add MemoryStore

Author: brokkoli71

src/main/java/dev/zarr/zarrjava/store/MemoryStore.java

@@ -0,0 +1,85 @@
+package dev.zarr.zarrjava.store;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.nio.ByteBuffer;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Stream;
+
+public class MemoryStore implements Store, Store.ListableStore {
+  private final Map<String[], byte[]> map = new HashMap<>();
+
+  @Override
+  public boolean exists(String[] keys) {
+    return map.containsKey(keys);
+  }
+
+  @Nullable
+  @Override
+  public ByteBuffer get(String[] keys) {
+      return get(keys, 0);
+  }
+
+  @Nullable
+  @Override
+  public ByteBuffer get(String[] keys, long start) {
+    return get(keys, start, -1);
+  }
+
+  @Nullable
+  @Override
+  public ByteBuffer get(String[] keys, long start, long end) {
+    if(end>Integer.MAX_VALUE) throw new RuntimeException("TODO");
+    if(!map.containsKey(keys)) return null; //TODO: necessary?
+    if (end < 0) end = map.get(keys).length - end;
+    return ByteBuffer.wrap(map.get(keys), (int) start, (int) end);
+  }
+
+
+  @Override
+  public void set(String[] keys, ByteBuffer bytes) {
+    map.put(keys, bytes.array());
+  }
+
+  @Override
+  public void delete(String[] keys) {
+    map.remove(keys);
+  }
+
+  public Stream<String> list(String[] keys) {
+    Set<String> allKeys = new HashSet<>();
+    for(String[] k: map.keySet()){
+      if (!equalFirstKeys(k, keys, keys.length));
+      String key = "";
+        for (String s : k) {
+            key += s + "/";
+            allKeys.add(key);
+        }
+    }
+    return allKeys.stream();
+  }
+
+  @Nonnull
+  @Override
+  public StoreHandle resolve(String... keys) {
+    return new StoreHandle(this, keys);
+  }
+
+  @Override
+  public String toString() {
+    return String.format("<MemoryStore {%s}>", hashCode());
+  }
+
+  private boolean equalFirstKeys(String[] k1, String[] k2, int n){
+    if (k1.length < n || k2.length < n) return false;
+    for (int i = 0; i < n; i++) {
+      if(!k1[i].equals(k2[i]))
+        return false;
+    }
+    return true;
+  }
+
+}