// File: lzham_match_accel.cpp
// See Copyright Notice and license at the end of include/lzham.h
#include "lzham_core.h"
#include "lzham_match_accel.h"
#include "lzham_timer.h"

namespace lzham
{
   static inline uint32 hash2_to_12(uint c0, uint c1)
   {
      return c0 ^ (c1 << 4);
   }

   static inline uint32 hash3_to_16(uint c0, uint c1, uint c2)
   {
      return (c0 | (c1 << 8)) ^ (c2 << 4);
   }

   search_accelerator::search_accelerator() :
      m_pLZBase(NULL),
      m_pTask_pool(NULL),
      m_max_helper_threads(0),
      m_max_dict_size(0),
      m_max_dict_size_mask(0),
      m_lookahead_pos(0),
      m_lookahead_size(0),
      m_cur_dict_size(0),
      m_fill_lookahead_pos(0),
      m_fill_lookahead_size(0),
      m_fill_dict_size(0),
      m_max_probes(0),
      m_max_matches(0),
      m_all_matches(false),
      m_next_match_ref(0),
      m_num_completed_helper_threads(0)
   {
   }

   bool search_accelerator::init(CLZBase* pLZBase, task_pool* pPool, uint max_helper_threads, uint max_dict_size, uint max_matches, bool all_matches, uint max_probes)
   {
      LZHAM_ASSERT(pLZBase);
      LZHAM_ASSERT(max_dict_size && math::is_power_of_2(max_dict_size));
      LZHAM_ASSERT(max_probes);

      m_max_probes = LZHAM_MIN(cMatchAccelMaxSupportedProbes, max_probes);

      m_pLZBase = pLZBase;
      m_pTask_pool = max_helper_threads ? pPool : NULL;
      m_max_helper_threads = m_pTask_pool ? max_helper_threads : 0;
      m_max_matches = LZHAM_MIN(m_max_probes, max_matches);
      m_all_matches = all_matches;

      m_max_dict_size = max_dict_size;
      m_max_dict_size_mask = m_max_dict_size - 1;
      m_cur_dict_size = 0;
      m_lookahead_size = 0;
      m_lookahead_pos = 0;
      m_fill_lookahead_pos = 0;
      m_fill_lookahead_size = 0;
      m_fill_dict_size = 0;
      m_num_completed_helper_threads = 0;

      if (!m_dict.try_resize_no_construct(max_dict_size + LZHAM_MIN(m_max_dict_size, static_cast<uint>(CLZBase::cMaxHugeMatchLen))))
         return false;

      if (!m_hash.try_resize_no_construct(cHashSize))
         return false;

      if (!m_nodes.try_resize_no_construct(max_dict_size))
         return false;

      memset(m_hash.get_ptr(), 0, m_hash.size_in_bytes());

      return true;
   }

   void search_accelerator::reset()
   {
      m_cur_dict_size = 0;
      m_lookahead_size = 0;
      m_lookahead_pos = 0;
      m_fill_lookahead_pos = 0;
      m_fill_lookahead_size = 0;
      m_fill_dict_size = 0;
      m_num_completed_helper_threads = 0;

      // Clearing the hash tables is only necessary for determinism (otherwise, it's possible the matches returned after a reset will depend on the data processes before the reset).
      if (m_hash.size()) 
         memset(m_hash.get_ptr(), 0, m_hash.size_in_bytes());
      if (m_digram_hash.size())
         memset(m_digram_hash.get_ptr(), 0, m_digram_hash.size_in_bytes());
   }

   void search_accelerator::flush()
   {
      m_cur_dict_size = 0;
   }

   uint search_accelerator::get_max_add_bytes() const
   {
      uint add_pos = static_cast<uint>(m_lookahead_pos & (m_max_dict_size - 1));
      return m_max_dict_size - add_pos;
   }

   static uint8 g_hamming_dist[256] =
   {
      0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
      1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
      1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
      1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
      3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
      1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
      3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
      3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
      3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
      4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
   };

   void search_accelerator::find_all_matches_callback(uint64 data, void* pData_ptr)
   {
      scoped_perf_section find_all_matches_timer("find_all_matches_callback");

