2 files changed, 92 insertions, 0 deletions

diff --git a/store/database.cpp b/store/database.cpp
index 7e2019e..2d93266 100644
--- a/store/database.cpp
+++ b/store/database.cpp
@@ -101,3 +101,77 @@ void Database::read(const std::string &sKey, const std::function<void(const std:
     mdb_txn_abort(txn);
 }
 
+
+
+ReadTransaction::ReadTransaction(const QString &path)
+{
+    int rc;
+
+    //create file
+    rc = mdb_env_create(&env);
+    //FIXME MDB_NOTLS required to so we can have multiple read-only transactions per resource?
+    rc = mdb_env_open(env, path.toStdString().data(), 0, 0664);
+    const int dbSize = 10485760*100; //10MB * 100
+    mdb_env_set_mapsize(env, dbSize);
+
+    if (rc) {
+        std::cerr << "mdb_env_open: " << rc << mdb_strerror(rc) << std::endl;
+    }
+}
+
+ReadTransaction::~ReadTransaction()
+{
+    mdb_txn_abort(txn);
+
+    mdb_dbi_close(env, dbi);
+    mdb_env_close(env);
+}
+
+void ReadTransaction::read(const std::string &sKey, const std::function<void(void *data, int size)> &resultHandler)
+{
+    int rc;
+    MDB_val key;
+    MDB_val data;
+    MDB_cursor *cursor;
+
+    key.mv_size = sKey.size();
+    key.mv_data = (void*)sKey.data();
+
+    {
+        //A write transaction is at least required the first time
+        rc = mdb_txn_begin(env, nullptr, 0, &txn);
+        //Open the database
+        //With this we could open multiple named databases if we wanted to
+        rc = mdb_dbi_open(txn, nullptr, 0, &dbi);
+        mdb_txn_abort(txn);
+    }
+
+    rc = mdb_txn_begin(env, nullptr, MDB_RDONLY, &txn);
+    rc = mdb_cursor_open(txn, dbi, &cursor);
+    if (rc) {
+        std::cerr << "mdb_cursor_open: " << rc << mdb_strerror(rc) << std::endl;
+    }
+    if (sKey.empty()) {
+        std::cout << "Iterating over all values of store!" << std::endl;
+        rc = mdb_cursor_get(cursor, &key, &data, MDB_FIRST);
+        while ((rc = mdb_cursor_get(cursor, &key, &data, MDB_NEXT)) == 0) {
+            resultHandler(data.mv_data, data.mv_size);
+        }
+        //We never find the last value
+        if (rc == MDB_NOTFOUND) {
+            rc = 0;
+        }
+    } else {
+        if ((rc = mdb_cursor_get(cursor, &key, &data, MDB_SET)) == 0) {
+            resultHandler(data.mv_data, data.mv_size);
+        } else {
+            std::cout << "couldn't find value " << sKey << std::endl;
+        }
+    }
+    if (rc) {
+        std::cerr << "mdb_cursor_get: " << rc << mdb_strerror(rc) << std::endl;
+    }
+    mdb_cursor_close(cursor);
+    //We keep the transaction open since we want to keep the returned values alive
+}
+
diff --git a/store/database.h b/store/database.h
index 999a89e..ab398a4 100644
--- a/store/database.h
+++ b/store/database.h
@@ -18,3 +18,21 @@ private:
     MDB_env *env;
     MDB_dbi dbi;
 };
+
+/*
+ * This opens the db for a single read transaction.
+ *
+ * The lifetime of all read values is tied to this transaction.
+ */
+class ReadTransaction {
+public:
+    ReadTransaction(const QString &path);
+    ~ReadTransaction();
+
+    void read(const std::string &sKey, const std::function<void(void *ptr, int size)> &);
+
+private:
+    MDB_env *env;
+    MDB_dbi dbi;
+    MDB_txn *txn;
+};