//-< GUESS.CPP >-----------------------------------------------------*--------*// FastDB                    Version 1.0         (c) 1999  GARRET    *     ?  *// (Main Memory Database Management System)                          *   /\|  *//                                                                   *  /  \  *//                          Created:     19-Mar-2001    K.A. Knizhnik  * / [] \ *//                          Last update: 19-Mar-2001    K.A. Knizhnik  * GARRET *//-------------------------------------------------------------------*--------*// Example of sharinf classes between databases//-------------------------------------------------------------------*--------*#include "fastdb.h"USE_FASTDB_NAMESPACEconst int maxStrLen = 256;dbDatabase  database[2];dbDatabase* db;class Guess {  public:    dbReference<Guess> yes;    dbReference<Guess> no;    char const* question;    TYPE_DESCRIPTOR((FIELD(yes), FIELD(question), FIELD(no)));};REGISTER_UNASSIGNED(Guess);void input(char const* prompt, char* buf, size_t buf_size){    char* p;    do {        printf(prompt);        *buf = '\0';        fgets(buf, buf_size, stdin);        p = buf + strlen(buf);    } while (p <= buf+1);    if (*(p-1) == '\n') {        *--p = '\0';    }}bool askQuestion(char const* question) {    char answer[maxStrLen];    input(question, answer, sizeof answer);    return *answer == 'y' || *answer == 'Y';}dbReference<Guess> whoIsIt(dbReference<Guess> const& parent) {    char animal[maxStrLen];    char difference[maxStrLen];    input("What is it ? ", animal, sizeof animal);    input("What is a difference from other ? ", difference, sizeof difference);    Guess node;    node.question = animal;    dbReference<Guess> child = db->insert(node);    node.question = difference;    node.yes = child;    node.no = parent;    return db->insert(node);}dbReference<Guess> dialog(dbCursor<Guess>& cur) {    char question[maxStrLen+16];    dbCursor<Guess> c(db, dbCursorForUpdate);    sprintf(question, "May be %s (y/n) ? ", cur->question);    if (askQuestion(question)) {        if (cur->yes == null) {            printf("It was very simple question for me...\n");        } else {            c.at(cur->yes);            dbReference<Guess> clarify = dialog(c);            if (clarify != null) {                cur->yes = clarify;                cur.update();            }        }    } else {        if (cur->no == null) {            if (cur->yes == null) {                return whoIsIt(cur.currentId());            } else {                cur->no = whoIsIt(null);                cur.update();            }        } else {            c.at(cur->no);            dbReference<Guess> clarify = dialog(c);            if (clarify != null) {                cur->no = clarify;                cur.update();            }        }    }    return null;}int main(){    if (database[0].open("guess1") && database[1].open("guess2")) {        int i = 0;        while (askQuestion("Think of an animal. Ready (y/n) ? ")) {            db = &database[i ^= 1];            dbCursor<Guess> cur(db, dbCursorForUpdate);            if (cur.select() != 0) {                cur.next(); // first question is in record number 2                dialog(cur);            } else {                whoIsIt(null);            }            db->commit();        }        database[0].close();        database[1].close();        printf("End of the game\n");        return EXIT_SUCCESS;    } else {        fprintf(stderr, "Failed to open database\n");        return EXIT_FAILURE;    }}