text: /*
  ** 2001 September 22
  **
  ** The author disclaims copyright to this source code.  In place of
  ** a legal notice, here is a blessing:
  **
  **    May you do good and not evil.
  **    May you find forgiveness for yourself and forgive others.
  **    May you share freely, never taking more than you give.
  **
  *************************************************************************
  ** This is the implementation of generic hash-tables used in SQLite.
  ** We've modified it slightly to serve as a standalone hash table
  ** implementation for the full-text indexing module.
  */
  
  /*
  ** The code in this file is only compiled if:
  **
  **     * The FTS3 module is being built as an extension
  **       (in which case SQLITE_CORE is not defined), or
  **
  **     * The FTS3 module is being built into the core of
  **       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
  */
  #include "fts3Int.h"
  #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
  
  #include <assert.h>
  #include <stdlib.h>
  #include <string.h>
  
  #include "fts3_hash.h"
  
  /*
  ** Malloc and Free functions
  */
  static void *fts3HashMalloc(sqlite3_int64 n){
    void *p = sqlite3_malloc64(n);
    if( p ){
      memset(p, 0, n);
    }
    return p;
  }
  static void fts3HashFree(void *p){
    sqlite3_free(p);
  }
  
  /* Turn bulk memory into a hash table object by initializing the
  ** fields of the Hash structure.
  **
  ** "pNew" is a pointer to the hash table that is to be initialized.
  ** keyClass is one of the constants 
  ** FTS3_HASH_BINARY or FTS3_HASH_STRING.  The value of keyClass 
  ** determines what kind of key the hash table will use.  "copyKey" is
  ** true if the hash table should make its own private copy of keys and
  ** false if it should just use the supplied pointer.
  */
  void sqlite3Fts3HashInit(Fts3Hash *pNew, char keyClass, char copyKey){
    assert( pNew!=0 );
    assert( keyClass>=FTS3_HASH_STRING && keyClass<=FTS3_HASH_BINARY );
    pNew->keyClass = keyClass;
    pNew->copyKey = copyKey;
    pNew->first = 0;
    pNew->count = 0;
    pNew->htsize = 0;
    pNew->ht = 0;
  }
  
  /* Remove all entries from a hash table.  Reclaim all memory.
  ** Call this routine to delete a hash table or to reset a hash table
  ** to the empty state.
  */
  void sqlite3Fts3HashClear(Fts3Hash *pH){
    Fts3HashElem *elem;         /* For looping over all elements of the table */
  
    assert( pH!=0 );
    elem = pH->first;
    pH->first = 0;
    fts3HashFree(pH->ht);
    pH->ht = 0;
    pH->htsize = 0;
    while( elem ){
      Fts3HashElem *next_elem = elem->next;
      if( pH->copyKey && elem->pKey ){
        fts3HashFree(elem->pKey);
      }
      fts3HashFree(elem);
      elem = next_elem;
    }
    pH->count = 0;
  }
  
  /*
  ** Hash and comparison functions when the mode is FTS3_HASH_STRING
  */
  static int fts3StrHash(const void *pKey, int nKey){
    const char *z = (const char *)pKey;
    unsigned h = 0;
    if( nKey<=0 ) nKey = (int) strlen(z);
    while( nKey > 0  ){
      h = (h<<3) ^ h ^ *z++;
      nKey--;
    }
    return (int)(h & 0x7fffffff);
  }
  static int fts3StrCompare(const void *pKey1, int n1, const void *pKey2, int n2){
    if( n1!=n2 ) return 1;
    return strncmp((const char*)pKey1,(const char*)pKey2,n1);
  }
  
  /*
  ** Hash and comparison functions when the mode is FTS3_HASH_BINARY
  */
  static int fts3BinHash(const void *pKey, int nKey){
    int h = 0;
    const char *z = (const char *)pKey;
    while( nKey-- > 0 ){
      h = (h<<3) ^ h ^ *(z++);
    }
    return h & 0x7fffffff;
  }
  static int fts3BinCompare(const void *pKey1, int n1, const void *pKey2, int n2){
    if( n1!=n2 ) return 1;
    return memcmp(pKey1,pKey2,n1);
  }
  
