js/ndnProtocol/components/ndnProtocolService.js - ndn-js - Gitiles

 /*
  * @author: Jeff Thompson
  * See COPYING for copyright and distribution information.
  * This is the ndn protocol handler.
  * Protocol handling code derived from http://mike.kaply.com/2011/01/18/writing-a-firefox-protocol-handler/
  */

 const Cc = Components.classes;
 const Ci = Components.interfaces;
 const Cr = Components.results;

 const nsIProtocolHandler = Ci.nsIProtocolHandler;

 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 Components.utils.import("chrome://modules/content/ndn-js.jsm");
 Components.utils.import("chrome://modules/content/ContentChannel.jsm");
 Components.utils.import("chrome://modules/content/NdnProtocolInfo.jsm");

 function NdnProtocol() {
     // TODO: Remove host: null when null is the default.
     this.ndn = new NDN({ getTransport: function() { return new XpcomTransport(); },
         host: null, verify: false });
 }

 NdnProtocol.prototype = {
     scheme: "ndn",
     protocolFlags: nsIProtocolHandler.URI_NORELATIVE |
                    nsIProtocolHandler.URI_NOAUTH |
                    nsIProtocolHandler.URI_LOADABLE_BY_ANYONE,

     newURI: function(aSpec, aOriginCharset, aBaseURI)
     {
         var uri = Cc["@mozilla.org/network/simple-uri;1"].createInstance(Ci.nsIURI);

         // We have to trim now because nsIURI converts spaces to %20 and we can't trim in newChannel.
         var uriParts = NdnProtocolInfo.splitUri(aSpec);
         if (aBaseURI == null || uriParts.name.length < 1 || uriParts.name[0] == '/')
             // Just reconstruct the trimmed URI.
             uri.spec = "ndn:" + uriParts.name + uriParts.search + uriParts.hash;
         else {
             // Make a URI relative to the base name up to the file name component.
             var baseUriParts = NdnProtocolInfo.splitUri(aBaseURI.spec);
             var baseName = new Name(baseUriParts.name);
             var iFileName = baseName.indexOfFileName();

             var relativeName = uriParts.name;
             // Handle ../
             while (true) {
                 if (relativeName.substr(0, 2) == "./")
                     relativeName = relativeName.substr(2);
                 else if (relativeName.substr(0, 3) == "../") {
                     relativeName = relativeName.substr(3);
                     if (iFileName > 0)
                         --iFileName;
                 }
                 else
                     break;
             }

             var prefixUri = "/";
             if (iFileName > 0)
                 prefixUri = new Name(baseName.components.slice(0, iFileName)).to_uri() + "/";
             uri.spec = "ndn:" + prefixUri + relativeName + uriParts.search + uriParts.hash;
         }

         return uri;
     },

     newChannel: function(aURI)
     {
         var thisNdnProtocol = this;

         try {
             var uriParts = NdnProtocolInfo.splitUri(aURI.spec);

             var template = new Interest(new Name([]));
             // Use the same default as NDN.expressInterest.
             template.interestLifetime = 4000; // milliseconds
             var searchWithoutNdn = extractNdnSearch(uriParts.search, template);

             var segmentTemplate = new Interest(new Name([]));
             // Only use the interest selectors which make sense for fetching further segments.
             segmentTemplate.publisherPublicKeyDigest = template.publisherPublicKeyDigest;
             segmentTemplate.scope = template.scope;
             segmentTemplate.interestLifetime = template.interestLifetime;

             var requestContent = function(contentListener) {
                 var name = new Name(uriParts.name);
                 // TODO: Strip off an ending implicit digest before checking the last component?
                 var uriEndsWithSegmentNumber = endsWithSegmentNumber(name);

                 // Use the same NDN object each time.
                 thisNdnProtocol.ndn.expressInterest(name,
                     new ContentClosure(thisNdnProtocol.ndn, contentListener, uriEndsWithSegmentNumber,
                             aURI.originCharset, searchWithoutNdn + uriParts.hash, segmentTemplate),
                     template);
             };

             return new ContentChannel(aURI, requestContent);
         } catch (ex) {
             dump("NdnProtocol.newChannel exception: " + ex + "\n" + ex.stack);
         }
     },

     classDescription: "ndn Protocol Handler",
     contractID: "@mozilla.org/network/protocol;1?name=" + "ndn",
     classID: Components.ID('{8122e660-1012-11e2-892e-0800200c9a66}'),
     QueryInterface: XPCOMUtils.generateQI([Ci.nsIProtocolHandler])
 };

 if (XPCOMUtils.generateNSGetFactory)
     var NSGetFactory = XPCOMUtils.generateNSGetFactory([NdnProtocol]);
 else
     var NSGetModule = XPCOMUtils.generateNSGetModule([NdnProtocol]);

