From 424594488fee0bd7d7740b74c2775241c7c60b7a Mon Sep 17 00:00:00 2001
From: Jonas Diemer <jonasdiemer@gmail.com>
Date: Thu, 18 Dec 2025 12:49:14 +0100
Subject: [PATCH] Caching of spine item sizes for faster book loading (saves
 1-4 seconds). (#54)

As discussed in
https://github.com/daveallie/crosspoint-reader/pull/38#issuecomment-3665142427,
#38
---
 lib/Epub/Epub.cpp | 55 ++++++++++++++++++++++++++++++++++++-----------
 lib/Epub/Epub.h   |  1 +
 src/main.cpp      |  2 +-
 3 files changed, 45 insertions(+), 13 deletions(-)

diff --git a/lib/Epub/Epub.cpp b/lib/Epub/Epub.cpp
index d1855cc..1477d72 100644
--- a/lib/Epub/Epub.cpp
+++ b/lib/Epub/Epub.cpp
@@ -148,23 +148,54 @@ bool Epub::load() {
     return false;
   }
 
-  // determine size of spine items
-  size_t spineItemsCount = getSpineItemsCount();
-  size_t spineItemsSize = 0;
-  for (size_t i = 0; i < spineItemsCount; i++) {
-    std::string spineItem = getSpineItem(i);
-    size_t s = 0;
-    getItemSize(spineItem, &s);
-    spineItemsSize += s;
-    cumulativeSpineItemSize.emplace_back(spineItemsSize);
-  }
-  Serial.printf("[%lu] [EBP] Book size: %u\n", millis(), spineItemsSize);
-
+  initializeSpineItemSizes();
   Serial.printf("[%lu] [EBP] Loaded ePub: %s\n", millis(), filepath.c_str());
 
   return true;
 }
 
+void Epub::initializeSpineItemSizes() {
+  setupCacheDir();
+
+  size_t spineItemsCount = getSpineItemsCount();
+  size_t cumSpineItemSize = 0;
+  if (SD.exists((getCachePath() + "/spine_size.bin").c_str())) {
+    File f = SD.open((getCachePath() + "/spine_size.bin").c_str());
+    uint8_t data[4];
+    for (size_t i = 0; i < spineItemsCount; i++) {
+      f.read(data, 4);
+      cumSpineItemSize = data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24);
+      cumulativeSpineItemSize.emplace_back(cumSpineItemSize);
+      // Serial.printf("[%lu] [EBP] Loading item %d size %u to %u %u\n", millis(),
+      //     i, cumSpineItemSize, data[1], data[0]);
+    }
+    f.close();
+  } else {
+    File f = SD.open((getCachePath() + "/spine_size.bin").c_str(), FILE_WRITE);
+    uint8_t data[4];
+    // determine size of spine items
+    for (size_t i = 0; i < spineItemsCount; i++) {
+      std::string spineItem = getSpineItem(i);
+      size_t s = 0;
+      getItemSize(spineItem, &s);
+      cumSpineItemSize += s;
+      cumulativeSpineItemSize.emplace_back(cumSpineItemSize);
+
+      // and persist to cache
+      data[0] = cumSpineItemSize & 0xFF;
+      data[1] = (cumSpineItemSize >> 8) & 0xFF;
+      data[2] = (cumSpineItemSize >> 16) & 0xFF;
+      data[3] = (cumSpineItemSize >> 24) & 0xFF;
+      // Serial.printf("[%lu] [EBP] Persisting item %d size %u to %u %u\n", millis(),
+      //     i, cumSpineItemSize, data[1], data[0]);
+      f.write(data, 4);
+    }
+
+    f.close();
+  }
+  Serial.printf("[%lu] [EBP] Book size: %lu\n", millis(), cumSpineItemSize);
+}
+
 bool Epub::clearCache() const {
   if (!SD.exists(cachePath.c_str())) {
     Serial.printf("[%lu] [EPB] Cache does not exist, no action needed\n", millis());
diff --git a/lib/Epub/Epub.h b/lib/Epub/Epub.h
index 1f2dfa9..f22b630 100644
--- a/lib/Epub/Epub.h
+++ b/lib/Epub/Epub.h
@@ -32,6 +32,7 @@ class Epub {
   bool findContentOpfFile(std::string* contentOpfFile) const;
   bool parseContentOpf(const std::string& contentOpfFilePath);
   bool parseTocNcxFile();
+  void initializeSpineItemSizes();
 
  public:
   explicit Epub(std::string filepath, const std::string& cacheDir) : filepath(std::move(filepath)) {
diff --git a/src/main.cpp b/src/main.cpp
index 39c5bd0..d12c701 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -216,7 +216,7 @@ void loop() {
     return;
   }
 
-  if (inputManager.wasReleased(InputManager::BTN_POWER) && inputManager.getHeldTime() > POWER_BUTTON_WAKEUP_MS) {
+  if (inputManager.wasReleased(InputManager::BTN_POWER) && inputManager.getHeldTime() > POWER_BUTTON_SLEEP_MS) {
     enterDeepSleep();
     // This should never be hit as `enterDeepSleep` calls esp_deep_sleep_start
     return;