LZ4Codec.Safe32.Dirty.cs

#region LZ4 original

/*
   LZ4 - Fast LZ compression algorithm
   Copyright (C) 2011-2012, Yann Collet.
   BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)

   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
   OWNER 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.

   You can contact the author at :
   - LZ4 homepage : http://fastcompression.blogspot.com/p/lz4.html
   - LZ4 source repository : http://code.google.com/p/lz4/
*/

#endregion

#region LZ4 port

/*
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

// ReSharper disable CheckNamespace
// ReSharper disable InconsistentNaming
// ReSharper disable TooWideLocalVariableScope
// ReSharper disable JoinDeclarationAndInitializer
// ReSharper disable RedundantIfElseBlock

namespace LZ4PCL
{
#if !INCLUDE_UNSAFE
    public static partial class LZ4Codec
    {
    #region LZ4_compressCtx

        private static int LZ4_compressCtx_safe32(
            int[] hash_table,
            byte[] src,
            byte[] dst,
            int src_0,
            int dst_0,
            int src_len,
            int dst_maxlen)
        {
            int[] debruijn32 = DEBRUIJN_TABLE_32;
            int _i;

            // ---- preprocessed source start here ----
            // r93
            int src_p = src_0;
            int src_base = src_0;
            int src_anchor = src_p;
            int src_end = src_p + src_len;
            int src_mflimit = src_end - MFLIMIT;

            int dst_p = dst_0;
            int dst_end = dst_p + dst_maxlen;

            int src_LASTLITERALS = src_end - LASTLITERALS;
            int src_LASTLITERALS_1 = src_LASTLITERALS - 1;

            int src_LASTLITERALS_STEPSIZE_1 = src_LASTLITERALS - (STEPSIZE_32 - 1);
            int dst_LASTLITERALS_1 = dst_end - (1 + LASTLITERALS);
            int dst_LASTLITERALS_3 = dst_end - (2 + 1 + LASTLITERALS);

            int length;

            uint h, h_fwd;

            // Init
            if (src_len < MINLENGTH) {
                goto _last_literals;
            }

            // First Byte
            hash_table[(((Peek4(src, src_p)) * 2654435761u) >> HASH_ADJUST)] = (src_p - src_base);
            src_p++;
            h_fwd = (((Peek4(src, src_p)) * 2654435761u) >> HASH_ADJUST);

            // Main Loop
            while (true) {
                int findMatchAttempts = (1 << SKIPSTRENGTH) + 3;
                int src_p_fwd = src_p;
                int src_ref;
                int dst_token;

                // Find a match
                do {
                    h = h_fwd;
                    int step = findMatchAttempts++ >> SKIPSTRENGTH;
                    src_p = src_p_fwd;
                    src_p_fwd = src_p + step;

                    if (src_p_fwd > src_mflimit) {
                        goto _last_literals;
                    }

                    h_fwd = (((Peek4(src, src_p_fwd)) * 2654435761u) >> HASH_ADJUST);
                    src_ref = src_base + hash_table[h];
                    hash_table[h] = (src_p - src_base);
                } while ((src_ref < src_p - MAX_DISTANCE) || (!Equal4(src, src_ref, src_p)));

                // Catch up
                while ((src_p > src_anchor) && (src_ref > src_0) && (src[src_p - 1] == src[src_ref - 1])) {
                    src_p--;
                    src_ref--;
                }

                // Encode Literal length
                length = (src_p - src_anchor);
                dst_token = dst_p++;

                if (dst_p + length + (length >> 8) > dst_LASTLITERALS_3) {
                    return 0; // Check output limit
                }

                if (length >= RUN_MASK) {
                    int len = length - RUN_MASK;
                    dst[dst_token] = (RUN_MASK << ML_BITS);
                    if (len > 254) {
                        do {
                            dst[dst_p++] = 255;
                            len -= 255;
                        } while (len > 254);
                        dst[dst_p++] = (byte) len;
                        BlockCopy(src, src_anchor, dst, dst_p, length);
                        dst_p += length;
                        goto _next_match;
                    } else {
                        dst[dst_p++] = (byte) len;
                    }
                } else {
                    dst[dst_token] = (byte) (length << ML_BITS);
                }

