From 233bbc67ab82fb242c6099e08b44d9e44eed05ed Mon Sep 17 00:00:00 2001
From: Kris Zyp <kriszyp@gmail.com>
Date: Wed, 13 Mar 2024 10:42:59 -0600
Subject: [PATCH] Write the freespace entries in a way that more carefully
 aligns with how they were reserved

---
 dependencies/lmdb/libraries/liblmdb/mdb.c | 47 ++++++++++++++---------
 src/writer.cpp                            |  1 -
 2 files changed, 28 insertions(+), 20 deletions(-)

diff --git a/dependencies/lmdb/libraries/liblmdb/mdb.c b/dependencies/lmdb/libraries/liblmdb/mdb.c
index 71a49a1e7..5a8f9e1cd 100644
--- a/dependencies/lmdb/libraries/liblmdb/mdb.c
+++ b/dependencies/lmdb/libraries/liblmdb/mdb.c
@@ -4321,25 +4321,31 @@ mdb_freelist_save(MDB_txn *txn)
 	for (txnid_t id = start_written; id <= pglast; id++) {
 		key.mv_size = sizeof(id);
 		key.mv_data = &id;
-		mdb_cursor_get(&mc, &key, &data, MDB_SET_KEY);
+		rc = mdb_cursor_get(&mc, &key, &data, MDB_SET_KEY);
+		if (rc == MDB_NOTFOUND) {
+			mdb_tassert(txn, mop_len == 0);
+			rc = 0; // this is acceptable as long as there are no entries to write
+			break;
+		}
+
+
 //		fprintf(stderr, "put %u: ", id);
 
-		int len = (data.mv_size / sizeof(id)) - 1;
+		int reserved_len = (data.mv_size / sizeof(id)) - 1;
+		ssize_t reserved_end = reserved_space;
 		ssize_t end = mop_len;
 		ssize_t save_end = mop[end];
 		if (save_end < 0) {
 			// ends with a block length, zero it out, was already handled by previous iteration
 			mop[end] = 0;
 		}
-		ssize_t start = mop_len - len;
-		if (start < 0) {
-			// oversized entry, just use the remaining length
-			len = mop_len;
-			start = 0;
-		}
+		ssize_t start = reserved_space - reserved_len;
+		int len = end - start;
+		if (len < 0) len = 0;
+
 		ssize_t save2 = 0;
 		ssize_t save = mop[start];
-		if (len > entry_size) {
+		if (reserved_len > entry_size) {
 			// full blocks
 			// we have an extra overlapping byte to handle block length prefix. But don't use it if it is a page number
 			// because it could be preceded by a block length prefix, instead zero it out
@@ -4347,23 +4353,26 @@ mdb_freelist_save(MDB_txn *txn)
 			if (save2 > 0) {
 				mop[start + 1] = 0;
 			}
-			mop_len -= entry_size;
+			reserved_space = start + 1;
+
 		} else {
-			if (mop_len > entry_size) {
-				fprintf(stderr, "mop_len to large %u %u %u %u %u %u", reserved_space, mop_len, entry_size, start_written, id, pglast);
+			if (reserved_space > entry_size) {
+				fprintf(stderr, "reserved_space to large %u %u %u %u %u %u", reserved_space, mop_len, entry_size, start_written, id, pglast);
 			}
-			mdb_tassert(txn, mop_len <= entry_size);
-			mop_len = 0; // nothing left to save
+			mdb_tassert(txn, reserved_space <= entry_size);
+			reserved_space -= reserved_len;
+			if (reserved_space < 0) reserved_space = 0;
+			mdb_tassert(txn, reserved_space == 0);
+		}
+		if (reserved_space < mop_len) {
+			mop_len = reserved_space;
 		}
-		char do_write = env->me_freelist_written_start <= end && env->me_freelist_written_end >= start ||
-				(!end && env->me_freelist_written_end);
+		char do_write = env->me_freelist_written_start <= reserved_end && env->me_freelist_written_end >= start;
 		if (fl_writes[i++] != do_write) {
 			fprintf(stderr, "Do write of page does not match");
 		}
 		// if it is in the written range
-		if (env->me_freelist_written_start <= end && env->me_freelist_written_end >= start ||
-			// if we have collapsed to an empty list, but there was data written
-			(!end && env->me_freelist_written_end)) {
+		if (do_write) {
 			// we are in part of the range of the freelist that was written, so we actually need to save it
 			// if end == 0 it means that the length was probably truncated and we need to rewrite the length byte
 			if (save_end <= 0 && len > 0) len--; // leave off the last byte if we are ignoring it
diff --git a/src/writer.cpp b/src/writer.cpp
index 9a92fad4a..a6df33fa8 100644
--- a/src/writer.cpp
+++ b/src/writer.cpp
@@ -593,7 +593,6 @@ Value EnvWrap::startWriting(const Napi::CallbackInfo& info) {
 	status = napi_create_object(n_env, &resource);
 	napi_value resource_name;
 	status = napi_create_string_latin1(n_env, "write", NAPI_AUTO_LENGTH, &resource_name);
-	//fprintf(stderr, "start write %p\n", instructionAddress);
 	auto worker = new WriteWorker(this->env, this, (uint32_t*) instructionAddress);
 	this->writeWorker = worker;
 	napi_create_reference(n_env, info[1].As<Function>(), 1, &worker->callback);