      LZHAM_NOTE_UNUSED(pData_ptr);
      const uint thread_index = (uint)data;

      dict_match temp_matches[cMatchAccelMaxSupportedProbes * 2];

      uint fill_lookahead_pos = m_fill_lookahead_pos;
      uint fill_dict_size = m_fill_dict_size;
      uint fill_lookahead_size = m_fill_lookahead_size;

      uint c0 = 0, c1 = 0;
      if (fill_lookahead_size >= 2)
      {
         c0 = m_dict[fill_lookahead_pos & m_max_dict_size_mask];
         c1 = m_dict[(fill_lookahead_pos & m_max_dict_size_mask) + 1];
      }

      const uint8* pDict = m_dict.get_ptr();

      while (fill_lookahead_size >= 3)
      {
         uint insert_pos = fill_lookahead_pos & m_max_dict_size_mask;

         uint c2 = pDict[insert_pos + 2];
         uint h = hash3_to_16(c0, c1, c2);
         c0 = c1;
         c1 = c2;

         LZHAM_ASSERT(!m_hash_thread_index.size() || (m_hash_thread_index[h] != UINT8_MAX));

         // Only process those strings that this worker thread was assigned to - this allows us to manipulate multiple trees in parallel with no worries about synchronization.
         if (m_hash_thread_index.size() && (m_hash_thread_index[h] != thread_index))
         {
            fill_lookahead_pos++;
            fill_lookahead_size--;
            fill_dict_size++;
            continue;
         }

         dict_match* pDstMatch = temp_matches;

         uint cur_pos = m_hash[h];
         m_hash[h] = static_cast<uint>(fill_lookahead_pos);

         uint *pLeft = &m_nodes[insert_pos].m_left;
         uint *pRight = &m_nodes[insert_pos].m_right;

         const uint max_match_len = LZHAM_MIN(static_cast<uint>(CLZBase::cMaxMatchLen), fill_lookahead_size);
         uint best_match_len = 2;

         const uint8* pIns = &pDict[insert_pos];

         uint n = m_max_probes;
         for ( ; ; )
         {
            uint delta_pos = fill_lookahead_pos - cur_pos;
            if ((n-- == 0) || (!delta_pos) || (delta_pos >= fill_dict_size))
            {
               *pLeft = 0;
               *pRight = 0;
               break;
            }

            uint pos = cur_pos & m_max_dict_size_mask;
            node *pNode = &m_nodes[pos];

            // Unfortunately, the initial compare match_len must be 0 because of the way we hash and truncate matches at the end of each block.
            uint match_len = 0;
            const uint8* pComp = &pDict[pos];

#if LZHAM_PLATFORM_X360
            for ( ; match_len < max_match_len; match_len++)
               if (pComp[match_len] != pIns[match_len])
                  break;
#else
            // Compare a qword at a time for a bit more efficiency.
            const uint64* pComp_end = reinterpret_cast<const uint64*>(pComp + max_match_len - 7);
            const uint64* pComp_cur = reinterpret_cast<const uint64*>(pComp);
            const uint64* pIns_cur = reinterpret_cast<const uint64*>(pIns);
            while (pComp_cur < pComp_end)
            {
               if (*pComp_cur != *pIns_cur)
                  break;
               pComp_cur++;
               pIns_cur++;
            }
            uint alt_match_len = static_cast<uint>(reinterpret_cast<const uint8*>(pComp_cur) - reinterpret_cast<const uint8*>(pComp));
            for ( ; alt_match_len < max_match_len; alt_match_len++)
               if (pComp[alt_match_len] != pIns[alt_match_len])
                  break;
#ifdef LZVERIFY
            for ( ; match_len < max_match_len; match_len++)
               if (pComp[match_len] != pIns[match_len])
                  break;
            LZHAM_VERIFY(alt_match_len == match_len);
#endif
            match_len = alt_match_len;
#endif

