Add OSTree encoding roundtrip tests and fix the bugs discovered.

Change-Id: I4c81329c5381d6ae843fee5da2bed035941011e3

5 files changed, 22 insertions, 44 deletions

diff --git a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/Checksum.java b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/Checksum.java
index 829664e..e9bdf84 100644
--- a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/Checksum.java
+++ b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/Checksum.java
@@ -18,7 +18,11 @@ public record Checksum(ByteString byteString) {
   private static final int SIZE = 32;
 
   private static final Decoder<Checksum> DECODER =
-      ByteString.decoder().map(Checksum::new, Checksum::byteString);
+      ByteString.decoder().map(Checksum::new, Checksum::optimizedByteString);
+
+  private static final ByteString NULL_BYTESTRING = new ByteString(new byte[0]);
+
+  private static final Checksum ZERO = new Checksum(new ByteString(new byte[SIZE]));
 
   public Checksum {
     if (byteString.size() == 0) {
@@ -47,7 +51,11 @@ public record Checksum(ByteString byteString) {
    * @return a checksum whose bits are all zero.
    */
   public static Checksum zero() {
-    return new Checksum(new ByteString(new byte[SIZE]));
+    return ZERO;
+  }
+
+  public ByteString optimizedByteString() {
+    return isEmpty() ? NULL_BYTESTRING : byteString;
   }
 
   /**
@@ -56,7 +64,7 @@ public record Checksum(ByteString byteString) {
    * @return {@code true} if the byte string is equal to {@link #zero()}, {@code false} otherwise.
    */
   public boolean isEmpty() {
-    return equals(zero());
+    return equals(ZERO);
   }
 
   /**
diff --git a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaMetaEntry.java b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaMetaEntry.java
index 2be0426..71419c6 100644
--- a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaMetaEntry.java
+++ b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaMetaEntry.java
@@ -67,8 +67,8 @@ public record DeltaMetaEntry(
     var output = new ByteArrayOutputStream();
 
     for (var deltaObject : deltaObjects) {
-      output.write(deltaObject.objectType.byteValue());
-      output.writeBytes(deltaObject.checksum.byteString().bytes());
+      output.write(deltaObject.objectType().byteValue());
+      output.writeBytes(deltaObject.checksum().byteString().bytes());
     }
 
     return output.toByteArray();
diff --git a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaOperation.java b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaOperation.java
index d753a48..42b7056 100644
--- a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaOperation.java
+++ b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaOperation.java
@@ -69,16 +69,16 @@ public sealed interface DeltaOperation {
   }
 
   default void writeTo(ByteArrayOutputStream output) {
-    if (this instanceof OpenSpliceAndCloseMeta openSpliceAndCloseMeta) {
-      output.write(DeltaOperationType.OPEN_SPLICE_AND_CLOSE.byteValue());
-      writeVarint64(output, openSpliceAndCloseMeta.offset);
-      writeVarint64(output, openSpliceAndCloseMeta.size);
-    } else if (this instanceof OpenSpliceAndCloseReal openSpliceAndCloseReal) {
+    if (this instanceof OpenSpliceAndCloseReal openSpliceAndCloseReal) {
       output.write(DeltaOperationType.OPEN_SPLICE_AND_CLOSE.byteValue());
       writeVarint64(output, openSpliceAndCloseReal.modeOffset);
       writeVarint64(output, openSpliceAndCloseReal.xattrOffset);
       writeVarint64(output, openSpliceAndCloseReal.size);
       writeVarint64(output, openSpliceAndCloseReal.offset);
+    } else if (this instanceof OpenSpliceAndCloseMeta openSpliceAndCloseMeta) {
+      output.write(DeltaOperationType.OPEN_SPLICE_AND_CLOSE.byteValue());
+      writeVarint64(output, openSpliceAndCloseMeta.size);
+      writeVarint64(output, openSpliceAndCloseMeta.offset);
     } else if (this instanceof Open open) {
       output.write(DeltaOperationType.OPEN.byteValue());
       writeVarint64(output, open.modeOffset);
@@ -130,16 +130,13 @@ public sealed interface DeltaOperation {
    * @see #readVarint64
    */
   private static void writeVarint64(ByteArrayOutputStream output, long value) {
-    while (value != 0) {
+    do {
       byte b = (byte) (value & 0x7F);
       value >>= 7;
       if (value != 0) {
         b |= (byte) 0x80;
       }
       output.write(b);
-      if (value == 0) {
-        break;
-      }
-    }
+    } while (value != 0);
   }
 }
diff --git a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaPartPayload.java b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaPartPayload.java
index 31c192d..ccd5630 100644
--- a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaPartPayload.java
+++ b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaPartPayload.java
@@ -156,7 +156,7 @@ public record DeltaPartPayload(
             Decoder.ofByteArray()
                 .map(
                     bytes -> parseDeltaOperationList(bytes, objectTypes),
-                    deltaOperations -> serializeDeltaOperationList(deltaOperations)))
+                    DeltaPartPayload::serializeDeltaOperationList))
         .contramap(DeltaPartPayload::decompress, DeltaPartPayload::compress);
   }
 }
diff --git a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaSuperblock.java b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaSuperblock.java
index 9513fa0..b8143af 100644
--- a/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaSuperblock.java
+++ b/jgvariant-ostree/src/main/java/eu/mulk/jgvariant/ostree/DeltaSuperblock.java
@@ -5,16 +5,11 @@
 package eu.mulk.jgvariant.ostree;
 
 import eu.mulk.jgvariant.core.Decoder;
-import eu.mulk.jgvariant.core.Signature;
-import eu.mulk.jgvariant.core.Variant;
 import java.io.ByteArrayOutputStream;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
-import java.text.ParseException;
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 
 /**
  * A static delta.
@@ -78,29 +73,7 @@ public record DeltaSuperblock(
                       DeltaSuperblock::parseDeltaNameList, DeltaSuperblock::serializeDeltaNameList),
               Decoder.ofArray(DeltaMetaEntry.decoder()).withByteOrder(ByteOrder.LITTLE_ENDIAN),
               Decoder.ofArray(DeltaFallback.decoder()).withByteOrder(ByteOrder.LITTLE_ENDIAN))
-          .map(DeltaSuperblock::byteSwappedIfBigEndian, DeltaSuperblock::withSpecifiedByteOrder);
-
-  private DeltaSuperblock withSpecifiedByteOrder() {
-    Map<String, Variant> extendedMetadataMap = new HashMap<>(metadata().fields());
-
-    try {
-      extendedMetadataMap.putIfAbsent(
-          "ostree.endianness", new Variant(Signature.parse("y"), (byte) 'l'));
-    } catch (ParseException e) {
-      // impossible
-      throw new IllegalStateException(e);
-    }
-
-    return new DeltaSuperblock(
-        new Metadata(extendedMetadataMap),
-        timestamp,
-        fromChecksum,
-        toChecksum,
-        commit,
-        dependencies,
-        entries,
-        fallbacks);
-  }
+          .map(DeltaSuperblock::byteSwappedIfBigEndian, DeltaSuperblock::byteSwappedIfBigEndian);
 
   private DeltaSuperblock byteSwappedIfBigEndian() {
     // Fix up the endianness of the 'entries' and 'fallbacks' fields, which have