SQLite

**    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.
**
** $Id: hash.c,v 1.35 2009/04/28 15:43:45 drh Exp $
*/
#include "sqliteInt.h"
#include <assert.h>

/* Turn bulk memory into a hash table object by initializing the
** fields of the Hash structure.
**

  }
  pH->count = 0;
}

/*
** Hash and comparison functions when the mode is SQLITE_HASH_STRING
*/
static unsigned int strHash(const void *pKey, int nKey){
  const char *z = (const char *)pKey;
  int h = 0;
  assert( nKey>0 );
  while( nKey > 0  ){
    h = (h<<3) ^ h ^ sqlite3UpperToLower[(unsigned char)*z++];
    nKey--;
  }
  return h;
}
static int strCompare(const void *pKey1, int n1, const void *pKey2, int n2){
  if( n1!=n2 ) return 1;
  return sqlite3StrNICmp((const char*)pKey1,(const char*)pKey2,n1);
}


/* Link pNew element into the hash table pH.  If pEntry!=0 then also
** insert pNew into the pEntry hash bucket.
*/
static void insertElement(
  Hash *pH,              /* The complete hash table */
  struct _ht *pEntry,    /* The entry into which pNew is inserted */
  HashElem *pNew         /* The element to be inserted */
){
  HashElem *pHead;       /* First element already in pEntry */
  if( pEntry ){
    pHead = pEntry->count ? pEntry->chain : 0;
    pEntry->count++;
    pEntry->chain = pNew;
  }else{
    pHead = 0;
  }
  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;
  }


}


/* Resize the hash table so that it cantains "new_size" buckets.
**
** The hash table might fail to resize if sqlite3_malloc() fails or
** if the new size is the same as the prior size.
** Return TRUE if the resize occurs and false if not.
*/
static int rehash(Hash *pH, unsigned int new_size){
  struct _ht *new_ht;            /* The new hash table */
  HashElem *elem, *next_elem;    /* For looping over existing elements */

#if SQLITE_MALLOC_SOFT_LIMIT>0
  if( new_size*sizeof(struct _ht)>SQLITE_MALLOC_SOFT_LIMIT ){
    new_size = SQLITE_MALLOC_SOFT_LIMIT/sizeof(struct _ht);
  }
  if( new_size==pH->htsize ) return 0;
#endif

  /* The inability to allocates space for a larger hash table is

  ** a performance hit but it is not a fatal error.  So mark the
  ** allocation as a benign.
  */
  sqlite3BeginBenignMalloc();
  new_ht = (struct _ht *)sqlite3Malloc( new_size*sizeof(struct _ht) );
  sqlite3EndBenignMalloc();

  if( new_ht==0 ) return 0;
  sqlite3_free(pH->ht);
  pH->ht = new_ht;
  pH->htsize = new_size = sqlite3MallocSize(new_ht)/sizeof(struct _ht);
  memset(new_ht, 0, new_size*sizeof(struct _ht));
  for(elem=pH->first, pH->first=0; elem; elem = next_elem){
    unsigned int h = strHash(elem->pKey, elem->nKey) % new_size;
    next_elem = elem->next;
    insertElement(pH, &new_ht[h], elem);
  }
  return 1;
}

/* 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 HashElem *findElementGivenHash(
  const Hash *pH,     /* The pH to be searched */
  const void *pKey,   /* The key we are searching for */
  int nKey,           /* Bytes in key (not counting zero terminator) */
  unsigned int h      /* The hash for this key. */
){
  HashElem *elem;                /* Used to loop thru the element list */
  int count;                     /* Number of elements left to test */