            if (match_len > best_match_len)
            {
               pDstMatch->m_len = static_cast<uint16>(match_len - CLZBase::cMinMatchLen);
               pDstMatch->m_dist = delta_pos;
               pDstMatch++;

               best_match_len = match_len;

               if (match_len == max_match_len)
               {
                  *pLeft = pNode->m_left;
                  *pRight = pNode->m_right;
                  break;
               }
            }
            else if (m_all_matches)
            {
               pDstMatch->m_len = static_cast<uint16>(match_len - CLZBase::cMinMatchLen);
               pDstMatch->m_dist = delta_pos;
               pDstMatch++;
            }
            else if ((best_match_len > 2) && (best_match_len == match_len))
            {
               uint bestMatchDist = pDstMatch[-1].m_dist;
               uint compMatchDist = delta_pos;

               uint bestMatchSlot, bestMatchSlotOfs;
               m_pLZBase->compute_lzx_position_slot(bestMatchDist, bestMatchSlot, bestMatchSlotOfs);

               uint compMatchSlot, compMatchOfs;
               m_pLZBase->compute_lzx_position_slot(compMatchDist, compMatchSlot, compMatchOfs);

               // If both matches uses the same match slot, choose the one with the offset containing the lowest nibble as these bits separately entropy coded.
               // This could choose a match which is further away in the absolute sense, but closer in a coding sense.
               if ( (compMatchSlot < bestMatchSlot) ||
                  ((compMatchSlot >= 8) && (compMatchSlot == bestMatchSlot) && ((compMatchOfs & 15) < (bestMatchSlotOfs & 15))) )
               {
                  LZHAM_ASSERT((pDstMatch[-1].m_len + (uint)CLZBase::cMinMatchLen) == best_match_len);
                  pDstMatch[-1].m_dist = delta_pos;
               }
               else if ((match_len < max_match_len) && (compMatchSlot <= bestMatchSlot))
               {
                  // Choose the match which has lowest hamming distance in the mismatch byte for a tiny win on binary files.
                  // TODO: This competes against the prev. optimization.
                  uint desired_mismatch_byte = pIns[match_len];

                  uint cur_mismatch_byte = pDict[(insert_pos - bestMatchDist + match_len) & m_max_dict_size_mask];
                  uint cur_mismatch_dist = g_hamming_dist[cur_mismatch_byte ^ desired_mismatch_byte];

                  uint new_mismatch_byte = pComp[match_len];
                  uint new_mismatch_dist = g_hamming_dist[new_mismatch_byte ^ desired_mismatch_byte];
                  if (new_mismatch_dist < cur_mismatch_dist)
                  {
                     LZHAM_ASSERT((pDstMatch[-1].m_len + (uint)CLZBase::cMinMatchLen) == best_match_len);
                     pDstMatch[-1].m_dist = delta_pos;
                  }
               }
            }

            uint new_pos;
            if (pComp[match_len] < pIns[match_len])
            {
               *pLeft = cur_pos;
               pLeft = &pNode->m_right;
               new_pos = pNode->m_right;
            }
            else
            {
               *pRight = cur_pos;
               pRight = &pNode->m_left;
               new_pos = pNode->m_left;
            }
            if (new_pos == cur_pos)
               break;
            cur_pos = new_pos;
         }

         const uint num_matches = (uint)(pDstMatch - temp_matches);

         if (num_matches)
         {
            pDstMatch[-1].m_dist |= 0x80000000;

            const uint num_matches_to_write = LZHAM_MIN(num_matches, m_max_matches);

            const uint match_ref_ofs = atomic_exchange_add(&m_next_match_ref, num_matches_to_write);

            memcpy(&m_matches[match_ref_ofs],
                   temp_matches + (num_matches - num_matches_to_write),
                   sizeof(temp_matches[0]) * num_matches_to_write);

