MDEV-31117 Fix spider connection info parsing

Spider connection string is a comma-separated parameter definitions,
where each definition is of the form "<param_title> <param_value>",
where <param_value> is quote delimited on both ends, with backslashes
acting as an escaping prefix.

Despite the simple syntax, the existing spider connection string
parser was poorly-written, complex, hard to reason and error-prone,
causing issues like the one described in MDEV-31117. For example it
treated param title the same way as param value when assigning, and
have nonsensical fields like delim_title_len and delim_title.

Thus as part of the bugfix, we clean up the spider comment connection
string parsing, including:

- Factoring out some code from the parsing function
- Simplify the struct `st_spider_param_string_parse`
- And any necessary changes caused by the above changes

storage/spider/mysql-test/spider/bugfix/r/mdev_31117.result

+#
+# MDEV-31117 Spider UBSAN runtime error: applying non-zero offset x to null pointer in st_spider_param_string_parse::restore_delims
+#
+for master_1
+for child2
+for child3
+CREATE TABLE t (c INT) ENGINE=Spider COMMENT='abc';
+ERROR HY000: The connect info 'abc' is invalid
+ALTER TABLE mysql.help_topic ENGINE=Spider;
+ERROR HY000: The connect info 'help topics' is invalid
+CREATE SERVER srv FOREIGN DATA WRAPPER MYSQL OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+create table t2 (c int);
+create table t1 (c int) ENGINE=Spider COMMENT='WRAPPER "mysql", "srv" "srv",TABLE "t2"';
+ERROR HY000: The connect info '"srv" "srv",TABLE "t2"' is invalid
+create table t1 (c int) ENGINE=Spider CONNECTION='WRAPPER "mysql", srv \'srv\',TABLE "t2", password "say \\"hello\\ world!\\""';
+drop table t1, t2;
+for master_1
+for child2
+for child3

storage/spider/mysql-test/spider/bugfix/t/mdev_31117.test

+--echo #
+--echo # MDEV-31117 Spider UBSAN runtime error: applying non-zero offset x to null pointer in st_spider_param_string_parse::restore_delims
+--echo #
+
+--disable_query_log
+--disable_result_log
+--source ../../t/test_init.inc
+--enable_result_log
+--enable_query_log
+
+--error 12501
+CREATE TABLE t (c INT) ENGINE=Spider COMMENT='abc';
+
+--error 12501
+ALTER TABLE mysql.help_topic ENGINE=Spider;
+
+evalp CREATE SERVER srv FOREIGN DATA WRAPPER MYSQL OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+create table t2 (c int);
+# param title should not have delimiter
+--error 12501
+create table t1 (c int) ENGINE=Spider COMMENT='WRAPPER "mysql", "srv" "srv",TABLE "t2"';
+# test escaping
+create table t1 (c int) ENGINE=Spider CONNECTION='WRAPPER "mysql", srv \'srv\',TABLE "t2", password "say \\"hello\\ world!\\""';
+drop table t1, t2;
+
+--disable_query_log
+--disable_result_log
+--source ../t/test_deinit.inc
+--enable_query_log
+--enable_result_log

