fix: #724

HMCLCore/src/main/java/org/jackhuang/hmcl/download/game/GameAssetDownloadTask.java

@@ -65,15 +65,7 @@ public final class GameAssetDownloadTask extends Task<Void> {
         this.assetIndexFile = dependencyManager.getGameRepository().getIndexFile(version.getId(), assetIndexInfo.getId());
         this.integrityCheck = integrityCheck;
 
-        if (!assetIndexFile.exists() || forceDownloadingIndex) {
+        dependents.add(new GameAssetIndexDownloadTask(dependencyManager, this.version, forceDownloadingIndex));
-            dependents.add(new GameAssetIndexDownloadTask(dependencyManager, this.version));
-        } else {
-            try {
-                JsonUtils.fromNonNullJson(FileUtils.readText(assetIndexFile), AssetIndex.class);
-            } catch (IOException | JsonParseException e) {
-                dependents.add(new GameAssetIndexDownloadTask(dependencyManager, this.version));
-            }
-        }
     }
 
     @Override

HMCLCore/src/main/java/org/jackhuang/hmcl/download/game/GameAssetIndexDownloadTask.java

@@ -17,16 +17,26 @@
  */
 package org.jackhuang.hmcl.download.game;
 
+import com.google.gson.JsonParseException;
 import org.jackhuang.hmcl.download.AbstractDependencyManager;
+import org.jackhuang.hmcl.game.AssetIndex;
 import org.jackhuang.hmcl.game.AssetIndexInfo;
 import org.jackhuang.hmcl.game.Version;
 import org.jackhuang.hmcl.task.FileDownloadTask;
 import org.jackhuang.hmcl.task.Task;
+import org.jackhuang.hmcl.util.DigestUtils;
+import org.jackhuang.hmcl.util.Hex;
+import org.jackhuang.hmcl.util.StringUtils;
+import org.jackhuang.hmcl.util.gson.JsonUtils;
+import org.jackhuang.hmcl.util.io.FileUtils;
 
 import java.io.File;
 import java.io.IOException;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.logging.Level;
+
+import static org.jackhuang.hmcl.util.Logging.LOG;
 
 /**
  * This task is to download asset index file provided in minecraft.json.
@@ -37,6 +47,7 @@ public final class GameAssetIndexDownloadTask extends Task<Void> {
 
     private final AbstractDependencyManager dependencyManager;
     private final Version version;
+    private final boolean forceDownloading;
     private final List<Task<?>> dependencies = new LinkedList<>();
 
     /**
@@ -45,9 +56,10 @@ public final class GameAssetIndexDownloadTask extends Task<Void> {
      * @param dependencyManager the dependency manager that can provides {@link org.jackhuang.hmcl.game.GameRepository}
      * @param version the <b>resolved</b> version
      */
-    public GameAssetIndexDownloadTask(AbstractDependencyManager dependencyManager, Version version) {
+    public GameAssetIndexDownloadTask(AbstractDependencyManager dependencyManager, Version version, boolean forceDownloading) {
         this.dependencyManager = dependencyManager;
         this.version = version;
+        this.forceDownloading = forceDownloading;
         setSignificance(TaskSignificance.MODERATE);
     }
 
@@ -60,12 +72,34 @@ public final class GameAssetIndexDownloadTask extends Task<Void> {
     public void execute() {
         AssetIndexInfo assetIndexInfo = version.getAssetIndex();
         File assetIndexFile = dependencyManager.getGameRepository().getIndexFile(version.getId(), assetIndexInfo.getId());
+        boolean verifyHashCode = StringUtils.isNotBlank(assetIndexInfo.getSha1()) && assetIndexInfo.getUrl().contains(assetIndexInfo.getSha1());
+
+        if (assetIndexFile.exists() && !forceDownloading) {
+            // verify correctness of file content
+            if (verifyHashCode) {
+                try {
+                    String actualSum = Hex.encodeHex(DigestUtils.digest("SHA-1", assetIndexFile.toPath()));
+                    if (actualSum.equalsIgnoreCase(assetIndexInfo.getSha1()))
+                        return;
+                } catch (IOException e) {
+                    LOG.log(Level.WARNING, "Failed to calculate sha1sum of file " + assetIndexInfo, e);
+                    // continue downloading
+                }
+            } else {
+                try {
+                    JsonUtils.fromNonNullJson(FileUtils.readText(assetIndexFile), AssetIndex.class);
+                    return;
+                } catch (IOException | JsonParseException ignore) {
+                }
+            }
+        }
 
         // We should not check the hash code of asset index file since this file is not consistent
         // And Mojang will modify this file anytime. So assetIndex.hash might be outdated.
         FileDownloadTask task = new FileDownloadTask(
                 dependencyManager.getDownloadProvider().injectURLWithCandidates(assetIndexInfo.getUrl()),
-                assetIndexFile
+                assetIndexFile,
+                verifyHashCode ? new FileDownloadTask.IntegrityCheck("SHA-1", assetIndexInfo.getSha1()) : null
         );
         task.setCacheRepository(dependencyManager.getCacheRepository());
         dependencies.add(task);