363 lines
10 KiB
C#
363 lines
10 KiB
C#
using System;
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using System.Diagnostics;
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using System.Text;
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using u8 = System.Byte;
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using u32 = System.UInt32;
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namespace Community.CsharpSqlite
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{
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public partial class Sqlite3
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{
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/*
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** 2001 September 22
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This is the implementation of generic hash-tables
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** used in SQLite.
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*************************************************************************
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** Included in SQLite3 port to C#-SQLite; 2008 Noah B Hart
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** C#-SQLite is an independent reimplementation of the SQLite software library
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**
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** SQLITE_SOURCE_ID: 2010-08-23 18:52:01 42537b60566f288167f1b5864a5435986838e3a3
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**
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*************************************************************************
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*/
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//#include "sqliteInt.h"
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//#include <assert.h>
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/* Turn bulk memory into a hash table object by initializing the
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** fields of the Hash structure.
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**
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** "pNew" is a pointer to the hash table that is to be initialized.
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*/
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static void sqlite3HashInit( Hash pNew )
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{
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Debug.Assert( pNew != null );
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pNew.first = null;
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pNew.count = 0;
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pNew.htsize = 0;
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pNew.ht = null;
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}
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/* Remove all entries from a hash table. Reclaim all memory.
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** Call this routine to delete a hash table or to reset a hash table
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** to the empty state.
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*/
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static void sqlite3HashClear( Hash pH )
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{
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HashElem elem; /* For looping over all elements of the table */
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Debug.Assert( pH != null );
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elem = pH.first;
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pH.first = null;
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//sqlite3_free( ref pH.ht );
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pH.ht = null;
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pH.htsize = 0;
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while ( elem != null )
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{
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HashElem next_elem = elem.next;
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////sqlite3_free(ref elem );
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elem = next_elem;
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}
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pH.count = 0;
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}
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/*
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** The hashing function.
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*/
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static u32 strHash( string z, int nKey )
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{
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int h = 0;
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Debug.Assert( nKey >= 0 );
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int _z = 0;
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while ( nKey > 0 )
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{
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h = ( h << 3 ) ^ h ^ ( ( _z < z.Length ) ? (int)sqlite3UpperToLower[(byte)z[_z++]] : 0 );
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nKey--;
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}
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return (u32)h;
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}
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/* Link pNew element into the hash table pH. If pEntry!=0 then also
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** insert pNew into the pEntry hash bucket.
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*/
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static void insertElement(
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Hash pH, /* The complete hash table */
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_ht pEntry, /* The entry into which pNew is inserted */
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HashElem pNew /* The element to be inserted */
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)
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{
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HashElem pHead; /* First element already in pEntry */
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if ( pEntry != null )
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{
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pHead = pEntry.count != 0 ? pEntry.chain : null;
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pEntry.count++;
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pEntry.chain = pNew;
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}
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else
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{
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pHead = null;
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}
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if ( pHead != null )
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{
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pNew.next = pHead;
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pNew.prev = pHead.prev;
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if ( pHead.prev != null )
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{
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pHead.prev.next = pNew;
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}
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else
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{
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pH.first = pNew;
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}
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pHead.prev = pNew;
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}
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else
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{
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pNew.next = pH.first;
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if ( pH.first != null )
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{
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pH.first.prev = pNew;
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}
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pNew.prev = null;
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pH.first = pNew;
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}
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}
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/* Resize the hash table so that it cantains "new_size" buckets.
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**
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** The hash table might fail to resize if sqlite3_malloc() fails or
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** if the new size is the same as the prior size.
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** Return TRUE if the resize occurs and false if not.
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*/
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static bool rehash( ref Hash pH, u32 new_size )
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{
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_ht[] new_ht; /* The new hash table */
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HashElem elem;
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HashElem next_elem; /* For looping over existing elements */
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#if SQLITE_MALLOC_SOFT_LIMIT
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if( new_size*sizeof(struct _ht)>SQLITE_MALLOC_SOFT_LIMIT ){
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new_size = SQLITE_MALLOC_SOFT_LIMIT/sizeof(struct _ht);
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}
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if( new_size==pH->htsize ) return false;
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#endif
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/* There is a call to sqlite3Malloc() inside rehash(). If there is
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** already an allocation at pH.ht, then if this malloc() fails it
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** is benign (since failing to resize a hash table is a performance
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** hit only, not a fatal error).
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*/
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sqlite3BeginBenignMalloc();
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new_ht = new _ht[new_size]; //(struct _ht )sqlite3Malloc( new_size*sizeof(struct _ht) );
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for ( int i = 0; i < new_size; i++ )
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new_ht[i] = new _ht();
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sqlite3EndBenignMalloc();
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if ( new_ht == null )
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return false;
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//sqlite3_free( ref pH.ht );
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pH.ht = new_ht;
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// pH.htsize = new_size = sqlite3MallocSize(new_ht)/sizeof(struct _ht);
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//memset(new_ht, 0, new_size*sizeof(struct _ht));
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pH.htsize = new_size;
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for ( elem = pH.first, pH.first = null; elem != null; elem = next_elem )
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{
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u32 h = strHash( elem.pKey, elem.nKey ) % new_size;
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next_elem = elem.next;
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insertElement( pH, new_ht[h], elem );
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}
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return true;
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}
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/* This function (for internal use only) locates an element in an
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** hash table that matches the given key. The hash for this key has
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** already been computed and is passed as the 4th parameter.
