nix-super/src/db.cc

#include "db.hh"
#include "util.hh"

#include <memory>


/* Wrapper class to ensure proper destruction. */
class DestroyDbc 
{
    Dbc * dbc;
public:
    DestroyDbc(Dbc * _dbc) : dbc(_dbc) { }
    ~DestroyDbc() { dbc->close(); /* close() frees dbc */ }
};


static void rethrow(DbException & e)
{
    throw Error(e.what());
}


Transaction::Transaction()
    : txn(0)
{
}


Transaction::Transaction(Database & db)
{
    db.requireEnv();
    try {
        db.env->txn_begin(0, &txn, 0);
    } catch (DbException e) { rethrow(e); }
}


Transaction::~Transaction()
{
    if (txn) abort();
}


void Transaction::commit()
{
    if (!txn) throw Error("commit called on null transaction");
    debug(format("committing transaction %1%") % (void *) txn);
    DbTxn * txn2 = txn;
    txn = 0;
    try {
        txn2->commit(0);
    } catch (DbException e) { rethrow(e); }
}


void Transaction::abort()
{
    if (!txn) throw Error("abort called on null transaction");
    debug(format("aborting transaction %1%") % (void *) txn);
    DbTxn * txn2 = txn;
    txn = 0;
    try {
        txn2->abort();
    } catch (DbException e) { rethrow(e); }
}


void Database::requireEnv()
{
    if (!env) throw Error("database environment not open");
}


Db * Database::getDb(TableId table)
{
    map<TableId, Db *>::iterator i = tables.find(table);
    if (i == tables.end())
        throw Error("unknown table id");
    return i->second;
}


Database::Database()
    : env(0)
    , nextId(1)
{
}


Database::~Database()
{
    if (env) {
        debug(format("closing database environment"));

        try {

            for (map<TableId, Db *>::iterator i = tables.begin();
                 i != tables.end(); i++)
            {
                debug(format("closing table %1%") % i->first);
                Db * db = i->second;
                db->close(0);
                delete db;
            }

            env->txn_checkpoint(0, 0, 0);
            env->close(0);

        } catch (DbException e) { rethrow(e); }

        delete env;
    }
}


void Database::open(const string & path)
{
    try {
        
        if (env) throw Error(format("environment already open"));

        env = new DbEnv(0);

        env->set_lg_bsize(32 * 1024); /* default */
        env->set_lg_max(256 * 1024); /* must be > 4 * lg_bsize */
        env->set_lk_detect(DB_LOCK_DEFAULT);
        
        env->open(path.c_str(),
            DB_INIT_LOCK | DB_INIT_LOG | DB_INIT_MPOOL | DB_INIT_TXN |
            DB_CREATE,
            0666);

    } catch (DbException e) { rethrow(e); }
}


TableId Database::openTable(const string & tableName)
{
    requireEnv();
    TableId table = nextId++;

    try {

        Db * db = new Db(env, 0);

        try {
            // !!! fixme when switching to BDB 4.1: use txn.
            db->open(tableName.c_str(), 0, DB_HASH, DB_CREATE, 0666);
        } catch (...) {
            delete db;
            throw;
        }

        tables[table] = db;

    } catch (DbException e) { rethrow(e); }

    return table;
}


bool Database::queryString(const Transaction & txn, TableId table, 
    const string & key, string & data)
{
    try {
        Db * db = getDb(table);

        Dbt kt((void *) key.c_str(), key.length());
        Dbt dt;

        int err = db->get(txn.txn, &kt, &dt, 0);
        if (err) return false;

        if (!dt.get_data())
            data = "";
        else
            data = string((char *) dt.get_data(), dt.get_size());
    
    } catch (DbException e) { rethrow(e); }

    return true;
}


bool Database::queryStrings(const Transaction & txn, TableId table, 
    const string & key, Strings & data)
{
    string d;

    if (!queryString(txn, table, key, d))
        return false;

    string::iterator it = d.begin();
    
    while (it != d.end()) {

        if (it + 4 > d.end())
            throw Error(format("short db entry: `%1%'") % d);
        
        unsigned int len;
        len = (unsigned char) *it++;
        len |= ((unsigned char) *it++) << 8;
        len |= ((unsigned char) *it++) << 16;
        len |= ((unsigned char) *it++) << 24;
        
        if (it + len > d.end())
            throw Error(format("short db entry: `%1%'") % d);

        string s;
        while (len--) s += *it++;

        data.push_back(s);
    }

    return true;
}


void Database::setString(const Transaction & txn, TableId table,
    const string & key, const string & data)
{
    try {
        Db * db = getDb(table);
        Dbt kt((void *) key.c_str(), key.length());
        Dbt dt((void *) data.c_str(), data.length());
        db->put(txn.txn, &kt, &dt, 0);
    } catch (DbException e) { rethrow(e); }
}


void Database::setStrings(const Transaction & txn, TableId table,
    const string & key, const Strings & data)
{
    string d;
    
    for (Strings::const_iterator it = data.begin();
         it != data.end(); it++)
    {
        string s = *it;
        unsigned int len = s.size();

        d += len & 0xff;
        d += (len >> 8) & 0xff;
        d += (len >> 16) & 0xff;
        d += (len >> 24) & 0xff;
        
        d += s;
    }

    setString(txn, table, key, d);
}


void Database::delPair(const Transaction & txn, TableId table,
    const string & key)
{
    try {
        Db * db = getDb(table);
        Dbt kt((void *) key.c_str(), key.length());
        db->del(txn.txn, &kt, 0);
    } catch (DbException e) { rethrow(e); }
}


void Database::enumTable(const Transaction & txn, TableId table,
    Strings & keys)
{
    try {
        Db * db = getDb(table);

        Dbc * dbc;
        db->cursor(txn.txn, &dbc, 0);
        DestroyDbc destroyDbc(dbc);

        Dbt kt, dt;
        while (dbc->get(&kt, &dt, DB_NEXT) != DB_NOTFOUND)
            keys.push_back(
                string((char *) kt.get_data(), kt.get_size()));

    } catch (DbException e) { rethrow(e); }
}