                // Copy Literals
                if (length > 0) {
                    _i = dst_p + length;
                    WildCopy(src, src_anchor, dst, dst_p, _i);
                    dst_p = _i;
                }

                _next_match:
                // Encode Offset
                Poke2(dst, dst_p, (ushort) (src_p - src_ref));
                dst_p += 2;

                // Start Counting
                src_p += MINMATCH;
                src_ref += MINMATCH; // MinMatch already verified
                src_anchor = src_p;

                while (src_p < src_LASTLITERALS_STEPSIZE_1) {
                    var diff = (int) Xor4(src, src_ref, src_p);
                    if (diff == 0) {
                        src_p += STEPSIZE_32;
                        src_ref += STEPSIZE_32;
                        continue;
                    }
                    src_p += debruijn32[((uint) ((diff) & -(diff)) * 0x077CB531u) >> 27];
                    goto _endCount;
                }

                if ((src_p < src_LASTLITERALS_1) && (Equal2(src, src_ref, src_p))) {
                    src_p += 2;
                    src_ref += 2;
                }
                if ((src_p < src_LASTLITERALS) && (src[src_ref] == src[src_p])) {
                    src_p++;
                }

                _endCount:
                // Encode MatchLength
                length = (src_p - src_anchor);

                if (dst_p + (length >> 8) > dst_LASTLITERALS_1) {
                    return 0; // Check output limit
                }

                if (length >= ML_MASK) {
                    dst[dst_token] += ML_MASK;
                    length -= ML_MASK;
                    for (; length > 509; length -= 510) {
                        dst[dst_p++] = 255;
                        dst[dst_p++] = 255;
                    }
                    if (length > 254) {
                        length -= 255;
                        dst[dst_p++] = 255;
                    }
                    dst[dst_p++] = (byte) length;
                } else {
                    dst[dst_token] += (byte) length;
                }

                // Test end of chunk
                if (src_p > src_mflimit) {
                    src_anchor = src_p;
                    break;
                }

                // Fill table
                hash_table[(((Peek4(src, src_p - 2)) * 2654435761u) >> HASH_ADJUST)] = (src_p - 2 - src_base);

                // Test next position

                h = (((Peek4(src, src_p)) * 2654435761u) >> HASH_ADJUST);
                src_ref = src_base + hash_table[h];
                hash_table[h] = (src_p - src_base);

                if ((src_ref > src_p - (MAX_DISTANCE + 1)) && (Equal4(src, src_ref, src_p))) {
                    dst_token = dst_p++;
                    dst[dst_token] = 0;
                    goto _next_match;
                }

                // Prepare next loop
                src_anchor = src_p++;
                h_fwd = (((Peek4(src, src_p)) * 2654435761u) >> HASH_ADJUST);
            }

            _last_literals:
            // Encode Last Literals
            {
                int lastRun = (src_end - src_anchor);

                if (dst_p + lastRun + 1 + ((lastRun + 255 - RUN_MASK) / 255) > dst_end) {
                    return 0;
                }

                if (lastRun >= RUN_MASK) {
                    dst[dst_p++] = (RUN_MASK << ML_BITS);
                    lastRun -= RUN_MASK;
                    for (; lastRun > 254; lastRun -= 255) {
                        dst[dst_p++] = 255;
                    }
                    dst[dst_p++] = (byte) lastRun;
                } else {
                    dst[dst_p++] = (byte) (lastRun << ML_BITS);
                }
                BlockCopy(src, src_anchor, dst, dst_p, src_end - src_anchor);
                dst_p += src_end - src_anchor;
            }

