text: // Copyright 2013 Google Inc. All Rights Reserved.
  //
  // 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.
  
  //
  // Author: dsites@google.com (Dick Sites)
  //
  
  #include "cldutil.h"
  #include <string>
  
  #include "cld2tablesummary.h"
  #include "integral_types.h"
  #include "port.h"
  #include "utf8statetable.h"
  
  namespace CLD2 {
  
  // Caller supplies the right tables in scoringcontext
  
  // Runtime routines for hashing, looking up, and scoring
  // unigrams (CJK), bigrams (CJK), quadgrams, and octagrams.
  // Unigrams and bigrams are for CJK languages only, including simplified/
  // traditional Chinese, Japanese, Korean, Vietnamese Han characters, and
  // Zhuang Han characters. Surrounding spaces are not considered.
  // Quadgrams and octagrams for for non-CJK and include two bits indicating
  // preceding and trailing spaces (word boundaries).
  
  
  static const int kMinCJKUTF8CharBytes = 3;
  
  static const int kMinGramCount = 3;
  static const int kMaxGramCount = 16;
  
  static const int UTFmax = 4;        // Max number of bytes in a UTF-8 character
  
    // 1 to skip ASCII space, vowels AEIOU aeiou and UTF-8 continuation bytes 80-BF
    static const uint8 kSkipSpaceVowelContinue[256] = {
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
      1,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
      0,1,0,0,0,1,0,0, 0,1,0,0,0,0,0,1, 0,0,0,0,0,1,0,0, 0,0,0,0,0,0,0,0,
      0,1,0,0,0,1,0,0, 0,1,0,0,0,0,0,1, 0,0,0,0,0,1,0,0, 0,0,0,0,0,0,0,0,
  
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
    };
  
    // 1 to skip ASCII space, and UTF-8 continuation bytes 80-BF
    static const uint8 kSkipSpaceContinue[256] = {
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
      1,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
  
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
    };
  
  
    // Always advances one UTF-8 character
    static const uint8 kAdvanceOneChar[256] = {
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
  
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2,
      3,3,3,3,3,3,3,3, 3,3,3,3,3,3,3,3, 4,4,4,4,4,4,4,4, 4,4,4,4,4,4,4,4,
    };
  
    // Advances *only* on space (or illegal byte)
    static const uint8 kAdvanceOneCharSpace[256] = {
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      1,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
  
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
      0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
    };
  
  
  // Routines to access a hash table of <key:wordhash, value:probs> pairs
  // Buckets have 4-byte wordhash for sizes < 32K buckets, but only
  // 2-byte wordhash for sizes >= 32K buckets, with other wordhash bits used as
  // bucket subscript.
  // Probs is a packed: three languages plus a subscript for probability table
  // Buckets have all the keys together, then all the values.Key array never
  // crosses a cache-line boundary, so no-match case takes exactly one cache miss.
  // Match case may sometimes take an additional cache miss on value access.
  //
  // Other possibilites include 5 or 10 6-byte entries plus pad to make 32 or 64
  // byte buckets with single cache miss.
  // Or 2-byte key and 6-byte value, allowing 5 languages instead  of three.
  //------------------------------------------------------------------------------
  
  //----------------------------------------------------------------------------//
  // Hashing groups of 1/2/4/8 letters, perhaps with spaces or underscores      //
  //----------------------------------------------------------------------------//
  
  //----------------------------------------------------------------------------//
  // Scoring single groups of letters                                           //
  //----------------------------------------------------------------------------//
  
  // BIGRAM, QUADGRAM, OCTAGRAM score one => tote
  // Input: 4-byte entry of 3 language numbers and one probability subscript, plus
  //  an accumulator tote. (language 0 means unused entry)
  // Output: running sums in tote updated
  void ProcessProbV2Tote(uint32 probs, Tote* tote) {
    uint8 prob123 = (probs >> 0) & 0xff;
    const uint8* prob123_entry = LgProb2TblEntry(prob123);
  
    uint8 top1 = (probs >> 8) & 0xff;
    if (top1 > 0) {tote->Add(top1, LgProb3(prob123_entry, 0));}
    uint8 top2 = (probs >> 16) & 0xff;
    if (top2 > 0) {tote->Add(top2, LgProb3(prob123_entry, 1));}
    uint8 top3 = (probs >> 24) & 0xff;
    if (top3 > 0) {tote->Add(top3, LgProb3(prob123_entry, 2));}
  }
  