 /*
  * Create a closure for calling expressInterest.
  * contentListener is from the call to requestContent.
  * uriEndsWithSegmentNumber is true if the URI passed to newChannel has a segment number
  *    (used to determine whether to request only that segment number and for updating the URL bar).
  * uriOriginCharset is the charset of the URI passed to newChannel (used for making a new URI)
  * uriSearchAndHash is the search and hash part of the URI passed to newChannel, including the '?'
  *    and/or '#' but without the interest selector fields.
  * segmentTemplate is the template used in expressInterest to fetch further segments.
  */
 var ContentClosure = function ContentClosure
         (ndn, contentListener, uriEndsWithSegmentNumber, uriOriginCharset, uriSearchAndHash,
          segmentTemplate) {
     // Inherit from Closure.
     Closure.call(this);

     this.ndn = ndn;
     this.contentListener = contentListener;
     this.uriEndsWithSegmentNumber = uriEndsWithSegmentNumber;
     this.uriOriginCharset = uriOriginCharset;
     this.uriSearchAndHash = uriSearchAndHash;
     this.segmentTemplate = segmentTemplate;

     this.segmentStore = new SegmentStore();
     this.contentSha256 = new Sha256();
     this.didRequestFinalSegment = false;
     this.finalSegmentNumber = null;
 };

 ContentClosure.prototype.upcall = function(kind, upcallInfo) {
   try {
     if (!(kind == Closure.UPCALL_CONTENT ||
           kind == Closure.UPCALL_CONTENT_UNVERIFIED))
         // The upcall is not for us.
         return Closure.RESULT_ERR;

     var contentObject = upcallInfo.contentObject;
     if (contentObject.content == null) {
         dump("NdnProtocol.ContentClosure: contentObject.content is null\n");
         return Closure.RESULT_ERR;
     }

     // Now that we're connected, report the host and port.
     NdnProtocolInfo.setConnectedNdnHub(this.ndn.host, this.ndn.port);

     // If !this.uriEndsWithSegmentNumber, we use the segmentNumber to load multiple segments.
     // If this.uriEndsWithSegmentNumber, then we leave segmentNumber null.
     var segmentNumber = null;
     if (!this.uriEndsWithSegmentNumber && endsWithSegmentNumber(contentObject.name)) {
         segmentNumber = DataUtils.bigEndianToUnsignedInt
             (contentObject.name.components[contentObject.name.components.length - 1]);
         this.segmentStore.storeContent(segmentNumber, contentObject);
     }

     if (segmentNumber == null || segmentNumber == 0) {
         // This is the first or only segment, so start.
         // Get the URI from the ContentObject including the version.
         var contentUriSpec;
         if (!this.uriEndsWithSegmentNumber && endsWithSegmentNumber(contentObject.name)) {
             var nameWithoutSegmentNumber = new Name
                 (contentObject.name.components.slice(0, contentObject.name.components.length - 1));
             contentUriSpec = "ndn:" + nameWithoutSegmentNumber.to_uri();
         }
         else
             contentUriSpec = "ndn:" + contentObject.name.to_uri();

         // Include the search and hash.
         contentUriSpec += this.uriSearchAndHash;

         var contentTypeEtc = getNameContentTypeAndCharset(contentObject.name);
         var ioService = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
         this.contentListener.onStart(contentTypeEtc.contentType, contentTypeEtc.contentCharset,
             ioService.newURI(contentUriSpec, this.uriOriginCharset, null));
     }

     if (segmentNumber == null) {
         // We are not doing segments, so just finish.
         this.contentListener.onReceivedContent(DataUtils.toString(contentObject.content));
         this.contentSha256.update(contentObject.content);
         this.contentListener.onStop();

         if (!this.uriEndsWithSegmentNumber) {
             var nameContentDigest = contentObject.name.getContentDigestValue();
             if (nameContentDigest != null &&
                 !DataUtils.arraysEqual(nameContentDigest, this.contentSha256.finalize()))
                 // TODO: How to show the user an error for invalid digest?
                 dump("Content does not match digest in name " + contentObject.name.to_uri());
         }
         return Closure.RESULT_OK;
     }

     if (contentObject.signedInfo != null && contentObject.signedInfo.finalBlockID != null)
         this.finalSegmentNumber = DataUtils.bigEndianToUnsignedInt(contentObject.signedInfo.finalBlockID);

