From ba9787994770dab80403ee21539bd5bbba912d47 Mon Sep 17 00:00:00 2001
From: ubq323 <ubq323@ubq323.website>
Date: Sun, 19 Mar 2023 20:39:34 +0000
Subject: add #db operator for number of entries in db

---
 README.md |  3 +++
 lmdb.c    | 14 ++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/README.md b/README.md
index b63c4e3..e8187d3 100644
--- a/README.md
+++ b/README.md
@@ -57,3 +57,6 @@ write `value` as the value of `key` into the database.
 
 ### `pairs(db)`
 returns `lmdb.next, db, nil`.
+
+## `#db`
+return the number of entries in the database.
diff --git a/lmdb.c b/lmdb.c
index 60ddca2..03c696f 100644
--- a/lmdb.c
+++ b/lmdb.c
@@ -288,6 +288,19 @@ static int db_put(lua_State *L) {
 	return 0;
 }
 
+static int db_len(lua_State *L) {
+	lua_settop(L, 1);
+	MDB_dbi dbi = *(MDB_dbi *) luaL_checkudata(L, 1, "lmdb.db");
+	check_env(L, 1);
+
+	get_parent(L, 1);
+	struct handle *tud = lua_touserdata(L, -1);
+	struct MDB_stat stat;
+	asserr(mdb_stat(tud->obj, dbi, &stat));
+	lua_pushinteger(L, stat.ms_entries);
+	return 1;
+}
+
 static int db_next(lua_State *L) {
 	lua_settop(L, 2);
 	MDB_dbi dbi = *(MDB_dbi *) luaL_checkudata(L, 1, "lmdb.db");
@@ -377,6 +390,7 @@ static const struct luaL_Reg lmdb_db[] = {
 	{"__index", db_get},
 	{"__newindex", db_put},
 	{"__pairs", db_pairs},
+	{"__len", db_len},
 	{NULL, NULL},
 };
 
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