  // Return score for a particular per-script language, or zero
  int GetLangScore(uint32 probs, uint8 pslang) {
    uint8 prob123 = (probs >> 0) & 0xff;
    const uint8* prob123_entry = LgProb2TblEntry(prob123);
    int retval = 0;
    uint8 top1 = (probs >> 8) & 0xff;
    if (top1 == pslang) {retval += LgProb3(prob123_entry, 0);}
    uint8 top2 = (probs >> 16) & 0xff;
    if (top2 == pslang) {retval += LgProb3(prob123_entry, 1);}
    uint8 top3 = (probs >> 24) & 0xff;
    if (top3 == pslang) {retval += LgProb3(prob123_entry, 2);}
    return retval;
  }
  
  //----------------------------------------------------------------------------//
  // Routines to accumulate probabilities                                       //
  //----------------------------------------------------------------------------//
  
  
  // BIGRAM, using hash table, always advancing by 1 char
  // Caller supplies table, such as &kCjkBiTable_obj or &kGibberishTable_obj
  // Score all bigrams in isrc, using languages that have bigrams (CJK)
  // Return number of bigrams that hit in the hash table
  int DoBigramScoreV3(const CLD2TableSummary* bigram_obj,
                           const char* isrc, int srclen, Tote* chunk_tote) {
    int hit_count = 0;
    const char* src = isrc;
  
    // Hashtable-based CJK bigram lookup
    const uint8* usrc = reinterpret_cast<const uint8*>(src);
    const uint8* usrclimit1 = usrc + srclen - UTFmax;
  
    while (usrc < usrclimit1) {
      int len = kAdvanceOneChar[usrc[0]];
      int len2 = kAdvanceOneChar[usrc[len]] + len;
  
      if ((kMinCJKUTF8CharBytes * 2) <= len2) {      // Two CJK chars possible
        // Lookup and score this bigram
        // Always ignore pre/post spaces
        uint32 bihash = BiHashV2(reinterpret_cast<const char*>(usrc), len2);
        uint32 probs = QuadHashV3Lookup4(bigram_obj, bihash);
        // Now go indirect on the subscript
        probs = bigram_obj->kCLDTableInd[probs &
          ~bigram_obj->kCLDTableKeyMask];
  
        // Process the bigram
        if (probs != 0) {
          ProcessProbV2Tote(probs, chunk_tote);
          ++hit_count;
        }
      }
      usrc += len;  // Advance by one char
    }
  
    return hit_count;
  }
  
  
  // Score up to 64KB of a single script span in one pass
  // Make a dummy entry off the end to calc length of last span
  // Return offset of first unused input byte
  int GetUniHits(const char* text,
                       int letter_offset, int letter_limit,
                       ScoringContext* scoringcontext,
                       ScoringHitBuffer* hitbuffer) {
    const char* isrc = &text[letter_offset];
    const char* src = isrc;
    // Limit is end, which has extra 20 20 20 00 past len
    const char* srclimit = &text[letter_limit];
  
    // Local copies
    const UTF8PropObj* unigram_obj =
      scoringcontext->scoringtables->unigram_obj;
    int next_base = hitbuffer->next_base;
    int next_base_limit = hitbuffer->maxscoringhits;
  
    // Visit all unigrams
    if (src[0] == ' ') {++src;}   // skip any initial space
    while (src < srclimit) {
      const uint8* usrc = reinterpret_cast<const uint8*>(src);
      int len = kAdvanceOneChar[usrc[0]];
      src += len;
      // Look up property of one UTF-8 character and advance over it.
      // Updates usrc and len (bad interface design), hence increment above
      int propval = UTF8GenericPropertyBigOneByte(unigram_obj, &usrc, &len);
      if (propval > 0) {
        // Save indirect subscript for later scoring; 1 or 2 langprobs
        int indirect_subscr = propval;
        hitbuffer->base[next_base].offset = src - text;     // Offset in text
        hitbuffer->base[next_base].indirect = indirect_subscr;
        ++next_base;
      }
  
      if (next_base >= next_base_limit) {break;}
    }
  
    hitbuffer->next_base = next_base;
  
