/usr/include/odb/prepared-query.hxx is in libodb-dev 2.4.0-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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// copyright : Copyright (c) 2009-2015 Code Synthesis Tools CC
// license : GNU GPL v2; see accompanying LICENSE file
#ifndef ODB_PREPARED_QUERY_HXX
#define ODB_PREPARED_QUERY_HXX
#include <odb/pre.hxx>
#include <odb/forward.hxx> // odb::core
#include <odb/traits.hxx>
#include <odb/result.hxx>
#include <odb/statement.hxx>
#include <odb/details/export.hxx>
#include <odb/details/shared-ptr.hxx>
namespace odb
{
class LIBODB_EXPORT prepared_query_impl: public details::shared_base
{
public:
virtual
~prepared_query_impl ();
prepared_query_impl (connection&);
bool cached;
connection& conn;
const char* name;
details::shared_ptr<statement> stmt;
details::shared_ptr<result_impl> (*execute) (prepared_query_impl&);
private:
prepared_query_impl (const prepared_query_impl&);
prepared_query_impl& operator= (const prepared_query_impl&);
// Doubly-linked list of results.
//
// prev_ == 0 means we are the first element.
// next_ == 0 means we are the last element.
// next_ == this means we are not on the list.
//
protected:
friend class connection;
void
list_remove ();
prepared_query_impl* prev_;
prepared_query_impl* next_;
};
template <typename T>
struct prepared_query
{
// Cached version.
//
explicit
prepared_query (prepared_query_impl* impl = 0): impl_ (impl) {}
// Uncached version.
//
explicit
prepared_query (const details::shared_ptr<prepared_query_impl>& impl)
: impl_ (impl.get ())
{
impl_->_inc_ref ();
}
result<T>
execute (bool cache = true)
{
typedef
typename result_base<T, class_traits<T>::kind>::result_impl_type
derived_type;
details::shared_ptr<result_impl> ri (impl_->execute (*impl_));
result<T> r (
details::shared_ptr<derived_type> (
static_cast<derived_type*> (ri.release ())));
if (cache)
r.cache ();
return r;
}
typename object_traits<T>::pointer_type
execute_one ()
{
return execute (false).one ();
}
bool
execute_one (T& object)
{
return execute (false).one (object);
}
T
execute_value ()
{
// Compiler error pointing here? The object must be default-
// constructible in order to use the return-by-value API.
//
T o;
execute (false).value (o);
return o;
}
const char*
name () const
{
return impl_->name;
}
typedef odb::statement statement_type;
statement_type&
statement () const
{
return *impl_->stmt;
}
typedef prepared_query_impl* prepared_query::*unspecified_bool_type;
operator unspecified_bool_type () const
{
return impl_ ? &prepared_query::impl_ : 0;
}
public:
~prepared_query ()
{
if (impl_ != 0 && !impl_->cached && impl_->_dec_ref ())
delete impl_;
}
prepared_query (const prepared_query& x)
: impl_ (x.impl_)
{
if (!impl_->cached)
impl_->_inc_ref ();
}
prepared_query&
operator= (const prepared_query& x)
{
if (impl_ != x.impl_)
{
if (impl_ != 0 && !impl_->cached && impl_->_dec_ref ())
delete impl_;
impl_ = x.impl_;
if (!impl_->cached)
impl_->_inc_ref ();
}
return *this;
}
private:
// Ideally, we would just use shared_ptr to manage the impl object.
// However, there is a problem if the prepared query is cached on
// the connection and the connection is released early when the
// transaction is committed or rolled back. In this case, the
// prepared_query object might still be around pointing to impl. If
// this connection and the prepared query are then used by another
// thread while we release the impl object, then we have a race
// condition.
//
// To work around this problem we will simply "reference" the impl
// object without counting if the prepared query is cached. For
// transition from pointer to reference, see cache_query_() in
// connection.cxx.
//
// You may also observe that in order to know whether this is a
// cached prepared query or not, we have to read the cached data
// member in the impl object. This does not cause a race because,
// unlike the reference count, this member is immutable once set
// to true.
//
friend class connection;
prepared_query_impl* impl_;
};
namespace common
{
using odb::prepared_query;
}
}
#include <odb/post.hxx>
#endif // ODB_PREPARED_QUERY_HXX
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