gecko/rdf/base/nsContainerEnumerator.cpp

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
2012-05-21 04:12:37 -07:00
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
A simple cursor that enumerates the elements of an RDF container
(RDF:Bag, RDF:Seq, or RDF:Alt).
Caveats
-------
1. This uses an implementation-specific detail to determine the
index of the last element in the container; specifically, the RDF
utilities maintain a counter attribute on the container that
holds the numeric value of the next value that is to be
assigned. So, this cursor will bust if you use it with a bag that
hasn't been created using the RDF utility routines.
*/
#include "nscore.h"
#include "nsCOMPtr.h"
#include "nsIRDFContainerUtils.h"
#include "nsIRDFDataSource.h"
#include "nsIRDFNode.h"
#include "nsIRDFService.h"
#include "nsIServiceManager.h"
#include "nsRDFCID.h"
#include "nsString.h"
#include "nsXPIDLString.h"
#include "prlog.h"
#include "rdf.h"
#include "rdfutil.h"
////////////////////////////////////////////////////////////////////////
class ContainerEnumeratorImpl : public nsISimpleEnumerator {
private:
// pseudo-constants
static nsrefcnt gRefCnt;
static nsIRDFResource* kRDF_nextVal;
static nsIRDFContainerUtils* gRDFC;
nsCOMPtr<nsIRDFDataSource> mDataSource;
nsCOMPtr<nsIRDFResource> mContainer;
nsCOMPtr<nsIRDFResource> mOrdinalProperty;
nsCOMPtr<nsISimpleEnumerator> mCurrent;
nsCOMPtr<nsIRDFNode> mResult;
int32_t mNextIndex;
virtual ~ContainerEnumeratorImpl();
public:
ContainerEnumeratorImpl(nsIRDFDataSource* ds, nsIRDFResource* container);
nsresult Init();
NS_DECL_ISUPPORTS
NS_DECL_NSISIMPLEENUMERATOR
};
nsrefcnt ContainerEnumeratorImpl::gRefCnt;
nsIRDFResource* ContainerEnumeratorImpl::kRDF_nextVal;
nsIRDFContainerUtils* ContainerEnumeratorImpl::gRDFC;
ContainerEnumeratorImpl::ContainerEnumeratorImpl(nsIRDFDataSource* aDataSource,
nsIRDFResource* aContainer)
: mDataSource(aDataSource),
mContainer(aContainer),
mNextIndex(1)
{
}
nsresult
ContainerEnumeratorImpl::Init()
{
if (gRefCnt++ == 0) {
nsresult rv;
NS_DEFINE_CID(kRDFServiceCID, NS_RDFSERVICE_CID);
nsCOMPtr<nsIRDFService> rdf = do_GetService(kRDFServiceCID);
NS_ASSERTION(rdf != nullptr, "unable to acquire resource manager");
if (! rdf)
return NS_ERROR_FAILURE;
rv = rdf->GetResource(NS_LITERAL_CSTRING(RDF_NAMESPACE_URI "nextVal"), &kRDF_nextVal);
NS_ASSERTION(NS_SUCCEEDED(rv), "unable to get resource");
if (NS_FAILED(rv)) return rv;
NS_DEFINE_CID(kRDFContainerUtilsCID, NS_RDFCONTAINERUTILS_CID);
rv = CallGetService(kRDFContainerUtilsCID, &gRDFC);
if (NS_FAILED(rv)) return rv;
}
return NS_OK;
}
ContainerEnumeratorImpl::~ContainerEnumeratorImpl()
{
if (--gRefCnt == 0) {
NS_IF_RELEASE(kRDF_nextVal);
NS_IF_RELEASE(gRDFC);
}
}
NS_IMPL_ISUPPORTS(ContainerEnumeratorImpl, nsISimpleEnumerator)
NS_IMETHODIMP
ContainerEnumeratorImpl::HasMoreElements(bool* aResult)
{
NS_PRECONDITION(aResult != nullptr, "null ptr");
if (! aResult)
return NS_ERROR_NULL_POINTER;
nsresult rv;
// If we've already queued up a next value, then we know there are more elements.
if (mResult) {
*aResult = true;
return NS_OK;
}
// Otherwise, we need to grovel
// Figure out the upper bound so we'll know when we're done. Since it's
// possible that we're targeting a composite datasource, we'll need to
// "GetTargets()" and take the maximum value of "nextVal" to know the
// upper bound.
