guess.cpp

FastDb是高效的内存数据库系统

//-< GUESS.CPP >-----------------------------------------------------*--------*
// FastDB                    Version 1.0         (c) 1999  GARRET    *     ?  *
// (Main Memory Database Management System)                          *   /\|  *
//                                                                   *  /  \  *
//                          Created:     10-Dec-98    K.A. Knizhnik  * / [] \ *
//                          Last update: 19-Dec-98    K.A. Knizhnik  * GARRET *
//-------------------------------------------------------------------*--------*
// Sample of database application: game "Guess an animal"
//-------------------------------------------------------------------*--------*

#include "fastdb.h"

USE_FASTDB_NAMESPACE

const int maxStrLen = 256;


class Guess { 
  public:
    dbReference<Guess> yes;
    dbReference<Guess> no;
    char const* question;

    TYPE_DESCRIPTOR((FIELD(yes), FIELD(question), FIELD(no)));
};

REGISTER(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 = insert(node);
    node.question = difference;
    node.yes = child;
    node.no = parent;
    return insert(node);
}


dbReference<Guess> dialog(dbCursor<Guess>& cur) {
    char question[maxStrLen+16];
    dbCursor<Guess> c(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(int argc, char* argv[])
{
#ifdef REPLICATION_SUPPORT
    dbReplicatedDatabase db; 
    char* servers[3] = {"localhost:6101", "localhost:6102", "localhost:6103"};
    char dbName[64], fileName[64];
    int id = argc > 1 ? atoi(argv[1]) : 0;
    sprintf(dbName, "guess%d", id);
    sprintf(fileName, "guess%d.dbs", id);
    if (db.open(dbName, fileName, id, servers, 3)) {
#else
    dbDatabase db; 
    if (db.open("guess")) {
#endif 

        // db.scheduleBackup("guess.bck-?", 10);
        dbCursor<Guess> cur(dbCursorForUpdate);
        while (askQuestion("Think of an animal. Ready (y/n) ? ")) { 
            if (cur.select() != 0) { 
                cur.next(); // first question is in record number 2
                dialog(cur);
            } else { 
                whoIsIt(null);
            }
            db.commit();
        } 
        db.close();
        printf("End of the game\n");
        return EXIT_SUCCESS;
    } else { 
        fprintf(stderr, "Failed to open database\n");
        return EXIT_FAILURE;
    }
}