Minor changes in .aseprite decoder/encoder to avoid depending on exceptions to control flow

src/app/file/ase_format.cpp

@@ -1526,23 +1526,23 @@ static void ase_file_write_properties_maps(FILE* f, FileOp* fop,
   for (auto propertiesMap : propertiesMaps) {
     const UserData::Properties& properties = propertiesMap.second;
     // Skip properties map if it doesn't have any property
-    if (properties.size() == 0) continue;
+    if (properties.empty())
+      continue;
 
     const std::string& extensionKey = propertiesMap.first;
-    try {
-      uint32_t extensionId = extensionKey == "" ? 0 : ext_files.to_id.at(extensionKey);
-      fputl(extensionId, f);
-    }
-    catch(const std::out_of_range&) {
-      ASSERT(false); // This shouldn't ever happen, but if it does...
-                     // most likely it is because we forgot to add the
-                     // extensionID to the ext_files object. And this
-                     // Could happen if someone adds the possibility to
-                     // store custom properties to some object that
-                     // didn't support it previously.
+    uint32_t extensionId = 0;
+    if (!extensionKey.empty() &&
+        !ext_files.getIDByFilename(extensionKey, extensionId)) {
+      // This shouldn't ever happen, but if it does...  most likely
+      // it is because we forgot to add the extensionID to the
+      // ext_files object. And this could happen if someone adds the
+      // possibility to store custom properties to some object that
+      // didn't support it previously.
+      ASSERT(false);
       fop->setError("Error writing properties for extension '%s'.\n", extensionKey.c_str());
       continue;
     }
+    fputl(extensionId, f);
     ase_file_write_properties(f, properties);
   }
   long endPos = ftell(f);

src/dio/aseprite_common.h

@@ -111,6 +111,7 @@ struct AsepriteExternalFiles {
   std::map<uint32_t, uint8_t> types; // ID -> type (type has one of the ASE_EXTERNAL_FILE_* values)
 
   uint32_t lastid = 0;
+
   // Adds the external filename with the next autogenerated ID and specified type.
   void put(const std::string& filename, uint8_t type) {
     auto id = ++lastid;
@@ -118,12 +119,31 @@ struct AsepriteExternalFiles {
     to_id[filename] = id;
     types[id] = type;
   }
+
   // Adds the external filename using the specified ID and type.
   void put(uint32_t id, const std::string& filename, uint8_t type) {
     to_fn[id] = filename;
     to_id[filename] = id;
     types[id] = type;
   }
+
+  // Returns true if the given filename exists in the external files
+  // chunk, and assign its ID in "id"
+  bool getIDByFilename(const std::string& fn, uint32_t& id) const {
+    auto it = to_id.find(fn);
+    if (it == to_id.end())
+      return false;
+    id = it->second;
+    return true;
+  }
+
+  bool getFilenameByID(uint32_t id, std::string& fn) const {
+    auto it = to_fn.find(id);
+    if (it == to_fn.end())
+      return false;
+    fn = it->second;
+    return true;
+  }
 };
 
 } // namespace dio

src/dio/aseprite_decoder.cpp

@@ -1248,18 +1248,14 @@ void AsepriteDecoder::readPropertiesMaps(doc::UserData::PropertiesMaps& properti
   auto numMaps = read32();
   for (int i=0; i<numMaps; ++i) {
     auto id = read32();
-    std::string extensionId = "";
-    if (id) {
-      try {
-        extensionId = extFiles.to_fn.at(id);
-      }
-      catch (const std::out_of_range&) {
-        // This shouldn't happen, but if it does, we put the properties
-        // in an artificial extensionId.
-        extensionId = fmt::format("__missed__{}", id);
-        delegate()->error(
-          fmt::format("Error: Invalid extension ID (id={0} not found)", id));
-      }
+    std::string extensionId; // extensionId = empty by default (when id == 0)
+    if (id &&
+        !extFiles.getFilenameByID(id, extensionId)) {
+      // This shouldn't happen, but if it does, we put the properties
+      // in an artificial extensionId.
+      extensionId = fmt::format("__missed__{}", id);
+      delegate()->error(
+        fmt::format("Error: Invalid extension ID (id={0} not found)", id));
     }
     auto properties = readPropertyValue(USER_DATA_PROPERTY_TYPE_PROPERTIES);
     propertiesMaps[extensionId] = *std::get_if<doc::UserData::Properties>(&properties);