     // The content was already put in the store.  Retrieve as much as possible.
     var entry;
     while ((entry = this.segmentStore.maybeRetrieveNextEntry()) != null) {
         segmentNumber = entry.key;
         contentObject = entry.value;
         this.contentListener.onReceivedContent(DataUtils.toString(contentObject.content));
         this.contentSha256.update(contentObject.content);

         if (this.finalSegmentNumber != null && segmentNumber == this.finalSegmentNumber) {
             // Finished.
             this.contentListener.onStop();
             var nameContentDigest = contentObject.name.getContentDigestValue();
             if (nameContentDigest != null &&
                 !DataUtils.arraysEqual(nameContentDigest, this.contentSha256.finalize()))
                 // TODO: How to show the user an error for invalid digest?
                 dump("Content does not match digest in name " + contentObject.name.to_uri());

             return Closure.RESULT_OK;
         }
     }

     if (this.finalSegmentNumber == null && !this.didRequestFinalSegment) {
         this.didRequestFinalSegment = true;
         // Try to determine the final segment now.
         var components = contentObject.name.components.slice
             (0, contentObject.name.components.length - 1);

         // Temporarily set the childSelector in the segmentTemplate.
         this.segmentTemplate.childSelector = 1;
         this.ndn.expressInterest(new Name(components), this, this.segmentTemplate);
         this.segmentTemplate.childSelector = null;
     }

     // Request new segments.
     var toRequest = this.segmentStore.requestSegmentNumbers(2);
     for (var i = 0; i < toRequest.length; ++i) {
         if (this.finalSegmentNumber != null && toRequest[i] > this.finalSegmentNumber)
             continue;

         // Make a name for the segment and get it.
         var segmentNumberBigEndian = DataUtils.nonNegativeIntToBigEndian(toRequest[i]);
         // Put a 0 byte in front.
         var segmentNumberComponent = new Uint8Array(segmentNumberBigEndian.length + 1);
         segmentNumberComponent.set(segmentNumberBigEndian, 1);

         var components = contentObject.name.components.slice
             (0, contentObject.name.components.length - 1);
         components.push(segmentNumberComponent);
         this.ndn.expressInterest(new Name(components), this, this.segmentTemplate);
     }

     return Closure.RESULT_OK;
   } catch (ex) {
         dump("ContentClosure.upcall exception: " + ex + "\n" + ex.stack);
         return Closure.RESULT_ERR;
   }
 };

 /*
  * A SegmentStore stores segments until they are retrieved in order starting with segment 0.
  */
 var SegmentStore = function SegmentStore() {
     // Each entry is an object where the key is the segment number and value is null if
     //   the segment number is requested or the contentObject if received.
     this.store = new SortedArray();
     this.maxRetrievedSegmentNumber = -1;
 };

 SegmentStore.prototype.storeContent = function(segmentNumber, contentObject) {
     // We don't expect to try to store a segment that has already been retrieved, but check anyway.
     if (segmentNumber > this.maxRetrievedSegmentNumber)
         this.store.set(segmentNumber, contentObject);
 };

 /*
  * If the min segment number is this.maxRetrievedSegmentNumber + 1 and its value is not null,
  *   then delete from the store, return the entry with key and value, and update maxRetrievedSegmentNumber.
  * Otherwise return null.
  */
 SegmentStore.prototype.maybeRetrieveNextEntry = function() {
     if (this.store.entries.length > 0 && this.store.entries[0].value != null &&
         this.store.entries[0].key == this.maxRetrievedSegmentNumber + 1) {
         var entry = this.store.entries[0];
         this.store.removeAt(0);
         ++this.maxRetrievedSegmentNumber;
         return entry;
     }
     else
         return null;
 };

 /*
  * Return an array of the next segment numbers that need to be requested so that the total
  *   requested segments is totalRequestedSegments.  If a segment store entry value is null, it is
  *   already requested and is not returned.  If a segment number is returned, create a
  *   entry in the segment store with a null value.
  */
 SegmentStore.prototype.requestSegmentNumbers = function(totalRequestedSegments) {
     // First, count how many are already requested.
     var nRequestedSegments = 0;
     for (var i = 0; i < this.store.entries.length; ++i) {
         if (this.store.entries[i].value == null) {
             ++nRequestedSegments;
             if (nRequestedSegments >= totalRequestedSegments)
                 // Already maxed out on requests.
                 return [];
         }
     }

