SEI CERT Oracle Coding Standard for Java

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Comment: made sure code compiles, also closed open streams

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The read methods (readByte, readShort, readInt, readLong, readFloat and readDouble) and the corresponding write methods defined by class java.io.DataInputStream operate only on big-endian data. Use of these methods while interoperating with traditional languages, such as C or C++, is insecure because such languages lack any guarantees about endianness. This noncompliant code example shows such a discrepancy.

Code Block
bgColor#FFcccc
try {
  DataInputStream dis = null;
  try {
    dis = new DataInputStream(
  new FileInputStream("data"));
    // Little-endian data might be read as big-endian
    int serialNumber = dis.readInt();
  } finally {
    if (dis != null) {
      dis.close();
    }
  } catch (IOException x) {
    // handle error
  }
}

Compliant Solution (Use ByteBuffer)

Wiki Markup
This compliant solution uses methods provided by class {{ByteBuffer}} (see \[[API 2006|AA. Bibliography#API 06]\] [ByteBuffer|http://download.oracle.com/javase/6/docs/api/java/nio/ByteBuffer.html]) to correctly extract an {{int}} from the original input value. It wraps the input byte array with a {{ByteBuffer}}, sets the byte order to little-endian, and extracts the {{int}}. The result is stored in the integer {{serialNumber}}.

Code Block
bgColor#ccccff
	 
try {
  DataInputStream dis = null;
  try {
    dis = new DataInputStream( new FileInputStream("data"));
    byte[] buffer = new byte[4];
    int bytesRead = dis.read(buffer);  // Bytes are read into buffer
    if (bytesRead != 4) {
      throw new IOException("Unexpected End of Stream");
    }
    int serialNumber = ByteBuffer.wrap(buffer).order(ByteOrder.LITTLE_ENDIAN).getInt();
  } finally {
    if (dis != null) {
      dis.close();
    }
  }
} catch (IOException x) {
  // handle error
}

Class ByteBuffer provides analogous get and put methods for the other numeric types.

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[[API 2006

AA. Bibliography#API 06]]

Class [ByteBuffer

http://download.oracle.com/javase/6/docs/api/java/nio/ByteBuffer.html]: Methods wrap and order. Class [Integer

http://download.oracle.com/javase/6/docs/api/java/lang/Integer.html]: method reverseBytes

]]></ac:plain-text-body></ac:structured-macro>

<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="0a62283898add198-c884343d-4b024e36-b40a8ce6-e571de72914a4f9ccc9e8fd5"><ac:plain-text-body><![CDATA[

[[Cohen 1981

AA. Bibliography#Cohen 81]]

"On Holy Wars and a Plea for Peace"

]]></ac:plain-text-body></ac:structured-macro>

<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="ac6ccb20d08f062d-8cd820bc-491e4566-975c9db5-ca9ccd8375933cd73a486356"><ac:plain-text-body><![CDATA[

[[Harold 1997

AA. Bibliography#Harold 97]]

Chapter 2: "Primitive Data Types, Cross Platform issues"

]]></ac:plain-text-body></ac:structured-macro>

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