ObjXMPP  Artifact [f3a2775abf]

Artifact f3a2775abf84505271d18167b64b184045c9d05f7e98c67bc1102c489dbdabd2:

• File src/XMPPSRVEnumerator.m — part of check-in [e240aaaf2a] at 2011-05-25 22:41:26 on branch trunk — Get rid of an unnecessary loop.

  The loop is not required as we recalculate each entry's
  accumulatedWeight on each call, thus there is always an entry that will
  be found for the random number. (user: js, size: 8255) [annotate] [blame] [check-ins using]

/*
 * Copyright (c) 2011, Jonathan Schleifer <js@webkeks.org>
 * Copyright (c) 2011, Florian Zeitz <florob@babelmonkeys.de>
 *
 * https://webkeks.org/hg/objxmpp/
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice is present in all copies.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <assert.h>

#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <resolv.h>
#include <sys/types.h>
#include <openssl/rand.h>

#import "XMPPSRVEnumerator.h"

@implementation XMPPSRVEntry
+ entryWithPriority: (uint16_t)priority
	     weight: (uint16_t)weight
	       port: (uint16_t)port
	     target: (OFString*)target
{
	return [[[self alloc] initWithPriority: priority
					weight: weight
					  port: port
					target: target] autorelease];
}

+ entryWithResourceRecord: (ns_rr)resourceRecord
		   handle: (ns_msg)handle
{
	return [[[self alloc] initWithResourceRecord: resourceRecord
					      handle: handle] autorelease];
}

- init
{
	Class c = isa;
	[self release];
	@throw [OFNotImplementedException newWithClass: c
					      selector: _cmd];
}

- initWithPriority: (uint16_t)priority_
	    weight: (uint16_t)weight_
	      port: (uint16_t)port_
	    target: (OFString*)target_
{
	self = [super init];

	@try {
		priority = priority_;
		weight = weight_;
		port = port_;
		target = [target_ copy];
	} @catch (id e) {
		[self release];
		@throw e;
	}

	return self;
}

- initWithResourceRecord: (ns_rr)resourceRecord
		  handle: (ns_msg)handle
{
	self = [super init];

	@try {
		const uint16_t *rdata;
		char buffer[NS_MAXDNAME];

		rdata = (const uint16_t*)(void*)ns_rr_rdata(resourceRecord);
		priority = ntohs(rdata[0]);
		weight = ntohs(rdata[1]);
		port = ntohs(rdata[2]);

		if (dn_expand(ns_msg_base(handle), ns_msg_end(handle),
		    (uint8_t*)&rdata[3], buffer, NS_MAXDNAME) < 1)
			@throw [OFInitializationFailedException
			    newWithClass: isa];

		target = [[OFString alloc] initWithCString: buffer];
	} @catch (id e) {
		[self release];
		@throw e;
	}

	return self;
}

- (void)dealloc
{
	[target release];

	[super dealloc];
}

- (OFString*)description
{
	return [OFString stringWithFormat: @"<%@ priority: %" PRIu16
					   @", weight: %" PRIu16
					   @", target: %@:%" PRIu16 @">",
					   isa, priority, weight, target, port];
}

- (uint16_t)priority
{
	return priority;
}

- (uint16_t)weight
{
	return weight;
}

- (void)setAccumulatedWeight: (uint16_t)accumulatedWeight_
{
	accumulatedWeight = accumulatedWeight_;
}

- (uint16_t)accumulatedWeight
{
	return accumulatedWeight;
}

- (uint16_t)port
{
	return port;
}

- (OFString*)target
{
	OF_GETTER(target, YES)
}
@end

@implementation XMPPSRVEnumerator
+ enumeratorWithDomain: (OFString*)domain_
{
	return [[[self alloc] initWithDomain: domain_] autorelease];
}

- initWithDomain: (OFString*)domain_
{
	self = [super init];

	@try {
		list = [[OFList alloc] init];
		domain = [domain_ copy];
	} @catch (id e) {
		[self release];
		@throw e;
	}

	return self;
}

- (void)dealloc
{
	[list release];
	[domain release];
	[subListCopy release];

	[super dealloc];
}

- (OFString*)domain;
{
	OF_GETTER(domain, YES)
}

- (void)lookUpEntries
{
	OFAutoreleasePool *pool = [[OFAutoreleasePool alloc] init];
	unsigned char *answer = NULL;
	OFString *request;

	request = [OFString stringWithFormat: @"_xmpp-client._tcp.%@", domain];

