OTL 4.0, Example 750 (VARCHAR column bound as RAW[XXX] for reading/writing std::strings that have null terminators ('\0') in the middle)

This example demonstrates a technique that allows to read / write std::string values that have null terminators in the middle.

Source Code

#include <iostream>
using namespace std; #include <stdio.h>

#define OTL_STL
#define OTL_ODBC_MSSQL_2008 // Compile OTL 4.0/MSSQL SNAC

#if (defined(__clang__) || defined(__GNUC__)) && \
(defined(OTL_CPP_14_ON) || defined(OTL_CPP_17_ON))
#include <experimental/string_view>
#define OTL_STD_STRING_VIEW_CLASS std::experimental::string_view
#elif defined(_MSC_VER) && (_MSC_VER>=1910) && defined(OTL_CPP_17_ON)
// VC++ 2017 or higher when /std=c++latest is used
#include <string_view>
#define OTL_STD_STRING_VIEW_CLASS std::string_view
#endif
#include <otlv4.h> // include the OTL 4.0 header file
string str_val("123456" "\0" "7890", 11); // std::string with a null terminator in the middle. otl_connect db; // connect object void insert() // insert rows into table { otl_stream o(10, // buffer size "insert into test_tab values(:f1<int>,:f2<raw[30]>)", // SQL statement db // connect object ); for(int i=1;i<=4;++i){ #if defined(OTL_STD_STRING_VIEW_CLASS)
OTL_STD_STRING_VIEW_CLASS str_val_sv(str_val.c_str(),str_val.length());
o<<i<<str_val_sv;
#else
o<<i<<str_val;
#endif
} } void select() { otl_stream i(10, // buffer size "select f1, f2 :#2<raw[30]> "
"from test_tab "
"where f2>=:f2in<raw[30]>", // SELECT statement db // connect object ); // create select stream int f1; string f2; i<<str_val; // assigning :f2in = str_val // SELECT automatically executes when all input variables are // assigned. First portion of output rows is fetched to the buffer while(!i.eof()){ // while not end-of-data i>>f1>>f2; cout<<"f1="<<f1<<", f2="; for(size_t j=0;j<f2.length();++j)
if(f2[j]==0)
cout<<"\\0";
else
cout<<f2[j];
cout<<endl;
} } int main() { otl_connect::otl_initialize(); // initialize the database API environment try{ db.rlogon("scott/tiger@mssql2008"); // connect to the database otl_cursor::direct_exec ( db, "drop table test_tab", otl_exception::disabled // disable OTL exceptions ); // drop table otl_cursor::direct_exec ( db, "create table test_tab(f1 int, f2 varchar(30))" ); // create table insert(); // insert records into table select(); // select records from table } catch(otl_exception& p){ // intercept OTL exceptions cerr<<p.msg<<endl; // print out error message cerr<<p.stm_text<<endl; // print out SQL that caused the error cerr<<p.var_info<<endl; // print out the variable that caused the error } db.logoff(); // disconnect from the database return 0; }

Output

f1=1, f2=123456\07890
f1=2, f2=123456\07890
f1=3, f2=123456\07890
f1=4, f2=123456\07890

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Copyright © 1996-2023, Sergei Kuchin, email: skuchin@gmail.com.

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