/*
 * expand_block_v2.c - LZSA2 block decompressor implementation
 *
 * Copyright (C) 2019 Emmanuel Marty
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */

/*
 * Uses the libdivsufsort library Copyright (c) 2003-2008 Yuta Mori
 *
 * Inspired by LZ4 by Yann Collet. https://github.com/lz4/lz4
 * With help, ideas, optimizations and speed measurements by spke <zxintrospec@gmail.com>
 * With ideas from Lizard by Przemyslaw Skibinski and Yann Collet. https://github.com/inikep/lizard
 * Also with ideas from smallz4 by Stephan Brumme. https://create.stephan-brumme.com/smallz4/
 *
 */

#include <stdlib.h>
#include <string.h>
#include "format.h"
#include "expand_block_v2.h"

#ifdef _MSC_VER
#define FORCE_INLINE __forceinline
#else /* _MSC_VER */
#define FORCE_INLINE __attribute__((always_inline))
#endif /* _MSC_VER */

static inline FORCE_INLINE unsigned int lzsa_get_nibble_v2(const unsigned char **ppInBlock, const unsigned char *pInBlockEnd, int *nCurNibbles, unsigned char *nibbles, unsigned int *nValue) {
   if ((*nCurNibbles ^= 1) != 0) {
      const unsigned char *pInBlock = *ppInBlock;
      if (pInBlock < pInBlockEnd) {
         (*nibbles) = *pInBlock++;
         *ppInBlock = pInBlock;
         (*nValue) = ((unsigned int)((*nibbles) & 0xf0)) >> 4;
         return 0;
      }
      else {
         return -1;
      }
   }

   (*nValue) = (unsigned int)((*nibbles) & 0x0f);
   return 0;
}

static inline FORCE_INLINE int lzsa_build_len_v2(const unsigned char **ppInBlock, const unsigned char *pInBlockEnd, int *nCurNibbles, unsigned char *nibbles, unsigned int *nLength) {
   unsigned int nValue;

   if (!lzsa_get_nibble_v2(ppInBlock, pInBlockEnd, nCurNibbles, nibbles, &nValue)) {
      (*nLength) += nValue;

      if (nValue == 15) {
         const unsigned char *pInBlock = *ppInBlock;

         if (pInBlock < pInBlockEnd) {
            (*nLength) += ((unsigned int)*pInBlock++);

            if ((*nLength) == 257) {
               if ((pInBlock + 1) < pInBlockEnd) {
                  (*nLength) = ((unsigned int)*pInBlock++);
                  (*nLength) |= (((unsigned int)*pInBlock++) << 8);
               }
               else {
                  return -1;
               }
            }
            else if ((*nLength) == 256) {
               (*nLength) = 0;
            }
         }
         else {
            return -1;
         }

         *ppInBlock = pInBlock;
      }

      return 0;
   }
   else {
      return -1;
   }
}

/**
 * Decompress one LZSA2 data block
 *
 * @param pInBlock pointer to compressed data
 * @param nBlockSize size of compressed data, in bytes
 * @param pOutData pointer to output decompression buffer (previously decompressed bytes + room for decompressing this block)
 * @param nOutDataOffset starting index of where to store decompressed bytes in output buffer (and size of previously decompressed bytes)
 * @param nBlockMaxSize total size of output decompression buffer, in bytes
 *
 * @return size of decompressed data in bytes, or -1 for error
 */
int lzsa_decompressor_expand_block_v2(const unsigned char *pInBlock, const int nBlockSize, unsigned char *pOutData, const int nOutDataOffset, const int nBlockMaxSize) {
   const unsigned char *pInBlockEnd = pInBlock + nBlockSize;
   unsigned char *pCurOutData = pOutData + nOutDataOffset;
   const unsigned char *pOutDataEnd = pCurOutData + nBlockMaxSize;
   const unsigned char *pOutDataFastEnd = pOutDataEnd - 20;
   int nCurNibbles = 0;
   unsigned char nibbles;
   int nMatchOffset = 0;

   while (pInBlock < pInBlockEnd) {
      const unsigned char token = *pInBlock++;
      unsigned int nLiterals = (unsigned int)((token & 0x18) >> 3);

      if (nLiterals != LITERALS_RUN_LEN_V2 && (pInBlock + 4) <= pInBlockEnd && pCurOutData < pOutDataFastEnd) {
         memcpy(pCurOutData, pInBlock, 4);
         pInBlock += nLiterals;
         pCurOutData += nLiterals;
      }
      else {
         if (nLiterals == LITERALS_RUN_LEN_V2) {
            if (lzsa_build_len_v2(&pInBlock, pInBlockEnd, &nCurNibbles, &nibbles, &nLiterals))
               return -1;
         }