    // Make a dummy entry off the end to calc length of last span
    int dummy_offset = src - text;
    hitbuffer->base[hitbuffer->next_base].offset = dummy_offset;
    hitbuffer->base[hitbuffer->next_base].indirect = 0;
  
    return src - text;
  }
  
  // Score up to 64KB of a single script span, doing both delta-bi and
  // distinct bis in one pass
  void GetBiHits(const char* text,
                       int letter_offset, int letter_limit,
                       ScoringContext* scoringcontext,
                       ScoringHitBuffer* hitbuffer) {
    const char* isrc = &text[letter_offset];
    const char* src = isrc;
    // Limit is end
    const char* srclimit1 = &text[letter_limit];
  
    // Local copies
    const CLD2TableSummary* deltabi_obj =
      scoringcontext->scoringtables->deltabi_obj;
    const CLD2TableSummary* distinctbi_obj =
      scoringcontext->scoringtables->distinctbi_obj;
    int next_delta = hitbuffer->next_delta;
    int next_delta_limit = hitbuffer->maxscoringhits;
    int next_distinct = hitbuffer->next_distinct;
    // We can do 2 inserts per loop, so -1
    int next_distinct_limit = hitbuffer->maxscoringhits - 1;
  
    while (src < srclimit1) {
      const uint8* usrc = reinterpret_cast<const uint8*>(src);
      int len = kAdvanceOneChar[usrc[0]];
      int len2 = kAdvanceOneChar[usrc[len]] + len;
  
      if ((kMinCJKUTF8CharBytes * 2) <= len2) {      // Two CJK chars possible
        // Lookup and this bigram and save <offset, indirect>
        uint32 bihash = BiHashV2(src, len2);
        uint32 probs = QuadHashV3Lookup4(deltabi_obj, bihash);
        // Now go indirect on the subscript
        if (probs != 0) {
          // Save indirect subscript for later scoring; 1 langprob
          int indirect_subscr = probs & ~deltabi_obj->kCLDTableKeyMask;
          hitbuffer->delta[next_delta].offset = src - text;
          hitbuffer->delta[next_delta].indirect = indirect_subscr;
          ++next_delta;
        }
        // Lookup this distinct bigram and save <offset, indirect>
        probs = QuadHashV3Lookup4(distinctbi_obj, bihash);
        if (probs != 0) {
          int indirect_subscr = probs & ~distinctbi_obj->kCLDTableKeyMask;
          hitbuffer->distinct[next_distinct].offset = src - text;
          hitbuffer->distinct[next_distinct].indirect = indirect_subscr;
          ++next_distinct;
        }
      }
      src += len;  // Advance by one char (not two)
  
      // Almost always srclimit hit first
      if (next_delta >= next_delta_limit) {break;}
      if (next_distinct >= next_distinct_limit) {break;}
    }
  
    hitbuffer->next_delta = next_delta;
    hitbuffer->next_distinct = next_distinct;
  
    // Make a dummy entry off the end to calc length of last span
    int dummy_offset = src - text;
    hitbuffer->delta[hitbuffer->next_delta].offset = dummy_offset;
    hitbuffer->delta[hitbuffer->next_delta].indirect = 0;
    hitbuffer->distinct[hitbuffer->next_distinct].offset = dummy_offset;
    hitbuffer->distinct[hitbuffer->next_distinct].indirect = 0;
  }
  
  // Score up to 64KB of a single script span in one pass
  // Make a dummy entry off the end to calc length of last span
  // Return offset of first unused input byte
  int GetQuadHits(const char* text,
                       int letter_offset, int letter_limit,
                       ScoringContext* scoringcontext,
                       ScoringHitBuffer* hitbuffer) {
    const char* isrc = &text[letter_offset];
    const char* src = isrc;
    // Limit is end, which has extra 20 20 20 00 past len
    const char* srclimit = &text[letter_limit];
  
