michael@0: /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: /*
michael@0: 
michael@0:   A simple cursor that enumerates the elements of an RDF container
michael@0:   (RDF:Bag, RDF:Seq, or RDF:Alt).
michael@0: 
michael@0:   Caveats
michael@0:   -------
michael@0: 
michael@0:   1. This uses an implementation-specific detail to determine the
michael@0:      index of the last element in the container; specifically, the RDF
michael@0:      utilities maintain a counter attribute on the container that
michael@0:      holds the numeric value of the next value that is to be
michael@0:      assigned. So, this cursor will bust if you use it with a bag that
michael@0:      hasn't been created using the RDF utility routines.
michael@0: 
michael@0:  */
michael@0: 
michael@0: #include "nscore.h"
michael@0: #include "nsCOMPtr.h"
michael@0: #include "nsIRDFContainerUtils.h"
michael@0: #include "nsIRDFDataSource.h"
michael@0: #include "nsIRDFNode.h"
michael@0: #include "nsIRDFService.h"
michael@0: #include "nsIServiceManager.h"
michael@0: #include "nsRDFCID.h"
michael@0: #include "nsString.h"
michael@0: #include "nsXPIDLString.h"
michael@0: #include "prlog.h"
michael@0: #include "rdf.h"
michael@0: #include "rdfutil.h"
michael@0: 
michael@0: ////////////////////////////////////////////////////////////////////////
michael@0: 
michael@0: class ContainerEnumeratorImpl : public nsISimpleEnumerator {
michael@0: private:
michael@0:     // pseudo-constants
michael@0:     static nsrefcnt              gRefCnt;
michael@0:     static nsIRDFResource*       kRDF_nextVal;
michael@0:     static nsIRDFContainerUtils* gRDFC;
michael@0: 
michael@0:     nsCOMPtr<nsIRDFDataSource>      mDataSource;
michael@0:     nsCOMPtr<nsIRDFResource>        mContainer;
michael@0:     nsCOMPtr<nsIRDFResource>        mOrdinalProperty;
michael@0: 
michael@0:     nsCOMPtr<nsISimpleEnumerator>   mCurrent;
michael@0:     nsCOMPtr<nsIRDFNode>            mResult;
michael@0:     int32_t mNextIndex;
michael@0: 
michael@0: public:
michael@0:     ContainerEnumeratorImpl(nsIRDFDataSource* ds, nsIRDFResource* container);
michael@0:     virtual ~ContainerEnumeratorImpl();
michael@0: 
michael@0:     nsresult Init();
michael@0: 
michael@0:     NS_DECL_ISUPPORTS
michael@0:     NS_DECL_NSISIMPLEENUMERATOR
michael@0: };
michael@0: 
michael@0: nsrefcnt              ContainerEnumeratorImpl::gRefCnt;
michael@0: nsIRDFResource*       ContainerEnumeratorImpl::kRDF_nextVal;
michael@0: nsIRDFContainerUtils* ContainerEnumeratorImpl::gRDFC;
michael@0: 
michael@0: 
michael@0: ContainerEnumeratorImpl::ContainerEnumeratorImpl(nsIRDFDataSource* aDataSource,
michael@0:                                                  nsIRDFResource* aContainer)
michael@0:     : mDataSource(aDataSource),
michael@0:       mContainer(aContainer),
michael@0:       mNextIndex(1)
michael@0: {
michael@0: }
michael@0: 
michael@0: nsresult
michael@0: ContainerEnumeratorImpl::Init()
michael@0: {
michael@0:     if (gRefCnt++ == 0) {
michael@0:         nsresult rv;
michael@0: 
michael@0:         NS_DEFINE_CID(kRDFServiceCID, NS_RDFSERVICE_CID);
michael@0:         nsCOMPtr<nsIRDFService> rdf = do_GetService(kRDFServiceCID);
michael@0:         NS_ASSERTION(rdf != nullptr, "unable to acquire resource manager");