     var toRequest = [];
     var nextSegmentNumber = this.maxRetrievedSegmentNumber + 1;
     for (var i = 0; i < this.store.entries.length; ++i) {
         var entry = this.store.entries[i];
         // Fill in the gap before the segment number in the entry.
         while (nextSegmentNumber < entry.key) {
             toRequest.push(nextSegmentNumber);
             ++nextSegmentNumber;
             ++nRequestedSegments;
             if (nRequestedSegments >= totalRequestedSegments)
                 break;
         }
         if (nRequestedSegments >= totalRequestedSegments)
             break;

         nextSegmentNumber = entry.key + 1;
     }

     // We already filled in the gaps for the segments in the store. Continue after the last.
     while (nRequestedSegments < totalRequestedSegments) {
         toRequest.push(nextSegmentNumber);
         ++nextSegmentNumber;
         ++nRequestedSegments;
     }

     // Mark the new segment numbers as requested.
     for (var i = 0; i < toRequest.length; ++i)
         this.store.set(toRequest[i], null);
     return toRequest;
 }

 /*
  * A SortedArray is an array of objects with key and value, where the key is an integer.
  */
 var SortedArray = function SortedArray() {
     this.entries = [];
 }

 SortedArray.prototype.sortEntries = function() {
     this.entries.sort(function(a, b) { return a.key - b.key; });
 };

 SortedArray.prototype.indexOfKey = function(key) {
     for (var i = 0; i < this.entries.length; ++i) {
         if (this.entries[i].key == key)
             return i;
     }

     return -1;
 }

 SortedArray.prototype.set = function(key, value) {
     var i = this.indexOfKey(key);
     if (i >= 0) {
         this.entries[i].value = value;
         return;
     }

     this.entries.push({ key: key, value: value});
     this.sortEntries();
 }

 SortedArray.prototype.removeAt = function(index) {
     this.entries.splice(index, 1);
 }

 /*
  * Scan the name from the last component to the first (skipping special name components)
  *   for a recognized file name extension, and return an object with properties contentType and charset.
  */
 function getNameContentTypeAndCharset(name) {
     var iFileName = name.indexOfFileName();
     if (iFileName < 0)
         // Get the default mime type.
         return MimeTypes.getContentTypeAndCharset("");

     return MimeTypes.getContentTypeAndCharset
         (DataUtils.toString(name.components[iFileName]).toLowerCase());
 }

 /*
  * Return true if the last component in the name is a segment number..
  */
 function endsWithSegmentNumber(name) {
     return name.components != null && name.components.length >= 1 &&
         name.components[name.components.length - 1].length >= 1 &&
         name.components[name.components.length - 1][0] == 0;
 }

 /*
  * Find all search keys starting with "ndn." and set the attribute in template.
  * Return the search string including the starting "?" but with the "ndn." keys removed,
  *   or return "" if there are no search terms left.
  */
 function extractNdnSearch(search, template) {
     if (!(search.length >= 1 && search[0] == '?'))
         return search;

     var terms = search.substr(1).split('&');
     var i = 0;
     while (i < terms.length) {
         var keyValue = terms[i].split('=');
         var key = keyValue[0].trim();
         if (key.substr(0, 4) == "ndn.") {
             if (keyValue.length >= 1) {
                 var value = keyValue[1].trim();
                 var nonNegativeInt = parseInt(value);

                 if (key == "ndn.MinSuffixComponents" && nonNegativeInt >= 0)
                     template.minSuffixComponents = nonNegativeInt;
                 if (key == "ndn.MaxSuffixComponents" && nonNegativeInt >= 0)
                     template.maxSuffixComponents = nonNegativeInt;
                 if (key == "ndn.ChildSelector" && nonNegativeInt >= 0)
                     template.childSelector = nonNegativeInt;
                 if (key == "ndn.AnswerOriginKind" && nonNegativeInt >= 0)
                     template.answerOriginKind = nonNegativeInt;
                 if (key == "ndn.Scope" && nonNegativeInt >= 0)
                     template.scope = nonNegativeInt;
                 if (key == "ndn.InterestLifetime" && nonNegativeInt >= 0)
                     template.interestLifetime = nonNegativeInt;
                 if (key == "ndn.PublisherPublicKeyDigest" && nonNegativeInt >= 0)
                     template.publisherPublicKeyDigest = DataUtils.toNumbersFromString(unescape(value));
                 if (key == "ndn.Nonce" && nonNegativeInt >= 0)
                     template.nonce = DataUtils.toNumbersFromString(unescape(value));
                 // TODO: handle Exclude.
             }