            // FIXME: This is going to really hurt on platforms requiring export barriers.
            LZHAM_MEMORY_EXPORT_BARRIER

            atomic_exchange32((atomic32_t*)&m_match_refs[static_cast<uint>(fill_lookahead_pos - m_fill_lookahead_pos)], match_ref_ofs);
         }
         else
         {
            atomic_exchange32((atomic32_t*)&m_match_refs[static_cast<uint>(fill_lookahead_pos - m_fill_lookahead_pos)], -2);
         }

         fill_lookahead_pos++;
         fill_lookahead_size--;
         fill_dict_size++;
      }

      while (fill_lookahead_size)
      {
         uint insert_pos = fill_lookahead_pos & m_max_dict_size_mask;
         m_nodes[insert_pos].m_left = 0;
         m_nodes[insert_pos].m_right = 0;

         atomic_exchange32((atomic32_t*)&m_match_refs[static_cast<uint>(fill_lookahead_pos - m_fill_lookahead_pos)], -2);

         fill_lookahead_pos++;
         fill_lookahead_size--;
         fill_dict_size++;
      }
      
      atomic_increment32(&m_num_completed_helper_threads);
   }

   bool search_accelerator::find_len2_matches()
   {
      if (!m_digram_hash.size())
      {
         if (!m_digram_hash.try_resize(cDigramHashSize))
            return false;
      }

      if (m_digram_next.size() < m_lookahead_size)
      {
         if (!m_digram_next.try_resize(m_lookahead_size))
            return false;
      }

      uint lookahead_dict_pos = m_lookahead_pos & m_max_dict_size_mask;

      for (int lookahead_ofs = 0; lookahead_ofs < ((int)m_lookahead_size - 1); ++lookahead_ofs, ++lookahead_dict_pos)
      {
         uint c0 = m_dict[lookahead_dict_pos];
         uint c1 = m_dict[lookahead_dict_pos + 1];

         uint h = hash2_to_12(c0, c1) & (cDigramHashSize - 1);

         m_digram_next[lookahead_ofs] = m_digram_hash[h];
         m_digram_hash[h] = m_lookahead_pos + lookahead_ofs;
      }

      m_digram_next[m_lookahead_size - 1] = 0;

      return true;
   }

   uint search_accelerator::get_len2_match(uint lookahead_ofs)
   {
      if ((m_fill_lookahead_size - lookahead_ofs) < 2)
         return 0;

      uint cur_pos = m_lookahead_pos + lookahead_ofs;

      uint next_match_pos = m_digram_next[cur_pos - m_fill_lookahead_pos];

      uint match_dist = cur_pos - next_match_pos;

      if ((!match_dist) || (match_dist > CLZBase::cMaxLen2MatchDist) || (match_dist > (m_cur_dict_size + lookahead_ofs)))
         return 0;

      const uint8* pCur = &m_dict[cur_pos & m_max_dict_size_mask];
      const uint8* pMatch = &m_dict[next_match_pos & m_max_dict_size_mask];

      if ((pCur[0] == pMatch[0]) && (pCur[1] == pMatch[1]))
         return match_dist;

      return 0;
   }

   bool search_accelerator::find_all_matches(uint num_bytes)
   {
      if (!m_matches.try_resize_no_construct(m_max_probes * num_bytes))
         return false;

      if (!m_match_refs.try_resize_no_construct(num_bytes))
         return false;

      memset(m_match_refs.get_ptr(), 0xFF, m_match_refs.size_in_bytes());

      m_fill_lookahead_pos = m_lookahead_pos;
      m_fill_lookahead_size = num_bytes;
      m_fill_dict_size = m_cur_dict_size;

      m_next_match_ref = 0;

      if (!m_pTask_pool)
      {
         find_all_matches_callback(0, NULL);
         
         m_num_completed_helper_threads = 0;
      }
      else
      {
         if (!m_hash_thread_index.try_resize_no_construct(0x10000))
            return false;

         memset(m_hash_thread_index.get_ptr(), 0xFF, m_hash_thread_index.size_in_bytes());

         uint next_thread_index = 0;
         const uint8* pDict = &m_dict[m_lookahead_pos & m_max_dict_size_mask];
         uint num_unique_trigrams = 0;

