SQLite

**
** Return SQLITE_ROW on success.  Return SQLITE_DONE if there are no
** more opcodes to be displayed.
*/
int sqlite3VdbeNextOpcode(
  Vdbe *p,         /* The statement being explained */
  Mem *pSub,       /* Storage for keeping track of subprogram nesting */
  int eMode,       /* 0: normal.  1: EQP.  2:  TablesUsed */
  int *piPc,       /* IN/OUT: Current rowid.  Overwritten with next rowid */
  int *piAddr,     /* OUT: Write index into (*paOp)[] here */
  Op **paOp        /* OUT: Write the opcode array here */
){
  int nRow;                            /* Stop when row count reaches this */
  int nSub = 0;                        /* Number of sub-vdbes seen so far */
  SubProgram **apSub = 0;              /* Array of sub-vdbes */

        apSub = (SubProgram **)pSub->z;
        apSub[nSub++] = aOp[i].p4.pProgram;
        MemSetTypeFlag(pSub, MEM_Blob);
        pSub->n = nSub*sizeof(SubProgram*);
        nRow += aOp[i].p4.pProgram->nOp;
      }
    }
    if( eMode==0 ) break;
#ifdef SQLITE_ENABLE_BYTECODE_VTAB
    if( eMode==2 ){
      Op *pOp = aOp + i;
      if( pOp->opcode==OP_OpenRead ) break;
      if( pOp->opcode==OP_OpenWrite && (pOp->p5 & OPFLAG_P2ISREG)==0 ) break;
      if( pOp->opcode==OP_ReopenIdx ) break;      
    }else
#endif
    {
      assert( eMode==1 );
      if( aOp[i].opcode==OP_Explain ) break;
      if( aOp[i].opcode==OP_Init && p->pc>1 ) break;
    }
  }
  *piPc = iPc;
  *piAddr = i;
  *paOp = aOp;
  return rc;
}
#endif /* SQLITE_ENABLE_BYTECODE_VTAB || !SQLITE_OMIT_EXPLAIN */

/* An instance of the bytecode() table-valued function.
*/
typedef struct bytecodevtab bytecodevtab;
struct bytecodevtab {
  sqlite3_vtab base;     /* Base class - must be first */
  sqlite3 *db;           /* Database connection */
  int bTablesUsed;       /* 2 for tables_used().  0 for bytecode(). */
};

/* A cursor for scanning through the bytecode
*/
typedef struct bytecodevtab_cursor bytecodevtab_cursor;
struct bytecodevtab_cursor {
  sqlite3_vtab_cursor base;  /* Base class - must be first */
  sqlite3_stmt *pStmt;       /* The statement whose bytecode is displayed */
  int iRowid;                /* The rowid of the output table */
  int iAddr;                 /* Address */
  int needFinalize;          /* Cursors owns pStmt and must finalize it */
  int showSubprograms;       /* Provide a listing of subprograms */
  Op *aOp;                   /* Operand array */
  char *zP4;                 /* Rendered P4 value */
  const char *zType;         /* tables_used.type */
  const char *zSchema;       /* tables_used.schema */
  const char *zName;         /* tables_used.name */
  Mem sub;                   /* Subprograms */
};

/*
** Create a new bytecode() table-valued function.
*/
static int bytecodevtabConnect(
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  bytecodevtab *pNew;
  int rc;
  int isTabUsed = pAux!=0;
  const char *azSchema[2] = {
    /* bytecode() schema */
    "CREATE TABLE x("
      "addr INT,"
      "opcode TEXT,"
      "p1 INT,"
      "p2 INT,"
      "p3 INT,"
      "p4 TEXT,"
      "p5 INT,"
      "comment TEXT,"
      "subprog TEXT," 
      "stmt HIDDEN"
    ");",