    // Local copies
    const CLD2TableSummary* quadgram_obj =
      scoringcontext->scoringtables->quadgram_obj;
    int next_base = hitbuffer->next_base;
    int next_base_limit = hitbuffer->maxscoringhits;
  
    // Run a little cache of last quad hits to catch overly-repetitive "text"
    // We don't care if we miss a couple repetitions at scriptspan boundaries
    int next_prior_quadhash = 0;
    uint32 prior_quadhash[2] = {0, 0};
  
    // Visit all quadgrams
    if (src[0] == ' ') {++src;}   // skip any initial space
    while (src < srclimit) {
      // Find one quadgram
      const char* src_end = src;
      src_end += kAdvanceOneCharButSpace[(uint8)src_end[0]];
      src_end += kAdvanceOneCharButSpace[(uint8)src_end[0]];
      const char* src_mid = src_end;
      src_end += kAdvanceOneCharButSpace[(uint8)src_end[0]];
      src_end += kAdvanceOneCharButSpace[(uint8)src_end[0]];
      int len = src_end - src;
      // Hash the quadgram
      uint32 quadhash = QuadHashV2(src, len);
  
      // Filter out recent repeats
      if ((quadhash != prior_quadhash[0]) && (quadhash != prior_quadhash[1])) {
        // Look up this quadgram and save <offset, indirect>
        uint32 probs = QuadHashV3Lookup4(quadgram_obj, quadhash);
        if (probs != 0) {
          // Round-robin two entries of actual hits
          prior_quadhash[next_prior_quadhash] = quadhash;
          next_prior_quadhash = (next_prior_quadhash + 1) & 1;
  
          // Save indirect subscript for later scoring; 1 or 2 langprobs
          int indirect_subscr = probs & ~quadgram_obj->kCLDTableKeyMask;
          hitbuffer->base[next_base].offset = src - text;     // Offset in text
          hitbuffer->base[next_base].indirect = indirect_subscr;
          ++next_base;
        }
      }
  
      // Advance: all the way past word if at end-of-word, else 2 chars
      if (src_end[0] == ' ') {
        src = src_end;
      } else {
        src = src_mid;
      }
  
      // Skip over space at end of word, or ASCII vowel in middle of word
      // Use kAdvanceOneCharSpace instead to get rid of vowel hack
      if (src < srclimit) {
        src += kAdvanceOneCharSpaceVowel[(uint8)src[0]];
      } else {
        // Advancing by 4/8/16 can overshoot, but we are about to exit anyway
        src = srclimit;
      }
  
      if (next_base >= next_base_limit) {break;}
    }
  
    hitbuffer->next_base = next_base;
  
    // Make a dummy entry off the end to calc length of last span
    int dummy_offset = src - text;
    hitbuffer->base[hitbuffer->next_base].offset = dummy_offset;
    hitbuffer->base[hitbuffer->next_base].indirect = 0;
  
    return src - text;
  }
  
  // inputs:
  //  const tables
  //  const char* isrc, int srclen (in sscriptbuffer)
  // intermediates:
  //  vector of octa <offset, probs>   (which need quadgram_obj indirect tbale ot decode)
  //  vector of distinct <offset, probs>   (which need quadgram_obj indirect tbale ot decode)
  
  // Score up to 64KB of a single script span, doing both delta-octa and
  // distinct words in one pass
  void GetOctaHits(const char* text,
                       int letter_offset, int letter_limit,
                       ScoringContext* scoringcontext,
                       ScoringHitBuffer* hitbuffer) {
    const char* isrc = &text[letter_offset];
    const char* src = isrc;
    // Limit is end+1, to include extra space char (0x20) off the end
    const char* srclimit = &text[letter_limit + 1];
  
    // Local copies
    const CLD2TableSummary* deltaocta_obj =
      scoringcontext->scoringtables->deltaocta_obj;
    int next_delta = hitbuffer->next_delta;
    int next_delta_limit = hitbuffer->maxscoringhits;
  
    const CLD2TableSummary* distinctocta_obj =
      scoringcontext->scoringtables->distinctocta_obj;
    int next_distinct = hitbuffer->next_distinct;
    // We can do 2 inserts per loop, so -1
    int next_distinct_limit = hitbuffer->maxscoringhits - 1;
  
