XByteArrayInputStream - A CPU and Memory Friendly XInputStream Implem…

src/main/java/com/google/code/or/io/impl/XByteArrayInputStream.java

@@ -0,0 +1,216 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.code.or.io.impl;
+
+import com.google.code.or.common.glossary.UnsignedLong;
+import com.google.code.or.common.glossary.column.BitColumn;
+import com.google.code.or.common.glossary.column.StringColumn;
+import com.google.code.or.common.util.CodecUtils;
+import com.google.code.or.io.ExceedLimitException;
+import com.google.code.or.io.XInputStream;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * This class will be used by XDeserializer to read data from the input byte array.
+ *
+ * @author Litao Deng
+ */
+public class XByteArrayInputStream extends InputStream implements XInputStream
+{
+  private InputStream inputStream;
+  private int readCount = 0;
+  private int readLimit = 0;
+
+  /**
+   * The underlying ByteArrayInputStream will directly point to the input
+   * byte array instead of allocating a new one.
+   */
+  public XByteArrayInputStream(byte[] data) {
+    this.inputStream = new ByteArrayInputStream(data);
+  }
+
+  @Override
+  public void close() throws IOException {
+    this.inputStream.close();
+  }
+
+  @Override
+  public int available() throws IOException {
+    if (this.readLimit > 0) {
+      return this.readLimit - this.readCount;
+    } else {
+      return this.inputStream.available();
+    }
+  }
+
+  public boolean hasMore() throws IOException {
+    return this.inputStream.available() > 0;
+  }
+
+  public void setReadLimit(final int limit) throws IOException {
+    this.readCount = 0;
+    this.readLimit = limit;
+  }
+
+  @Override
+  public long skip(final long n) throws IOException {
+    if (this.readLimit > 0 && (this.readCount + n) > this.readLimit) {
+      this.readCount += this.inputStream.skip(this.readLimit - this.readCount);
+      throw new ExceedLimitException();
+    } else {
+      this.readCount += this.inputStream.skip(n);
+      return n;
+    }
+  }
+
+  @Override
+  public int read() throws IOException {
+    if (this.readLimit > 0 && (this.readCount + 1) > this.readLimit) {
+      throw new ExceedLimitException();
+    } else {
+      final int r = this.inputStream.read() & 0xFF;
+      ++this.readCount;
+      return r;
+    }
+  }
+
+  public byte[] readBytes(final int length) throws IOException {
+    final byte[] r = new byte[length];
+    fill(r, 0, length);
+    return r;
+  }
+
+  public void fill(final byte[] b, final int off, final int len) throws IOException {
+    if (this.readLimit > 0 && (this.readCount + len) > this.readLimit) {
+      this.readCount += read(b, off, this.readLimit - this.readCount);
+      throw new ExceedLimitException();
+    } else {
+	   int data = this.inputStream.read(b, off, len);
+      this.readCount += (data == -1 ? 0 : data)
+    }
+  }
+
+  public StringColumn readLengthCodedString() throws IOException {
+    final UnsignedLong length = readUnsignedLong();
+    return length == null ? null : readFixedLengthString(length.intValue());
+  }
+
+  public StringColumn readNullTerminatedString() throws IOException {
+    ByteArrayOutputStream s = new ByteArrayOutputStream();
+    for (int b; (b = this.read()) != 0; ) {
+      s.write(b);
+    }
+    return StringColumn.valueOf(s.toByteArray());
+  }
+
+  public StringColumn readFixedLengthString(final int length) throws IOException {
+    return StringColumn.valueOf(readBytes(length));
+  }
+
+  public int readSignedInt(int length) throws IOException {
+    int r = 0;
+    for (int i = 0; i < length; ++i) {
+      final int v = this.read();
+      r |= (v << (i << 3));
+      if ((i == length - 1) && ((v & 0x80) == 0x80)) {
+        for (int j = length; j < 4; ++j) {
+          r |= (255 << (j << 3));
+        }
+      }
+    }
+    return r;
+  }
+
+  public long readSignedLong(int length) throws IOException {
+    long r = 0;
+    for (int i = 0; i < length; ++i) {
+      final long v = this.read();
+      r |= (v << (i << 3));
+      if ((i == length - 1) && ((v & 0x80) == 0x80)) {
+        for (int j = length; j < 8; ++j) {
+          r |= (255 << (j << 3));
+        }
+      }
+    }
+    return r;
+  }
+
+  public int readInt(int length) throws IOException {
+    int r = 0;
+    for (int i = 0; i < length; ++i) {
+      r |= (this.read() << (i << 3));
+    }
+    return r;
+  }
+
+  public long readLong(int length) throws IOException {
+    long r = 0;
+    for (int i = 0; i < length; ++i) {
+      r |= ((long)this.read() << (i << 3));
+    }
+    return r;
+  }
+
+  public int readInt(int length, boolean littleEndian) throws IOException {
+    int r = 0;
+    for (int i = 0; i < length; ++i) {
+      final int v = this.read();
+      if (littleEndian) {
+        r |= (v << (i << 3));
+      } else {
+        r = (r << 8) | v;
+      }
+    }
+    return r;
+  }
+
+  public long readLong(int length, boolean littleEndian) throws IOException {
+    long r = 0;
+    for (int i = 0; i < length; ++i) {
+      final long v = this.read();
+      if (littleEndian) {
+        r |= (v << (i << 3));
+      } else {
+        r = (r << 8) | v;
+      }
+    }
+    return r;
+  }
+
+  public UnsignedLong readUnsignedLong() throws IOException {
+    final int v = this.read();
+    if (v < 251) return UnsignedLong.valueOf(v);
+    else if (v == 251) return null;
+    else if (v == 252) return UnsignedLong.valueOf(readInt(2));
+    else if (v == 253) return UnsignedLong.valueOf(readInt(3));
+    else if (v == 254) return UnsignedLong.valueOf(readLong(8));
+    else throw new RuntimeException("assertion failed, should NOT reach here");
+  }
+
+  public BitColumn readBit(int length) throws IOException {
+    return readBit(length, true);
+  }
+
+  public BitColumn readBit(int length, boolean littleEndian) throws IOException {
+    byte[] bytes = readBytes((length + 7) >> 3);
+    if (!littleEndian) bytes = CodecUtils.toBigEndian(bytes);
+    return BitColumn.valueOf(length, bytes);
+  }

src/main/java/com/google/code/or/io/util/XDeserializer.java

@@ -23,6 +23,7 @@
 import com.google.code.or.common.glossary.column.BitColumn;
 import com.google.code.or.common.glossary.column.StringColumn;
 import com.google.code.or.io.XInputStream;
+import com.google.code.or.io.impl.XByteArrayInputStream;
 import com.google.code.or.io.impl.XInputStreamImpl;
 
 /**
@@ -37,7 +38,7 @@ public class XDeserializer implements XInputStream {
 	 * 
 	 */
 	public XDeserializer(byte[] data) {
-		this.tis = new XInputStreamImpl(new ByteArrayInputStream(data));
+        this.tis = new XByteArrayInputStream(data);
 	}
 
 	/**