    /* Tables_used() schema */
    "CREATE TABLE x("
      "type TEXT,"
      "schema TEXT,"
      "name TEXT,"
      "wr INT,"
      "subprog TEXT," 
      "stmt HIDDEN"
   ");"
  };

  rc = sqlite3_declare_vtab(db, azSchema[isTabUsed]);
  if( rc==SQLITE_OK ){
    pNew = sqlite3_malloc( sizeof(*pNew) );
    *ppVtab = (sqlite3_vtab*)pNew;
    if( pNew==0 ) return SQLITE_NOMEM;
    memset(pNew, 0, sizeof(*pNew));
    pNew->db = db;
    pNew->bTablesUsed = isTabUsed*2;
  }
  return rc;
}

/*
** This method is the destructor for bytecodevtab objects.
*/

  sqlite3VdbeMemRelease(&pCur->sub);
  sqlite3VdbeMemSetNull(&pCur->sub);
  if( pCur->needFinalize ){
    sqlite3_finalize(pCur->pStmt);
  }
  pCur->pStmt = 0;
  pCur->needFinalize = 0;
  pCur->zType = 0;
  pCur->zSchema = 0;
  pCur->zName = 0;
}

/*
** Destructor for a bytecodevtab_cursor.
*/
static int bytecodevtabClose(sqlite3_vtab_cursor *cur){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
  bytecodevtabCursorClear(pCur);
  sqlite3_free(pCur);
  return SQLITE_OK;
}


/*
** Advance a bytecodevtab_cursor to its next row of output.
*/
static int bytecodevtabNext(sqlite3_vtab_cursor *cur){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
  bytecodevtab *pTab = (bytecodevtab*)cur->pVtab;
  int rc;
  if( pCur->zP4 ){
    sqlite3_free(pCur->zP4);
    pCur->zP4 = 0;
  }
  if( pCur->zName ){
    pCur->zName = 0;
    pCur->zType = 0;
    pCur->zSchema = 0;
  }
  rc = sqlite3VdbeNextOpcode(
           (Vdbe*)pCur->pStmt, 
           pCur->showSubprograms ? &pCur->sub : 0,

           pTab->bTablesUsed,
           &pCur->iRowid,
           &pCur->iAddr,
           &pCur->aOp);
  if( rc!=SQLITE_OK ){
    sqlite3VdbeMemSetNull(&pCur->sub);
    pCur->aOp = 0;
  }

*/
static int bytecodevtabColumn(
  sqlite3_vtab_cursor *cur,   /* The cursor */
  sqlite3_context *ctx,       /* First argument to sqlite3_result_...() */
  int i                       /* Which column to return */
){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
  bytecodevtab *pVTab = (bytecodevtab*)cur->pVtab;
  Op *pOp = pCur->aOp + pCur->iAddr;
  if( pVTab->bTablesUsed ){
    if( i==4 ){
      i = 8;
    }else{
      if( i<=2 && pCur->zType==0 ){
        Schema *pSchema;
        HashElem *k;
        int iDb = pOp->p3;
        int iRoot = pOp->p2;
        sqlite3 *db = pVTab->db;
        pSchema = db->aDb[iDb].pSchema;
        pCur->zSchema = db->aDb[iDb].zDbSName;
        for(k=sqliteHashFirst(&pSchema->tblHash); k; k=sqliteHashNext(k)){
          Table *pTab = (Table*)sqliteHashData(k);
          if( !IsVirtual(pTab) && pTab->tnum==iRoot ){
            pCur->zName = pTab->zName;
            pCur->zType = "table";
            break;
          }
        }
        if( pCur->zName==0 ){
          for(k=sqliteHashFirst(&pSchema->idxHash); k; k=sqliteHashNext(k)){
            Index *pIdx = (Index*)sqliteHashData(k);
            if( pIdx->tnum==iRoot ){
              pCur->zName = pIdx->zName;
              pCur->zType = "index";
              break;
            }
          }
        }
      }
      i += 10;
    }
  }
  switch( i ){
    case 0:   /* addr */
      sqlite3_result_int(ctx, pCur->iAddr);
      break;
    case 1:   /* opcode */
      sqlite3_result_text(ctx, (char*)sqlite3OpcodeName(pOp->opcode),
                          -1, SQLITE_STATIC);
      break;
    case 2:   /* p1 */
      sqlite3_result_int(ctx, pOp->p1);
      break;
    case 3:   /* p2 */
      sqlite3_result_int(ctx, pOp->p2);
      break;
    case 4:   /* p3 */
      sqlite3_result_int(ctx, pOp->p3);
      break;
    case 5:   /* p4 */
    case 7:   /* comment */