  /*
  ** Return a pointer to the appropriate hash function given the key class.
  **
  ** The C syntax in this function definition may be unfamilar to some 
  ** programmers, so we provide the following additional explanation:
  **
  ** The name of the function is "ftsHashFunction".  The function takes a
  ** single parameter "keyClass".  The return value of ftsHashFunction()
  ** is a pointer to another function.  Specifically, the return value
  ** of ftsHashFunction() is a pointer to a function that takes two parameters
  ** with types "const void*" and "int" and returns an "int".
  */
  static int (*ftsHashFunction(int keyClass))(const void*,int){
    if( keyClass==FTS3_HASH_STRING ){
      return &fts3StrHash;
    }else{
      assert( keyClass==FTS3_HASH_BINARY );
      return &fts3BinHash;
    }
  }
  
  /*
  ** Return a pointer to the appropriate hash function given the key class.
  **
  ** For help in interpreted the obscure C code in the function definition,
  ** see the header comment on the previous function.
  */
  static int (*ftsCompareFunction(int keyClass))(const void*,int,const void*,int){
    if( keyClass==FTS3_HASH_STRING ){
      return &fts3StrCompare;
    }else{
      assert( keyClass==FTS3_HASH_BINARY );
      return &fts3BinCompare;
    }
  }
  
  /* Link an element into the hash table
  */
  static void fts3HashInsertElement(
    Fts3Hash *pH,            /* The complete hash table */
    struct _fts3ht *pEntry,  /* The entry into which pNew is inserted */
    Fts3HashElem *pNew       /* The element to be inserted */
  ){
    Fts3HashElem *pHead;     /* First element already in pEntry */
    pHead = pEntry->chain;
    if( pHead ){
      pNew->next = pHead;
      pNew->prev = pHead->prev;
      if( pHead->prev ){ pHead->prev->next = pNew; }
      else             { pH->first = pNew; }
      pHead->prev = pNew;
    }else{
      pNew->next = pH->first;
      if( pH->first ){ pH->first->prev = pNew; }
      pNew->prev = 0;
      pH->first = pNew;
    }
    pEntry->count++;
    pEntry->chain = pNew;
  }
  
  
  /* Resize the hash table so that it cantains "new_size" buckets.
  ** "new_size" must be a power of 2.  The hash table might fail 
  ** to resize if sqliteMalloc() fails.
  **
  ** Return non-zero if a memory allocation error occurs.
  */
  static int fts3Rehash(Fts3Hash *pH, int new_size){
    struct _fts3ht *new_ht;          /* The new hash table */
    Fts3HashElem *elem, *next_elem;  /* For looping over existing elements */
    int (*xHash)(const void*,int);   /* The hash function */
  
    assert( (new_size & (new_size-1))==0 );
    new_ht = (struct _fts3ht *)fts3HashMalloc( new_size*sizeof(struct _fts3ht) );
    if( new_ht==0 ) return 1;
    fts3HashFree(pH->ht);
    pH->ht = new_ht;
    pH->htsize = new_size;
    xHash = ftsHashFunction(pH->keyClass);
    for(elem=pH->first, pH->first=0; elem; elem = next_elem){
      int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1);
      next_elem = elem->next;
      fts3HashInsertElement(pH, &new_ht[h], elem);
    }
    return 0;
  }
  
  /* This function (for internal use only) locates an element in an
  ** hash table that matches the given key.  The hash for this key has
  ** already been computed and is passed as the 4th parameter.
  */
  static Fts3HashElem *fts3FindElementByHash(
    const Fts3Hash *pH, /* The pH to be searched */
    const void *pKey,   /* The key we are searching for */
    int nKey,
    int h               /* The hash for this key. */
  ){
    Fts3HashElem *elem;            /* Used to loop thru the element list */
    int count;                     /* Number of elements left to test */
    int (*xCompare)(const void*,int,const void*,int);  /* comparison function */
  
    if( pH->ht ){
      struct _fts3ht *pEntry = &pH->ht[h];
      elem = pEntry->chain;
      count = pEntry->count;
      xCompare = ftsCompareFunction(pH->keyClass);
      while( count-- && elem ){
        if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){ 
          return elem;
        }
        elem = elem->next;
      }
    }
    return 0;
  }
  
  /* Remove a single entry from the hash table given a pointer to that
  ** element and a hash on the element's key.
  */
  static void fts3RemoveElementByHash(
    Fts3Hash *pH,         /* The pH containing "elem" */
    Fts3HashElem* elem,   /* The element to be removed from the pH */
    int h                 /* Hash value for the element */
  ){
    struct _fts3ht *pEntry;
    if( elem->prev ){
      elem->prev->next = elem->next; 
    }else{
      pH->first = elem->next;
    }
    if( elem->next ){
      elem->next->prev = elem->prev;
    }
    pEntry = &pH->ht[h];
    if( pEntry->chain==elem ){
      pEntry->chain = elem->next;
    }
    pEntry->count--;
    if( pEntry->count<=0 ){
      pEntry->chain = 0;
    }
    if( pH->copyKey && elem->pKey ){
      fts3HashFree(elem->pKey);
    }
    fts3HashFree( elem );
    pH->count--;
    if( pH->count<=0 ){
      assert( pH->first==0 );
      assert( pH->count==0 );
      fts3HashClear(pH);
    }
  }
  
