/*
    * 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
    *
    *      https://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 org.apache.commons.io;
  
  import static org.apache.commons.io.IOUtils.EOF;
  
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  
  /**
   * Helps with reading and writing primitive numeric types ({@code short},
   * {@code int}, {@code long}, {@code float}, and {@code double}) that are
   * encoded in little-endian using two's complement or unsigned representations.
   * <p>
   * 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 &mdash; e.g. {@code DataInputStream} and
   * {@code Double.longBitsToDouble()} &mdash; 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.
   * </p>
   * <p>
   * Provenance: Excalibur
   * </p>
   *
   * @see org.apache.commons.io.input.SwappedDataInputStream
   */
  public class EndianUtils {
  
      /**
       * Reads the next byte from the input stream.
       *
       * @param input  the stream.
       * @return the byte.
       * @throws IOException if the end of file is reached.
       */
      private static int read(final InputStream input) throws IOException {
          final int value = input.read();
          if (EOF == value) {
              throw new EOFException("Unexpected EOF reached");
          }
          return value;
      }
  
      /**
       * Reads a little-endian {@code double} value from a byte array at a given offset.
       *
       * @param data source byte array.
       * @param offset starting offset in the byte array.
       * @return the value read.
       * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 8 bytes.
       */
      public static double readSwappedDouble(final byte[] data, final int offset) {
          return Double.longBitsToDouble(readSwappedLong(data, offset));
      }
  
      /**
       * Reads a little-endian {@code double} value from an InputStream.
       *
       * @param input source InputStream.
       * @return the value just read.
       * @throws IOException in case of an I/O problem.
       */
      public static double readSwappedDouble(final InputStream input) throws IOException {
          return Double.longBitsToDouble(readSwappedLong(input));
      }
  
      /**
       * Reads a little-endian {@code float} value from a byte array at a given offset.
       *
       * @param data source byte array.
       * @param offset starting offset in the byte array.
       * @return the value read.
       * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 4 bytes.
       */
      public static float readSwappedFloat(final byte[] data, final int offset) {
          return Float.intBitsToFloat(readSwappedInteger(data, offset));
      }
 
     /**
      * Reads a little-endian {@code float} value from an InputStream.
      *
      * @param input source InputStream.
      * @return the value just read.
      * @throws IOException in case of an I/O problem.
      */
     public static float readSwappedFloat(final InputStream input) throws IOException {
         return Float.intBitsToFloat(readSwappedInteger(input));
     }
 
     /**
      * Reads a little-endian {@code int} value from a byte array at a given offset.
      *
      * @param data source byte array.
      * @param offset starting offset in the byte array.
      * @return the value read.
      * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 4 bytes.
      */
     public static int readSwappedInteger(final byte[] data, final int offset) {
         validateByteArrayOffset(data, offset, Integer.SIZE / Byte.SIZE);
         return
             ((data[offset + 0] & 0xff) << 0) +
             ((data[offset + 1] & 0xff) << 8) +
             ((data[offset + 2] & 0xff) << 16) +
             ((data[offset + 3] & 0xff) << 24);
     }
 
     /**
      * Reads a little-endian {@code int} value from an InputStream.
      *
      * @param input source InputStream.
      * @return the value just read.
      * @throws IOException in case of an I/O problem.
      */
     public static int readSwappedInteger(final InputStream input) throws IOException {
         final int value1 = read(input);
         final int value2 = read(input);
         final int value3 = read(input);
         final int value4 = read(input);
         return
             ((value1 & 0xff) << 0) +
             ((value2 & 0xff) << 8) +
             ((value3 & 0xff) << 16) +
             ((value4 & 0xff) << 24);
     }
 
     /**
      * Reads a little-endian {@code long} value from a byte array at a given offset.
      *
      * @param data source byte array.
      * @param offset starting offset in the byte array.
      * @return the value read.
      * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 8 bytes.
      */
     public static long readSwappedLong(final byte[] data, final int offset) {
         validateByteArrayOffset(data, offset, Long.SIZE / Byte.SIZE);
         final long low = readSwappedInteger(data, offset);
         final long high = readSwappedInteger(data, offset + 4);
         return (high << 32) + (0xffffffffL & low);
     }
 
