/*
    * This file is part of Waarp Project (named also Waarp or GG).
    *
    *  Copyright (c) 2019, Waarp SAS, and individual contributors by the @author
    *  tags. See the COPYRIGHT.txt in the distribution for a full listing of
    * individual contributors.
    *
    *  All Waarp Project is free software: you can redistribute it and/or
    * modify it under the terms of the GNU General Public License as published by
   * the Free Software Foundation, either version 3 of the License, or (at your
   * option) any later version.
   *
   * Waarp is distributed in the hope that it will be useful, but WITHOUT ANY
   * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
   * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License along with
   * Waarp . If not, see <http://www.gnu.org/licenses/>.
   */
  
  /*
   * 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 org.waarp.compress.zstdunsafe;
  
  /**
   * Bit streams are encoded as a byte-aligned little-endian stream. Thus, bits are laid out
   * in the following manner, and the stream is read from right to left.
   * <p>
   * <p>
   * ... [16 17 18 19 20 21 22 23] [8 9 10 11 12 13 14 15] [0 1 2 3 4 5 6 7]
   */
  class BitInputStream {
    private BitInputStream() {
    }
  
    public static boolean isEndOfStream(final long startAddress,
                                        final long currentAddress,
                                        final int bitsConsumed) {
      return startAddress == currentAddress && bitsConsumed == Long.SIZE;
    }
  
    static long readTail(final Object inputBase, final long inputAddress,
                         final int inputSize) {
      long bits = UnsafeUtil.UNSAFE.getByte(inputBase, inputAddress) & 0xFF;
  
      switch (inputSize) {
        case 7:
          bits |=
              (UnsafeUtil.UNSAFE.getByte(inputBase, inputAddress + 6) & 0xFFL) <<
              48;
        case 6:
          bits |=
              (UnsafeUtil.UNSAFE.getByte(inputBase, inputAddress + 5) & 0xFFL) <<
              40;
        case 5:
          bits |=
              (UnsafeUtil.UNSAFE.getByte(inputBase, inputAddress + 4) & 0xFFL) <<
              32;
        case 4:
          bits |=
              (UnsafeUtil.UNSAFE.getByte(inputBase, inputAddress + 3) & 0xFFL) <<
              24;
        case 3:
          bits |=
              (UnsafeUtil.UNSAFE.getByte(inputBase, inputAddress + 2) & 0xFFL) <<
              16;
        case 2:
          bits |=
              (UnsafeUtil.UNSAFE.getByte(inputBase, inputAddress + 1) & 0xFFL) <<
              8;
      }
  
      return bits;
    }
  
    /**
     * @return numberOfBits in the low order bits of a long
     */
    public static long peekBits(final int bitsConsumed, final long bitContainer,
                                final int numberOfBits) {
      return (((bitContainer << bitsConsumed) >>> 1) >>> (63 - numberOfBits));
    }
  
    /**
     * numberOfBits must be > 0
     *
     * @return numberOfBits in the low order bits of a long
     */
   public static long peekBitsFast(final int bitsConsumed,
                                   final long bitContainer,
                                   final int numberOfBits) {
     return ((bitContainer << bitsConsumed) >>> (64 - numberOfBits));
   }
 
   static class Initializer {
     private final Object inputBase;
     private final long startAddress;
     private final long endAddress;
     private long bits;
     private long currentAddress;
     private int bitsConsumed;
 
     public Initializer(final Object inputBase, final long startAddress,
                        final long endAddress) {
       this.inputBase = inputBase;
       this.startAddress = startAddress;
       this.endAddress = endAddress;
     }
 
     public long getBits() {
       return bits;
     }
 
     public long getCurrentAddress() {
       return currentAddress;
     }
 
     public int getBitsConsumed() {
       return bitsConsumed;
     }
 
     public void initialize() {
       Util.verify(endAddress - startAddress >= 1, startAddress,
                   "Bitstream is empty");
 
       final int lastByte =
           UnsafeUtil.UNSAFE.getByte(inputBase, endAddress - 1) & 0xFF;
       Util.verify(lastByte != 0, endAddress, "Bitstream end mark not present");
 
       bitsConsumed = Constants.SIZE_OF_LONG - Util.highestBit(lastByte);
 
       final int inputSize = (int) (endAddress - startAddress);
       if (inputSize >= Constants.SIZE_OF_LONG) {  /* normal case */
         currentAddress = endAddress - Constants.SIZE_OF_LONG;
         bits = UnsafeUtil.UNSAFE.getLong(inputBase, currentAddress);
       } else {
         currentAddress = startAddress;
         bits = readTail(inputBase, startAddress, inputSize);
 
         bitsConsumed += (Constants.SIZE_OF_LONG - inputSize) * 8;
       }
     }
   }
 
   static final class Loader {
     private final Object inputBase;
     private final long startAddress;
     private long bits;
     private long currentAddress;
     private int bitsConsumed;
     private boolean overflow;
 
     public Loader(final Object inputBase, final long startAddress,
                   final long currentAddress, final long bits,
                   final int bitsConsumed) {
       this.inputBase = inputBase;
       this.startAddress = startAddress;
       this.bits = bits;
       this.currentAddress = currentAddress;
       this.bitsConsumed = bitsConsumed;
     }
 
     public long getBits() {
       return bits;
     }
 
     public long getCurrentAddress() {
       return currentAddress;
     }
 
     public int getBitsConsumed() {
       return bitsConsumed;
     }
 
     public boolean isOverflow() {
       return overflow;
     }
 
     public boolean load() {
       if (bitsConsumed > 64) {
         overflow = true;
         return true;
       } else if (currentAddress == startAddress) {
         return true;
       }
 
       int bytes = bitsConsumed >>> 3; // divide by 8
       if (currentAddress >= startAddress + Constants.SIZE_OF_LONG) {
         if (bytes > 0) {
           currentAddress -= bytes;
           bits = UnsafeUtil.UNSAFE.getLong(inputBase, currentAddress);
         }
         bitsConsumed &= 0x7;
       } else if (currentAddress - bytes < startAddress) {
         bytes = (int) (currentAddress - startAddress);
         currentAddress = startAddress;
         bitsConsumed -= bytes * Constants.SIZE_OF_LONG;
         bits = UnsafeUtil.UNSAFE.getLong(inputBase, startAddress);
         return true;
       } else {
         currentAddress -= bytes;
         bitsConsumed -= bytes * Constants.SIZE_OF_LONG;
         bits = UnsafeUtil.UNSAFE.getLong(inputBase, currentAddress);
       }
 
       return false;
     }
   }
 }