CHARSET_INFO *cs __attribute__((unused)),
 }
 
 
-static int my_wc_mb_bin(CHARSET_INFO *cs __attribute__((unused)),
-			my_wc_t wc,
-			uchar *s,
-			uchar *e __attribute__((unused)))
+int my_wc_mb_bin(CHARSET_INFO *cs __attribute__((unused)),
+                 my_wc_t wc, uchar *s, uchar *e)
 {
   if (s >= e)
     return MY_CS_TOOSMALL;
@@ -552,6 +550,7 @@ static MY_CHARSET_HANDLER my_charset_handler=
   my_charlen_8bit,
   my_well_formed_char_length_8bit,
   my_copy_8bit,
+  my_wc_mb_bin,
 };
 
 

strings/ctype-cp932.c

@@ -34722,6 +34722,7 @@ static MY_CHARSET_HANDLER my_charset_handler=
   my_charlen_cp932,
   my_well_formed_char_length_cp932,
   my_copy_fix_mb,
+  my_native_to_mb_cp932,
 };
 
 

strings/ctype-euc_kr.c

@@ -10016,6 +10016,7 @@ static MY_CHARSET_HANDLER my_charset_handler=
   my_charlen_euckr,
   my_well_formed_char_length_euckr,
   my_copy_fix_mb,
+  my_native_to_mb_euckr,
 };
 
 

strings/ctype-eucjpms.c

@@ -67549,6 +67549,7 @@ static MY_CHARSET_HANDLER my_charset_handler=
     my_charlen_eucjpms,
     my_well_formed_char_length_eucjpms,
     my_copy_fix_mb,
+    my_native_to_mb_eucjpms,
 };
 
 

strings/ctype-gb2312.c

@@ -6420,6 +6420,7 @@ static MY_CHARSET_HANDLER my_charset_handler=
   my_charlen_gb2312,
   my_well_formed_char_length_gb2312,
   my_copy_fix_mb,
+  my_native_to_mb_gb2312,
 };
 
 

strings/ctype-gbk.c

@@ -10732,6 +10732,7 @@ static MY_CHARSET_HANDLER my_charset_handler=
   my_charlen_gbk,
   my_well_formed_char_length_gbk,
   my_copy_fix_mb,
+  my_native_to_mb_gbk,
 };
 
 

strings/ctype-latin1.c

@@ -425,6 +425,7 @@ static MY_CHARSET_HANDLER my_charset_handler=
     my_charlen_8bit,
     my_well_formed_char_length_8bit,
     my_copy_8bit,
+    my_wc_mb_bin, /* native_to_mb */
 };
 
 

strings/ctype-mb.c

@@ -811,25 +811,8 @@ my_hash_sort_mb_bin(CHARSET_INFO *cs __attribute__((unused)),
 static void pad_max_char(CHARSET_INFO *cs, char *str, char *end)
 {
   char buf[10];
-  char buflen;
-
-  if (!(cs->state & MY_CS_UNICODE))
-  {
-    if (cs->max_sort_char <= 255)
-    {
-      bfill(str, end - str, cs->max_sort_char);
-      return;
-    }
-    buf[0]= cs->max_sort_char >> 8;
-    buf[1]= cs->max_sort_char & 0xFF;
-    buflen= 2;
-  }
-  else
-  {
-    buflen= cs->cset->wc_mb(cs, cs->max_sort_char, (uchar*) buf,
-                            (uchar*) buf + sizeof(buf));
-  }
-
+  char buflen= cs->cset->native_to_mb(cs, cs->max_sort_char, (uchar*) buf,
+                                      (uchar*) buf + sizeof(buf));
   DBUG_ASSERT(buflen > 0);
   do
   {

strings/ctype-mb.ic

@@ -33,6 +33,7 @@
 #define DEFINE_WELL_FORMED_LEN
 #define DEFINE_WELL_FORMED_CHAR_LENGTH
 #define DEFINE_CHARLEN
+#define DEFINE_NATIVE_TO_MB_VARLEN
 #endif
 
 
@@ -257,4 +258,67 @@ MY_FUNCTION_NAME(well_formed_char_length)(CHARSET_INFO *cs __attribute__((unused
 }
 #endif /* DEFINE_WELL_FORMED_CHAR_LENGTH_USING_CHARLEN */
 
