Reducing duplicate code and simplifying well formed string copying

by adding a new class String_copier.

This is a pre-requisite patch for MDEV-6566 and MDEV-6572,
to avoid adding more similar code.

sql/field.cc

@@ -6262,10 +6262,9 @@ bool Field_datetimef::get_date(MYSQL_TIME *ltime, ulonglong fuzzydate)
 
   SYNOPSIS
     check_string_copy_error()
-    field                    - Field
-    well_formed_error_pos    - where not well formed data was first met
-    cannot_convert_error_pos - where a not-convertable character was first met
-    end                      - end of the string
+    copier                   - the conversion status
+    end                      - the very end of the source string
+                               that was just copied
     cs                       - character set of the string
 
   NOTES
@@ -6282,30 +6281,25 @@ bool Field_datetimef::get_date(MYSQL_TIME *ltime, ulonglong fuzzydate)
     TRUE  - If an error happened
 */
 
-static bool
-check_string_copy_error(Field_str *field,
-                        const char *well_formed_error_pos,
-                        const char *cannot_convert_error_pos,
-                        const char *end,
-                        CHARSET_INFO *cs)
+bool
+Field_longstr::check_string_copy_error(const String_copier *copier,
+                                       const char *end,
+                                       CHARSET_INFO *cs)
 {
   const char *pos;
   char tmp[32];
-  THD *thd;
 
-  thd= field->get_thd();
-
-  if (!(pos= well_formed_error_pos) &&
-      !(pos= cannot_convert_error_pos))
+  if (!(pos= copier->most_important_error_pos()))
     return FALSE;
 
   convert_to_printable(tmp, sizeof(tmp), pos, (end - pos), cs, 6);
 
+  THD *thd= get_thd();
   push_warning_printf(thd,
                       Sql_condition::WARN_LEVEL_WARN,
                       ER_TRUNCATED_WRONG_VALUE_FOR_FIELD,
                       ER(ER_TRUNCATED_WRONG_VALUE_FOR_FIELD),
-                      "string", tmp, field->field_name,
+                      "string", tmp, field_name,
                       thd->get_stmt_da()->current_row_for_warning());
   return TRUE;
 }
@@ -6362,20 +6356,15 @@ int Field_string::store(const char *from,uint length,CHARSET_INFO *cs)
 {
   ASSERT_COLUMN_MARKED_FOR_WRITE_OR_COMPUTED;
   uint copy_length;
-  const char *well_formed_error_pos;
-  const char *cannot_convert_error_pos;
-  const char *from_end_pos;
+  String_copier copier;
 
   /* See the comment for Field_long::store(long long) */
   DBUG_ASSERT(!table || table->in_use == current_thd);
 
-  copy_length= well_formed_copy_nchars(field_charset,
+  copy_length= copier.well_formed_copy(field_charset,
                                        (char*) ptr, field_length,
                                        cs, from, length,
-                                       field_length / field_charset->mbmaxlen,
-                                       &well_formed_error_pos,
-                                       &cannot_convert_error_pos,
-                                       &from_end_pos);
+                                       field_length / field_charset->mbmaxlen);
 
   /* Append spaces if the string was shorter than the field. */
   if (copy_length < field_length)
@@ -6383,11 +6372,7 @@ int Field_string::store(const char *from,uint length,CHARSET_INFO *cs)
                               field_length-copy_length,
                               field_charset->pad_char);
 
-  if (check_string_copy_error(this, well_formed_error_pos,
-                              cannot_convert_error_pos, from + length, cs))
-    return 2;
-
-  return report_if_important_data(from_end_pos, from + length, FALSE);
+  return check_conversion_status(&copier, from + length, cs, false);
 }
 
 
@@ -6874,29 +6859,19 @@ int Field_varstring::store(const char *from,uint length,CHARSET_INFO *cs)
 {
   ASSERT_COLUMN_MARKED_FOR_WRITE_OR_COMPUTED;
   uint copy_length;
-  const char *well_formed_error_pos;
-  const char *cannot_convert_error_pos;
-  const char *from_end_pos;
+  String_copier copier;
 
-  copy_length= well_formed_copy_nchars(field_charset,
+  copy_length= copier.well_formed_copy(field_charset,
                                        (char*) ptr + length_bytes,
                                        field_length,
                                        cs, from, length,
-                                       field_length / field_charset->mbmaxlen,
-                                       &well_formed_error_pos,
-                                       &cannot_convert_error_pos,
-                                       &from_end_pos);
-
+                                       field_length / field_charset->mbmaxlen);
   if (length_bytes == 1)
     *ptr= (uchar) copy_length;
   else
     int2store(ptr, copy_length);
 