michael@0:         if (! rdf)
michael@0:             return NS_ERROR_FAILURE;
michael@0: 
michael@0:         rv = rdf->GetResource(NS_LITERAL_CSTRING(RDF_NAMESPACE_URI "nextVal"), &kRDF_nextVal);
michael@0:         NS_ASSERTION(NS_SUCCEEDED(rv), "unable to get resource");
michael@0:         if (NS_FAILED(rv)) return rv;
michael@0: 
michael@0:         NS_DEFINE_CID(kRDFContainerUtilsCID, NS_RDFCONTAINERUTILS_CID);
michael@0:         rv = CallGetService(kRDFContainerUtilsCID, &gRDFC);
michael@0:         if (NS_FAILED(rv)) return rv;
michael@0:     }
michael@0: 
michael@0:     return NS_OK;
michael@0: }
michael@0: 
michael@0: 
michael@0: ContainerEnumeratorImpl::~ContainerEnumeratorImpl()
michael@0: {
michael@0:     if (--gRefCnt == 0) {
michael@0:         NS_IF_RELEASE(kRDF_nextVal);
michael@0:         NS_IF_RELEASE(gRDFC);
michael@0:     }
michael@0: }
michael@0: 
michael@0: NS_IMPL_ISUPPORTS(ContainerEnumeratorImpl, nsISimpleEnumerator)
michael@0: 
michael@0: 
michael@0: NS_IMETHODIMP
michael@0: ContainerEnumeratorImpl::HasMoreElements(bool* aResult)
michael@0: {
michael@0:     NS_PRECONDITION(aResult != nullptr, "null ptr");
michael@0:     if (! aResult)
michael@0:         return NS_ERROR_NULL_POINTER;
michael@0: 
michael@0:     nsresult rv;
michael@0: 
michael@0:     // If we've already queued up a next value, then we know there are more elements.
michael@0:     if (mResult) {
michael@0:         *aResult = true;
michael@0:         return NS_OK;
michael@0:     }
michael@0: 
michael@0:     // Otherwise, we need to grovel
michael@0: 
michael@0:     // Figure out the upper bound so we'll know when we're done. Since it's
michael@0:     // possible that we're targeting a composite datasource, we'll need to
michael@0:     // "GetTargets()" and take the maximum value of "nextVal" to know the
michael@0:     // upper bound.
michael@0:     //
michael@0:     // Remember that since nextVal is the next index that we'd assign
michael@0:     // to an element in a container, it's *one more* than count of
michael@0:     // elements in the container.
michael@0:     int32_t max = 0;
michael@0: 
michael@0:     nsCOMPtr<nsISimpleEnumerator> targets;
michael@0:     rv = mDataSource->GetTargets(mContainer, kRDF_nextVal, true, getter_AddRefs(targets));
michael@0:     if (NS_FAILED(rv)) return rv;
michael@0: 
michael@0:     while (1) {
michael@0:         bool hasmore;
michael@0:         targets->HasMoreElements(&hasmore);
michael@0:         if (! hasmore)
michael@0:             break;
michael@0: 
michael@0:         nsCOMPtr<nsISupports> isupports;
michael@0:         targets->GetNext(getter_AddRefs(isupports));
michael@0: 
michael@0:         nsCOMPtr<nsIRDFLiteral> nextValLiteral = do_QueryInterface(isupports);
michael@0:         if (! nextValLiteral)
michael@0:              continue;
michael@0: 
michael@0:          const char16_t *nextValStr;
michael@0:          nextValLiteral->GetValueConst(&nextValStr);
michael@0: 		 
michael@0:          nsresult err;
michael@0:          int32_t nextVal = nsAutoString(nextValStr).ToInteger(&err);
michael@0: 
michael@0:          if (nextVal > max)
michael@0:              max = nextVal;
michael@0:     }
michael@0: 
michael@0:     // Now pre-fetch our next value into mResult.
