#region license

/*
Copyright (c) 2013, Milosz Krajewski
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided 
that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this list of conditions 
  and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice, this list of conditions 
  and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED 
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE 
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN 
IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#endregion

using System;
using System.Diagnostics;

// ReSharper disable CheckNamespace
// ReSharper disable InconsistentNaming

namespace MessagePack.LZ4
{
    /// <summary>Safe LZ4 codec.</summary>
    public static partial class LZ4Codec
    {
        #region Helper

        // ReSharper disable UnusedParameter.Local

        [Conditional("DEBUG")]
        private static void Assert(bool condition, string errorMessage)
        {
            if (!condition) throw new ArgumentException(errorMessage);
            Debug.Assert(condition, errorMessage);
        }

        // ReSharper restore UnusedParameter.Local

        #endregion

        #region Byte manipulation

        // ReSharper disable RedundantCast

        internal static void Poke2(byte[] buffer, int offset, ushort value)
        {
            buffer[offset] = (byte)value;
            buffer[offset + 1] = (byte)(value >> 8);
        }

        internal static ushort Peek2(byte[] buffer, int offset)
        {
            // NOTE: It's faster than BitConverter.ToUInt16 (suprised? me too)
            return (ushort)(((uint)buffer[offset]) | ((uint)buffer[offset + 1] << 8));
        }

        internal static uint Peek4(byte[] buffer, int offset)
        {
            // NOTE: It's faster than BitConverter.ToUInt32 (suprised? me too)
            return
                ((uint)buffer[offset]) |
                ((uint)buffer[offset + 1] << 8) |
                ((uint)buffer[offset + 2] << 16) |
                ((uint)buffer[offset + 3] << 24);
        }

        private static uint Xor4(byte[] buffer, int offset1, int offset2)
        {
            // return Peek4(buffer, offset1) ^ Peek4(buffer, offset2);
            var value1 =
                ((uint)buffer[offset1]) |
                ((uint)buffer[offset1 + 1] << 8) |
                ((uint)buffer[offset1 + 2] << 16) |
                ((uint)buffer[offset1 + 3] << 24);
            var value2 =
                ((uint)buffer[offset2]) |
                ((uint)buffer[offset2 + 1] << 8) |
                ((uint)buffer[offset2 + 2] << 16) |
                ((uint)buffer[offset2 + 3] << 24);
            return value1 ^ value2;
        }

        private static ulong Xor8(byte[] buffer, int offset1, int offset2)
        {
            // return Peek8(buffer, offset1) ^ Peek8(buffer, offset2);
            var value1 =
                ((ulong)buffer[offset1]) |
                ((ulong)buffer[offset1 + 1] << 8) |
                ((ulong)buffer[offset1 + 2] << 16) |
                ((ulong)buffer[offset1 + 3] << 24) |
                ((ulong)buffer[offset1 + 4] << 32) |
                ((ulong)buffer[offset1 + 5] << 40) |
                ((ulong)buffer[offset1 + 6] << 48) |
                ((ulong)buffer[offset1 + 7] << 56);
            var value2 =
                ((ulong)buffer[offset2]) |
                ((ulong)buffer[offset2 + 1] << 8) |
                ((ulong)buffer[offset2 + 2] << 16) |
                ((ulong)buffer[offset2 + 3] << 24) |
                ((ulong)buffer[offset2 + 4] << 32) |
                ((ulong)buffer[offset2 + 5] << 40) |
                ((ulong)buffer[offset2 + 6] << 48) |
                ((ulong)buffer[offset2 + 7] << 56);
            return value1 ^ value2;
        }

        private static bool Equal2(byte[] buffer, int offset1, int offset2)
        {
            // return Peek2(buffer, offset1) == Peek2(buffer, offset2);
            if (buffer[offset1] != buffer[offset2]) return false;
            return buffer[offset1 + 1] == buffer[offset2 + 1];
        }

        private static bool Equal4(byte[] buffer, int offset1, int offset2)
        {
            // return Peek4(buffer, offset1) == Peek4(buffer, offset2);
            if (buffer[offset1] != buffer[offset2]) return false;
            if (buffer[offset1 + 1] != buffer[offset2 + 1]) return false;
            if (buffer[offset1 + 2] != buffer[offset2 + 2]) return false;
            return buffer[offset1 + 3] == buffer[offset2 + 3];
        }