-  if (check_string_copy_error(this, well_formed_error_pos,
-                              cannot_convert_error_pos, from + length, cs))
-    return 2;
-
-  return report_if_important_data(from_end_pos, from + length, TRUE);
+  return check_conversion_status(&copier, from + length, cs, true);
 }
 
 
@@ -7351,9 +7326,8 @@ int Field_blob::store(const char *from,uint length,CHARSET_INFO *cs)
 {
   ASSERT_COLUMN_MARKED_FOR_WRITE_OR_COMPUTED;
   uint copy_length, new_length;
-  const char *well_formed_error_pos;
-  const char *cannot_convert_error_pos;
-  const char *from_end_pos, *tmp;
+  String_copier copier;
+  const char *tmp;
   char buff[STRING_BUFFER_USUAL_SIZE];
   String tmpstr(buff,sizeof(buff), &my_charset_bin);
 
@@ -7401,28 +7375,14 @@ int Field_blob::store(const char *from,uint length,CHARSET_INFO *cs)
     bmove(ptr + packlength, (uchar*) &tmp, sizeof(char*));
     return 0;
   }
-  /*
-    "length" is OK as "nchars" argument to well_formed_copy_nchars as this
-    is never used to limit the length of the data. The cut of long data
-    is done with the new_length value.
-  */
-  copy_length= well_formed_copy_nchars(field_charset,
+  copy_length= copier.well_formed_copy(field_charset,
                                        (char*) value.ptr(), new_length,
-                                       cs, from, length,
-                                       length,
-                                       &well_formed_error_pos,
-                                       &cannot_convert_error_pos,
-                                       &from_end_pos);
-
+                                       cs, from, length);
   Field_blob::store_length(copy_length);
   tmp= value.ptr();
   bmove(ptr+packlength,(uchar*) &tmp,sizeof(char*));
 
-  if (check_string_copy_error(this, well_formed_error_pos,
-                              cannot_convert_error_pos, from + length, cs))
-    return 2;
-
-  return report_if_important_data(from_end_pos, from + length, TRUE);
+  return check_conversion_status(&copier, from + length, cs, true);
 
 oom_error:
   /* Fatal OOM error */

sql/field.h

@@ -1132,6 +1132,17 @@ class Field_longstr :public Field_str
 protected:
   int report_if_important_data(const char *ptr, const char *end,
                                bool count_spaces);
+  bool check_string_copy_error(const String_copier *copier,
+                               const char *end, CHARSET_INFO *cs);
+  int check_conversion_status(const String_copier *copier,
+                              const char *end, CHARSET_INFO *cs,
+                              bool count_spaces)
+  {
+    if (check_string_copy_error(copier, end, cs))
+      return 2;
+    return report_if_important_data(copier->source_end_pos(),
+                                    end, count_spaces);
+  }
 public:
   Field_longstr(uchar *ptr_arg, uint32 len_arg, uchar *null_ptr_arg,
                 uchar null_bit_arg, utype unireg_check_arg,

sql/sql_class.cc

@@ -2986,9 +2986,7 @@ int select_export::send_data(List<Item> &items)
     if (res && !my_charset_same(write_cs, res->charset()) &&
         !my_charset_same(write_cs, &my_charset_bin))
     {
-      const char *well_formed_error_pos;
-      const char *cannot_convert_error_pos;
-      const char *from_end_pos;
+      String_copier copier;
       const char *error_pos;
       uint32 bytes;
       uint64 estimated_bytes=
@@ -3001,16 +2999,11 @@ int select_export::send_data(List<Item> &items)
         goto err;
       }
 