michael@0:     while (mCurrent || mNextIndex < max) {
michael@0: 
michael@0:         // If mCurrent has been depleted, then conjure up a new one
michael@0:         if (! mCurrent) {
michael@0:             rv = gRDFC->IndexToOrdinalResource(mNextIndex, getter_AddRefs(mOrdinalProperty));
michael@0:             if (NS_FAILED(rv)) return rv;
michael@0: 
michael@0:             rv = mDataSource->GetTargets(mContainer, mOrdinalProperty, true, getter_AddRefs(mCurrent));
michael@0:             if (NS_FAILED(rv)) return rv;
michael@0: 
michael@0:             ++mNextIndex;
michael@0:         }
michael@0: 
michael@0:         if (mCurrent) {
michael@0:             bool hasMore;
michael@0:             rv = mCurrent->HasMoreElements(&hasMore);
michael@0:             if (NS_FAILED(rv)) return rv;
michael@0: 
michael@0:             // Is the current enumerator depleted? If so, iterate to
michael@0:             // the next index.
michael@0:             if (! hasMore) {
michael@0:                 mCurrent = nullptr;
michael@0:                 continue;
michael@0:             }
michael@0: 
michael@0:             // "Peek" ahead and pull out the next target.
michael@0:             nsCOMPtr<nsISupports> result;
michael@0:             rv = mCurrent->GetNext(getter_AddRefs(result));
michael@0:             if (NS_FAILED(rv)) return rv;
michael@0: 
michael@0:             mResult = do_QueryInterface(result, &rv);
michael@0:             if (NS_FAILED(rv)) return rv;
michael@0: 
michael@0:             *aResult = true;
michael@0:             return NS_OK;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     // If we get here, we ran out of elements. The cursor is empty.
michael@0:     *aResult = false;
michael@0:     return NS_OK;
michael@0: }
michael@0: 
michael@0: 
michael@0: NS_IMETHODIMP
michael@0: ContainerEnumeratorImpl::GetNext(nsISupports** aResult)
michael@0: {
michael@0:     nsresult rv;
michael@0: 
michael@0:     bool hasMore;
michael@0:     rv = HasMoreElements(&hasMore);
michael@0:     if (NS_FAILED(rv)) return rv;
michael@0: 
michael@0:     if (! hasMore)
michael@0:         return NS_ERROR_UNEXPECTED;
michael@0: 
michael@0:     NS_ADDREF(*aResult = mResult);
michael@0:     mResult = nullptr;
michael@0: 
michael@0:     return NS_OK;
michael@0: }
michael@0: 
michael@0: 
michael@0: ////////////////////////////////////////////////////////////////////////
michael@0: 
michael@0: nsresult
michael@0: NS_NewContainerEnumerator(nsIRDFDataSource* aDataSource,
michael@0:                           nsIRDFResource* aContainer,
michael@0:                           nsISimpleEnumerator** aResult)
michael@0: {
michael@0:     NS_PRECONDITION(aDataSource != nullptr, "null ptr");
michael@0:     if (! aDataSource)
michael@0:         return NS_ERROR_NULL_POINTER;
michael@0: 
michael@0:     NS_PRECONDITION(aContainer != nullptr, "null ptr");
michael@0:     if (! aContainer)
michael@0:         return NS_ERROR_NULL_POINTER;
michael@0: 
michael@0:     NS_PRECONDITION(aResult != nullptr, "null ptr");
michael@0:     if (! aResult)
michael@0:         return NS_ERROR_NULL_POINTER;
michael@0: 
michael@0:     ContainerEnumeratorImpl* result = new ContainerEnumeratorImpl(aDataSource, aContainer);
michael@0:     if (! result)
michael@0:         return NS_ERROR_OUT_OF_MEMORY;
michael@0: 
michael@0:     NS_ADDREF(result);
michael@0: 
michael@0:     nsresult rv = result->Init();
michael@0:     if (NS_FAILED(rv))
michael@0:         NS_RELEASE(result);
michael@0: 
michael@0:     *aResult = result;
michael@0:     return rv;
michael@0: }