             // Remove the "ndn." term and don't advance i.
             terms.splice(i, 1);
         }
         else
             ++i;
     }

     if (terms.length == 0)
         return "";
     else
         return "?" + terms.join('&');
 }
	/*
	* @author: Jeff Thompson
	* See COPYING for copyright and distribution information.
	* This is the ndn protocol handler.
	* Protocol handling code derived from http://mike.kaply.com/2011/01/18/writing-a-firefox-protocol-handler/
	*/

	const Cc = Components.classes;
	const Ci = Components.interfaces;
	const Cr = Components.results;

	const nsIProtocolHandler = Ci.nsIProtocolHandler;

	Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
	Components.utils.import("chrome://modules/content/ndn-js.jsm");
	Components.utils.import("chrome://modules/content/ContentChannel.jsm");
	Components.utils.import("chrome://modules/content/NdnProtocolInfo.jsm");

	function NdnProtocol() {
	// TODO: Remove host: null when null is the default.
	this.ndn = new NDN({ getTransport: function() { return new XpcomTransport(); },
	host: null, verify: false });
	}

	NdnProtocol.prototype = {
	scheme: "ndn",
	protocolFlags: nsIProtocolHandler.URI_NORELATIVE \|
	nsIProtocolHandler.URI_NOAUTH \|
	nsIProtocolHandler.URI_LOADABLE_BY_ANYONE,

	newURI: function(aSpec, aOriginCharset, aBaseURI)
	{
	var uri = Cc["@mozilla.org/network/simple-uri;1"].createInstance(Ci.nsIURI);

	// We have to trim now because nsIURI converts spaces to %20 and we can't trim in newChannel.
	var uriParts = NdnProtocolInfo.splitUri(aSpec);
	if (aBaseURI == null \|\| uriParts.name.length < 1 \|\| uriParts.name[0] == '/')
	// Just reconstruct the trimmed URI.
	uri.spec = "ndn:" + uriParts.name + uriParts.search + uriParts.hash;
	else {
	// Make a URI relative to the base name up to the file name component.
	var baseUriParts = NdnProtocolInfo.splitUri(aBaseURI.spec);
	var baseName = new Name(baseUriParts.name);
	var iFileName = baseName.indexOfFileName();

	var relativeName = uriParts.name;
	// Handle ../
	while (true) {
	if (relativeName.substr(0, 2) == "./")
	relativeName = relativeName.substr(2);
	else if (relativeName.substr(0, 3) == "../") {
	relativeName = relativeName.substr(3);
	if (iFileName > 0)
	--iFileName;
	}
	else
	break;
	}

	var prefixUri = "/";
	if (iFileName > 0)
	prefixUri = new Name(baseName.components.slice(0, iFileName)).to_uri() + "/";
	uri.spec = "ndn:" + prefixUri + relativeName + uriParts.search + uriParts.hash;
	}

	return uri;
	},

	newChannel: function(aURI)
	{
	var thisNdnProtocol = this;

	try {
	var uriParts = NdnProtocolInfo.splitUri(aURI.spec);

	var template = new Interest(new Name([]));
	// Use the same default as NDN.expressInterest.
	template.interestLifetime = 4000; // milliseconds
	var searchWithoutNdn = extractNdnSearch(uriParts.search, template);

	var segmentTemplate = new Interest(new Name([]));
	// Only use the interest selectors which make sense for fetching further segments.
	segmentTemplate.publisherPublicKeyDigest = template.publisherPublicKeyDigest;
	segmentTemplate.scope = template.scope;
	segmentTemplate.interestLifetime = template.interestLifetime;

	var requestContent = function(contentListener) {
	var name = new Name(uriParts.name);
	// TODO: Strip off an ending implicit digest before checking the last component?
	var uriEndsWithSegmentNumber = endsWithSegmentNumber(name);

	// Use the same NDN object each time.
	thisNdnProtocol.ndn.expressInterest(name,
	new ContentClosure(thisNdnProtocol.ndn, contentListener, uriEndsWithSegmentNumber,
	aURI.originCharset, searchWithoutNdn + uriParts.hash, segmentTemplate),
	template);
	};

	return new ContentChannel(aURI, requestContent);
	} catch (ex) {
	dump("NdnProtocol.newChannel exception: " + ex + "\n" + ex.stack);
	}
	},

	classDescription: "ndn Protocol Handler",
	contractID: "@mozilla.org/network/protocol;1?name=" + "ndn",
	classID: Components.ID('{8122e660-1012-11e2-892e-0800200c9a66}'),
	QueryInterface: XPCOMUtils.generateQI([Ci.nsIProtocolHandler])
	};

	if (XPCOMUtils.generateNSGetFactory)
	var NSGetFactory = XPCOMUtils.generateNSGetFactory([NdnProtocol]);
	else
	var NSGetModule = XPCOMUtils.generateNSGetModule([NdnProtocol]);

