Package org.apache.commons.io

Class EndianUtils

java.lang.Object
org.apache.commons.io.EndianUtils
public class EndianUtils extends Object
Helps with reading and writing primitive numeric types (short, int, long, float, and double) that are encoded in little endian using two's complement or unsigned representations.

Different computer architectures have different conventions for byte ordering. In "Little Endian" architectures (e.g. X86), the low-order byte is stored in memory at the lowest address, and subsequent bytes at higher addresses. In "Big Endian" architectures (e.g. Motorola 680X0), the situation is reversed. Most methods and classes throughout Java — e.g. DataInputStream and Double.longBitsToDouble() — assume data is laid out in big endian order with the most significant byte first. The methods in this class read and write data in little endian order, generally by reversing the bytes and then using the regular Java methods to convert the swapped bytes to a primitive type.

Provenance: Excalibur

See Also:

  • Constructor Summary

    Constructors
    Constructor
    Description
    EndianUtils()
    Deprecated.
    TODO Make private in 3.0.

  • Method Summary

    Modifier and Type
    Method
    Description
    static double
    readSwappedDouble(byte[] data, int offset)
    Reads a little endian double value from a byte array at a given offset.
    static double
    readSwappedDouble(InputStream input)
    Reads a little endian double value from an InputStream.
    static float
    readSwappedFloat(byte[] data, int offset)
    Reads a little endian float value from a byte array at a given offset.
    static float
    readSwappedFloat(InputStream input)
    Reads a little endian float value from an InputStream.
    static int
    readSwappedInteger(byte[] data, int offset)
    Reads a little endian int value from a byte array at a given offset.
    static int
    readSwappedInteger(InputStream input)
    Reads a little endian int value from an InputStream.
    static long
    readSwappedLong(byte[] data, int offset)
    Reads a little endian long value from a byte array at a given offset.
    static long
    readSwappedLong(InputStream input)
    Reads a little endian long value from an InputStream.
    static short
    readSwappedShort(byte[] data, int offset)
    Reads a little endian short value from a byte array at a given offset.
    static short
    readSwappedShort(InputStream input)
    Reads a little endian short value from an InputStream.
    static long
    readSwappedUnsignedInteger(byte[] data, int offset)
    Reads a little endian unsigned integer (32-bit) value from a byte array at a given offset.
    static long
    readSwappedUnsignedInteger(InputStream input)
    Reads a little endian unsigned integer (32-bit) from an InputStream.
    static int
    readSwappedUnsignedShort(byte[] data, int offset)
    Reads an unsigned short (16-bit) value from a byte array in little endian order at a given offset.
    static int
    readSwappedUnsignedShort(InputStream input)
    Reads an unsigned short (16-bit) from an InputStream in little endian order.
    static double
    swapDouble(double value)
    Converts a double value from big endian to little endian and vice versa.
    static float
    swapFloat(float value)
    Converts a float value from big endian to little endian and vice versa.
    static int
    swapInteger(int value)
    Converts an int value from big endian to little endian and vice versa.
    static long
    swapLong(long value)
    Converts a long value from big endian to little endian and vice versa.
    static short
    swapShort(short value)
    Converts a short value from big endian to little endian and vice versa.
    static void
    writeSwappedDouble(byte[] data, int offset, double value)
    Writes the 8 bytes of a double to a byte array at a given offset in little endian order.
    static void
    writeSwappedDouble(OutputStream output, double value)
    Writes the 8 bytes of a double to an output stream in little endian order.
    static void
    writeSwappedFloat(byte[] data, int offset, float value)
    Writes the 4 bytes of a float to a byte array at a given offset in little endian order.
    static void
    writeSwappedFloat(OutputStream output, float value)
    Writes the 4 bytes of a float to an output stream in little endian order.
    static void
    writeSwappedInteger(byte[] data, int offset, int value)
    Writes the 4 bytes of an int to a byte array at a given offset in little endian order.
    static void
    writeSwappedInteger(OutputStream output, int value)
    Writes the 4 bytes of an int to an output stream in little endian order.
    static void
    writeSwappedLong(byte[] data, int offset, long value)
    Writes the 8 bytes of a long to a byte array at a given offset in little endian order.
    static void
    writeSwappedLong(OutputStream output, long value)
    Writes the 8 bytes of a long to an output stream in little endian order.
    static void
    writeSwappedShort(byte[] data, int offset, short value)
    Writes the 2 bytes of a short to a byte array at a given offset in little endian order.
    static void
    writeSwappedShort(OutputStream output, short value)
    Writes the 2 bytes of a short to an output stream using little endian encoding.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • EndianUtils

      @Deprecated public EndianUtils()
      Deprecated.
      TODO Make private in 3.0.
      Instances should NOT be constructed in standard programming.