            // End
            return ((dst_p) - dst_0);
        }

        #endregion

    #region LZ4_compress64kCtx

        private static int LZ4_compress64kCtx_safe32(
            ushort[] hash_table,
            byte[] src,
            byte[] dst,
            int src_0,
            int dst_0,
            int src_len,
            int dst_maxlen)
        {
            int[] debruijn32 = DEBRUIJN_TABLE_32;
            int _i;

            // ---- preprocessed source start here ----
            // r93
            int src_p = src_0;
            int src_anchor = src_p;
            int src_base = src_p;
            int src_end = src_p + src_len;
            int src_mflimit = src_end - MFLIMIT;

            int dst_p = dst_0;
            int dst_end = dst_p + dst_maxlen;

            int src_LASTLITERALS = src_end - LASTLITERALS;
            int src_LASTLITERALS_1 = src_LASTLITERALS - 1;

            int src_LASTLITERALS_STEPSIZE_1 = src_LASTLITERALS - (STEPSIZE_32 - 1);
            int dst_LASTLITERALS_1 = dst_end - (1 + LASTLITERALS);
            int dst_LASTLITERALS_3 = dst_end - (2 + 1 + LASTLITERALS);

            int len, length;

            uint h, h_fwd;

            // Init
            if (src_len < MINLENGTH) {
                goto _last_literals;
            }

            // First Byte
            src_p++;
            h_fwd = (((Peek4(src, src_p)) * 2654435761u) >> HASH64K_ADJUST);

            // Main Loop
            while (true) {
                int findMatchAttempts = (1 << SKIPSTRENGTH) + 3;
                int src_p_fwd = src_p;
                int src_ref;
                int dst_token;

                // Find a match
                do {
                    h = h_fwd;
                    int step = findMatchAttempts++ >> SKIPSTRENGTH;
                    src_p = src_p_fwd;
                    src_p_fwd = src_p + step;

                    if (src_p_fwd > src_mflimit) {
                        goto _last_literals;
                    }

                    h_fwd = (((Peek4(src, src_p_fwd)) * 2654435761u) >> HASH64K_ADJUST);
                    src_ref = src_base + hash_table[h];
                    hash_table[h] = (ushort) (src_p - src_base);
                } while (!Equal4(src, src_ref, src_p));

                // Catch up
                while ((src_p > src_anchor) && (src_ref > src_0) && (src[src_p - 1] == src[src_ref - 1])) {
                    src_p--;
                    src_ref--;
                }

                // Encode Literal length
                length = (src_p - src_anchor);
                dst_token = dst_p++;

                if (dst_p + length + (length >> 8) > dst_LASTLITERALS_3) {
                    return 0; // Check output limit
                }

                if (length >= RUN_MASK) {
                    len = length - RUN_MASK;
                    dst[dst_token] = (RUN_MASK << ML_BITS);
                    if (len > 254) {
                        do {
                            dst[dst_p++] = 255;
                            len -= 255;
                        } while (len > 254);
                        dst[dst_p++] = (byte) len;
                        BlockCopy(src, src_anchor, dst, dst_p, length);
                        dst_p += length;
                        goto _next_match;
                    } else {
                        dst[dst_p++] = (byte) len;
                    }
                } else {
                    dst[dst_token] = (byte) (length << ML_BITS);
                }

                // Copy Literals
                if (length > 0) {
                    _i = dst_p + length;
                    WildCopy(src, src_anchor, dst, dst_p, _i);
                    dst_p = _i;
                }

                _next_match:
                // Encode Offset
                Poke2(dst, dst_p, (ushort) (src_p - src_ref));
                dst_p += 2;

                // Start Counting
                src_p += MINMATCH;
                src_ref += MINMATCH; // MinMatch verified
                src_anchor = src_p;

                while (src_p < src_LASTLITERALS_STEPSIZE_1) {
                    var diff = (int) Xor4(src, src_ref, src_p);
                    if (diff == 0) {
                        src_p += STEPSIZE_32;
                        src_ref += STEPSIZE_32;
                        continue;
                    }
                    src_p += debruijn32[((uint) ((diff) & -(diff)) * 0x077CB531u) >> 27];
                    goto _endCount;
                }

                if ((src_p < src_LASTLITERALS_1) && (Equal2(src, src_ref, src_p))) {
                    src_p += 2;
                    src_ref += 2;
                }
                if ((src_p < src_LASTLITERALS) && (src[src_ref] == src[src_p])) {
                    src_p++;
                }

