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diff --git a/store/write_backend.cpp b/store/write_backend.cpp
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+// Copyright 2011 The Kyua Authors.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+//   notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright
+//   notice, this list of conditions and the following disclaimer in the
+//   documentation and/or other materials provided with the distribution.
+// * Neither the name of Google Inc. nor the names of its contributors
+//   may be used to endorse or promote products derived from this software
+//   without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "store/write_backend.hpp"
+
+#include <stdexcept>
+
+#include "store/exceptions.hpp"
+#include "store/metadata.hpp"
+#include "store/read_backend.hpp"
+#include "store/write_transaction.hpp"
+#include "utils/env.hpp"
+#include "utils/format/macros.hpp"
+#include "utils/fs/path.hpp"
+#include "utils/logging/macros.hpp"
+#include "utils/noncopyable.hpp"
+#include "utils/sanity.hpp"
+#include "utils/stream.hpp"
+#include "utils/sqlite/database.hpp"
+#include "utils/sqlite/exceptions.hpp"
+#include "utils/sqlite/statement.ipp"
+
+namespace fs = utils::fs;
+namespace sqlite = utils::sqlite;
+
+
+/// The current schema version.
+///
+/// Any new database gets this schema version.  Existing databases with an older
+/// schema version must be first migrated to the current schema with
+/// migrate_schema() before they can be used.
+///
+/// This must be kept in sync with the value in the corresponding schema_vX.sql
+/// file, where X matches this version number.
+///
+/// This variable is not const to allow tests to modify it.  No other code
+/// should change its value.
+int store::detail::current_schema_version = 3;
+
+
+namespace {
+
+
+/// Checks if a database is empty (i.e. if it is new).
+///
+/// \param db The database to check.
+///
+/// \return True if the database is empty.
+static bool
+empty_database(sqlite::database& db)
+{
+    sqlite::statement stmt = db.create_statement("SELECT * FROM sqlite_master");
+    return !stmt.step();
+}
+
+
+}  // anonymous namespace
+
+
+/// Calculates the path to the schema file for the database.
+///
+/// \return The path to the installed schema_vX.sql file that matches the
+/// current_schema_version.
+fs::path
+store::detail::schema_file(void)
+{
+    return fs::path(utils::getenv_with_default("KYUA_STOREDIR", KYUA_STOREDIR))
+        / (F("schema_v%s.sql") % current_schema_version);
+}
+
+
+/// Initializes an empty database.
+///
+/// \param db The database to initialize.
+///
+/// \return The metadata record written into the new database.
+///
+/// \throw store::error If there is a problem initializing the database.
+store::metadata
+store::detail::initialize(sqlite::database& db)
+{
+    PRE(empty_database(db));
+
+    const fs::path schema = schema_file();
+
+    LI(F("Populating new database with schema from %s") % schema);
+    try {
+        db.exec(utils::read_file(schema));
+
+        const metadata metadata = metadata::fetch_latest(db);
+        LI(F("New metadata entry %s") % metadata.timestamp());
+        if (metadata.schema_version() != detail::current_schema_version) {
+            UNREACHABLE_MSG(F("current_schema_version is out of sync with "
+                              "%s") % schema);
+        }
+        return metadata;
+    } catch (const store::integrity_error& e) {
+        // Could be raised by metadata::fetch_latest.
+        UNREACHABLE_MSG("Inconsistent code while creating a database");
+    } catch (const sqlite::error& e) {
+        throw error(F("Failed to initialize database: %s") % e.what());
+    } catch (const std::runtime_error& e) {
+        throw error(F("Cannot read database schema '%s'") % schema);
+    }
+}
+
+
+/// Internal implementation for the backend.
+struct store::write_backend::impl : utils::noncopyable {
+    /// The SQLite database this backend talks to.
+    sqlite::database database;
+
+    /// Constructor.
+    ///
+    /// \param database_ The SQLite database instance.
+    impl(sqlite::database& database_) : database(database_)
+    {
+    }
+};
+
+
+/// Constructs a new backend.
+///
+/// \param pimpl_ The internal data.
+store::write_backend::write_backend(impl* pimpl_) :
+    _pimpl(pimpl_)
+{
+}
+
+
+/// Destructor.
+store::write_backend::~write_backend(void)
+{
+}
+
+
+/// Opens a database in read-write mode and creates it if necessary.
+///
+/// \param file The database file to be opened.
+///
+/// \return The backend representation.
+///
+/// \throw store::error If there is any problem opening or creating
+///     the database.
+store::write_backend
+store::write_backend::open_rw(const fs::path& file)
+{
+    sqlite::database db = detail::open_and_setup(
+        file, sqlite::open_readwrite | sqlite::open_create);
+    if (!empty_database(db))
+        throw error(F("%s already exists and is not empty; cannot open "
+                      "for write") % file);
+    detail::initialize(db);
+    return write_backend(new impl(db));
+}
+
+
+/// Closes the SQLite database.
+void
+store::write_backend::close(void)
+{
+    _pimpl->database.close();
+}
+
+
+/// Gets the connection to the SQLite database.
+///
+/// \return A database connection.
+sqlite::database&
+store::write_backend::database(void)
+{
+    return _pimpl->database;
+}
+
+
+/// Opens a write-only transaction.
+///
+/// \return A new transaction.
+store::write_transaction
+store::write_backend::start_write(void)
+{
+    return write_transaction(*this);
+}