-      bytes= well_formed_copy_nchars(write_cs, (char *) cvt_str.ptr(),
+      bytes= copier.well_formed_copy(write_cs, (char *) cvt_str.ptr(),
                                      cvt_str.alloced_length(),
-                                     res->charset(), res->ptr(), res->length(),
-                                     UINT_MAX32, // copy all input chars,
-                                                 // i.e. ignore nchars parameter
-                                     &well_formed_error_pos,
-                                     &cannot_convert_error_pos,
-                                     &from_end_pos);
-      error_pos= well_formed_error_pos ? well_formed_error_pos
-                                       : cannot_convert_error_pos;
+                                     res->charset(),
+                                     res->ptr(), res->length());
+      error_pos= copier.most_important_error_pos();
       if (error_pos)
       {
         char printable_buff[32];
@@ -3023,7 +3016,7 @@ int select_export::send_data(List<Item> &items)
                             "string", printable_buff,
                             item->name, static_cast<long>(row_count));
       }
-      else if (from_end_pos < res->ptr() + res->length())
+      else if (copier.source_end_pos() < res->ptr() + res->length())
       { 
         /*
           result is longer than UINT_MAX32 and doesn't fit into String

sql/sql_signal.cc

@@ -195,16 +195,9 @@ static bool assign_fixed_string(MEM_ROOT *mem_root,
     dst_str= (char*) alloc_root(mem_root, dst_len + 1);
     if (dst_str)
     {
-      const char* well_formed_error_pos;
-      const char* cannot_convert_error_pos;
-      const char* from_end_pos;
-
-      dst_copied= well_formed_copy_nchars(dst_cs, dst_str, dst_len,
-                                          src_cs, src_str, src_len,
-                                          numchars,
-                                          & well_formed_error_pos,
-                                          & cannot_convert_error_pos,
-                                          & from_end_pos);
+      dst_copied= String_copier().well_formed_copy(dst_cs, dst_str, dst_len,
+                                                   src_cs, src_str, src_len,
+                                                   numchars);
       DBUG_ASSERT(dst_copied <= dst_len);
       dst_len= dst_copied; /* In case the copy truncated the data */
       dst_str[dst_copied]= '\0';

sql/sql_string.cc

@@ -875,41 +875,44 @@ my_copy_with_hex_escaping(CHARSET_INFO *cs,
 
 
 /*
-  copy a string,
+  Copy a string,
   with optional character set conversion,
   with optional left padding (for binary -> UCS2 conversion)
-  
-  SYNOPSIS
-    well_formed_copy_nchars()
-    to			     Store result here
-    to_length                Maxinum length of "to" string
-    to_cs		     Character set of "to" string
-    from		     Copy from here
-    from_length		     Length of from string
-    from_cs		     From character set
-    nchars                   Copy not more that nchars characters
-    well_formed_error_pos    Return position when "from" is not well formed
+
+  In case if there is a Unicode conversion (i.e. to_cs and from_cs are
+  different character sets and both are not &my_charset_bin), bad input bytes
+  as well as characters that cannot be encoded in to_cs are replaced to '?'.
+
+  In case of non-Unicode copying (i.e. to_cs and from_cs are same character set,
+  or from_cs is &my_charset_bin),  the function stops on the first bad
+  byte sequence.
+
+  The string that is written to "to" is always well-formed.
+
+  @param to                  The destination string
+  @param to_length           Space available in "to"
+  @param to_cs               Character set of the "to" string
+  @param from                The source string
+  @param from_length         Length of the "from" string
+  @param from_cs             Character set of the "from" string
+  @param nchars              Copy not more than "nchars" characters
+
+  The members as set as follows:
+  m_well_formed_error_pos    To the position when "from" is not well formed
                              or NULL otherwise.
-    cannot_convert_error_pos Return position where a not convertable
+  m_cannot_convert_error_pos To the position where a not convertable
                              character met, or NULL otherwise.
-    from_end_pos             Return position where scanning of "from"
+  m_source_end_pos           To the position where scanning of the "from"
                              string stopped.
-  NOTES
 
-  RETURN
-    length of bytes copied to 'to'
+  @returns                   number of bytes that were written to 'to'
 */
-
-
-uint32
-well_formed_copy_nchars(CHARSET_INFO *to_cs,
-                        char *to, uint to_length,
-                        CHARSET_INFO *from_cs,
-                        const char *from, uint from_length,
-                        uint nchars,
-                        const char **well_formed_error_pos,
-                        const char **cannot_convert_error_pos,
-                        const char **from_end_pos)
+uint
+String_copier::well_formed_copy(CHARSET_INFO *to_cs,
+                                char *to, uint to_length,
+                                CHARSET_INFO *from_cs,
+                                const char *from, uint from_length,
+                                uint nchars)
 {
   uint res;
 