storage/spider/spd_table.h

@@ -30,281 +30,21 @@
 
 typedef struct st_spider_param_string_parse
 {
-  char *start_ptr;         /* Pointer to the start of the parameter string */
-  char *end_ptr;           /* Pointer to the end   of the parameter string */
-  char *start_title_ptr;   /* Pointer to the start of the current parameter
-                              title */
-  char *end_title_ptr;     /* Pointer to the end   of the current parameter
-                              title */
-  char *start_value_ptr;   /* Pointer to the start of the current parameter
-                              value */
-  char *end_value_ptr;     /* Pointer to the end   of the current parameter
-                              value */
-  int  error_num;          /* Error code of the error message to print when
-                              an error is detected */
-  uint delim_title_len;    /* Length of the paramater title's delimiter */
-  uint delim_value_len;    /* Length of the paramater value's delimiter */
-  char delim_title;        /* Current parameter title's delimiter character */
-  char delim_value;        /* Current parameter value's delimiter character */
-
-  /**
-    Initialize the parameter string parse information.
-
-    @param  param_string      Pointer to the parameter string being parsed.
-    @param  error_code        Error code of the error message to print when
-                              an error is detected.
-  */
-
-  inline void init(char *param_string, int error_code)
-  {
-    start_ptr = param_string;
-    end_ptr = start_ptr + strlen(start_ptr);
-
-    init_param_title();
-    init_param_value();
-
-    error_num = error_code;
-  }
-
-  /**
-    Initialize the current parameter title.
-  */
-
-  inline void init_param_title()
-  {
-    start_title_ptr = end_title_ptr = NULL;
-    delim_title_len = 0;
-    delim_title = '\0';
-  }
-
-  /**
-    Save pointers to the start and end positions of the current parameter
-    title in the parameter string.  Also save the parameter title's
-    delimiter character.
-
-    @param  start_value       Pointer to the start position of the current
-                              parameter title.
-    @param  end_value         Pointer to the end   position of the current
-                              parameter title.
-  */
-
-  inline void set_param_title(char *start_title, char *end_title)
-  {
-    start_title_ptr = start_title;
-    end_title_ptr = end_title;
-
-    if (*start_title == '"' ||
-        *start_title == '\'')
-    {
-      delim_title = *start_title;
-
-      if (start_title >= start_ptr && *--start_title == '\\')
-        delim_title_len = 2;
-      else
-        delim_title_len = 1;
-    }
-  }
-
-  /**
-    Initialize the current parameter value.
-  */
-
-  inline void init_param_value()
-  {
-    start_value_ptr = end_value_ptr = NULL;
-    delim_value_len = 0;
-    delim_value = '\0';
-  }
-
-  /**
-    Save pointers to the start and end positions of the current parameter
-    value in the parameter string.  Also save the parameter value's
-    delimiter character.
-
-    @param  start_value       Pointer to the start position of the current
-                              parameter value.
-    @param  end_value         Pointer to the end   position of the current
-                              parameter value.
-  */
-
-  inline void set_param_value(char *start_value, char *end_value)
-  {
-    start_value_ptr = start_value--;
-    end_value_ptr = end_value;
-
-    if (*start_value == '"' ||
-        *start_value == '\'')
-    {
-      delim_value = *start_value;
-
-      if (*--start_value == '\\')
-        delim_value_len = 2;
-      else
-        delim_value_len = 1;
-    }
-  }
-
-  /**
-    Determine whether the current parameter in the parameter string has
-    extra parameter values.
-
-    @return   0               Current parameter value in the parameter string
-                              does not have extra parameter values.
-              <> 0            Error code indicating that the current parameter
-                              value in the parameter string has extra
-                              parameter values.
-  */
-
-  inline int has_extra_parameter_values()
-  {
-    int error_num = 0;
-    DBUG_ENTER("has_extra_parameter_values");
-
-    if (end_value_ptr)
-    {
-      /* There is a current parameter value */
-      char *end_param_ptr =  end_value_ptr;
-
-      while (end_param_ptr < end_ptr &&