  if( pH->ht ){
    struct _ht *pEntry = &pH->ht[h];
    elem = pEntry->chain;
    count = pEntry->count;
  }else{
    elem = pH->first;
    count = pH->count;
  }
  while( count-- && ALWAYS(elem) ){
    if( strCompare(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 removeElementGivenHash(
  Hash *pH,         /* The pH containing "elem" */
  HashElem* elem,   /* The element to be removed from the pH */
  unsigned int h    /* Hash value for the element */
){
  struct _ht *pEntry;
  if( elem->prev ){
    elem->prev->next = elem->next; 
  }else{
    pH->first = elem->next;
  }
  if( elem->next ){
    elem->next->prev = elem->prev;
  }
  if( pH->ht ){
    pEntry = &pH->ht[h];
    if( pEntry->chain==elem ){
      pEntry->chain = elem->next;
    }
    pEntry->count--;
    assert( pEntry->count>=0 );

  }
  if( pH->copyKey ){
    sqlite3_free(elem->pKey);
  }
  sqlite3_free( elem );
  pH->count--;
  if( pH->count<=0 ){
    assert( pH->first==0 );
    assert( pH->count==0 );
    sqlite3HashClear(pH);
  }
}
















/* 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 *sqlite3HashFind(const Hash *pH, const void *pKey, int nKey){
  HashElem *elem;    /* The element that matches key */
  unsigned int h;    /* A hash on key */

  assert( pH!=0 );
  assert( pKey!=0 );
  assert( nKey>0 );
  if( pH->ht ){
    h = strHash(pKey, nKey) % pH->htsize;
  }else{
    h = 0;
  }
  elem = findElementGivenHash(pH, pKey, nKey, h);
  return elem ? elem->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 *sqlite3HashInsert(Hash *pH, const void *pKey, int nKey, void *data){

  unsigned int h;       /* the hash of the key modulo hash table size */
  HashElem *elem;       /* Used to loop thru the element list */
  HashElem *new_elem;   /* New element added to the pH */

  assert( pH!=0 );
  assert( pKey!=0 );
  assert( nKey>0 );
  if( pH->htsize ){
    h = strHash(pKey, nKey) % pH->htsize;
  }else{
    h = 0;
  }
  elem = findElementGivenHash(pH,pKey,nKey,h);
  if( elem ){
    void *old_data = elem->data;
    if( data==0 ){
      removeElementGivenHash(pH,elem,h);
    }else{
      elem->data = data;
      if( !pH->copyKey ){
        elem->pKey = (void *)pKey;
      }
      assert(nKey==elem->nKey);
    }
    return old_data;
  }

  if( data==0 ) return 0;
  new_elem = (HashElem*)sqlite3Malloc( sizeof(HashElem) );
  if( new_elem==0 ) return data;
  if( pH->copyKey ){
    new_elem->pKey = sqlite3Malloc( nKey );
    if( new_elem->pKey==0 ){
      sqlite3_free(new_elem);
      return data;
    }
    memcpy((void*)new_elem->pKey, pKey, nKey);
  }else{
    new_elem->pKey = (void*)pKey;
  }
  new_elem->nKey = nKey;
  new_elem->data = data;
  pH->count++;
  if( pH->count>=10 && pH->count > 2*pH->htsize ){
    if( rehash(pH, pH->count*2) && pH->htsize ){
      h = strHash(pKey, nKey) % pH->htsize;



    }


  }

  if( pH->ht ){




    insertElement(pH, &pH->ht[h], new_elem);
  }else{
    insertElement(pH, 0, new_elem);
  }
  return 0;
}

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This is the header file for the generic hash-table implemenation
** used in SQLite.
**
** $Id: hash.h,v 1.13 2009/04/28 15:43:45 drh Exp $
*/
#ifndef _SQLITE_HASH_H_
#define _SQLITE_HASH_H_

/* Forward declarations of structures. */
typedef struct Hash Hash;
typedef struct HashElem HashElem;