  • Method Details

    • readSwappedDouble

      public static double readSwappedDouble(byte[] data, int offset)
      Reads a little endian double value from a byte array at a given offset.
      Parameters:
      data - source byte array
      offset - starting offset in the byte array
      Returns:
      the value read
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 8 bytes

    • readSwappedDouble

      public static double readSwappedDouble(InputStream input) throws IOException
      Reads a little endian double value from an InputStream.
      Parameters:
      input - source InputStream
      Returns:
      the value just read
      Throws:
      IOException - in case of an I/O problem

    • readSwappedFloat

      public static float readSwappedFloat(byte[] data, int offset)
      Reads a little endian float value from a byte array at a given offset.
      Parameters:
      data - source byte array
      offset - starting offset in the byte array
      Returns:
      the value read
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 4 bytes

    • readSwappedFloat

      public static float readSwappedFloat(InputStream input) throws IOException
      Reads a little endian float value from an InputStream.
      Parameters:
      input - source InputStream
      Returns:
      the value just read
      Throws:
      IOException - in case of an I/O problem

    • readSwappedInteger

      public static int readSwappedInteger(byte[] data, int offset)
      Reads a little endian int value from a byte array at a given offset.
      Parameters:
      data - source byte array
      offset - starting offset in the byte array
      Returns:
      the value read
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 4 bytes

    • readSwappedInteger

      public static int readSwappedInteger(InputStream input) throws IOException
      Reads a little endian int value from an InputStream.
      Parameters:
      input - source InputStream
      Returns:
      the value just read
      Throws:
      IOException - in case of an I/O problem

    • readSwappedLong

      public static long readSwappedLong(byte[] data, int offset)
      Reads a little endian long value from a byte array at a given offset.
      Parameters:
      data - source byte array
      offset - starting offset in the byte array
      Returns:
      the value read
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 8 bytes

    • readSwappedLong

      public static long readSwappedLong(InputStream input) throws IOException
      Reads a little endian long value from an InputStream.
      Parameters:
      input - source InputStream
      Returns:
      the value just read
      Throws:
      IOException - in case of an I/O problem

    • readSwappedShort

      public static short readSwappedShort(byte[] data, int offset)
      Reads a little endian short value from a byte array at a given offset.
      Parameters:
      data - source byte array
      offset - starting offset in the byte array
      Returns:
      the value read
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 2 bytes

    • readSwappedShort

      public static short readSwappedShort(InputStream input) throws IOException
      Reads a little endian short value from an InputStream.
      Parameters:
      input - source InputStream
      Returns:
      the value just read
      Throws:
      IOException - in case of an I/O problem

    • readSwappedUnsignedInteger

      public static long readSwappedUnsignedInteger(byte[] data, int offset)
      Reads a little endian unsigned integer (32-bit) value from a byte array at a given offset.
      Parameters:
      data - source byte array
      offset - starting offset in the byte array
      Returns:
      the value read
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 4 bytes

    • readSwappedUnsignedInteger

      public static long readSwappedUnsignedInteger(InputStream input) throws IOException
      Reads a little endian unsigned integer (32-bit) from an InputStream.
      Parameters:
      input - source InputStream
      Returns:
      the value just read
      Throws:
      IOException - in case of an I/O problem

    • readSwappedUnsignedShort

      public static int readSwappedUnsignedShort(byte[] data, int offset)
      Reads an unsigned short (16-bit) value from a byte array in little endian order at a given offset.
      Parameters:
      data - source byte array
      offset - starting offset in the byte array
      Returns:
      the value read
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 2 bytes