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*/
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static HashElem findElementGivenHash(
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Hash pH, /* The pH to be searched */
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string pKey, /* The key we are searching for */
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int nKey, /* Bytes in key (not counting zero terminator) */
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u32 h /* The hash for this key. */
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)
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{
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HashElem elem; /* Used to loop thru the element list */
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int count; /* Number of elements left to test */
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if ( pH.ht != null && pH.ht[h] != null )
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{
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_ht pEntry = pH.ht[h];
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elem = pEntry.chain;
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count = (int)pEntry.count;
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}
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else
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{
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elem = pH.first;
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count = (int)pH.count;
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}
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while ( count-- > 0 && ALWAYS( elem ) )
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{
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if ( elem.nKey == nKey && elem.pKey.Equals( pKey, StringComparison.OrdinalIgnoreCase ) )
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{
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return elem;
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}
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elem = elem.next;
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}
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return null;
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}
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/* Remove a single entry from the hash table given a pointer to that
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** element and a hash on the element's key.
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*/
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static void removeElementGivenHash(
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Hash pH, /* The pH containing "elem" */
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ref HashElem elem, /* The element to be removed from the pH */
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u32 h /* Hash value for the element */
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)
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{
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_ht pEntry;
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if ( elem.prev != null )
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{
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elem.prev.next = elem.next;
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}
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else
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{
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pH.first = elem.next;
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}
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if ( elem.next != null )
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{
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elem.next.prev = elem.prev;
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}
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if ( pH.ht != null && pH.ht[h] != null )
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{
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pEntry = pH.ht[h];
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if ( pEntry.chain == elem )
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{
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pEntry.chain = elem.next;
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}
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pEntry.count--;
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Debug.Assert( pEntry.count >= 0 );
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}
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//sqlite3_free( ref elem );
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pH.count--;
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if ( pH.count <= 0 )
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{
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Debug.Assert( pH.first == null );
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Debug.Assert( pH.count == 0 );
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sqlite3HashClear( pH );
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}
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}
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/* Attempt to locate an element of the hash table pH with a key
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** that matches pKey,nKey. Return the data for this element if it is
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** found, or NULL if there is no match.
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*/
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static T sqlite3HashFind<T>( Hash pH, string pKey, int nKey, T nullType ) where T : class
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{
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HashElem elem; /* The element that matches key */
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u32 h; /* A hash on key */
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Debug.Assert( pH != null );
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Debug.Assert( pKey != null );
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Debug.Assert( nKey >= 0 );
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if ( pH.ht != null )
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{
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h = strHash( pKey, nKey ) % pH.htsize;
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}
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else
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{
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h = 0;
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}
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elem = findElementGivenHash( pH, pKey, nKey, h );
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return elem != null ? (T)elem.data : nullType;
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}
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/* Insert an element into the hash table pH. The key is pKey,nKey
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** and the data is "data".
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**
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** If no element exists with a matching key, then a new
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** element is created and NULL is returned.
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**
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** If another element already exists with the same key, then the
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** new data replaces the old data and the old data is returned.
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** The key is not copied in this instance. If a malloc fails, then
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** the new data is returned and the hash table is unchanged.
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**
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** If the "data" parameter to this function is NULL, then the
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** element corresponding to "key" is removed from the hash table.
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*/
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static T sqlite3HashInsert<T>( ref Hash pH, string pKey, int nKey, T data ) where T : class
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{
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u32 h; /* the hash of the key modulo hash table size */
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HashElem elem; /* Used to loop thru the element list */
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HashElem new_elem; /* New element added to the pH */
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Debug.Assert( pH != null );
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Debug.Assert( pKey != null );
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Debug.Assert( nKey >= 0 );
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if ( pH.htsize != 0 )
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{
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h = strHash( pKey, nKey ) % pH.htsize;
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}
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else
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{
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h = 0;
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}
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elem = findElementGivenHash( pH, pKey, nKey, h );
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if ( elem != null )
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{
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T old_data = (T)elem.data;
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if ( data == null )
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{
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removeElementGivenHash( pH, ref elem, h );
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}
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else
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{
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elem.data = data;
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elem.pKey = pKey;
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Debug.Assert( nKey == elem.nKey );
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}
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return old_data;
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}
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if ( data == null )
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return data;
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new_elem = new HashElem();//(HashElem)sqlite3Malloc( sizeof(HashElem) );
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if ( new_elem == null )
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return data;
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new_elem.pKey = pKey;
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new_elem.nKey = nKey;
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new_elem.data = data;
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pH.count++;
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if ( pH.count >= 10 && pH.count > 2 * pH.htsize )
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{
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if ( rehash( ref pH, pH.count * 2 ) )
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{
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Debug.Assert( pH.htsize > 0 );
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h = strHash( pKey, nKey ) % pH.htsize;
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}
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}
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if ( pH.ht != null )
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{
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insertElement( pH, pH.ht[h], new_elem );
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}
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else
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{
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insertElement( pH, null, new_elem );
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}
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return null;
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}
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}
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}
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