	@try {
		int answerLen, resourceRecordCount, i;
		ns_rr resourceRecord;
		ns_msg handle;

		if (res_ninit(&resState))
			@throw [OFAddressTranslationFailedException
			    newWithClass: isa
				  socket: nil
				    host: domain];

		answer = [self allocMemoryWithSize: of_pagesize];
		answerLen = res_nsearch(&resState, [request cString], ns_c_in,
		    ns_t_srv, answer, (int)of_pagesize);

		if (answerLen < 1 || answerLen > of_pagesize)
			@throw [OFAddressTranslationFailedException
			    newWithClass: isa
				  socket: nil
				    host: domain];

		if (ns_initparse(answer, answerLen, &handle))
			@throw [OFAddressTranslationFailedException
			    newWithClass: isa
				  socket: nil
				    host: domain];

		resourceRecordCount = ns_msg_count(handle, ns_s_an);
		for (i = 0; i < resourceRecordCount; i++) {
			if (ns_parserr(&handle, ns_s_an, i, &resourceRecord))
				continue;

			if (ns_rr_type(resourceRecord) != ns_t_srv ||
			    ns_rr_class(resourceRecord) != ns_c_in)
				continue;

			[self XMPP_addEntry: [XMPPSRVEntry
			    entryWithResourceRecord: resourceRecord
					     handle: handle]];
		}
	} @finally {
		[self freeMemory: answer];
		res_ndestroy(&resState);
	}

	[pool release];
}

- (void)XMPP_addEntry: (XMPPSRVEntry*)entry
{
	OFAutoreleasePool *pool;
	OFList *subList;
	of_list_object_t *iter;

	/* Look if there already is a list with the priority */
	for (iter = [list firstListObject]; iter != NULL; iter = iter->next) {
		if ([[iter->object firstObject] priority] == [entry priority]) {
			/*
			 * RFC 2782 says those with weight 0 should be at the
			 * beginning of the list.
			 */
			if ([entry weight] > 0)
				[iter->object appendObject: entry];
			else
				[iter->object prependObject: entry];

			return;
		}

		/* We can't have one if the priority is already bigger */
		if ([[iter->object firstObject] priority] > [entry priority])
			break;
	}

	/* No list with the priority -> create one at the correct place */
	for (iter = [list firstListObject]; iter != NULL; iter = iter->next) {
		if ([[iter->object firstObject] priority] > [entry priority]) {
			OFAutoreleasePool *pool;

			pool = [[OFAutoreleasePool alloc] init];

			subList = [OFList list];

			/*
			 * RFC 2782 says those with weight 0 should be at the
			 * beginning of the list.
			 */
			if ([entry weight] > 0)
				[subList appendObject: entry];
			else
				[subList prependObject: entry];

			[list insertObject: subList
			  beforeListObject: iter];

			[pool release];

			return;
		}
	}

	/* There is no list with a bigger priority -> append */
	pool = [[OFAutoreleasePool alloc] init];

	subList = [OFList list];

	/*
	 * RFC 2782 says those with weight 0 should be at the beginning of the
	 * list.
	 */
	if ([entry weight] > 0)
		[subList appendObject: entry];
	else
		[subList prependObject: entry];

	[list appendObject: subList];

	[pool release];
}

- (id)nextObject
{
	XMPPSRVEntry *ret;
	of_list_object_t *iter;
	uint32_t totalWeight = 0;

	if (done)
		return nil;

	if (listIter == NULL)
		listIter = [list lastListObject];

	if (listIter == NULL)
		return nil;

	if (subListCopy == nil)
		subListCopy = [listIter->object copy];

	for (iter = [subListCopy firstListObject]; iter != NULL;
	     iter = iter->next) {
		totalWeight += [iter->object weight];
		[iter->object setAccumulatedWeight: totalWeight];
	}

	if ([subListCopy count] > 0)  {
		uint32_t randomWeight;

		RAND_pseudo_bytes((uint8_t*)&randomWeight, sizeof(uint32_t));
		randomWeight %= (totalWeight + 1);

		for (iter = [subListCopy firstListObject]; iter != NULL;
		     iter = iter->next) {
			if ([iter->object accumulatedWeight] >= randomWeight) {
				ret = [[iter->object retain] autorelease];

				[subListCopy removeListObject: iter];

				break;
			}
		}
	}

	if ([subListCopy count] == 0) {
		[subListCopy release];
		subListCopy = nil;

		listIter = listIter->previous;

		if (listIter == NULL)
			done = YES;
	}

	return ret;
}

- (void)reset
{
	listIter = NULL;
	[subListCopy release];
	subListCopy = nil;
	done = NO;
}
@end