1 files changed, 100 insertions, 0 deletions
diff --git a/src/main/java/com/google/escapevelocity/ImmutableAsciiSet.java b/src/main/java/com/google/escapevelocity/ImmutableAsciiSet.java
new file mode 100644
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--- /dev/null
+++ b/src/main/java/com/google/escapevelocity/ImmutableAsciiSet.java
@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2017 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.escapevelocity;
+
+import java.util.AbstractSet;
+import java.util.BitSet;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * An immutable set of ASCII characters.
+ *
+ * @author emcmanus@google.com (Éamonn McManus)
+ */
+class ImmutableAsciiSet extends AbstractSet<Integer> {
+  private final BitSet bits;
+
+  ImmutableAsciiSet(BitSet bits) {
+    this.bits = bits;
+  }
+
+  static ImmutableAsciiSet of(char c) {
+    return ofRange(c, c);
+  }
+
+  static ImmutableAsciiSet ofRange(char from, char to) {
+    if (from > to) {
+      throw new IllegalArgumentException("from > to");
+    }
+    if (to >= 128) {
+      throw new IllegalArgumentException("Not ASCII");
+    }
+    BitSet bits = new BitSet();
+    bits.set(from, to + 1);
+    return new ImmutableAsciiSet(bits);
+  }
+
+  ImmutableAsciiSet union(ImmutableAsciiSet that) {
+    BitSet union = (BitSet) bits.clone();
+    union.or(that.bits);
+    return new ImmutableAsciiSet(union);
+  }
+
+  @Override
+  public boolean contains(Object o) {
+    int i = -1;
+    if (o instanceof Character) {
+      i = (Character) o;
+    } else if (o instanceof Integer) {
+      i = (Integer) o;
+    }
+    return contains(i);
+  }
+
+  boolean contains(int i) {
+    if (i < 0) {
+      return false;
+    } else {
+      return bits.get(i);
+    }
+  }
+
+  @Override
+  public Iterator<Integer> iterator() {
+    return new Iterator<Integer>() {
+      private int index;
+
+      @Override
+      public boolean hasNext() {
+        return bits.nextSetBit(index) >= 0;
+      }
+
+      @Override
+      public Integer next() {
+        if (!hasNext()) {
+          throw new NoSuchElementException();
+        }
+        int next = bits.nextSetBit(index);
+        index = next + 1;
+        return next;
+      }
+    };
+  }
+
+  @Override
+  public int size() {
+    return bits.cardinality();
+  }
+}