        // ReSharper restore RedundantCast

        #endregion

        #region Byte block copy

        private static void Copy4(byte[] buf, int src, int dst)
        {
            Assert(dst > src, "Copying backwards is not implemented");
            buf[dst + 3] = buf[src + 3];
            buf[dst + 2] = buf[src + 2];
            buf[dst + 1] = buf[src + 1];
            buf[dst] = buf[src];
        }

        private static void Copy8(byte[] buf, int src, int dst)
        {
            Assert(dst > src, "Copying backwards is not implemented");
            buf[dst + 7] = buf[src + 7];
            buf[dst + 6] = buf[src + 6];
            buf[dst + 5] = buf[src + 5];
            buf[dst + 4] = buf[src + 4];
            buf[dst + 3] = buf[src + 3];
            buf[dst + 2] = buf[src + 2];
            buf[dst + 1] = buf[src + 1];
            buf[dst] = buf[src];
        }

        private static void BlockCopy(byte[] src, int src_0, byte[] dst, int dst_0, int len)
        {
            Assert(src != dst, "BlockCopy does not handle copying to the same buffer");

            if (len >= BLOCK_COPY_LIMIT)
            {
                Buffer.BlockCopy(src, src_0, dst, dst_0, len);
            }
            else
            {
                while (len >= 8)
                {
                    dst[dst_0] = src[src_0];
                    dst[dst_0 + 1] = src[src_0 + 1];
                    dst[dst_0 + 2] = src[src_0 + 2];
                    dst[dst_0 + 3] = src[src_0 + 3];
                    dst[dst_0 + 4] = src[src_0 + 4];
                    dst[dst_0 + 5] = src[src_0 + 5];
                    dst[dst_0 + 6] = src[src_0 + 6];
                    dst[dst_0 + 7] = src[src_0 + 7];
                    len -= 8;
                    src_0 += 8;
                    dst_0 += 8;
                }

                while (len >= 4)
                {
                    dst[dst_0] = src[src_0];
                    dst[dst_0 + 1] = src[src_0 + 1];
                    dst[dst_0 + 2] = src[src_0 + 2];
                    dst[dst_0 + 3] = src[src_0 + 3];
                    len -= 4;
                    src_0 += 4;
                    dst_0 += 4;
                }

                while (len-- > 0)
                {
                    dst[dst_0++] = src[src_0++];
                }
            }
        }

        private static int WildCopy(byte[] src, int src_0, byte[] dst, int dst_0, int dst_end)
        {
            var len = dst_end - dst_0;

            Assert(src != dst, "BlockCopy does not handle copying to the same buffer");
            Assert(len > 0, "Length have to be greater than 0");

            if (len >= BLOCK_COPY_LIMIT)
            {
                Buffer.BlockCopy(src, src_0, dst, dst_0, len);
            }
            else
            {
                // apparently (tested) this is an overkill
                // it seems to be faster without this 8-byte loop
                //while (len >= 8)
                //{
                //	dst[dst_0] = src[src_0];
                //	dst[dst_0 + 1] = src[src_0 + 1];
                //	dst[dst_0 + 2] = src[src_0 + 2];
                //	dst[dst_0 + 3] = src[src_0 + 3];
                //	dst[dst_0 + 4] = src[src_0 + 4];
                //	dst[dst_0 + 5] = src[src_0 + 5];
                //	dst[dst_0 + 6] = src[src_0 + 6];
                //	dst[dst_0 + 7] = src[src_0 + 7];
                //	len -= 8; src_0 += 8; dst_0 += 8;
                //}

                while (len >= 4)
                {
                    dst[dst_0] = src[src_0];
                    dst[dst_0 + 1] = src[src_0 + 1];
                    dst[dst_0 + 2] = src[src_0 + 2];
                    dst[dst_0 + 3] = src[src_0 + 3];
                    len -= 4;
                    src_0 += 4;
                    dst_0 += 4;
                }

                while (len-- > 0)
                {
                    dst[dst_0++] = src[src_0++];
                }
            }

            return len;
        }

        private static int SecureCopy(byte[] buffer, int src, int dst, int dst_end)
        {
            var diff = dst - src;
            var length = dst_end - dst;
            var len = length;

            Assert(diff >= 4, "Target must be at least 4 bytes further than source");
            Assert(BLOCK_COPY_LIMIT > 4, "This method requires BLOCK_COPY_LIMIT > 4");
            Assert(len > 0, "Length have to be greater than 0");

            if (diff >= BLOCK_COPY_LIMIT)
            {
                if (diff >= length)
                {
                    Buffer.BlockCopy(buffer, src, buffer, dst, length);
                    return length; // done
                }

                do
                {
                    Buffer.BlockCopy(buffer, src, buffer, dst, diff);
                    src += diff;
                    dst += diff;
                    len -= diff;
                } while (len >= diff);
            }

