Merge branch 10.5 into 10.6

sql/sql_class.cc

@@ -2366,6 +2366,58 @@ bool THD::convert_string(LEX_STRING *to, CHARSET_INFO *to_cs,
 }
 
 
+/*
+  Reinterpret a binary string to a character string
+
+  @param[OUT] to    The result will be written here,
+                    either the original string as is,
+                    or a newly alloced fixed string with
+                    some zero bytes prepended.
+  @param cs         The destination character set
+  @param str        The binary string
+  @param length     The length of the binary string
+
+  @return           false on success
+  @return           true on error
+*/
+
+bool THD::reinterpret_string_from_binary(LEX_CSTRING *to, CHARSET_INFO *cs,
+                                         const char *str, size_t length)
+{
+  /*
+    When reinterpreting from binary to tricky character sets like
+    UCS2, UTF16, UTF32, we may need to prepend some zero bytes.
+    This is possible in scenarios like this:
+      SET COLLATION_CONNECTION=utf32_general_ci, CHARACTER_SET_CLIENT=binary;
+    This code is similar to String::copy_aligned().
+  */
+  size_t incomplete= length % cs->mbminlen; // Bytes in an incomplete character
+  if (incomplete)
+  {
+    size_t zeros= cs->mbminlen - incomplete;
+    size_t aligned_length= zeros + length;
+    char *dst= (char*) alloc(aligned_length + 1);
+    if (!dst)
+    {
+      to->str= NULL; // Safety
+      to->length= 0;
+      return true;
+    }
+    bzero(dst, zeros);
+    memcpy(dst + zeros, str, length);
+    dst[aligned_length]= '\0';
+    to->str= dst;
+    to->length= aligned_length;
+  }
+  else
+  {
+    to->str= str;
+    to->length= length;
+  }
+  return check_string_for_wellformedness(to->str, to->length, cs);
+}
+
+
 /*
   Convert a string between two character sets.
   dstcs and srccs cannot be &my_charset_bin.