[feat] gva: block

Add GVA query for block.

Chez moi ça marche, par contre quand le bloc n'existe pas c'est le bloc par défaut qui est retourné. Que faut-il renvoyer dans ce cas ?

Pour des clients qui veulent lire la blockchain, ça serait utile de pouvoir demander plusieurs blocs avec pagination. Si c'est pas trop compliqué j'essaierai de faire ça.

rust-libs/modules/gva/dbs-reader/src/block.rs

+//  Copyright (C) 2021 Pascal Engélibert
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+use crate::*;
+
+impl DbsReader {
+    pub fn block(
+        &self,
+        bc_db: &BcV2DbRo<FileBackend>,
+        number: U32BE,
+    ) -> KvResult<Option<duniter_dbs::BlockMetaV2>> {
+        bc_db.blocks_meta().get(&number)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use duniter_dbs::databases::bc_v2::BcV2DbWritable;
+    use duniter_gva_db::GvaV1DbWritable;
+
+    #[test]
+    fn test_block() -> KvResult<()> {
+        let bc_db = duniter_dbs::databases::bc_v2::BcV2Db::<Mem>::open(MemConf::default())?;
+        let gva_db = duniter_gva_db::GvaV1Db::<Mem>::open(MemConf::default())?;
+        let bc_db_ro = bc_db.get_ro_handler();
+        let db_reader = create_dbs_reader(unsafe { std::mem::transmute(&gva_db.get_ro_handler()) });
+
+        bc_db
+            .blocks_meta_write()
+            .upsert(U32BE(0), duniter_dbs::BlockMetaV2::default())?;
+
+        assert_eq!(
+            db_reader.block(&bc_db_ro, U32BE(0))?,
+            Some(duniter_dbs::BlockMetaV2::default())
+        );
+
+        Ok(())
+    }
+}