-        (*end_param_ptr == ' ' || *end_param_ptr == '\r' ||
-         *end_param_ptr == '\n' || *end_param_ptr == '\t'))
-        end_param_ptr++;
-
-      if (end_param_ptr < end_ptr && *end_param_ptr != '\0')
-      {
-        /* Extra values in parameter definition */
-        error_num = print_param_error();
-      }
-    }
-
-    DBUG_RETURN(error_num);
-  }
-
-  inline int get_next_parameter_head(char *st, char **nx)
-  {
-    DBUG_ENTER("get_next_parameter_head");
-    char *sq = strchr(st, '\'');
-    char *dq = strchr(st, '"');
-    if (!sq && !dq)
-    {
-      DBUG_RETURN(print_param_error());
-    }
-
-    if (dq && (!sq || sq > dq))
-    {
-      while (1)
-      {
-        ++dq;
-        if (*dq == '\\')
-        {
-          ++dq;
-        }
-        else if (*dq == '"')
-        {
-          break;
-        }
-        else if (*dq == '\0')
-        {
-          DBUG_RETURN(print_param_error());
-        }
-      }
-      while (1)
-      {
-        ++dq;
-        if (*dq == '\0')
-        {
-          *nx = dq;
-          break;
-        }
-        else if (*dq == ',')
-        {
-          *dq = '\0';
-          *nx = dq + 1;
-          break;
-        }
-        else if (*dq != ' ' && *dq != '\r' && *dq != '\n' && *dq != '\t')
-        {
-          DBUG_RETURN(print_param_error());
-        }
-      }
-    }
-    else /* sq && (!dq || sq <= dq) */
-    {
-      while (1)
-      {
-        ++sq;
-        if (*sq == '\\')
-        {
-          ++sq;
-        }
-        else if (*sq == '\'')
-        {
-          break;
-        }
-        else if (*sq == '\0')
-        {
-          DBUG_RETURN(print_param_error());
-        }
-      }
-      while (1)
-      {
-        ++sq;
-        if (*sq == '\0')
-        {
-          *nx = sq;
-          break;
-        }
-        else if (*sq == ',')
-        {
-          *sq = '\0';
-          *nx = sq + 1;
-          break;
-        }
-        else if (*sq != ' ' && *sq != '\r' && *sq != '\n' && *sq != '\t')
-        {
-          DBUG_RETURN(print_param_error());
-        }
-      }
-    }
-    DBUG_RETURN(0);
-  }
-
-  /**
-    Restore the current parameter's input delimiter characters in the
-    parameter string.  They were NULLed during parameter parsing.
-  */
-
-  inline void restore_delims()
-  {
-    char *end = end_title_ptr - 1;
-
-    switch (delim_title_len)
-    {
-    case 2:
-      *end++ = '\\';
-      /* Fall through */
-    case 1:
-      *end = delim_title;
-    }
-
-    end = end_value_ptr - 1;
-    switch (delim_value_len)
-    {
-    case 2:
-      *end++ = '\\';
-      /* Fall through */
-    case 1:
-      *end = delim_value;
-    }
-  }
-
-  /**
-    Print a parameter string error message.
-
-    @return                   Error code.
-  */
-
-  int print_param_error();
+  char *start_title;   /* Pointer to the start of the current parameter
+                         title */
+  char *end_title;     /* Pointer to the end   of the current
+                         parameter value */
+  char *start_value;   /* Pointer to the start of the current parameter
+                         value */
+  char *end_value;     /* Pointer to the end   of the current parameter
+                         value */
+  char delim_value;    /* Current parameter value's delimiter
+                         character, either a single or a double quote */
+  int  error_num;      /* Error code of the error message to print when
+                         an error is detected */
+
+  int fail(bool restore_delim);
+  bool locate_param_def(char*& start_param);
 } SPIDER_PARAM_STRING_PARSE;
 
 uchar *spider_tbl_get_key(
@@ -352,19 +92,12 @@ void spider_free_tmp_share_alloc(
   SPIDER_SHARE *share
 );
 
-char *spider_get_string_between_quote(
-  char *ptr,
-  bool alloc,
-  SPIDER_PARAM_STRING_PARSE *param_string_parse = NULL
-);
-
 int spider_create_string_list(
   char ***string_list,
   uint **string_length_list,
   uint *list_length,
   char *str,
-  uint length,
-  SPIDER_PARAM_STRING_PARSE *param_string_parse
+  uint length
 );
 
 int spider_create_long_list(
@@ -373,8 +106,7 @@ int spider_create_long_list(
   char *str,
   uint length,
   long min_val,
-  long max_val,
-  SPIDER_PARAM_STRING_PARSE *param_string_parse
+  long max_val
 );
 
 int spider_create_longlong_list(
@@ -383,8 +115,7 @@ int spider_create_longlong_list(
   char *str,
   uint length,
   longlong min_val,
-  longlong max_val,
-  SPIDER_PARAM_STRING_PARSE *param_string_parse
+  longlong max_val
 );
 
 int spider_increase_string_list(