I am having some problems with the functions mapi_param*().
1. It seems mapi_param() really wants a char* cast to a char**. (See the inner workings of mapi_param() vs. mapi_param_string().)
2. If mapi_param(), mapi_param_string() and mapi_param_type() get a char*, the value used in the query does not change as the char* is updated.
Using mapi_bind_var( , , MAPI_INT, int*) and mapi_bind_var( , , MAPI_VARCHAR, char**) works as expected, while mapi_param_type( , , MAPI_INT, MAPI_INT, int*) and mapi_param_type( , , MAPI_VARCHAR, MAPI_VARCHAR, char**) do not.
Is there something wrong with interface, or am I just using it wrong?
Here is how I have tried using the functions:
#include <cassert> #include <cstdio> #include <cstdlib> #include <cstring> #include <Mapi.h>
using namespace std;
Mapi dbh;
void check(MapiHdl hdl, int ret = MOK, bool fatal = true) { if (ret != MOK || hdl == NULL || mapi_error(dbh)) { if (hdl) { mapi_explain_result(hdl,stderr); } else { mapi_explain(dbh,stderr); } if (fatal) assert(0);//exit(-1); } }
void paramInt(MapiHdl hdl, int fldnr, int* val) { int ret = mapi_param_type(hdl, fldnr, MAPI_INT, MAPI_INT, val); check(hdl, ret); }
void paramStr(MapiHdl hdl, int fldnr, char** val) { // int ret = mapi_param(hdl, fldnr, val); /* Case 1: * QUERY = INSERT INTO t VALUES(1, p`) * ERROR = !SELECT: identifier 'p`' unknown * Cast to (void*) in call to mapi_param_type() in mapi_param(). */ int ret = mapi_param(hdl, fldnr, (char**)*val); /* Case 2: * Works, sort of. * Seems it wants a (char*) really. * But 'foo' is inserted the second time instead of bar. */ // int ret = mapi_param_string(hdl, fldnr, MAPI_VARCHAR, *val, NULL); /* 'foo' twice. */ // int ret = mapi_param_string(hdl, fldnr, MAPI_VARCHAR, (char*)val, NULL); /* As Case 1. */ // int ret = mapi_param_type(hdl, fldnr, MAPI_VARCHAR, MAPI_VARCHAR, val); /* As Case 1. */ // int ret = mapi_param_type(hdl, fldnr, MAPI_VARCHAR, MAPI_VARCHAR, *val); /* 'foo' twice. */ check(hdl, ret); }
int main() { dbh = mapi_connect("localhost", 50000, "nilsgri", "nilsgri", "sql", "proto");
MapiHdl hdl = mapi_query(dbh, "DROP TABLE t"); check(hdl, MOK, false); mapi_close_handle(hdl);
hdl = mapi_query(dbh, "CREATE TABLE t (a INT, b VARCHAR(255))"); check(hdl); mapi_close_handle(hdl);
hdl = mapi_prepare(dbh, "INSERT INTO t VALUES(?, ?)"); check(hdl);
int a = 1; paramInt(hdl, 0, &a); char* b1 = strdup("'foo'"); char* b = b1; paramStr(hdl, 1, &b); int ret = mapi_execute(hdl); check(hdl, ret);
a = 2; char* b2 = strdup("'bar'"); b = b2; // paramStr(hdl, 1, &b); // I would like not having to do this. ret = mapi_execute(hdl); check(hdl, ret);
mapi_close_handle(hdl);
hdl = mapi_quick_query(dbh, "SELECT * FROM t", stderr); check(hdl, ret); mapi_close_handle(hdl);
mapi_disconnect(dbh); mapi_destroy(dbh);
free(b1); free(b2); }