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/* hasher.cpp
*
* Defines a simple hash function class
*/
/**
* Copyright (C) 2012 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/db/hasher.h"
#include "mongo/db/jsobj.h"
#include "mongo/util/startup_test.h"
namespace mongo {
Hasher::Hasher( HashSeed seed ) : _seed( seed ) {
md5_init( &_md5State );
md5_append( &_md5State , reinterpret_cast< const md5_byte_t * >( & _seed ) , sizeof( _seed ) );
}
void Hasher::addData( const void * keyData , size_t numBytes ) {
md5_append( &_md5State , static_cast< const md5_byte_t * >( keyData ), numBytes );
}
void Hasher::finish( HashDigest out ) {
md5_finish( &_md5State , out );
}
long long int BSONElementHasher::hash64( const BSONElement& e , HashSeed seed ){
scoped_ptr<Hasher> h( HasherFactory::createHasher( seed ) );
recursiveHash( h.get() , e , false );
HashDigest d;
h->finish(d);
//HashDigest is actually 16 bytes, but we just get 8 via truncation
// NOTE: assumes little-endian
return *reinterpret_cast< long long int * >( d );
}
void BSONElementHasher::recursiveHash( Hasher* h ,
const BSONElement& e ,
bool includeFieldName ) {
int canonicalType = e.canonicalType();
h->addData( &canonicalType , sizeof( canonicalType ) );
if ( includeFieldName ){
h->addData( e.fieldName() , e.fieldNameSize() );
}
if ( !e.mayEncapsulate() ){
//if there are no embedded objects (subobjects or arrays),
//compute the hash, squashing numeric types to 64-bit ints
if ( e.isNumber() ){
long long int i = e.safeNumberLong(); //well-defined for troublesome doubles
h->addData( &i , sizeof( i ) );
}
else {
h->addData( e.value() , e.valuesize() );
}
}
else {
//else identify the subobject.
//hash any preceding stuff (in the case of codeWscope)
//then each sub-element
//then finish with the EOO element.
BSONObj b;
if ( e.type() == CodeWScope ) {
h->addData( e.codeWScopeCode() , e.codeWScopeCodeLen() );
b = e.codeWScopeObject();
}
else {
b = e.embeddedObject();
}
BSONObjIterator i(b);
while( i.moreWithEOO() ) {
BSONElement el = i.next();
recursiveHash( h , el , true );
}
}
}
struct HasherUnitTest : public StartupTest {
void run() {
// Hard-coded check to ensure the hash function is consistent across platforms
BSONObj o = BSON( "check" << 42 );
verify( BSONElementHasher::hash64( o.firstElement(), 0 ) == -944302157085130861LL );
}
} hasherUnitTest;
}
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