                _endCount:

                // Encode MatchLength
                len = (src_p - src_anchor);

                if (dst_p + (len >> 8) > dst_LASTLITERALS_1) {
                    return 0; // Check output limit
                }

                if (len >= ML_MASK) {
                    dst[dst_token] += ML_MASK;
                    len -= ML_MASK;
                    for (; len > 509; len -= 510) {
                        dst[dst_p++] = 255;
                        dst[dst_p++] = 255;
                    }
                    if (len > 254) {
                        len -= 255;
                        dst[dst_p++] = 255;
                    }
                    dst[dst_p++] = (byte) len;
                } else {
                    dst[dst_token] += (byte) len;
                }

                // Test end of chunk
                if (src_p > src_mflimit) {
                    src_anchor = src_p;
                    break;
                }

                // Fill table
                hash_table[(((Peek4(src, src_p - 2)) * 2654435761u) >> HASH64K_ADJUST)] =
                    (ushort) (src_p - 2 - src_base);

                // Test next position

                h = (((Peek4(src, src_p)) * 2654435761u) >> HASH64K_ADJUST);
                src_ref = src_base + hash_table[h];
                hash_table[h] = (ushort) (src_p - src_base);

                if (Equal4(src, src_ref, src_p)) {
                    dst_token = dst_p++;
                    dst[dst_token] = 0;
                    goto _next_match;
                }

                // Prepare next loop
                src_anchor = src_p++;
                h_fwd = (((Peek4(src, src_p)) * 2654435761u) >> HASH64K_ADJUST);
            }

            _last_literals:
            // Encode Last Literals
            int lastRun = (src_end - src_anchor);
            if (dst_p + lastRun + 1 + (lastRun - RUN_MASK + 255) / 255 > dst_end) {
                return 0;
            }
            if (lastRun >= RUN_MASK) {
                dst[dst_p++] = (RUN_MASK << ML_BITS);
                lastRun -= RUN_MASK;
                for (; lastRun > 254; lastRun -= 255) {
                    dst[dst_p++] = 255;
                }
                dst[dst_p++] = (byte) lastRun;
            } else {
                dst[dst_p++] = (byte) (lastRun << ML_BITS);
            }
            BlockCopy(src, src_anchor, dst, dst_p, src_end - src_anchor);
            dst_p += src_end - src_anchor;

            // End
            return ((dst_p) - dst_0);
        }

        #endregion

    #region LZ4_uncompress

        private static int LZ4_uncompress_safe32(
            byte[] src,
            byte[] dst,
            int src_0,
            int dst_0,
            int dst_len)
        {
            int[] dec32table = DECODER_TABLE_32;
            int _i;

            // ---- preprocessed source start here ----
            // r93
            int src_p = src_0;
            int dst_ref;

            int dst_p = dst_0;
            int dst_end = dst_p + dst_len;
            int dst_cpy;

            int dst_LASTLITERALS = dst_end - LASTLITERALS;
            int dst_COPYLENGTH = dst_end - COPYLENGTH;
            int dst_COPYLENGTH_STEPSIZE_4 = dst_end - COPYLENGTH - (STEPSIZE_32 - 4);

            byte token;

            // Main Loop
            while (true) {
                int length;

                // get runlength
                token = src[src_p++];
                if ((length = (token >> ML_BITS)) == RUN_MASK) {
                    int len;
                    for (; (len = src[src_p++]) == 255; length += 255) {
                        /* do nothing */
                    }
                    length += len;
                }