	/*
	* Create a closure for calling expressInterest.
	* contentListener is from the call to requestContent.
	* uriEndsWithSegmentNumber is true if the URI passed to newChannel has a segment number
	* (used to determine whether to request only that segment number and for updating the URL bar).
	* uriOriginCharset is the charset of the URI passed to newChannel (used for making a new URI)
	* uriSearchAndHash is the search and hash part of the URI passed to newChannel, including the '?'
	* and/or '#' but without the interest selector fields.
	* segmentTemplate is the template used in expressInterest to fetch further segments.
	*/
	var ContentClosure = function ContentClosure
	(ndn, contentListener, uriEndsWithSegmentNumber, uriOriginCharset, uriSearchAndHash,
	segmentTemplate) {
	// Inherit from Closure.
	Closure.call(this);

	this.ndn = ndn;
	this.contentListener = contentListener;
	this.uriEndsWithSegmentNumber = uriEndsWithSegmentNumber;
	this.uriOriginCharset = uriOriginCharset;
	this.uriSearchAndHash = uriSearchAndHash;
	this.segmentTemplate = segmentTemplate;

	this.segmentStore = new SegmentStore();
	this.contentSha256 = new Sha256();
	this.didRequestFinalSegment = false;
	this.finalSegmentNumber = null;
	};

	ContentClosure.prototype.upcall = function(kind, upcallInfo) {
	try {
	if (!(kind == Closure.UPCALL_CONTENT \|\|
	kind == Closure.UPCALL_CONTENT_UNVERIFIED))
	// The upcall is not for us.
	return Closure.RESULT_ERR;

	var contentObject = upcallInfo.contentObject;
	if (contentObject.content == null) {
	dump("NdnProtocol.ContentClosure: contentObject.content is null\n");
	return Closure.RESULT_ERR;
	}

	// Now that we're connected, report the host and port.
	NdnProtocolInfo.setConnectedNdnHub(this.ndn.host, this.ndn.port);

	// If !this.uriEndsWithSegmentNumber, we use the segmentNumber to load multiple segments.
	// If this.uriEndsWithSegmentNumber, then we leave segmentNumber null.
	var segmentNumber = null;
	if (!this.uriEndsWithSegmentNumber && endsWithSegmentNumber(contentObject.name)) {
	segmentNumber = DataUtils.bigEndianToUnsignedInt
	(contentObject.name.components[contentObject.name.components.length - 1]);
	this.segmentStore.storeContent(segmentNumber, contentObject);
	}

	if (segmentNumber == null \|\| segmentNumber == 0) {
	// This is the first or only segment, so start.
	// Get the URI from the ContentObject including the version.
	var contentUriSpec;
	if (!this.uriEndsWithSegmentNumber && endsWithSegmentNumber(contentObject.name)) {
	var nameWithoutSegmentNumber = new Name
	(contentObject.name.components.slice(0, contentObject.name.components.length - 1));
	contentUriSpec = "ndn:" + nameWithoutSegmentNumber.to_uri();
	}
	else
	contentUriSpec = "ndn:" + contentObject.name.to_uri();

	// Include the search and hash.
	contentUriSpec += this.uriSearchAndHash;

	var contentTypeEtc = getNameContentTypeAndCharset(contentObject.name);
	var ioService = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
	this.contentListener.onStart(contentTypeEtc.contentType, contentTypeEtc.contentCharset,
	ioService.newURI(contentUriSpec, this.uriOriginCharset, null));
	}

	if (segmentNumber == null) {
	// We are not doing segments, so just finish.
	this.contentListener.onReceivedContent(DataUtils.toString(contentObject.content));
	this.contentSha256.update(contentObject.content);
	this.contentListener.onStop();

	if (!this.uriEndsWithSegmentNumber) {
	var nameContentDigest = contentObject.name.getContentDigestValue();
	if (nameContentDigest != null &&
	!DataUtils.arraysEqual(nameContentDigest, this.contentSha256.finalize()))
	// TODO: How to show the user an error for invalid digest?
	dump("Content does not match digest in name " + contentObject.name.to_uri());
	}
	return Closure.RESULT_OK;
	}

	if (contentObject.signedInfo != null && contentObject.signedInfo.finalBlockID != null)
	this.finalSegmentNumber = DataUtils.bigEndianToUnsignedInt(contentObject.signedInfo.finalBlockID);