         if (num_bytes >= 3)
         {
            uint c0 = pDict[0];
            uint c1 = pDict[1];

            const int limit = ((int)num_bytes - 2);
            for (int i = 0; i < limit; i++)
            {
               uint c2 = pDict[2];
               uint t = hash3_to_16(c0, c1, c2);
               c0 = c1;
               c1 = c2;

               pDict++;

               if (m_hash_thread_index[t] == UINT8_MAX)
               {
                  num_unique_trigrams++;

                  m_hash_thread_index[t] = static_cast<uint8>(next_thread_index);
                  if (++next_thread_index == m_max_helper_threads)
                        next_thread_index = 0;
               }
            }
         }
         
         m_num_completed_helper_threads = 0;

         if (!m_pTask_pool->queue_multiple_object_tasks(this, &search_accelerator::find_all_matches_callback, 0, m_max_helper_threads))
            return false;
      }

      return find_len2_matches();
   }

   bool search_accelerator::add_bytes_begin(uint num_bytes, const uint8* pBytes)
   {
      LZHAM_ASSERT(num_bytes <= m_max_dict_size);
      LZHAM_ASSERT(!m_lookahead_size);

      uint add_pos = m_lookahead_pos & m_max_dict_size_mask;
      LZHAM_ASSERT((add_pos + num_bytes) <= m_max_dict_size);

      memcpy(&m_dict[add_pos], pBytes, num_bytes);

      uint dict_bytes_to_mirror = LZHAM_MIN(static_cast<uint>(CLZBase::cMaxHugeMatchLen), m_max_dict_size);
      if (add_pos < dict_bytes_to_mirror)
         memcpy(&m_dict[m_max_dict_size], &m_dict[0], dict_bytes_to_mirror);

      m_lookahead_size = num_bytes;

      uint max_possible_dict_size = m_max_dict_size - num_bytes;
      m_cur_dict_size = LZHAM_MIN(m_cur_dict_size, max_possible_dict_size);

      m_next_match_ref = 0;

      return find_all_matches(num_bytes);
   }

   void search_accelerator::add_bytes_end()
   {
      if (m_pTask_pool)
      {
         m_pTask_pool->join();
      }

      LZHAM_ASSERT((uint)m_next_match_ref <= m_matches.size());
   }

   dict_match* search_accelerator::find_matches(uint lookahead_ofs, bool spin)
   {
      LZHAM_ASSERT(lookahead_ofs < m_lookahead_size);

      const uint match_ref_ofs = static_cast<uint>(m_lookahead_pos - m_fill_lookahead_pos + lookahead_ofs);

      int match_ref;
      uint spin_count = 0;

      // This may spin until the match finder job(s) catch up to the caller's lookahead position.
      for ( ; ; )
      {
         match_ref = m_match_refs[match_ref_ofs];
         if (match_ref == -2)
            return NULL;
         else if (match_ref != -1)
            break;

         spin_count++;
         const uint cMaxSpinCount = 1000;
         if ((spin) && (spin_count < cMaxSpinCount))
         {
            lzham_yield_processor();
            lzham_yield_processor();
            lzham_yield_processor();
            lzham_yield_processor();
            lzham_yield_processor();
            lzham_yield_processor();
            lzham_yield_processor();
            lzham_yield_processor();

            LZHAM_MEMORY_IMPORT_BARRIER
         }
         else
         {
            spin_count = cMaxSpinCount;

            lzham_sleep(1);
         }
      }

      LZHAM_MEMORY_IMPORT_BARRIER

      return &m_matches[match_ref];
   }

   void search_accelerator::advance_bytes(uint num_bytes)
   {
      LZHAM_ASSERT(num_bytes <= m_lookahead_size);

      m_lookahead_pos += num_bytes;
      m_lookahead_size -= num_bytes;

      m_cur_dict_size += num_bytes;
      LZHAM_ASSERT(m_cur_dict_size <= m_max_dict_size);
   }
}