/* A complete hash table is an instance of the following structure.
** The internals of this structure are intended to be opaque -- client
** code should not attempt to access or modify the fields of this structure
** directly.  Change this structure only by using the routines below.
** However, some of the "procedures" and "functions" for modifying and
** accessing this structure are really macros, so we can't really make
** this structure opaque.
**
** All elements of the hash table are on a single doubly-linked list.
** Hash.first points to the head of this list.
**
** There are Hash.htsize buckets.  Each bucket points to a spot in
** the global doubly-linked list.  The contents of the bucket are the
** element pointed to plus the next _ht.count-1 elements in the list.
**
** Hash.htsize and Hash.ht may be zero.  In that case lookup is done
** by a linear search of the global list.  For small tables, the 
** Hash.ht table is never allocated because if there are few elements
** in the table, it is faster to do a linear search than to manage
** the hash table.
*/
struct Hash {
  unsigned int copyKey : 1; /* True if copy of key made on insert */
  unsigned int htsize : 31; /* Number of buckets in the hash table */
  unsigned int count;       /* Number of entries in this table */
  HashElem *first;          /* The first element of the array */
  struct _ht {              /* the hash table */
    int count;                 /* Number of entries with this hash */
    HashElem *chain;           /* Pointer to first entry with this hash */
  } *ht;

**     SomeStructure *pData = sqliteHashData(p);
**     // do something with pData
**   }
*/
#define sqliteHashFirst(H)  ((H)->first)
#define sqliteHashNext(E)   ((E)->next)
#define sqliteHashData(E)   ((E)->data)
/* #define sqliteHashKey(E)    ((E)->pKey) // NOT USED */
/* #define sqliteHashKeysize(E) ((E)->nKey)  // NOT USED */

/*
** Number of entries in a hash table
*/
/* #define sqliteHashCount(H)  ((H)->count) // NOT USED */

#endif /* _SQLITE_HASH_H_ */

/*
** 2001 September 15
**
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.862 2009/04/28 15:43:45 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Include the configuration header output by 'configure' if we're using the
** autoconf-based build

#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)+\
    defined(SQLITE_MEMORY_SIZE)+defined(SQLITE_MMAP_HEAP_SIZE)+\
    defined(SQLITE_POW2_MEMORY_SIZE)==0
# define SQLITE_SYSTEM_MALLOC 1
#endif

/*
** If SQLITE_MALLOC_SOFT_LIMIT is not zero, then try to keep the
** sizes of memory allocations below this value where possible.
*/
#if !defined(SQLITE_MALLOC_SOFT_LIMIT)
# define SQLITE_MALLOC_SOFT_LIMIT 1024
#endif

/*
** We need to define _XOPEN_SOURCE as follows in order to enable
** recursive mutexes on most Unix systems.  But Mac OS X is different.
** The _XOPEN_SOURCE define causes problems for Mac OS X we are told,

# 2001 September 15
#
# 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 file implements regression tests for SQLite library.  The
# focus of this file is testing the CREATE TABLE statement.
#
# $Id: table.test,v 1.51 2009/04/28 15:43:45 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Create a basic table and verify it is added to sqlite_master
#
do_test table-1.1 {

do_test table-2.1d {
  catchsql {CREATE TABLE IF NOT EXISTS test2(x,y)}
} {0 {}}
do_test table-2.1e {
  catchsql {CREATE TABLE IF NOT EXISTS test2(x UNIQUE, y TEXT PRIMARY KEY)}
} {0 {}}
do_test table-2.1f {
breakpoint
  execsql {DROP TABLE test2; SELECT name FROM sqlite_master WHERE type!='meta'}
} {}

# Verify that we cannot make a table with the same name as an index
#
do_test table-2.2a {
  execsql {CREATE TABLE test2(one text)}
  execsql {CREATE INDEX test3 ON test2(one)}
  catchsql {CREATE TABLE test3(two text)}

} {1 {there is already an index named test3}}
do_test table-2.2b {
  db close
  sqlite3 db test.db
  set v [catch {execsql {CREATE TABLE test3(two text)}} msg]
  lappend v $msg
} {1 {there is already an index named test3}}