1 files changed, 149 insertions, 0 deletions
diff --git a/jimfs/src/main/java/com/google/common/jimfs/Options.java b/jimfs/src/main/java/com/google/common/jimfs/Options.java
new file mode 100644
index 0000000..a575b88
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+++ b/jimfs/src/main/java/com/google/common/jimfs/Options.java
@@ -0,0 +1,149 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.common.jimfs;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static java.nio.file.StandardCopyOption.ATOMIC_MOVE;
+import static java.nio.file.StandardOpenOption.APPEND;
+import static java.nio.file.StandardOpenOption.CREATE;
+import static java.nio.file.StandardOpenOption.READ;
+import static java.nio.file.StandardOpenOption.TRUNCATE_EXISTING;
+import static java.nio.file.StandardOpenOption.WRITE;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Lists;
+import java.nio.file.CopyOption;
+import java.nio.file.LinkOption;
+import java.nio.file.OpenOption;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Set;
+
+/**
+ * Utility methods for normalizing user-provided options arrays and sets to canonical immutable sets
+ * of options.
+ *
+ * @author Colin Decker
+ */
+final class Options {
+
+  private Options() {}
+
+  /** Immutable set containing LinkOption.NOFOLLOW_LINKS. */
+  public static final ImmutableSet<LinkOption> NOFOLLOW_LINKS =
+      ImmutableSet.of(LinkOption.NOFOLLOW_LINKS);
+
+  /** Immutable empty LinkOption set. */
+  public static final ImmutableSet<LinkOption> FOLLOW_LINKS = ImmutableSet.of();
+
+  private static final ImmutableSet<OpenOption> DEFAULT_READ = ImmutableSet.<OpenOption>of(READ);
+
+  private static final ImmutableSet<OpenOption> DEFAULT_READ_NOFOLLOW_LINKS =
+      ImmutableSet.<OpenOption>of(READ, LinkOption.NOFOLLOW_LINKS);
+
+  private static final ImmutableSet<OpenOption> DEFAULT_WRITE =
+      ImmutableSet.<OpenOption>of(WRITE, CREATE, TRUNCATE_EXISTING);
+
+  /** Returns an immutable set of link options. */
+  public static ImmutableSet<LinkOption> getLinkOptions(LinkOption... options) {
+    return options.length == 0 ? FOLLOW_LINKS : NOFOLLOW_LINKS;
+  }
+
+  /** Returns an immutable set of open options for opening a new file channel. */
+  public static ImmutableSet<OpenOption> getOptionsForChannel(Set<? extends OpenOption> options) {
+    if (options.isEmpty()) {
+      return DEFAULT_READ;
+    }
+
+    boolean append = options.contains(APPEND);
+    boolean write = append || options.contains(WRITE);
+    boolean read = !write || options.contains(READ);
+
+    if (read) {
+      if (append) {
+        throw new UnsupportedOperationException("'READ' + 'APPEND' not allowed");
+      }
+
+      if (!write) {
+        // ignore all write related options
+        return options.contains(LinkOption.NOFOLLOW_LINKS)
+            ? DEFAULT_READ_NOFOLLOW_LINKS
+            : DEFAULT_READ;
+      }
+    }
+
+    // options contains write or append and may also contain read
+    // it does not contain both read and append
+    return addWrite(options);
+  }
+
+  /** Returns an immutable set of open options for opening a new input stream. */
+  @SuppressWarnings("unchecked") // safe covariant cast
+  public static ImmutableSet<OpenOption> getOptionsForInputStream(OpenOption... options) {
+    boolean nofollowLinks = false;
+    for (OpenOption option : options) {
+      if (checkNotNull(option) != READ) {
+        if (option == LinkOption.NOFOLLOW_LINKS) {
+          nofollowLinks = true;
+        } else {
+          throw new UnsupportedOperationException("'" + option + "' not allowed");
+        }
+      }
+    }
+
+    // just return the link options for finding the file, nothing else is needed
+    return (ImmutableSet<OpenOption>)
+        (ImmutableSet<?>) (nofollowLinks ? NOFOLLOW_LINKS : FOLLOW_LINKS);
+  }
+
+  /** Returns an immutable set of open options for opening a new output stream. */
+  public static ImmutableSet<OpenOption> getOptionsForOutputStream(OpenOption... options) {
+    if (options.length == 0) {
+      return DEFAULT_WRITE;
+    }
+
+    ImmutableSet<OpenOption> result = addWrite(Arrays.asList(options));
+    if (result.contains(READ)) {
+      throw new UnsupportedOperationException("'READ' not allowed");
+    }
+    return result;
+  }
+
+  /**
+   * Returns an {@link ImmutableSet} copy of the given {@code options}, adding {@link
+   * StandardOpenOption#WRITE} if it isn't already present.
+   */
+  private static ImmutableSet<OpenOption> addWrite(Collection<? extends OpenOption> options) {
+    return options.contains(WRITE)
+        ? ImmutableSet.copyOf(options)
+        : ImmutableSet.<OpenOption>builder().add(WRITE).addAll(options).build();
+  }
+
+  /** Returns an immutable set of the given options for a move. */
+  public static ImmutableSet<CopyOption> getMoveOptions(CopyOption... options) {
+    return ImmutableSet.copyOf(Lists.asList(LinkOption.NOFOLLOW_LINKS, options));
+  }
+
+  /** Returns an immutable set of the given options for a copy. */
+  public static ImmutableSet<CopyOption> getCopyOptions(CopyOption... options) {
+    ImmutableSet<CopyOption> result = ImmutableSet.copyOf(options);
+    if (result.contains(ATOMIC_MOVE)) {
+      throw new UnsupportedOperationException("'ATOMIC_MOVE' not allowed");
+    }
+    return result;
+  }
+}