            // apparently (tested) this is an overkill
            // it seems to be faster without this 8-byte loop
            //while (len >= 8)
            //{
            //	buffer[dst] = buffer[src];
            //	buffer[dst + 1] = buffer[src + 1];
            //	buffer[dst + 2] = buffer[src + 2];
            //	buffer[dst + 3] = buffer[src + 3];
            //	buffer[dst + 4] = buffer[src + 4];
            //	buffer[dst + 5] = buffer[src + 5];
            //	buffer[dst + 6] = buffer[src + 6];
            //	buffer[dst + 7] = buffer[src + 7];
            //	dst += 8; src += 8; len -= 8;
            //}

            while (len >= 4)
            {
                buffer[dst] = buffer[src];
                buffer[dst + 1] = buffer[src + 1];
                buffer[dst + 2] = buffer[src + 2];
                buffer[dst + 3] = buffer[src + 3];
                dst += 4;
                src += 4;
                len -= 4;
            }

            while (len-- > 0)
            {
                buffer[dst++] = buffer[src++];
            }

            return length; // done
        }

        #endregion

        /// <summary>Encodes the specified input.</summary>
        /// <param name="input">The input.</param>
        /// <param name="inputOffset">The input offset.</param>
        /// <param name="inputLength">Length of the input.</param>
        /// <param name="output">The output.</param>
        /// <param name="outputOffset">The output offset.</param>
        /// <param name="outputLength">Length of the output.</param>
        /// <returns>Number of bytes written.</returns>
        public static int Encode32Safe(
            byte[] input,
            int inputOffset,
            int inputLength,
            byte[] output,
            int outputOffset,
            int outputLength)
        {
            CheckArguments(input, inputOffset, inputLength, output, outputOffset, outputLength);
            if (outputLength == 0) return 0;

            if (inputLength < LZ4_64KLIMIT)
            {
                var hashTable = HashTablePool.GetUShortHashTablePool();
                return LZ4_compress64kCtx_safe32(hashTable, input, output, inputOffset, outputOffset, inputLength, outputLength);
            }
            else
            {
                var hashTable = HashTablePool.GetIntHashTablePool();
                return LZ4_compressCtx_safe32(hashTable, input, output, inputOffset, outputOffset, inputLength, outputLength);
            }
        }

        /// <summary>Encodes the specified input.</summary>
        /// <param name="input">The input.</param>
        /// <param name="inputOffset">The input offset.</param>
        /// <param name="inputLength">Length of the input.</param>
        /// <param name="output">The output.</param>
        /// <param name="outputOffset">The output offset.</param>
        /// <param name="outputLength">Length of the output.</param>
        /// <returns>Number of bytes written.</returns>
        public static int Encode64Safe(
            byte[] input,
            int inputOffset,
            int inputLength,
            byte[] output,
            int outputOffset,
            int outputLength)
        {
            CheckArguments(input, inputOffset, inputLength, output, outputOffset, outputLength);
            if (outputLength == 0) return 0;

            if (inputLength < LZ4_64KLIMIT)
            {
                var hashTable = HashTablePool.GetUShortHashTablePool();
                return LZ4_compress64kCtx_safe64(hashTable, input, output, inputOffset, outputOffset, inputLength, outputLength);
            }
            else
            {
                var hashTable = HashTablePool.GetIntHashTablePool();
                return LZ4_compressCtx_safe64(hashTable, input, output, inputOffset, outputOffset, inputLength, outputLength);
            }
        }

        /// <summary>Decodes the specified input.</summary>
        /// <param name="input">The input.</param>
        /// <param name="inputOffset">The input offset.</param>
        /// <param name="inputLength">Length of the input.</param>
        /// <param name="output">The output.</param>
        /// <param name="outputOffset">The output offset.</param>
        /// <param name="outputLength">Length of the output.</param>
        /// <returns>Number of bytes written.</returns>
        public static int Decode32Safe(
            byte[] input,
            int inputOffset,
            int inputLength,
            byte[] output,
            int outputOffset,
            int outputLength)
        {
            CheckArguments(input, inputOffset, inputLength, output, outputOffset, outputLength);

            if (outputLength == 0) return 0;

            var length = LZ4_uncompress_safe32(input, output, inputOffset, outputOffset, outputLength);
            if (length != inputLength)
                throw new ArgumentException("LZ4 block is corrupted, or invalid length has been given.");
            return outputLength;
        }

        /// <summary>Decodes the specified input.</summary>
        /// <param name="input">The input.</param>
        /// <param name="inputOffset">The input offset.</param>
        /// <param name="inputLength">Length of the input.</param>
        /// <param name="output">The output.</param>
        /// <param name="outputOffset">The output offset.</param>
        /// <param name="outputLength">Length of the output.</param>
        /// <returns>Number of bytes written.</returns>
        public static int Decode64Safe(
            byte[] input,
            int inputOffset,
            int inputLength,
            byte[] output,
            int outputOffset,
            int outputLength)
        {
            CheckArguments(
                input, inputOffset, inputLength,
                output, outputOffset, outputLength);

            if (outputLength == 0) return 0;

            var length = LZ4_uncompress_safe64(input, output, inputOffset, outputOffset, outputLength);
            if (length != inputLength)
                throw new ArgumentException("LZ4 block is corrupted, or invalid length has been given.");
            return outputLength;
        }
    }
}

// ReSharper restore InconsistentNaming
// ReSharper restore CheckNamespace