     /**
      * Reads a little-endian {@code long} value from an InputStream.
      *
      * @param input source InputStream.
      * @return the value just read.
      * @throws IOException in case of an I/O problem.
      */
     public static long readSwappedLong(final InputStream input) throws IOException {
         final byte[] bytes = new byte[8];
         for (int i = 0; i < 8; i++) {
             bytes[i] = (byte) read(input);
         }
         return readSwappedLong(bytes, 0);
     }
 
     /**
      * Reads a little-endian {@code short} value from a byte array at a given offset.
      *
      * @param data source byte array.
      * @param offset starting offset in the byte array.
      * @return the value read.
      * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 2 bytes.
      */
     public static short readSwappedShort(final byte[] data, final int offset) {
         validateByteArrayOffset(data, offset, Short.SIZE / Byte.SIZE);
         return (short) (
             ((data[offset + 0] & 0xff) << 0) +
             ((data[offset + 1] & 0xff) << 8)
         );
     }
 
     /**
      * Reads a little-endian {@code short} value from an InputStream.
      *
      * @param input source InputStream.
      * @return the value just read.
      * @throws IOException in case of an I/O problem.
      */
     public static short readSwappedShort(final InputStream input) throws IOException {
         return (short) (
             ((read(input) & 0xff) << 0) +
             ((read(input) & 0xff) << 8)
         );
     }
 
     /**
      * Reads a little-endian unsigned integer (32-bit) value from a byte array at a given
      * offset.
      *
      * @param data source byte array.
      * @param offset starting offset in the byte array.
      * @return the value read.
      * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 4 bytes.
     */
     public static long readSwappedUnsignedInteger(final byte[] data, final int offset) {
         validateByteArrayOffset(data, offset, Integer.SIZE / Byte.SIZE);
         final long low = ((data[offset + 0] & 0xff) << 0) +
                          ((data[offset + 1] & 0xff) << 8) +
                          ((data[offset + 2] & 0xff) << 16);
         final long high = data[offset + 3] & 0xff;
         return (high << 24) + (0xffffffffL & low);
     }
 
     /**
      * Reads a little-endian unsigned integer (32-bit) from an InputStream.
      *
      * @param input source InputStream.
      * @return the value just read.
      * @throws IOException in case of an I/O problem.
      */
     public static long readSwappedUnsignedInteger(final InputStream input) throws IOException {
         final int value1 = read(input);
         final int value2 = read(input);
         final int value3 = read(input);
         final int value4 = read(input);
         final long low = ((value1 & 0xff) << 0) +
                          ((value2 & 0xff) << 8) +
                          ((value3 & 0xff) << 16);
         final long high = value4 & 0xff;
         return (high << 24) + (0xffffffffL & low);
     }
 
     /**
      * Reads an unsigned short (16-bit) value from a byte array in little-endian order at a given
      * offset.
      *
      * @param data source byte array.
      * @param offset starting offset in the byte array.
      * @return the value read.
      * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 2 bytes.
      */
     public static int readSwappedUnsignedShort(final byte[] data, final int offset) {
         validateByteArrayOffset(data, offset, Short.SIZE / Byte.SIZE);
         return ((data[offset + 0] & 0xff) << 0) +
                ((data[offset + 1] & 0xff) << 8);
     }
 
     /**
      * Reads an unsigned short (16-bit) from an InputStream in little-endian order.
      *
      * @param input source InputStream.
      * @return the value just read.
      * @throws IOException in case of an I/O problem.
      */
     public static int readSwappedUnsignedShort(final InputStream input) throws IOException {
         final int value1 = read(input);
         final int value2 = read(input);
 
         return ((value1 & 0xff) << 0) +
                ((value2 & 0xff) << 8);
     }
 
     /**
      * Converts a {@code double} value from big-endian to little-endian
      * and vice versa. That is, it converts the {@code double} to bytes,
      * reverses the bytes, and then reinterprets those bytes as a new {@code double}.
      * This can be useful if you have a number that was read from the
      * underlying source in the wrong endianness.
      *
      * @param value value to convert.
      * @return the converted value.
      */
     public static double swapDouble(final double value) {
         return Double.longBitsToDouble(swapLong(Double.doubleToLongBits(value)));
     }
 
