From 67b50beb90c7187492a3b824ddd4fdb02fd302df Mon Sep 17 00:00:00 2001
From: p2r3 <p2r3@p2r3.com>
Date: Fri, 29 Aug 2025 06:22:05 +0300
Subject: [PATCH] support syncing to flash on esp-idf via littlefs

---
 include/globals.h   |  9 ++++++++-
 include/serialize.h |  2 +-
 src/serialize.c     | 45 ++++++++++++++++++++++++++++++++++++++-------
 3 files changed, 47 insertions(+), 9 deletions(-)

diff --git a/include/globals.h b/include/globals.h
index 25d4b45..c12e8cd 100644
--- a/include/globals.h
+++ b/include/globals.h
@@ -38,11 +38,18 @@
 // How many player-made block changes to allow
 // Determines the fixed amount of memory allocated to blocks
 #define MAX_BLOCK_CHANGES 20000
-// If defined, writes and reads world data to/from disk (PC only).
+// If defined, writes and reads world data to/from disk (or flash).
 // This is a synchronous operation, and can cause performance issues if
 // frequent random disk access is slow. Data is still stored in and
 // accessed from memory - reading from disk is only done on startup.
+// When targeting ESP-IDF, LittleFS is used to manage flash reads and
+// writes. Consider increasing DISK_SYNC_INTERVAL if wear is a concern.
 #define SYNC_WORLD_TO_DISK
+// The minimum interval (in microseconds) at which certain data is written
+// to disk/flash. Bounded on the low end by TIME_BETWEEN_TICKS. Currently
+// only applies to player data. Block changes are written as soon as they
+// are made, but in much smaller portions.
+#define DISK_SYNC_INTERVAL 15000000
 // If defined, scales the frequency at which player movement updates are
 // broadcast based on the amount of players, reducing overhead for higher
 // player counts. For very many players, makes movement look jittery.
diff --git a/include/serialize.h b/include/serialize.h
index 2c3cf71..eeffb46 100644
--- a/include/serialize.h
+++ b/include/serialize.h
@@ -3,7 +3,7 @@
 
 #include "globals.h"
 
-#if defined(SYNC_WORLD_TO_DISK) && !defined(ESP_PLATFORM)
+#ifdef SYNC_WORLD_TO_DISK
   int initSerializer ();
   void writeBlockChangesToDisk (int from, int to);
   void writeChestChangesToDisk (uint8_t *storage_ptr, uint8_t slot);
diff --git a/src/serialize.c b/src/serialize.c
index 627947d..422fb0c 100644
--- a/src/serialize.c
+++ b/src/serialize.c
@@ -1,18 +1,44 @@
 #include "globals.h"
 
-#if defined(SYNC_WORLD_TO_DISK) && !defined(ESP_PLATFORM)
+#ifdef SYNC_WORLD_TO_DISK
 
-#include <stdio.h>
-#include <stdlib.h>
+#ifdef ESP_PLATFORM
+  #include "esp_littlefs.h"
+  #define FILE_PATH "/littlefs/world.bin"
+#else
+  #include <stdio.h>
+  #define FILE_PATH "world.bin"
+#endif
 
+#include "tools.h"
 #include "registries.h"
 #include "serialize.h"
 
+int64_t last_disk_sync_time = 0;
+
 // Restores world data from disk, or writes world file if it doesn't exist
 int initSerializer () {
 
+  last_disk_sync_time = get_program_time();
+
+  #ifdef ESP_PLATFORM
+    esp_vfs_littlefs_conf_t conf = {
+      .base_path = "/littlefs",
+      .partition_label = "littlefs",
+      .format_if_mount_failed = true,
+      .dont_mount = false
+    };
+
+    esp_err_t ret = esp_vfs_littlefs_register(&conf);
+    if (ret != ESP_OK) {
+      printf("LittleFS error %d\n", ret);
+      perror("Failed to mount LittleFS. Aborting.");
+      return 1;
+    }
+  #endif
+
   // Attempt to open existing world file
-  FILE *file = fopen("world.bin", "rb");
+  FILE *file = fopen(FILE_PATH, "rb");
   if (file) {
 
     // Read block changes from the start of the file directly into memory
@@ -44,7 +70,7 @@ int initSerializer () {
     printf("No \"world.bin\" file found, creating one...\n\n");
 
     // Try to create the file in binary write mode
-    file = fopen("world.bin", "wb");
+    file = fopen(FILE_PATH, "wb");
     if (!file) {
       perror(
         "Failed to open \"world.bin\" for writing.\n"
@@ -83,13 +109,14 @@ int initSerializer () {
 
   }
 
+  return 0;
 }
 
 // Writes a range of block change entries to disk
 void writeBlockChangesToDisk (int from, int to) {
 
   // Try to open the file in rw (without overwriting)
-  FILE *file = fopen("world.bin", "r+b");
+  FILE *file = fopen(FILE_PATH, "r+b");
   if (!file) {
     perror("Failed to open \"world.bin\". Block updates have been dropped.");
     return;
@@ -116,8 +143,12 @@ void writeBlockChangesToDisk (int from, int to) {
 // Writes all player data to disk
 void writePlayerDataToDisk () {
 
+  // Skip this write if enough time hasn't passed since the last one
+  if (get_program_time() - last_disk_sync_time < DISK_SYNC_INTERVAL) return;
+  last_disk_sync_time = get_program_time();
+
   // Try to open the file in rw (without overwriting)
-  FILE *file = fopen("world.bin", "r+b");
+  FILE *file = fopen(FILE_PATH, "r+b");
   if (!file) {
     perror("Failed to open \"world.bin\". Player updates have been dropped.");
     return;