+
+#ifdef DEFINE_NATIVE_TO_MB_VARLEN
+/*
+  Write a native 2-byte character.
+  If the full character does not fit, only the first byte is written.
+*/
+static inline int
+my_native_to_mb_fixed2(my_wc_t wc, uchar *s, uchar *e)
+{
+  /* The caller must insure there is a space for at least one byte */
+  DBUG_ASSERT(s < e);
+  s[0]= wc >> 8;
+  if (s + 2 > e)
+    return MY_CS_TOOSMALL2;
+  s[1]= wc & 0xFF;
+  return 2;
+}
+
+
+/*
+  Write a native 3-byte character.
+  If the full character does not fit, only the leading bytes are written.
+*/
+static inline int
+my_native_to_mb_fixed3(my_wc_t wc, uchar *s, uchar *e)
+{
+  /* The caller must insure there is a space for at least one byte */
+  DBUG_ASSERT(s < e);
+  s[0]= wc >> 16;
+  if (s + 2 > e)
+    return MY_CS_TOOSMALL2;
+  s[1]= (wc >> 8) & 0xFF;
+  if (s + 3 > e)
+    return MY_CS_TOOSMALL3;
+  s[2]= wc & 0xFF;
+  return 3;
+}
+
+
+/*
+  Write a native 1-byte or 2-byte or 3-byte character.
+*/
+
+static int
+MY_FUNCTION_NAME(native_to_mb)(CHARSET_INFO *cs __attribute__((unused)),
+                               my_wc_t wc, uchar *s, uchar *e)
+{
+  if (s >= e)
+    return MY_CS_TOOSMALL;
+  if ((int) wc <= 0xFF)
+  {
+    s[0]= (uchar) wc;
+    return 1;
+  }
+#ifdef IS_MB3_HEAD
+  if (wc > 0xFFFF)
+    return my_native_to_mb_fixed3(wc, s, e);
+#endif
+  return my_native_to_mb_fixed2(wc, s, e);
+}
+#endif /* DEFINE_NATIVE_TO_MB_VARLEN */
+
+
 #undef MY_FUNCTION_NAME

strings/ctype-simple.c

@@ -1950,6 +1950,7 @@ MY_CHARSET_HANDLER my_charset_8bit_handler=
     my_charlen_8bit,
     my_well_formed_char_length_8bit,
     my_copy_8bit,
+    my_wc_mb_bin, /* native_to_mb */
 };
 
 MY_COLLATION_HANDLER my_collation_8bit_simple_ci_handler =

strings/ctype-sjis.c

@@ -34101,6 +34101,7 @@ static MY_CHARSET_HANDLER my_charset_handler=
   my_charlen_sjis,
   my_well_formed_char_length_sjis,
   my_copy_fix_mb,
+  my_native_to_mb_sjis,
 };
 
 

strings/ctype-tis620.c

@@ -889,6 +889,7 @@ static MY_CHARSET_HANDLER my_charset_handler=
     my_charlen_8bit,
     my_well_formed_char_length_8bit,
     my_copy_8bit,
+    my_wc_mb_bin, /* native_to_mb */
 };
 
 

strings/ctype-ucs2.c

@@ -1590,6 +1590,7 @@ MY_CHARSET_HANDLER my_charset_utf16_handler=
   my_charlen_utf16,
   my_well_formed_char_length_utf16,
   my_copy_fix_mb2_or_mb4,
+  my_uni_utf16,
 };
 
 
@@ -1812,6 +1813,7 @@ static MY_CHARSET_HANDLER my_charset_utf16le_handler=
   my_charlen_utf16,
   my_well_formed_char_length_utf16,
   my_copy_fix_mb2_or_mb4,
+  my_uni_utf16le,
 };
 
 
@@ -2556,6 +2558,7 @@ MY_CHARSET_HANDLER my_charset_utf32_handler=
   my_charlen_utf32,
   my_well_formed_char_length_utf32,
   my_copy_fix_mb2_or_mb4,
+  my_uni_utf32,
 };
 
 
@@ -3042,6 +3045,7 @@ MY_CHARSET_HANDLER my_charset_ucs2_handler=
     my_charlen_ucs2,
     my_well_formed_char_length_ucs2,
     my_copy_fix_mb2_or_mb4,
+    my_uni_ucs2,
 };
 
 

strings/ctype-ujis.c

@@ -67293,6 +67293,7 @@ static MY_CHARSET_HANDLER my_charset_handler=
     my_charlen_ujis,
     my_well_formed_char_length_ujis,
     my_copy_fix_mb,
+    my_native_to_mb_ujis,
 };
 
 

strings/ctype-utf8.c

@@ -5526,6 +5526,7 @@ MY_CHARSET_HANDLER my_charset_utf8_handler=
     my_charlen_utf8,
     my_well_formed_char_length_utf8,
     my_copy_fix_mb,
+    my_uni_utf8,
 };
 
 
@@ -7109,6 +7110,7 @@ static MY_CHARSET_HANDLER my_charset_filename_handler=
     my_charlen_filename,
     my_well_formed_char_length_filename,
     my_copy_fix_mb,
+    my_wc_mb_filename,
 };
 
 
@@ -7879,6 +7881,7 @@ MY_CHARSET_HANDLER my_charset_utf8mb4_handler=
   my_charlen_utf8mb4,
   my_well_formed_char_length_utf8mb4,
   my_copy_fix_mb,
+  my_wc_mb_utf8mb4,
 };