//
// Remember that since nextVal is the next index that we'd assign
// to an element in a container, it's *one more* than count of
// elements in the container.
int32_t max = 0;
nsCOMPtr<nsISimpleEnumerator> targets;
rv = mDataSource->GetTargets(mContainer, kRDF_nextVal, true, getter_AddRefs(targets));
if (NS_FAILED(rv)) return rv;
while (1) {
bool hasmore;
targets->HasMoreElements(&hasmore);
if (! hasmore)
break;
nsCOMPtr<nsISupports> isupports;
targets->GetNext(getter_AddRefs(isupports));
nsCOMPtr<nsIRDFLiteral> nextValLiteral = do_QueryInterface(isupports);
if (! nextValLiteral)
continue;
const char16_t *nextValStr;
nextValLiteral->GetValueConst(&nextValStr);
nsresult err;
int32_t nextVal = nsAutoString(nextValStr).ToInteger(&err);
if (nextVal > max)
max = nextVal;
}
// Now pre-fetch our next value into mResult.
while (mCurrent || mNextIndex < max) {
// If mCurrent has been depleted, then conjure up a new one
if (! mCurrent) {
rv = gRDFC->IndexToOrdinalResource(mNextIndex, getter_AddRefs(mOrdinalProperty));
if (NS_FAILED(rv)) return rv;
rv = mDataSource->GetTargets(mContainer, mOrdinalProperty, true, getter_AddRefs(mCurrent));
if (NS_FAILED(rv)) return rv;
++mNextIndex;
}
if (mCurrent) {
bool hasMore;
rv = mCurrent->HasMoreElements(&hasMore);
if (NS_FAILED(rv)) return rv;
// Is the current enumerator depleted? If so, iterate to
// the next index.
if (! hasMore) {
mCurrent = nullptr;
continue;
}
// "Peek" ahead and pull out the next target.
nsCOMPtr<nsISupports> result;
rv = mCurrent->GetNext(getter_AddRefs(result));
if (NS_FAILED(rv)) return rv;
mResult = do_QueryInterface(result, &rv);
if (NS_FAILED(rv)) return rv;
*aResult = true;
return NS_OK;
}
}
// If we get here, we ran out of elements. The cursor is empty.
*aResult = false;
return NS_OK;
}
NS_IMETHODIMP
ContainerEnumeratorImpl::GetNext(nsISupports** aResult)
{
nsresult rv;
bool hasMore;
rv = HasMoreElements(&hasMore);
if (NS_FAILED(rv)) return rv;
if (! hasMore)
return NS_ERROR_UNEXPECTED;
NS_ADDREF(*aResult = mResult);
mResult = nullptr;
return NS_OK;
}
////////////////////////////////////////////////////////////////////////
nsresult
NS_NewContainerEnumerator(nsIRDFDataSource* aDataSource,
nsIRDFResource* aContainer,
nsISimpleEnumerator** aResult)
{
NS_PRECONDITION(aDataSource != nullptr, "null ptr");
if (! aDataSource)
return NS_ERROR_NULL_POINTER;
NS_PRECONDITION(aContainer != nullptr, "null ptr");
if (! aContainer)
return NS_ERROR_NULL_POINTER;
NS_PRECONDITION(aResult != nullptr, "null ptr");
if (! aResult)
return NS_ERROR_NULL_POINTER;
ContainerEnumeratorImpl* result = new ContainerEnumeratorImpl(aDataSource, aContainer);
if (! result)
return NS_ERROR_OUT_OF_MEMORY;
NS_ADDREF(result);
nsresult rv = result->Init();
if (NS_FAILED(rv))
NS_RELEASE(result);
*aResult = result;
return rv;
}