Capture Matched regex and substitute - c

Question

I have a C program to match a particular regex in a string and perform some substitution. I want to match all patterns of string concatenation and convert it to another form.
For Example for the input string
This "is" + "an" + "example" + "string" to be matched and replaced
The Matched regex should be
"is" + "an" + "example" + "string"
So I want to convert this matched regex to
CONCAT("is", "an", "example", "string")
I am using C PCRE2 Library and my code is below. Can anyone help me fix the substitution part?
#define PCRE2_CODE_UNIT_WIDTH 8
#define BUFFERSIZE 100
#include <my_global.h>
#include <mysql.h>
#include <stdio.h>
#include <string.h>
#include <pcre2.h>
void finish_with_error(MYSQL *con)
{
fprintf(stderr, "%s\n", mysql_error(con));
mysql_close(con);
exit(1);
}
int main(int argc, char **argv)
{
pcre2_code *re;
PCRE2_SPTR pattern;
PCRE2_SPTR subject;
int errornumber;
int i;
int rc;
PCRE2_SIZE erroroffset;
PCRE2_SIZE *ovector;
size_t subject_length;
pcre2_match_data *match_data;
char buffer[BUFFERSIZE];
MYSQL *con = mysql_init(NULL);
/* Read Query String from standard input here*/
printf("Enter a Query to be substituted: \n");
while(fgets(buffer, BUFFERSIZE , stdin) != NULL)
{
printf("%s\n", buffer);
break;
}
pattern = (PCRE2_SPTR)'"[^"]*"(?: *\\+ *"[^"]*")+'; // Regex for string concatenation
subject = (PCRE2_SPTR)buffer;
subject_length = strlen((char *)subject);
/* Compile regex and perform matching here by wrapping match within CONCAT() and replace + with , */
re = pcre2_compile(
pattern,
PCRE2_ZERO_TERMINATED,
0,
&errornumber,
&erroroffset,
NULL);
if (re == NULL)
{
PCRE2_UCHAR buffer[256];
pcre2_get_error_message(errornumber, buffer, sizeof(buffer));
printf("PCRE2 compilation failed at offset %d: %s\n", (int)erroroffset,
buffer);
return 1;
}
match_data = pcre2_match_data_create_from_pattern(re, NULL);
rc = pcre2_match(
re,
subject,
subject_length,
0,
0,
match_data,
NULL);
if (rc < 0)
{
switch(rc)
{
case PCRE2_ERROR_NOMATCH: printf("No match\n"); break;
default: printf("Matching error %d\n", rc); break;
}
pcre2_match_data_free(match_data);
pcre2_code_free(re);
// return 1;
goto server;
}
ovector = pcre2_get_ovector_pointer(match_data);
printf("\nMatch succeeded at offset %d\n", (int)ovector[0]);
/* Do Substitution for matches found here. by wrapping match within CONCAT() and replace + with ,. For now only one match is handled*/
/* Use Connector C here to forward query that is rewritten to MariaDB/MySQL server */
server:
if (con == NULL)
{
fprintf(stderr, "%s\n", mysql_error(con));
exit(1);
}
if (mysql_real_connect(con, "localhost", "root", "root",
NULL, 0, NULL, 0) == NULL)
{
fprintf(stderr, "%s\n", mysql_error(con));
mysql_close(con);
exit(1);
}
printf("Connected to Database\n");
if (mysql_query(con, subject))
{
finish_with_error(con);
}
MYSQL_RES *result = mysql_store_result(con);
if (result == NULL)
{
finish_with_error(con);
}
int num_fields = mysql_num_fields(result);
MYSQL_ROW row;
while ((row = mysql_fetch_row(result)))
{
for(int i = 0; i < num_fields; i++)
{
printf("%s ", row[i] ? row[i] : "NULL");
}
printf("\n");
}
mysql_free_result(result);
mysql_close(con);
printf("\n");
pcre2_match_data_free(match_data);
pcre2_code_free(re);
return 0;
}