      if( pCur->zP4==0 ){
        pCur->zP4 = sqlite3VdbeDisplayP4(pVTab->db, pOp);
      }
      if( i==5 ){
        sqlite3_result_text(ctx, pCur->zP4, -1, SQLITE_STATIC);
      }else{
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS

       && strncmp(aOp[0].p4.z,"-- ", 3)==0 ){
         sqlite3_result_text(ctx, aOp[0].p4.z+3, -1, SQLITE_STATIC);
      }else{
         sqlite3_result_text(ctx, "(FK)", 4, SQLITE_STATIC);
      }
      break;
    }
    case 10:  /* tables_used.type */
      sqlite3_result_text(ctx, pCur->zType, -1, SQLITE_STATIC);
      break;
    case 11:  /* tables_used.schema */
      sqlite3_result_text(ctx, pCur->zSchema, -1, SQLITE_STATIC);
      break;
    case 12:  /* tables_used.name */
      sqlite3_result_text(ctx, pCur->zName, -1, SQLITE_STATIC);
      break;
    case 13:  /* tables_used.wr */
      sqlite3_result_int(ctx, pOp->opcode==OP_OpenWrite);
      break;
  }
  return SQLITE_OK;
}

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

      pCur->needFinalize = 1;
    }
  }else{
    pCur->pStmt = (sqlite3_stmt*)sqlite3_value_pointer(argv[0],"stmt-pointer");
  }
  if( pCur->pStmt==0 ){
    pVTab->base.zErrMsg = sqlite3_mprintf(
       "argument to %s() is not a valid SQL statement",
       pVTab->bTablesUsed ? "tables_used" : "bytecode"
    );
    rc = SQLITE_ERROR;
  }else{
    bytecodevtabNext(pVtabCursor);
  }
  return rc;
}

/*
** We must have a single stmt=? constraint that will be passed through
** into the xFilter method.  If there is no valid stmt=? constraint,
** then return an SQLITE_CONSTRAINT error.
*/
static int bytecodevtabBestIndex(
  sqlite3_vtab *tab,
  sqlite3_index_info *pIdxInfo
){
  int i;
  int rc = SQLITE_CONSTRAINT;
  struct sqlite3_index_constraint *p;
  bytecodevtab *pVTab = (bytecodevtab*)tab;
  int iBaseCol = pVTab->bTablesUsed ? 4 : 8;
  pIdxInfo->estimatedCost = (double)100;
  pIdxInfo->estimatedRows = 100;
  pIdxInfo->idxNum = 0;
  for(i=0, p=pIdxInfo->aConstraint; i<pIdxInfo->nConstraint; i++, p++){
    if( p->usable==0 ) continue;
    if( p->op==SQLITE_INDEX_CONSTRAINT_EQ && p->iColumn==iBaseCol+1 ){
      rc = SQLITE_OK;
      pIdxInfo->aConstraintUsage[i].omit = 1;
      pIdxInfo->aConstraintUsage[i].argvIndex = 1;
    }
    if( p->op==SQLITE_INDEX_CONSTRAINT_ISNULL && p->iColumn==iBaseCol ){
      pIdxInfo->aConstraintUsage[i].omit = 1;
      pIdxInfo->idxNum = 1;
    }
  }
  return rc;
}

  /* xShadowName */ 0
};


int sqlite3VdbeBytecodeVtabInit(sqlite3 *db){
  int rc;
  rc = sqlite3_create_module(db, "bytecode", &bytecodevtabModule, 0);
  if( rc==SQLITE_OK ){
    rc = sqlite3_create_module(db, "tables_used", &bytecodevtabModule, &db);
  }
  return rc;
}
#endif /* SQLITE_ENABLE_BYTECODE_VTAB */