     /**
      * Converts a {@code float} value from big-endian to little-endian and vice versa.
      *
      * @param value value to convert.
      * @return the converted value.
      */
     public static float swapFloat(final float value) {
         return Float.intBitsToFloat(swapInteger(Float.floatToIntBits(value)));
     }
 
     /**
      * Converts an {@code int} value from big-endian to little-endian and vice versa.
      *
      * @param value value to convert.
      * @return the converted value.
      */
     public static int swapInteger(final int value) {
         return
             ((value >> 0 & 0xff) << 24) +
             ((value >> 8 & 0xff) << 16) +
             ((value >> 16 & 0xff) << 8) +
             ((value >> 24 & 0xff) << 0);
     }
 
     /**
      * Converts a {@code long} value from big-endian to little-endian and vice versa.
      *
      * @param value value to convert.
      * @return the converted value.
      */
     public static long swapLong(final long value) {
         return
             ((value >> 0 & 0xff) << 56) +
             ((value >> 8 & 0xff) << 48) +
             ((value >> 16 & 0xff) << 40) +
             ((value >> 24 & 0xff) << 32) +
             ((value >> 32 & 0xff) << 24) +
             ((value >> 40 & 0xff) << 16) +
             ((value >> 48 & 0xff) << 8) +
             ((value >> 56 & 0xff) << 0);
     }
 
     /**
      * Converts a {@code short} value from big-endian to little-endian and vice versa.
      *
      * @param value value to convert.
      * @return the converted value.
      */
     public static short swapShort(final short value) {
         return (short) (
             ((value >> 0 & 0xff) << 8) +
             ((value >> 8 & 0xff) << 0)
         );
     }
 
     /**
      * Validates if the provided byte array has enough data.
      *
      * @param data the input byte array.
      * @param offset the input offset.
      * @param byteNeeded the needed number of bytes.
      * @throws IllegalArgumentException if the byte array does not have enough data.
      */
     private static void validateByteArrayOffset(final byte[] data, final int offset, final int byteNeeded) {
         if (data.length < offset + byteNeeded) {
             throw new IllegalArgumentException("Data only has " + data.length + "bytes, needed " + (offset + byteNeeded) + "bytes.");
         }
     }
 
     /**
      * Writes the 8 bytes of a {@code double} to a byte array at a given offset in little-endian order.
      *
      * @param data target byte array.
      * @param offset starting offset in the byte array.
      * @param value value to write.
      * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 8 bytes.
      */
     public static void writeSwappedDouble(final byte[] data, final int offset, final double value) {
         writeSwappedLong(data, offset, Double.doubleToLongBits(value));
     }
 
     /**
      * Writes the 8 bytes of a {@code double} to an output stream in little-endian order.
      *
      * @param output target OutputStream.
      * @param value value to write.
      * @throws IOException in case of an I/O problem.
      */
     public static void writeSwappedDouble(final OutputStream output, final double value) throws IOException {
         writeSwappedLong(output, Double.doubleToLongBits(value));
     }
 
     /**
      * Writes the 4 bytes of a {@code float} to a byte array at a given offset in little-endian order.
      *
      * @param data target byte array.
      * @param offset starting offset in the byte array.
      * @param value value to write.
      * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 4 bytes.
      */
     public static void writeSwappedFloat(final byte[] data, final int offset, final float value) {
         writeSwappedInteger(data, offset, Float.floatToIntBits(value));
     }
 
     /**
      * Writes the 4 bytes of a {@code float} to an output stream in little-endian order.
      *
      * @param output target OutputStream.
      * @param value value to write.
      * @throws IOException in case of an I/O problem.
     */
     public static void writeSwappedFloat(final OutputStream output, final float value) throws IOException {
         writeSwappedInteger(output, Float.floatToIntBits(value));
     }
 