         if (nLiterals != 0) {
            if ((pInBlock + nLiterals) <= pInBlockEnd &&
               (pCurOutData + nLiterals) <= pOutDataEnd) {
               memcpy(pCurOutData, pInBlock, nLiterals);
               pInBlock += nLiterals;
               pCurOutData += nLiterals;
            }
            else {
               return -1;
            }
         }
      }

      if (pInBlock < pInBlockEnd) { /* The last token in the block does not include match information */
         const unsigned char nOffsetMode = token & 0xc0;
         unsigned int nValue;

         switch (nOffsetMode) {
         case 0x00:
            /* 5 bit offset */
            if (lzsa_get_nibble_v2(&pInBlock, pInBlockEnd, &nCurNibbles, &nibbles, &nValue))
               return -1;
            nMatchOffset = nValue << 1;
            nMatchOffset |= ((token & 0x20) >> 5);
            nMatchOffset ^= 0x1e;
            nMatchOffset++;
            break;

         case 0x40:
            /* 9 bit offset */
            nMatchOffset = (unsigned int)(*pInBlock++);
            nMatchOffset |= (((unsigned int)(token & 0x20)) << 3);
            nMatchOffset ^= 0x0ff;
            nMatchOffset++;
            break;

         case 0x80:
            /* 13 bit offset */
            if (lzsa_get_nibble_v2(&pInBlock, pInBlockEnd, &nCurNibbles, &nibbles, &nValue))
               return -1;
            nMatchOffset = (unsigned int)(*pInBlock++);
            nMatchOffset |= (nValue << 9);
            nMatchOffset |= (((unsigned int)(token & 0x20)) << 3);
            nMatchOffset ^= 0x1eff;
            nMatchOffset += (512 + 1);
            break;

         default:
            /* Check if this is a 16 bit offset or a rep-match */
            if ((token & 0x20) == 0) {
               /* 16 bit offset */
               nMatchOffset = (((unsigned int)(*pInBlock++)) << 8);
               if (pInBlock >= pInBlockEnd) return -1;
               nMatchOffset |= (unsigned int)(*pInBlock++);
               nMatchOffset ^= 0xffff;
               nMatchOffset++;
            }
            break;
         }

         const unsigned char *pSrc = pCurOutData - nMatchOffset;
         if (pSrc >= pOutData) {
            unsigned int nMatchLen = (unsigned int)(token & 0x07);
            if (nMatchLen != MATCH_RUN_LEN_V2 && nMatchOffset >= 8 && pCurOutData < pOutDataFastEnd && (pSrc + 10) <= pOutDataEnd) {
               memcpy(pCurOutData, pSrc, 8);
               memcpy(pCurOutData + 8, pSrc + 8, 2);
               pCurOutData += (MIN_MATCH_SIZE_V2 + nMatchLen);
            }
            else {
               nMatchLen += MIN_MATCH_SIZE_V2;
               if (nMatchLen == (MATCH_RUN_LEN_V2 + MIN_MATCH_SIZE_V2)) {
                  if (lzsa_build_len_v2(&pInBlock, pInBlockEnd, &nCurNibbles, &nibbles, &nMatchLen))
                     return -1;
                  if (nMatchLen == 0)
                     break;
               }

               if ((pSrc + nMatchLen) <= pOutDataEnd) {
                  if ((pCurOutData + nMatchLen) <= pOutDataEnd) {
                     /* Do a deterministic, left to right byte copy instead of memcpy() so as to handle overlaps */

                     if (nMatchOffset >= 16 && (pCurOutData + nMatchLen) < (pOutDataFastEnd - 15)) {
                        const unsigned char *pCopySrc = pSrc;
                        unsigned char *pCopyDst = pCurOutData;
                        const unsigned char *pCopyEndDst = pCurOutData + nMatchLen;

                        do {
                           memcpy(pCopyDst, pCopySrc, 16);
                           pCopySrc += 16;
                           pCopyDst += 16;
                        } while (pCopyDst < pCopyEndDst);

                        pCurOutData += nMatchLen;
                     }
                     else {
                        while (nMatchLen) {
                           *pCurOutData++ = *pSrc++;
                           nMatchLen--;
                        }
                     }
                  }
                  else {
                     return -1;
                  }
               }
               else {
                  return -1;
               }
            }
         }
         else {
            return -1;
         }
      }
   }

   return (int)(pCurOutData - (pOutData + nOutDataOffset));
}