@@ -920,9 +923,9 @@ well_formed_copy_nchars(CHARSET_INFO *to_cs,
   {
     if (to_length < to_cs->mbminlen || !nchars)
     {
-      *from_end_pos= from;
-      *cannot_convert_error_pos= NULL;
-      *well_formed_error_pos= NULL;
+      m_source_end_pos= from;
+      m_cannot_convert_error_pos= NULL;
+      m_well_formed_error_pos= NULL;
       return 0;
     }
 
@@ -930,9 +933,9 @@ well_formed_copy_nchars(CHARSET_INFO *to_cs,
     {
       res= MY_MIN(MY_MIN(nchars, to_length), from_length);
       memmove(to, from, res);
-      *from_end_pos= from + res;
-      *well_formed_error_pos= NULL;
-      *cannot_convert_error_pos= NULL;
+      m_source_end_pos= from + res;
+      m_well_formed_error_pos= NULL;
+      m_cannot_convert_error_pos= NULL;
     }
     else
     {
@@ -964,8 +967,8 @@ well_formed_copy_nchars(CHARSET_INFO *to_cs,
                                          &well_formed_error) !=
                                          to_cs->mbminlen)
         {
-          *from_end_pos= *well_formed_error_pos= from;
-          *cannot_convert_error_pos= NULL;
+          m_source_end_pos= m_well_formed_error_pos= from;
+          m_cannot_convert_error_pos= NULL;
           return 0;
         }
         nchars--;
@@ -979,9 +982,9 @@ well_formed_copy_nchars(CHARSET_INFO *to_cs,
       res= to_cs->cset->well_formed_len(to_cs, from, from + from_length,
                                         nchars, &well_formed_error);
       memmove(to, from, res);
-      *from_end_pos= from + res;
-      *well_formed_error_pos= well_formed_error ? from + res : NULL;
-      *cannot_convert_error_pos= NULL;
+      m_source_end_pos= from + res;
+      m_well_formed_error_pos= well_formed_error ? from + res : NULL;
+      m_cannot_convert_error_pos= NULL;
       if (from_offset)
         res+= to_cs->mbminlen;
     }
@@ -995,8 +998,8 @@ well_formed_copy_nchars(CHARSET_INFO *to_cs,
     const uchar *from_end= (const uchar*) from + from_length;
     uchar *to_end= (uchar*) to + to_length;
     char *to_start= to;
-    *well_formed_error_pos= NULL;
-    *cannot_convert_error_pos= NULL;
+    m_well_formed_error_pos= NULL;
+    m_cannot_convert_error_pos= NULL;
 
     for ( ; nchars; nchars--)
     {
@@ -1005,8 +1008,8 @@ well_formed_copy_nchars(CHARSET_INFO *to_cs,
         from+= cnvres;
       else if (cnvres == MY_CS_ILSEQ)
       {
-        if (!*well_formed_error_pos)
-          *well_formed_error_pos= from;
+        if (!m_well_formed_error_pos)
+          m_well_formed_error_pos= from;
         from++;
         wc= '?';
       }
@@ -1016,8 +1019,8 @@ well_formed_copy_nchars(CHARSET_INFO *to_cs,
           A correct multibyte sequence detected
           But it doesn't have Unicode mapping.
         */
-        if (!*cannot_convert_error_pos)
-          *cannot_convert_error_pos= from;
+        if (!m_cannot_convert_error_pos)
+          m_cannot_convert_error_pos= from;
         from+= (-cnvres);
         wc= '?';
       }
@@ -1026,8 +1029,8 @@ well_formed_copy_nchars(CHARSET_INFO *to_cs,
         if ((uchar *) from >= from_end)
           break; // End of line
         // Incomplete byte sequence
-        if (!*well_formed_error_pos)
-          *well_formed_error_pos= from;
+        if (!m_well_formed_error_pos)
+          m_well_formed_error_pos= from;
         from++;
         wc= '?';
       }
@@ -1036,8 +1039,8 @@ outp:
         to+= cnvres;
       else if (cnvres == MY_CS_ILUNI && wc != '?')
       {
-        if (!*cannot_convert_error_pos)
-          *cannot_convert_error_pos= from_prev;
+        if (!m_cannot_convert_error_pos)
+          m_cannot_convert_error_pos= from_prev;
         wc= '?';
         goto outp;
       }
@@ -1047,10 +1050,10 @@ outp:
         break;
       }
     }
-    *from_end_pos= from;
+    m_source_end_pos= from;
     res= (uint) (to - to_start);
   }
-  return (uint32) res;
+  return res;
 }
 