	// The content was already put in the store. Retrieve as much as possible.
	var entry;
	while ((entry = this.segmentStore.maybeRetrieveNextEntry()) != null) {
	segmentNumber = entry.key;
	contentObject = entry.value;
	this.contentListener.onReceivedContent(DataUtils.toString(contentObject.content));
	this.contentSha256.update(contentObject.content);

	if (this.finalSegmentNumber != null && segmentNumber == this.finalSegmentNumber) {
	// Finished.
	this.contentListener.onStop();
	var nameContentDigest = contentObject.name.getContentDigestValue();
	if (nameContentDigest != null &&
	!DataUtils.arraysEqual(nameContentDigest, this.contentSha256.finalize()))
	// TODO: How to show the user an error for invalid digest?
	dump("Content does not match digest in name " + contentObject.name.to_uri());

	return Closure.RESULT_OK;
	}
	}

	if (this.finalSegmentNumber == null && !this.didRequestFinalSegment) {
	this.didRequestFinalSegment = true;
	// Try to determine the final segment now.
	var components = contentObject.name.components.slice
	(0, contentObject.name.components.length - 1);

	// Temporarily set the childSelector in the segmentTemplate.
	this.segmentTemplate.childSelector = 1;
	this.ndn.expressInterest(new Name(components), this, this.segmentTemplate);
	this.segmentTemplate.childSelector = null;
	}

	// Request new segments.
	var toRequest = this.segmentStore.requestSegmentNumbers(2);
	for (var i = 0; i < toRequest.length; ++i) {
	if (this.finalSegmentNumber != null && toRequest[i] > this.finalSegmentNumber)
	continue;

	// Make a name for the segment and get it.
	var segmentNumberBigEndian = DataUtils.nonNegativeIntToBigEndian(toRequest[i]);
	// Put a 0 byte in front.
	var segmentNumberComponent = new Uint8Array(segmentNumberBigEndian.length + 1);
	segmentNumberComponent.set(segmentNumberBigEndian, 1);

	var components = contentObject.name.components.slice
	(0, contentObject.name.components.length - 1);
	components.push(segmentNumberComponent);
	this.ndn.expressInterest(new Name(components), this, this.segmentTemplate);
	}

	return Closure.RESULT_OK;
	} catch (ex) {
	dump("ContentClosure.upcall exception: " + ex + "\n" + ex.stack);
	return Closure.RESULT_ERR;
	}
	};

	/*
	* A SegmentStore stores segments until they are retrieved in order starting with segment 0.
	*/
	var SegmentStore = function SegmentStore() {
	// Each entry is an object where the key is the segment number and value is null if
	// the segment number is requested or the contentObject if received.
	this.store = new SortedArray();
	this.maxRetrievedSegmentNumber = -1;
	};

	SegmentStore.prototype.storeContent = function(segmentNumber, contentObject) {
	// We don't expect to try to store a segment that has already been retrieved, but check anyway.
	if (segmentNumber > this.maxRetrievedSegmentNumber)
	this.store.set(segmentNumber, contentObject);
	};

	/*
	* If the min segment number is this.maxRetrievedSegmentNumber + 1 and its value is not null,
	* then delete from the store, return the entry with key and value, and update maxRetrievedSegmentNumber.
	* Otherwise return null.
	*/
	SegmentStore.prototype.maybeRetrieveNextEntry = function() {
	if (this.store.entries.length > 0 && this.store.entries[0].value != null &&
	this.store.entries[0].key == this.maxRetrievedSegmentNumber + 1) {
	var entry = this.store.entries[0];
	this.store.removeAt(0);
	++this.maxRetrievedSegmentNumber;
	return entry;
	}
	else
	return null;
	};

	/*
	* Return an array of the next segment numbers that need to be requested so that the total
	* requested segments is totalRequestedSegments. If a segment store entry value is null, it is
	* already requested and is not returned. If a segment number is returned, create a
	* entry in the segment store with a null value.
	*/
	SegmentStore.prototype.requestSegmentNumbers = function(totalRequestedSegments) {
	// First, count how many are already requested.
	var nRequestedSegments = 0;
	for (var i = 0; i < this.store.entries.length; ++i) {
	if (this.store.entries[i].value == null) {
	++nRequestedSegments;
	if (nRequestedSegments >= totalRequestedSegments)
	// Already maxed out on requests.
	return [];
	}
	}