    • readSwappedUnsignedShort

      public static int readSwappedUnsignedShort(InputStream input) throws IOException
      Reads an unsigned short (16-bit) from an InputStream in little endian order.
      Parameters:
      input - source InputStream
      Returns:
      the value just read
      Throws:
      IOException - in case of an I/O problem

    • swapDouble

      public static double swapDouble(double value)
      Converts a double value from big endian to little endian and vice versa. That is, it converts the double to bytes, reverses the bytes, and then reinterprets those bytes as a new double. This can be useful if you have a number that was read from the underlying source in the wrong endianness.
      Parameters:
      value - value to convert
      Returns:
      the converted value

    • swapFloat

      public static float swapFloat(float value)
      Converts a float value from big endian to little endian and vice versa.
      Parameters:
      value - value to convert
      Returns:
      the converted value

    • swapInteger

      public static int swapInteger(int value)
      Converts an int value from big endian to little endian and vice versa.
      Parameters:
      value - value to convert
      Returns:
      the converted value

    • swapLong

      public static long swapLong(long value)
      Converts a long value from big endian to little endian and vice versa.
      Parameters:
      value - value to convert
      Returns:
      the converted value

    • swapShort

      public static short swapShort(short value)
      Converts a short value from big endian to little endian and vice versa.
      Parameters:
      value - value to convert
      Returns:
      the converted value

    • writeSwappedDouble

      public static void writeSwappedDouble(byte[] data, int offset, double value)
      Writes the 8 bytes of a double to a byte array at a given offset in little endian order.
      Parameters:
      data - target byte array
      offset - starting offset in the byte array
      value - value to write
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 8 bytes

    • writeSwappedDouble

      public static void writeSwappedDouble(OutputStream output, double value) throws IOException
      Writes the 8 bytes of a double to an output stream in little endian order.
      Parameters:
      output - target OutputStream
      value - value to write
      Throws:
      IOException - in case of an I/O problem

    • writeSwappedFloat

      public static void writeSwappedFloat(byte[] data, int offset, float value)
      Writes the 4 bytes of a float to a byte array at a given offset in little endian order.
      Parameters:
      data - target byte array
      offset - starting offset in the byte array
      value - value to write
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 4 bytes

    • writeSwappedFloat

      public static void writeSwappedFloat(OutputStream output, float value) throws IOException
      Writes the 4 bytes of a float to an output stream in little endian order.
      Parameters:
      output - target OutputStream
      value - value to write
      Throws:
      IOException - in case of an I/O problem

    • writeSwappedInteger

      public static void writeSwappedInteger(byte[] data, int offset, int value)
      Writes the 4 bytes of an int to a byte array at a given offset in little endian order.
      Parameters:
      data - target byte array
      offset - starting offset in the byte array
      value - value to write
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 4 bytes

    • writeSwappedInteger

      public static void writeSwappedInteger(OutputStream output, int value) throws IOException
      Writes the 4 bytes of an int to an output stream in little endian order.
      Parameters:
      output - target OutputStream
      value - value to write
      Throws:
      IOException - in case of an I/O problem

    • writeSwappedLong

      public static void writeSwappedLong(byte[] data, int offset, long value)
      Writes the 8 bytes of a long to a byte array at a given offset in little endian order.
      Parameters:
      data - target byte array
      offset - starting offset in the byte array
      value - value to write
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 8 bytes

    • writeSwappedLong

      public static void writeSwappedLong(OutputStream output, long value) throws IOException
      Writes the 8 bytes of a long to an output stream in little endian order.
      Parameters:
      output - target OutputStream
      value - value to write
      Throws:
      IOException - in case of an I/O problem

    • writeSwappedShort

      public static void writeSwappedShort(byte[] data, int offset, short value)
      Writes the 2 bytes of a short to a byte array at a given offset in little endian order.
      Parameters:
      data - target byte array
      offset - starting offset in the byte array
      value - value to write
      Throws:
      IllegalArgumentException - if the part of the byte array starting at offset does not have at least 2 bytes

    • writeSwappedShort

      public static void writeSwappedShort(OutputStream output, short value) throws IOException
      Writes the 2 bytes of a short to an output stream using little endian encoding.
      Parameters:
      output - target OutputStream
      value - value to write
      Throws:
      IOException - in case of an I/O problem