 

sql/sql_string.h

@@ -41,14 +41,70 @@ inline uint32 copy_and_convert(char *to, uint32 to_length,
 {
   return my_convert(to, to_length, to_cs, from, from_length, from_cs, errors);
 }
-uint32 well_formed_copy_nchars(CHARSET_INFO *to_cs,
-                               char *to, uint to_length,
-                               CHARSET_INFO *from_cs,
-                               const char *from, uint from_length,
-                               uint nchars,
-                               const char **well_formed_error_pos,
-                               const char **cannot_convert_error_pos,
-                               const char **from_end_pos);
+
+
+class String_copier
+{
+  const char *m_source_end_pos;
+  const char *m_well_formed_error_pos;
+  const char *m_cannot_convert_error_pos;
+public:
+  const char *source_end_pos() const
+  { return m_source_end_pos; }
+  const char *well_formed_error_pos() const
+  { return m_well_formed_error_pos; }
+  const char *cannot_convert_error_pos() const
+  { return m_cannot_convert_error_pos; }
+  const char *most_important_error_pos() const
+  {
+    return well_formed_error_pos() ? well_formed_error_pos() :
+                                     cannot_convert_error_pos();
+  }
+  /*
+     Copy a string. Fix bad bytes/characters one Unicode conversion,
+     break on bad bytes in case of non-Unicode copying.
+  */
+  uint well_formed_copy(CHARSET_INFO *to_cs, char *to, uint to_length,
+                        CHARSET_INFO *from_cs, const char *from,
+                        uint from_length, uint nchars);
+  // Same as above, but without the "nchars" limit.
+  uint well_formed_copy(CHARSET_INFO *to_cs, char *to, uint to_length,
+                        CHARSET_INFO *from_cs, const char *from,
+                        uint from_length)
+  {
+    return well_formed_copy(to_cs, to, to_length,
+                            from_cs, from, from_length,
+                            from_length /* No limit on "nchars"*/);
+  }
+  /*
+    Copy a string. If a bad byte sequence is found in case of non-Unicode
+    copying, continues processing and replaces bad bytes to '?'.
+  */
+  uint copy_fix(CHARSET_INFO *to_cs, char *to, uint to_length,
+                CHARSET_INFO *from_cs, const char *from, uint from_length)
+  {
+    uint length= well_formed_copy(to_cs, to, to_length,
+                                  from_cs, from, from_length,
+                                  from_length /* No limit on nchars */);
+    if (well_formed_error_pos() && source_end_pos() < from + from_length)
+    {
+      /*
+        There was an error and there are still some bytes in the source string.
+        This is possible if there were no character set conversion and a
+        malformed byte sequence was found. Copy the rest and replace bad
+        bytes to '?'. Note: m_source_end_pos is not updated!!!
+      */
+      uint dummy_errors;
+      length+= copy_and_convert(to + length, to_length - length, to_cs,
+                                source_end_pos(),
+                                from_length - (source_end_pos() - from),
+                                from_cs, &dummy_errors);
+    }
+    return length;
+  }
+};
+
+
 size_t my_copy_with_hex_escaping(CHARSET_INFO *cs,
                                  char *dst, size_t dstlen,
                                  const char *src, size_t srclen);

storage/perfschema/table_session_connect.cc

@@ -61,8 +61,7 @@ bool parse_length_encoded_string(const char **ptr,
                  uint nchars_max)
 {
   ulong copy_length, data_length;
-  const char *well_formed_error_pos= NULL, *cannot_convert_error_pos= NULL,
-        *from_end_pos= NULL;
+  String_copier copier;
 
   copy_length= data_length= net_field_length((uchar **) ptr);
 
@@ -73,11 +72,8 @@ bool parse_length_encoded_string(const char **ptr,
   if (*ptr - start_ptr + data_length > input_length)
     return true;
 
-  copy_length= well_formed_copy_nchars(&my_charset_utf8_bin, dest, dest_size,
-                                       from_cs, *ptr, data_length, nchars_max,
-                                       &well_formed_error_pos,
-                                       &cannot_convert_error_pos,
-                                       &from_end_pos);
+  copy_length= copier.well_formed_copy(&my_charset_utf8_bin, dest, dest_size,
+                                       from_cs, *ptr, data_length, nchars_max);
   *copied_len= copy_length;
   (*ptr)+= data_length;