     /**
      * Writes the 4 bytes of an {@code int} to a byte array at a given offset in little-endian order.
      *
      * @param data target byte array.
      * @param offset starting offset in the byte array.
      * @param value value to write.
      * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 4 bytes.
      */
     public static void writeSwappedInteger(final byte[] data, final int offset, final int value) {
         validateByteArrayOffset(data, offset, Integer.SIZE / Byte.SIZE);
         data[offset + 0] = (byte) (value >> 0 & 0xff);
         data[offset + 1] = (byte) (value >> 8 & 0xff);
         data[offset + 2] = (byte) (value >> 16 & 0xff);
         data[offset + 3] = (byte) (value >> 24 & 0xff);
     }
 
     /**
      * Writes the 4 bytes of an {@code int} to an output stream in little-endian order.
      *
      * @param output target OutputStream.
      * @param value value to write.
      * @throws IOException in case of an I/O problem.
      */
     public static void writeSwappedInteger(final OutputStream output, final int value) throws IOException {
         output.write((byte) (value >> 0 & 0xff));
         output.write((byte) (value >> 8 & 0xff));
         output.write((byte) (value >> 16 & 0xff));
         output.write((byte) (value >> 24 & 0xff));
     }
 
     /**
      * Writes the 8 bytes of a {@code long} to a byte array at a given offset in little-endian order.
      *
      * @param data target byte array.
      * @param offset starting offset in the byte array.
      * @param value value to write.
      * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 8 bytes.
      */
     public static void writeSwappedLong(final byte[] data, final int offset, final long value) {
         validateByteArrayOffset(data, offset, Long.SIZE / Byte.SIZE);
         data[offset + 0] = (byte) (value >> 0 & 0xff);
         data[offset + 1] = (byte) (value >> 8 & 0xff);
         data[offset + 2] = (byte) (value >> 16 & 0xff);
         data[offset + 3] = (byte) (value >> 24 & 0xff);
         data[offset + 4] = (byte) (value >> 32 & 0xff);
         data[offset + 5] = (byte) (value >> 40 & 0xff);
         data[offset + 6] = (byte) (value >> 48 & 0xff);
         data[offset + 7] = (byte) (value >> 56 & 0xff);
     }
 
     /**
      * Writes the 8 bytes of a {@code long} to an output stream in little-endian order.
      *
      * @param output target OutputStream.
      * @param value value to write.
      * @throws IOException in case of an I/O problem.
      */
     public static void writeSwappedLong(final OutputStream output, final long value) throws IOException {
         output.write((byte) (value >> 0 & 0xff));
         output.write((byte) (value >> 8 & 0xff));
         output.write((byte) (value >> 16 & 0xff));
         output.write((byte) (value >> 24 & 0xff));
         output.write((byte) (value >> 32 & 0xff));
         output.write((byte) (value >> 40 & 0xff));
         output.write((byte) (value >> 48 & 0xff));
         output.write((byte) (value >> 56 & 0xff));
     }
 
     /**
      * Writes the 2 bytes of a {@code short} to a byte array at a given offset in little-endian order.
      *
      * @param data target byte array.
      * @param offset starting offset in the byte array.
      * @param value value to write.
      * @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 2 bytes.
      */
     public static void writeSwappedShort(final byte[] data, final int offset, final short value) {
         validateByteArrayOffset(data, offset, Short.SIZE / Byte.SIZE);
         data[offset + 0] = (byte) (value >> 0 & 0xff);
         data[offset + 1] = (byte) (value >> 8 & 0xff);
     }
 
     /**
      * Writes the 2 bytes of a {@code short} to an output stream using little-endian encoding.
      *
      * @param output target OutputStream.
      * @param value value to write.
      * @throws IOException in case of an I/O problem.
      */
     public static void writeSwappedShort(final OutputStream output, final short value) throws IOException {
         output.write((byte) (value >> 0 & 0xff));
         output.write((byte) (value >> 8 & 0xff));
     }
 
     /**
      * Instances should NOT be constructed in standard programming.
      *
      * @deprecated TODO Make private in 3.0.
      */
     @Deprecated
     public EndianUtils() {
         // empty
     }
 }