  Fts3HashElem *sqlite3Fts3HashFindElem(
    const Fts3Hash *pH, 
    const void *pKey, 
    int nKey
  ){
    int h;                          /* A hash on key */
    int (*xHash)(const void*,int);  /* The hash function */
  
    if( pH==0 || pH->ht==0 ) return 0;
    xHash = ftsHashFunction(pH->keyClass);
    assert( xHash!=0 );
    h = (*xHash)(pKey,nKey);
    assert( (pH->htsize & (pH->htsize-1))==0 );
    return fts3FindElementByHash(pH,pKey,nKey, h & (pH->htsize-1));
  }
  
  /* 
  ** Attempt to locate an element of the hash table pH with a key
  ** that matches pKey,nKey.  Return the data for this element if it is
  ** found, or NULL if there is no match.
  */
  void *sqlite3Fts3HashFind(const Fts3Hash *pH, const void *pKey, int nKey){
    Fts3HashElem *pElem;            /* The element that matches key (if any) */
  
    pElem = sqlite3Fts3HashFindElem(pH, pKey, nKey);
    return pElem ? pElem->data : 0;
  }
  
  /* Insert an element into the hash table pH.  The key is pKey,nKey
  ** and the data is "data".
  **
  ** If no element exists with a matching key, then a new
  ** element is created.  A copy of the key is made if the copyKey
  ** flag is set.  NULL is returned.
  **
  ** If another element already exists with the same key, then the
  ** new data replaces the old data and the old data is returned.
  ** The key is not copied in this instance.  If a malloc fails, then
  ** the new data is returned and the hash table is unchanged.
  **
  ** If the "data" parameter to this function is NULL, then the
  ** element corresponding to "key" is removed from the hash table.
  */
  void *sqlite3Fts3HashInsert(
    Fts3Hash *pH,        /* The hash table to insert into */
    const void *pKey,    /* The key */
    int nKey,            /* Number of bytes in the key */
    void *data           /* The data */
  ){
    int hraw;                 /* Raw hash value of the key */
    int h;                    /* the hash of the key modulo hash table size */
    Fts3HashElem *elem;       /* Used to loop thru the element list */
    Fts3HashElem *new_elem;   /* New element added to the pH */
    int (*xHash)(const void*,int);  /* The hash function */
  
    assert( pH!=0 );
    xHash = ftsHashFunction(pH->keyClass);
    assert( xHash!=0 );
    hraw = (*xHash)(pKey, nKey);
    assert( (pH->htsize & (pH->htsize-1))==0 );
    h = hraw & (pH->htsize-1);
    elem = fts3FindElementByHash(pH,pKey,nKey,h);
    if( elem ){
      void *old_data = elem->data;
      if( data==0 ){
        fts3RemoveElementByHash(pH,elem,h);
      }else{
        elem->data = data;
      }
      return old_data;
    }
    if( data==0 ) return 0;
    if( (pH->htsize==0 && fts3Rehash(pH,8))
     || (pH->count>=pH->htsize && fts3Rehash(pH, pH->htsize*2))
    ){
      pH->count = 0;
      return data;
    }
    assert( pH->htsize>0 );
    new_elem = (Fts3HashElem*)fts3HashMalloc( sizeof(Fts3HashElem) );
    if( new_elem==0 ) return data;
    if( pH->copyKey && pKey!=0 ){
      new_elem->pKey = fts3HashMalloc( nKey );
      if( new_elem->pKey==0 ){
        fts3HashFree(new_elem);
        return data;
      }
      memcpy((void*)new_elem->pKey, pKey, nKey);
    }else{
      new_elem->pKey = (void*)pKey;
    }
    new_elem->nKey = nKey;
    pH->count++;
    assert( pH->htsize>0 );
    assert( (pH->htsize & (pH->htsize-1))==0 );
    h = hraw & (pH->htsize-1);
    fts3HashInsertElement(pH, &pH->ht[h], new_elem);
    new_elem->data = data;
    return 0;
  }
  
  #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
  