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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/metadata.hpp"
+
+#include "store/exceptions.hpp"
+#include "utils/format/macros.hpp"
+#include "utils/sanity.hpp"
+#include "utils/sqlite/database.hpp"
+#include "utils/sqlite/exceptions.hpp"
+#include "utils/sqlite/statement.ipp"
+
+namespace sqlite = utils::sqlite;
+
+
+namespace {
+
+
+/// Fetches an integer column from a statement of the 'metadata' table.
+///
+/// \param stmt The statement from which to get the column value.
+/// \param column The name of the column to retrieve.
+///
+/// \return The value of the column.
+///
+/// \throw store::integrity_error If there is a problem fetching the value
+/// caused by an invalid schema or data.
+static int64_t
+int64_column(sqlite::statement& stmt, const char* column)
+{
+ int index;
+ try {
+ index = stmt.column_id(column);
+ } catch (const sqlite::invalid_column_error& e) {
+ UNREACHABLE_MSG("Invalid column specification; the SELECT statement "
+ "should have caught this");
+ }
+ if (stmt.column_type(index) != sqlite::type_integer)
+ throw store::integrity_error(F("The '%s' column in 'metadata' table "
+ "has an invalid type") % column);
+ return stmt.column_int64(index);
+}
+
+
+} // anonymous namespace
+
+
+/// Constructs a new metadata object.
+///
+/// \param schema_version_ The schema version.
+/// \param timestamp_ The time at which this version was created.
+store::metadata::metadata(const int schema_version_, const int64_t timestamp_) :
+ _schema_version(schema_version_),
+ _timestamp(timestamp_)
+{
+}
+
+
+/// Returns the timestamp of this entry.
+///
+/// \return The timestamp in this metadata entry.
+int64_t
+store::metadata::timestamp(void) const
+{
+ return _timestamp;
+}
+
+
+/// Returns the schema version.
+///
+/// \return The schema version in this metadata entry.
+int
+store::metadata::schema_version(void) const
+{
+ return _schema_version;
+}
+
+
+/// Reads the latest metadata entry from the database.
+///
+/// \param db The database from which to read the metadata from.
+///
+/// \return The current metadata of the database. It is not OK for the metadata
+/// table to be empty, so this is guaranteed to return a value unless there is
+/// an error.
+///
+/// \throw store::integrity_error If the metadata in the database is empty,
+/// has an invalid schema or its contents are bogus.
+store::metadata
+store::metadata::fetch_latest(sqlite::database& db)
+{
+ try {
+ sqlite::statement stmt = db.create_statement(
+ "SELECT schema_version, timestamp FROM metadata "
+ "ORDER BY schema_version DESC LIMIT 1");
+ if (!stmt.step())
+ throw store::integrity_error("The 'metadata' table is empty");
+
+ const int schema_version_ =
+ static_cast< int >(int64_column(stmt, "schema_version"));
+ const int64_t timestamp_ = int64_column(stmt, "timestamp");
+
+ if (stmt.step())
+ UNREACHABLE_MSG("Got more than one result from a query that "
+ "does not permit this; any pragmas defined?");
+
+ return metadata(schema_version_, timestamp_);
+ } catch (const sqlite::error& e) {
+ throw store::integrity_error(F("Invalid metadata schema: %s") %
+ e.what());
+ }
+}