                // copy literals
                dst_cpy = dst_p + length;

                if (dst_cpy > dst_COPYLENGTH) {
                    if (dst_cpy != dst_end) {
                        goto _output_error; // Error : not enough place for another match (min 4) + 5 literals
                    }
                    BlockCopy(src, src_p, dst, dst_p, length);
                    src_p += length;
                    break; // EOF
                }
                if (dst_p < dst_cpy) {
                    _i = WildCopy(src, src_p, dst, dst_p, dst_cpy);
                    src_p += _i;
                    dst_p += _i;
                }
                src_p -= (dst_p - dst_cpy);
                dst_p = dst_cpy;

                // get offset
                dst_ref = (dst_cpy) - Peek2(src, src_p);
                src_p += 2;
                if (dst_ref < dst_0) {
                    goto _output_error; // Error : offset outside destination buffer
                }

                // get matchlength
                if ((length = (token & ML_MASK)) == ML_MASK) {
                    for (; src[src_p] == 255; length += 255) {
                        src_p++;
                    }
                    length += src[src_p++];
                }

                // copy repeated sequence
                if ((dst_p - dst_ref) < STEPSIZE_32) {
                    const int dec64 = 0;
                    dst[dst_p + 0] = dst[dst_ref + 0];
                    dst[dst_p + 1] = dst[dst_ref + 1];
                    dst[dst_p + 2] = dst[dst_ref + 2];
                    dst[dst_p + 3] = dst[dst_ref + 3];
                    dst_p += 4;
                    dst_ref += 4;
                    dst_ref -= dec32table[dst_p - dst_ref];
                    Copy4(dst, dst_ref, dst_p);
                    dst_p += STEPSIZE_32 - 4;
                    dst_ref -= dec64;
                } else {
                    Copy4(dst, dst_ref, dst_p);
                    dst_p += 4;
                    dst_ref += 4;
                }
                dst_cpy = dst_p + length - (STEPSIZE_32 - 4);

                if (dst_cpy > dst_COPYLENGTH_STEPSIZE_4) {
                    if (dst_cpy > dst_LASTLITERALS) {
                        goto _output_error; // Error : last 5 bytes must be literals
                    }
                    if (dst_p < dst_COPYLENGTH) {
                        _i = SecureCopy(dst, dst_ref, dst_p, dst_COPYLENGTH);
                        dst_ref += _i;
                        dst_p += _i;
                    }

                    while (dst_p < dst_cpy) {
                        dst[dst_p++] = dst[dst_ref++];
                    }
                    dst_p = dst_cpy;
                    continue;
                }

                if (dst_p < dst_cpy) {
                    SecureCopy(dst, dst_ref, dst_p, dst_cpy);
                }
                dst_p = dst_cpy; // correction
            }

            // end of decoding
            return ((src_p) - src_0);

            // write overflow error detected
            _output_error:
            return (-((src_p) - src_0));
        }

        #endregion

    #region LZ4_uncompress_unknownOutputSize

        private static int LZ4_uncompress_unknownOutputSize_safe32(
            byte[] src,
            byte[] dst,
            int src_0,
            int dst_0,
            int src_len,
            int dst_maxlen)
        {
            int[] dec32table = DECODER_TABLE_32;
            int _i;

            // ---- preprocessed source start here ----
            // r93
            int src_p = src_0;
            int src_end = src_p + src_len;
            int dst_ref;

            int dst_p = dst_0;
            int dst_end = dst_p + dst_maxlen;
            int dst_cpy;

            int src_LASTLITERALS_3 = (src_end - (2 + 1 + LASTLITERALS));
            int src_LASTLITERALS_1 = (src_end - (LASTLITERALS + 1));
            int dst_COPYLENGTH = (dst_end - COPYLENGTH);
            int dst_COPYLENGTH_STEPSIZE_4 = (dst_end - (COPYLENGTH + (STEPSIZE_32 - 4)));
            int dst_LASTLITERALS = (dst_end - LASTLITERALS);
            int dst_MFLIMIT = (dst_end - MFLIMIT);

            // Special case
            if (src_p == src_end) {
                goto _output_error; // A correctly formed null-compressed LZ4 must have at least one byte (token=0)
            }

