import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

rdf/base/nsContainerEnumerator.cpp

@@ -0,0 +1,263 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* 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 "mozilla/Logging.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;
+}