/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * Licensed 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.android.tools.build.apkzlib.zip.utils;

import com.google.common.base.Preconditions;
import com.google.common.base.Verify;
import java.io.EOFException;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;

/**
 * Utilities to read and write 16, 32, and 64 bit integers with support for little-endian encoding,
 * as used in zip files. Zip files actually use unsigned data types. We use Java's native (signed)
 * data types but will use long (64 bit) to ensure we can fit the whole range for the 16 and 32
 * bit fields.
 */
public class LittleEndianUtils {
  /** Utility class, no constructor. */
  private LittleEndianUtils() {}

  /**
   * Reads 8 bytes in little-endian format and converts them into a 64-bit value.
   *
   * @param bytes from where should the bytes be read; the first 8 bytes of the source will be read.
   * @return the 64-bit value
   * @throws IOException failed to read the value.
   */
  public static long readUnsigned8Le(ByteBuffer bytes) throws IOException {
    Preconditions.checkNotNull(bytes, "bytes == null");

    if (bytes.remaining() < 8) {
      throw new EOFException(
              "Not enough data: 8 bytes expected, " + bytes.remaining() + " available.");
    }

    ByteOrder order = bytes.order();
    bytes.order(ByteOrder.LITTLE_ENDIAN);
    long r = bytes.getLong();
    bytes.order(order);
    return r;
  }

  /**
   * Reads 4 bytes in little-endian format and converts them into a 32-bit value.
   *
   * @param bytes from where should the bytes be read; the first 4 bytes of the source will be read
   * @return the 32-bit value
   * @throws IOException failed to read the value
   */
  public static long readUnsigned4Le(ByteBuffer bytes) throws IOException {
    Preconditions.checkNotNull(bytes, "bytes == null");

    if (bytes.remaining() < 4) {
      throw new EOFException(
          "Not enough data: 4 bytes expected, " + bytes.remaining() + " available.");
    }

    byte b0 = bytes.get();
    byte b1 = bytes.get();
    byte b2 = bytes.get();
    byte b3 = bytes.get();
    long r = (b0 & 0xff) | ((b1 & 0xff) << 8) | ((b2 & 0xff) << 16) | ((b3 & 0xffL) << 24);
    Verify.verify(r >= 0);
    Verify.verify(r <= 0x00000000ffffffffL);
    return r;
  }

  /**
   * Reads 2 bytes in little-endian format and converts them into a 16-bit value.
   *
   * @param bytes from where should the bytes be read; the first 2 bytes of the source will be read
   * @return the 16-bit value
   * @throws IOException failed to read the value
   */
  public static int readUnsigned2Le(ByteBuffer bytes) throws IOException {
    Preconditions.checkNotNull(bytes, "bytes == null");

    if (bytes.remaining() < 2) {
      throw new EOFException(
          "Not enough data: 2 bytes expected, " + bytes.remaining() + " available.");
    }

    byte b0 = bytes.get();
    byte b1 = bytes.get();
    int r = (b0 & 0xff) | ((b1 & 0xff) << 8);

    Verify.verify(r >= 0);
    Verify.verify(r <= 0x0000ffff);
    return r;
  }

  /**
   * Writes 8 bytes in little-endian format, converting them from a <em> signed </em> 64-bit value.
   *
   * @param output the output stream where the bytes will be written.
   * @param value the 64-bit value to convert.
   * @throws IOException failed to write the value data.
   */
  public static void writeUnsigned8Le(ByteBuffer output, long value) throws IOException {
    Preconditions.checkNotNull(output, "output == null");

    ByteOrder order = output.order();
    output.order(ByteOrder.LITTLE_ENDIAN);
    output.putLong(value);
    output.order(order);
  }

  /**
   * Writes 4 bytes in little-endian format, converting them from a 32-bit value.
   *
   * @param output the output stream where the bytes will be written
   * @param value the 32-bit value to convert
   * @throws IOException failed to write the value data
   */
  public static void writeUnsigned4Le(ByteBuffer output, long value) throws IOException {
    Preconditions.checkNotNull(output, "output == null");
    Preconditions.checkArgument(value >= 0, "value (%s) < 0", value);
    Preconditions.checkArgument(
        value <= 0x00000000ffffffffL, "value (%s) > 0x00000000ffffffffL", value);

    output.put((byte) (value & 0xff));
    output.put((byte) ((value >> 8) & 0xff));
    output.put((byte) ((value >> 16) & 0xff));
    output.put((byte) ((value >> 24) & 0xff));
  }

  /**
   * Writes 2 bytes in little-endian format, converting them from a 16-bit value.
   *
   * @param output the output stream where the bytes will be written
   * @param value the 16-bit value to convert
   * @throws IOException failed to write the value data
   */
  public static void writeUnsigned2Le(ByteBuffer output, int value) throws IOException {
    Preconditions.checkNotNull(output, "output == null");
    Preconditions.checkArgument(value >= 0, "value (%s) < 0", value);
    Preconditions.checkArgument(value <= 0x0000ffff, "value (%s) > 0x0000ffff", value);

    output.put((byte) (value & 0xff));
    output.put((byte) ((value >> 8) & 0xff));
  }
}