            // Main Loop
            while (true) {
                byte token;
                int length;

                // get runlength
                token = src[src_p++];
                if ((length = (token >> ML_BITS)) == RUN_MASK) {
                    int s = 255;
                    while ((src_p < src_end) && (s == 255)) {
                        length += (s = src[src_p++]);
                    }
                }

                // copy literals
                dst_cpy = dst_p + length;

                if ((dst_cpy > dst_MFLIMIT) || (src_p + length > src_LASTLITERALS_3)) {
                    if (dst_cpy > dst_end) {
                        goto _output_error; // Error : writes beyond output buffer
                    }
                    if (src_p + length != src_end) {
                        goto _output_error;
                            // Error : LZ4 format requires to consume all input at this stage (no match within the last 11 bytes, and at least 8 remaining input bytes for another match+literals)
                    }
                    BlockCopy(src, src_p, dst, dst_p, length);
                    dst_p += length;
                    break; // Necessarily EOF, due to parsing restrictions
                }
                if (dst_p < dst_cpy) {
                    _i = WildCopy(src, src_p, dst, dst_p, dst_cpy);
                    src_p += _i;
                    dst_p += _i;
                }
                src_p -= (dst_p - dst_cpy);
                dst_p = dst_cpy;

                // get offset
                dst_ref = (dst_cpy) - Peek2(src, src_p);
                src_p += 2;
                if (dst_ref < dst_0) {
                    goto _output_error; // Error : offset outside of destination buffer
                }

                // get matchlength
                if ((length = (token & ML_MASK)) == ML_MASK) {
                    while (src_p < src_LASTLITERALS_1)
                        // Error : a minimum input bytes must remain for LASTLITERALS + token
                    {
                        int s = src[src_p++];
                        length += s;
                        if (s == 255) {
                            continue;
                        }
                        break;
                    }
                }

                // copy repeated sequence
                if (dst_p - dst_ref < STEPSIZE_32) {
                    const int dec64 = 0;
                    dst[dst_p + 0] = dst[dst_ref + 0];
                    dst[dst_p + 1] = dst[dst_ref + 1];
                    dst[dst_p + 2] = dst[dst_ref + 2];
                    dst[dst_p + 3] = dst[dst_ref + 3];
                    dst_p += 4;
                    dst_ref += 4;
                    dst_ref -= dec32table[dst_p - dst_ref];
                    Copy4(dst, dst_ref, dst_p);
                    dst_p += STEPSIZE_32 - 4;
                    dst_ref -= dec64;
                } else {
                    Copy4(dst, dst_ref, dst_p);
                    dst_p += 4;
                    dst_ref += 4;
                }
                dst_cpy = dst_p + length - (STEPSIZE_32 - 4);

                if (dst_cpy > dst_COPYLENGTH_STEPSIZE_4) {
                    if (dst_cpy > dst_LASTLITERALS) {
                        goto _output_error; // Error : last 5 bytes must be literals
                    }
                    if (dst_p < dst_COPYLENGTH) {
                        _i = SecureCopy(dst, dst_ref, dst_p, dst_COPYLENGTH);
                        dst_ref += _i;
                        dst_p += _i;
                    }

                    while (dst_p < dst_cpy) {
                        dst[dst_p++] = dst[dst_ref++];
                    }
                    dst_p = dst_cpy;
                    continue;
                }

                if (dst_p < dst_cpy) {
                    SecureCopy(dst, dst_ref, dst_p, dst_cpy);
                }
                dst_p = dst_cpy; // correction
            }

            // end of decoding
            return ((dst_p) - dst_0);

            // write overflow error detected
            _output_error:
            return (-((src_p) - src_0));
        }

        #endregion
    }
#endif
}

// ReSharper restore RedundantIfElseBlock
// ReSharper restore JoinDeclarationAndInitializer
// ReSharper restore TooWideLocalVariableScope
// ReSharper restore InconsistentNaming
// ReSharper restore CheckNamespace