Package org.apache.commons.io

Class EndianUtils

  • public class EndianUtils
extends java.lang.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:
    SwappedDataInputStream

    • Constructor Summary

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

    • Method Summary

      All Methods Static Methods Concrete Methods 
      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​(java.io.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​(java.io.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​(java.io.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​(java.io.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​(java.io.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​(java.io.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​(java.io.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​(java.io.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​(java.io.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​(java.io.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​(java.io.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​(java.io.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

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

    • Constructor Detail

      • EndianUtils

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

    • Method Detail

      • 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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 8 bytes

      • readSwappedDouble

        public static double readSwappedDouble​(java.io.InputStream input)
                                throws java.io.IOException
        Reads a little endian double value from an InputStream.
        Parameters:
        input - source InputStream
        Returns:
        the value just read
        Throws:
        java.io.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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 4 bytes

      • readSwappedFloat

        public static float readSwappedFloat​(java.io.InputStream input)
                              throws java.io.IOException
        Reads a little endian float value from an InputStream.
        Parameters:
        input - source InputStream
        Returns:
        the value just read
        Throws:
        java.io.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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 4 bytes

      • readSwappedInteger

        public static int readSwappedInteger​(java.io.InputStream input)
                              throws java.io.IOException
        Reads a little endian int value from an InputStream.
        Parameters:
        input - source InputStream
        Returns:
        the value just read
        Throws:
        java.io.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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 8 bytes

      • readSwappedLong

        public static long readSwappedLong​(java.io.InputStream input)
                            throws java.io.IOException
        Reads a little endian long value from an InputStream.
        Parameters:
        input - source InputStream
        Returns:
        the value just read
        Throws:
        java.io.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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 2 bytes

      • readSwappedShort

        public static short readSwappedShort​(java.io.InputStream input)
                              throws java.io.IOException
        Reads a little endian short value from an InputStream.
        Parameters:
        input - source InputStream
        Returns:
        the value just read
        Throws:
        java.io.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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 4 bytes

      • readSwappedUnsignedInteger

        public static long readSwappedUnsignedInteger​(java.io.InputStream input)
                                       throws java.io.IOException
        Reads a little endian unsigned integer (32-bit) from an InputStream.
        Parameters:
        input - source InputStream
        Returns:
        the value just read
        Throws:
        java.io.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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 2 bytes

      • readSwappedUnsignedShort

        public static int readSwappedUnsignedShort​(java.io.InputStream input)
                                    throws java.io.IOException
        Reads an unsigned short (16-bit) from an InputStream in little endian order.
        Parameters:
        input - source InputStream
        Returns:
        the value just read
        Throws:
        java.io.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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 8 bytes

      • writeSwappedDouble

        public static void writeSwappedDouble​(java.io.OutputStream output,
                                      double value)
                               throws java.io.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:
        java.io.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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 4 bytes

      • writeSwappedFloat

        public static void writeSwappedFloat​(java.io.OutputStream output,
                                     float value)
                              throws java.io.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:
        java.io.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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 4 bytes

      • writeSwappedInteger

        public static void writeSwappedInteger​(java.io.OutputStream output,
                                       int value)
                                throws java.io.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:
        java.io.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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 8 bytes

      • writeSwappedLong

        public static void writeSwappedLong​(java.io.OutputStream output,
                                    long value)
                             throws java.io.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:
        java.io.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:
        java.lang.IllegalArgumentException - if the part of the byte array starting at offset does not have at least 2 bytes

      • writeSwappedShort

        public static void writeSwappedShort​(java.io.OutputStream output,
                                     short value)
                              throws java.io.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:
        java.io.IOException - in case of an I/O problem