SQLite

/*
** 2018-04-19
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file implements a template virtual-table.
** Developers can make a copy of this file as a baseline for writing
** new virtual tables and/or table-valued functions.
**
** Steps for writing a new virtual table implementation:
**
**     (1)  Make a copy of this file.  Perhaps call it "mynewvtab.c"
**
**     (2)  Replace this header comment with something appropriate for
**          the new virtual table
**
**     (3)  Change every occurrence of "templatevtab" to some other string
**          appropriate for the new virtual table.  Ideally, the new string
**          should be the basename of the source file: "mynewvtab".  Also
**          globally change "TEMPLATEVTAB" to "MYNEWVTAB".
**
**     (4)  Run a test compilation to make sure the unmodified virtual
**          table works.
**
**     (5)  Begin making incremental changes, testing as you go, to evolve



**          the new virtual table to do what you want it to do.
**
** This template is minimal, in the sense that it uses only the required
** methods on the sqlite3_module object.  As a result, templatevtab is
** a read-only and eponymous-only table.  Those limitation can be removed
** by adding new methods.
**
** This template implements an eponymous-only virtual table with a rowid and
** two columns named "a" and "b".  The table as 10 rows with fixed integer
** values. Usage example:
**
**     SELECT rowid, a, b FROM templatevtab;
*/
#if !defined(SQLITEINT_H)
#include "sqlite3ext.h"
#endif
SQLITE_EXTENSION_INIT1
#include <string.h>
#include <assert.h>

/* templatevtab_vtab is a subclass of sqlite3_vtab which is
** underlying representation of the virtual table
*/
typedef struct templatevtab_vtab templatevtab_vtab;
struct templatevtab_vtab {
  sqlite3_vtab base;  /* Base class - must be first */

){
  templatevtab_vtab *pNew;
  int rc;

  rc = sqlite3_declare_vtab(db,
           "CREATE TABLE x(a,b)"
       );
  /* For convenience, define symbolic names for the index to each column. */
#define TEMPLATEVTAB_A  0
#define TEMPLATEVTAB_B  1
  if( rc==SQLITE_OK ){
    pNew = sqlite3_malloc( sizeof(*pNew) );
    *ppVtab = (sqlite3_vtab*)pNew;
    if( pNew==0 ) return SQLITE_NOMEM;
    memset(pNew, 0, sizeof(*pNew));
  }
  return rc;

*/
static int templatevtabColumn(
  sqlite3_vtab_cursor *cur,   /* The cursor */
  sqlite3_context *ctx,       /* First argument to sqlite3_result_...() */
  int i                       /* Which column to return */
){
  templatevtab_cursor *pCur = (templatevtab_cursor*)cur;
  switch( i ){
    case TEMPLATEVTAB_A:
      sqlite3_result_int(ctx, 1000 + pCur->iRowid);
      break;
    default:
      assert( i==TEMPLATEVTAB_B );
      sqlite3_result_int(ctx, 2000 + pCur->iRowid);
      break;
  }
  return SQLITE_OK;
}

/*
** Return the rowid for the current row.  In this implementation, the
** rowid is the same as the output value.
*/