    // Run a little cache of last octa hits to catch overly-repetitive "text"
    // We don't care if we miss a couple repetitions at scriptspan boundaries
    int next_prior_octahash = 0;
    uint64 prior_octahash[2] = {0, 0};
  
    // Score all words truncated to 8 characters
    int charcount = 0;
    // Skip any initial space
    if (src[0] == ' ') {++src;}
  
    // Begin the first word
    const char* prior_word_start = src;
    const char* word_start = src;
    const char* word_end = word_start;
    while (src < srclimit) {
      // Terminate previous word or continue current word
      if (src[0] == ' ') {
        int len = word_end - word_start;
        // Hash the word
        uint64 wordhash40 = OctaHash40(word_start, len);
        uint32 probs;
  
        // Filter out recent repeats. Unlike quads, we update even if no hit,
        // so we can get hits on same word if separated by non-hit words
        if ((wordhash40 != prior_octahash[0]) &&
            (wordhash40 != prior_octahash[1])) {
          // Round-robin two entries of words
          prior_octahash[next_prior_octahash] = wordhash40;
          next_prior_octahash = 1 - next_prior_octahash;    // Alternates 0,1,0,1
  
          // (1) Lookup distinct word PAIR. For a pair, we want an asymmetrical
          // function of the two word hashs. For words A B C, B-A and C-B are good
          // enough and fast. We use the same table as distinct single words
          // Do not look up a pair of identical words -- all pairs hash to zero
          // Both 1- and 2-word distinct lookups are in distinctocta_obj now
          // Do this first, because it has the lowest offset
          uint64 tmp_prior_hash = prior_octahash[next_prior_octahash];
          if ((tmp_prior_hash != 0) && (tmp_prior_hash != wordhash40)) {
            uint64 pair_hash = PairHash(tmp_prior_hash, wordhash40);
            probs = OctaHashV3Lookup4(distinctocta_obj, pair_hash);
            if (probs != 0) {
              int indirect_subscr = probs & ~distinctocta_obj->kCLDTableKeyMask;
              hitbuffer->distinct[next_distinct].offset = prior_word_start - text;
              hitbuffer->distinct[next_distinct].indirect = indirect_subscr;
              ++next_distinct;
            }
          }
  
          // (2) Lookup this distinct word and save <offset, indirect>
          probs = OctaHashV3Lookup4(distinctocta_obj, wordhash40);
          if (probs != 0) {
            int indirect_subscr = probs & ~distinctocta_obj->kCLDTableKeyMask;
            hitbuffer->distinct[next_distinct].offset = word_start - text;
            hitbuffer->distinct[next_distinct].indirect = indirect_subscr;
            ++next_distinct;
          }
  
          // (3) Lookup this word and save <offset, indirect>
          probs = OctaHashV3Lookup4(deltaocta_obj, wordhash40);
          if (probs != 0) {
            // Save indirect subscript for later scoring; 1 langprob
            int indirect_subscr = probs & ~deltaocta_obj->kCLDTableKeyMask;
            hitbuffer->delta[next_delta].offset = word_start - text;
            hitbuffer->delta[next_delta].indirect = indirect_subscr;
            ++next_delta;
          }
        }
  
        // Begin the next word
        charcount = 0;
        prior_word_start = word_start;
        word_start = src + 1;   // Over the space
        word_end = word_start;
      } else {
        ++charcount;
      }
  
      // Advance to next char
      src += UTF8OneCharLen(src);
      if (charcount <= 8) {
        word_end = src;
      }
      // Almost always srclimit hit first
      if (next_delta >= next_delta_limit) {break;}
      if (next_distinct >= next_distinct_limit) {break;}
    }
  
    hitbuffer->next_delta = next_delta;
    hitbuffer->next_distinct = next_distinct;
  