	var toRequest = [];
	var nextSegmentNumber = this.maxRetrievedSegmentNumber + 1;
	for (var i = 0; i < this.store.entries.length; ++i) {
	var entry = this.store.entries[i];
	// Fill in the gap before the segment number in the entry.
	while (nextSegmentNumber < entry.key) {
	toRequest.push(nextSegmentNumber);
	++nextSegmentNumber;
	++nRequestedSegments;
	if (nRequestedSegments >= totalRequestedSegments)
	break;
	}
	if (nRequestedSegments >= totalRequestedSegments)
	break;

	nextSegmentNumber = entry.key + 1;
	}

	// We already filled in the gaps for the segments in the store. Continue after the last.
	while (nRequestedSegments < totalRequestedSegments) {
	toRequest.push(nextSegmentNumber);
	++nextSegmentNumber;
	++nRequestedSegments;
	}

	// Mark the new segment numbers as requested.
	for (var i = 0; i < toRequest.length; ++i)
	this.store.set(toRequest[i], null);
	return toRequest;
	}

	/*
	* A SortedArray is an array of objects with key and value, where the key is an integer.
	*/
	var SortedArray = function SortedArray() {
	this.entries = [];
	}

	SortedArray.prototype.sortEntries = function() {
	this.entries.sort(function(a, b) { return a.key - b.key; });
	};

	SortedArray.prototype.indexOfKey = function(key) {
	for (var i = 0; i < this.entries.length; ++i) {
	if (this.entries[i].key == key)
	return i;
	}

	return -1;
	}

	SortedArray.prototype.set = function(key, value) {
	var i = this.indexOfKey(key);
	if (i >= 0) {
	this.entries[i].value = value;
	return;
	}

	this.entries.push({ key: key, value: value});
	this.sortEntries();
	}

	SortedArray.prototype.removeAt = function(index) {
	this.entries.splice(index, 1);
	}

	/*
	* Scan the name from the last component to the first (skipping special name components)
	* for a recognized file name extension, and return an object with properties contentType and charset.
	*/
	function getNameContentTypeAndCharset(name) {
	var iFileName = name.indexOfFileName();
	if (iFileName < 0)
	// Get the default mime type.
	return MimeTypes.getContentTypeAndCharset("");

	return MimeTypes.getContentTypeAndCharset
	(DataUtils.toString(name.components[iFileName]).toLowerCase());
	}

	/*
	* Return true if the last component in the name is a segment number..
	*/
	function endsWithSegmentNumber(name) {
	return name.components != null && name.components.length >= 1 &&
	name.components[name.components.length - 1].length >= 1 &&
	name.components[name.components.length - 1][0] == 0;
	}

	/*
	* Find all search keys starting with "ndn." and set the attribute in template.
	* Return the search string including the starting "?" but with the "ndn." keys removed,
	* or return "" if there are no search terms left.
	*/
	function extractNdnSearch(search, template) {
	if (!(search.length >= 1 && search[0] == '?'))
	return search;

	var terms = search.substr(1).split('&');
	var i = 0;
	while (i < terms.length) {
	var keyValue = terms[i].split('=');
	var key = keyValue[0].trim();
	if (key.substr(0, 4) == "ndn.") {
	if (keyValue.length >= 1) {
	var value = keyValue[1].trim();
	var nonNegativeInt = parseInt(value);

	if (key == "ndn.MinSuffixComponents" && nonNegativeInt >= 0)
	template.minSuffixComponents = nonNegativeInt;
	if (key == "ndn.MaxSuffixComponents" && nonNegativeInt >= 0)
	template.maxSuffixComponents = nonNegativeInt;
	if (key == "ndn.ChildSelector" && nonNegativeInt >= 0)
	template.childSelector = nonNegativeInt;
	if (key == "ndn.AnswerOriginKind" && nonNegativeInt >= 0)
	template.answerOriginKind = nonNegativeInt;
	if (key == "ndn.Scope" && nonNegativeInt >= 0)
	template.scope = nonNegativeInt;
	if (key == "ndn.InterestLifetime" && nonNegativeInt >= 0)
	template.interestLifetime = nonNegativeInt;
	if (key == "ndn.PublisherPublicKeyDigest" && nonNegativeInt >= 0)
	template.publisherPublicKeyDigest = DataUtils.toNumbersFromString(unescape(value));
	if (key == "ndn.Nonce" && nonNegativeInt >= 0)
	template.nonce = DataUtils.toNumbersFromString(unescape(value));
	// TODO: handle Exclude.
	}

	// Remove the "ndn." term and don't advance i.
	terms.splice(i, 1);
	}
	else
	++i;
	}

	if (terms.length == 0)
	return "";
	else
	return "?" + terms.join('&');
	}