guess.cpp

全新的纯内存式实时数据库

/*******************************************************************
 *                                                                 *
 *  guess.cpp                                                      *
 *                                                                 *
 *  This file is a part of the eXtremeDB source code               *
 *  Copyright (c) 2001-2007 McObject LLC                           * 
 *  All Rights Reserved                                            *
 *                                                                 *
 *******************************************************************/
#include "guess.h"

void input(char const* prompt, char* buf, size_t buf_size)
{
    char* p;
    do {
        printf(prompt);
        *buf = '\0';
        fgets(buf, (int)buf_size, stdin);
        p = buf + strlen(buf);
    } while (p <= buf+1);

    if (*(p-1) == '\n') {
        *--p = '\0';
    }
}

bool askQuestion(char const* question) 
{
    char answer[MAX_STR_LENGTH];
    input(question, answer, sizeof answer);
    return *answer == 'y' || *answer == 'Y';
}


Reference* GuessGame::whoIsIt(Reference* parent) 
{
    char animal[MAX_STR_LENGTH];
    char difference[MAX_STR_LENGTH];
    input("What is it ? ", animal, sizeof animal);
    input("What is a difference from other ? ", difference, sizeof difference);
    
    Record* animalNode = table->createRecord(trans);
    questionField->set(animalNode, String::create(animal));
    
    Record* diffNode = table->createRecord(trans);
    questionField->set(diffNode, String::create(difference));
    yesField->set(diffNode, table->getRID(animalNode));
    noField->set(diffNode, parent);
    return table->getRID(diffNode);
}


Reference* GuessGame::dialog(Record* rec) 
{
    char question[MAX_STR_LENGTH+16];
    sprintf(question, "May be %s (y/n) ? ", questionField->get(rec)->stringValue()->cstr());
    if (askQuestion(question)) {
        Reference* yes = (Reference*)yesField->get(rec);
        if (yes->isNull()) {
            printf("It was very simple question for me...\n");
        } else {
            Reference* clarify = dialog(yes->dereference());
            if (clarify != NULL) {
                yesField->set(rec, clarify);
                rec->updateRecord();
            }
        }
    } else {
        Reference* no = (Reference*)noField->get(rec);
        if (no->isNull()) {
            if (yesField->get(rec)->isNull()) {
                return whoIsIt(table->getRID(rec));
            } else {
                noField->set(rec, whoIsIt(NULL));
                rec->updateRecord();
            }
        } else {
            Reference* clarify = dialog(no->dereference());
            if (clarify != NULL) {
                noField->set(rec, clarify);
                rec->updateRecord();
            }
        }
    }
    return NULL;
}

void GuessGame::loadMetadata(DataSource* source)
{
    Iterator<Field>* fields = source->fields();
    while (fields->hasNext()) {
        Field* f = fields->next();
        String* name = f->name();
        if (name->compare("yes") == 0) {
            yesField = f;
        } else if (name->compare("no") == 0) {
            noField = f;
        } else if (name->compare("question") == 0) {
            questionField = f;
        }
    }
    assert(yesField != NULL);
    assert(noField != NULL);
    assert(questionField != NULL);
    table = yesField->table();
}


void GuessGame::play()
{
    DataSource* result;
    Cursor* cursor;
    engine.open("guessdb", guessdb_get_dictionary(), DATABASE_SIZE, PAGE_SIZE, MAP_ADDRESS);

    while (askQuestion("Think of an animal. Ready (y/n) ? ")) {
        result = engine.executeQuery("select * from Guess for update");
        if (table == NULL) { 
            loadMetadata(result);
        }
        trans = result->currentTransaction();
        cursor = result->records();
        if (cursor->hasNext()) {
            cursor->next(); // first question is in record number 2
            dialog(cursor->next()); 
        } else {
            whoIsIt(NULL);
        }
        result->release();
    }
    engine.close();
    printf("End of the game\n");
}

GuessGame::GuessGame() 
{
    yesField = noField = questionField = NULL;
    table = NULL;
}


int main() 
{
    GuessGame game;
    game.play();
    return 0;
}