    // Make a dummy entry off the end to calc length of last span
    int dummy_offset = src - text;
    hitbuffer->delta[hitbuffer->next_delta].offset = dummy_offset;
    hitbuffer->delta[hitbuffer->next_delta].indirect = 0;
    hitbuffer->distinct[hitbuffer->next_distinct].offset = dummy_offset;
    hitbuffer->distinct[hitbuffer->next_distinct].indirect = 0;
  }
  
  
  //----------------------------------------------------------------------------//
  // Reliability calculations, for single language and between languages        //
  //----------------------------------------------------------------------------//
  
  // Return reliablity of result 0..100 for top two scores
  // delta==0 is 0% reliable, delta==fully_reliable_thresh is 100% reliable
  // (on a scale where +1 is a factor of  2 ** 1.6 = 3.02)
  // Threshold is uni/quadgram increment count, bounded above and below.
  //
  // Requiring a factor of 3 improvement (e.g. +1 log base 3)
  // for each scored quadgram is too stringent, so I've backed this off to a
  // factor of 2 (e.g. +5/8 log base 3).
  //
  // I also somewhat lowered the Min/MaxGramCount limits above
  //
  // Added: if fewer than 8 quads/unis, max reliability is 12*n percent
  //
  int ReliabilityDelta(int value1, int value2, int gramcount) {
    int max_reliability_percent = 100;
    if (gramcount < 8) {
      max_reliability_percent = 12 * gramcount;
    }
    int fully_reliable_thresh = (gramcount * 5) >> 3;     // see note above
    if (fully_reliable_thresh < kMinGramCount) {          // Fully = 3..16
      fully_reliable_thresh = kMinGramCount;
    } else if (fully_reliable_thresh > kMaxGramCount) {
      fully_reliable_thresh = kMaxGramCount;
    }
  
    int delta = value1 - value2;
    if (delta >= fully_reliable_thresh) {return max_reliability_percent;}
    if (delta <= 0) {return 0;}
    return minint(max_reliability_percent,
                       (100 * delta) / fully_reliable_thresh);
  }
  
  // Return reliablity of result 0..100 for top score vs. expected mainsteam score
  // Values are score per 1024 bytes of input
  // ratio = max(top/mainstream, mainstream/top)
  // ratio > 4.0 is 0% reliable, <= 2.0 is 100% reliable
  // Change: short-text word scoring can give unusually good results.
  //  Let top exceed mainstream by 4x at 50% reliable
  //
  // dsites April 2010: These could be tightened up. It would be
  // reasonable with newer data and round-robin table allocation to start ramping
  // down at mean * 1.5 and mean/1.5, while letting mean*2 and mean/2 pass,
  // but just barely.
  //
  // dsites March 2013: Tightened up a bit.
  static const double kRatio100 = 1.5;
  static const double kRatio0 = 4.0;
  int ReliabilityExpected(int actual_score_1kb, int expected_score_1kb) {
    if (expected_score_1kb == 0) {return 100;}    // No reliability data available yet
    if (actual_score_1kb == 0) {return 0;}        // zero score = unreliable
    double ratio;
    if (expected_score_1kb > actual_score_1kb) {
      ratio = (1.0 * expected_score_1kb) / actual_score_1kb;
    } else {
      ratio = (1.0 * actual_score_1kb) / expected_score_1kb;
    }
    // Ratio 1.0 .. 1.5 scores 100%
    // Ratio 2.0 scores 80%
    // Linear decline, to ratio 4.0 scores 0%
    if (ratio <= kRatio100) {return 100;}
    if (ratio > kRatio0) {return 0;}
  
    int percent_good = 100.0 * (kRatio0 - ratio) / (kRatio0 - kRatio100);
    return percent_good;
  }
  
  // Create a langprob packed value from its parts.
  // qprob is quantized [0..12]
  // We use Latn script to represent any RTypeMany language
  uint32 MakeLangProb(Language lang, int qprob) {
    uint32 pslang = PerScriptNumber(ULScript_Latin, lang);
    uint32 retval = (pslang << 8) | kLgProbV2TblBackmap[qprob];
    return retval;
  }
  
  }       // End namespace CLD2
  
  
  
  
  
  