зеркало из https://github.com/mozilla/gecko-dev.git
269 строки
10 KiB
C++
269 строки
10 KiB
C++
/* vim:set ts=4 sw=4 sts=4 et cin: */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is Mozilla.
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*
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* The Initial Developer of the Original Code is IBM Corporation.
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* Portions created by IBM Corporation are Copyright (C) 2003
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* IBM Corporation. All Rights Reserved.
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*
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* Contributor(s):
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* IBM Corp.
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#ifndef nsHostResolver_h__
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#define nsHostResolver_h__
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#include "nscore.h"
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#include "pratom.h"
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#include "prcvar.h"
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#include "prclist.h"
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#include "prnetdb.h"
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#include "pldhash.h"
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#include "nsISupportsImpl.h"
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class nsHostResolver;
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class nsHostRecord;
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class nsResolveHostCallback;
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/* XXX move this someplace more generic */
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#define NS_DECL_REFCOUNTED_THREADSAFE(classname) \
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private: \
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nsAutoRefCnt _refc; \
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public: \
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PRInt32 AddRef() { \
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PRInt32 n = PR_AtomicIncrement((PRInt32*)&_refc); \
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NS_LOG_ADDREF(this, n, #classname, sizeof(classname)); \
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return n; \
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} \
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PRInt32 Release() { \
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PRInt32 n = PR_AtomicDecrement((PRInt32*)&_refc); \
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NS_LOG_RELEASE(this, n, #classname); \
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if (n == 0) \
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delete this; \
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return n; \
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}
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#define MAX_RESOLVER_THREADS_FOR_ANY_PRIORITY 3
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#define MAX_RESOLVER_THREADS_FOR_HIGH_PRIORITY 5
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#define MAX_RESOLVER_THREADS (MAX_RESOLVER_THREADS_FOR_ANY_PRIORITY + \
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MAX_RESOLVER_THREADS_FOR_HIGH_PRIORITY)
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struct nsHostKey
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{
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const char *host;
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PRUint16 flags;
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PRUint16 af;
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};
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/**
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* nsHostRecord - ref counted object type stored in host resolver cache.
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*/
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class nsHostRecord : public PRCList, public nsHostKey
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{
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public:
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NS_DECL_REFCOUNTED_THREADSAFE(nsHostRecord)
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/* instantiates a new host record */
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static nsresult Create(const nsHostKey *key, nsHostRecord **record);
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/* a fully resolved host record has either a non-null |addr_info| or |addr|
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* field. if |addr_info| is null, it implies that the |host| is an IP
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* address literal. in which case, |addr| contains the parsed address.
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* otherwise, if |addr_info| is non-null, then it contains one or many
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* IP addresses corresponding to the given host name. if both |addr_info|
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* and |addr| are null, then the given host has not yet been fully resolved.
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* |af| is the address family of the record we are querying for.
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*/
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/* the lock protects |addr_info| and |addr_info_gencnt| because they
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* are mutable and accessed by the resolver worker thread and the
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* nsDNSService2 class. |addr| doesn't change after it has been
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* assigned a value. only the resolver worker thread modifies
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* nsHostRecord (and only in nsHostResolver::OnLookupComplete);
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* the other threads just read it. therefore the resolver worker
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* thread doesn't need to lock when reading |addr_info|.
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*/
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PRLock *addr_info_lock;
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int addr_info_gencnt; /* generation count of |addr_info| */
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PRAddrInfo *addr_info;
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PRNetAddr *addr;
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PRBool negative; /* True if this record is a cache of a failed lookup.
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Negative cache entries are valid just like any other
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(though never for more than 60 seconds), but a use
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of that negative entry forces an asynchronous refresh. */
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PRUint32 expiration; /* measured in minutes since epoch */
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PRBool HasResult() const { return addr_info || addr || negative; }
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private:
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friend class nsHostResolver;
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PRCList callbacks; /* list of callbacks */
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PRBool resolving; /* true if this record is being resolved, which means
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* that it is either on the pending queue or owned by
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* one of the worker threads. */
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PRBool onQueue; /* true if pending and on the queue (not yet given to getaddrinfo())*/
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PRBool usingAnyThread; /* true if off queue and contributing to mActiveAnyThreadCount */
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~nsHostRecord();
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};
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/**
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* ResolveHost callback object. It's PRCList members are used by
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* the nsHostResolver and should not be used by anything else.
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*/
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class NS_NO_VTABLE nsResolveHostCallback : public PRCList
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{
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public:
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/**
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* OnLookupComplete
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*
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* this function is called to complete a host lookup initiated by
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* nsHostResolver::ResolveHost. it may be invoked recursively from
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* ResolveHost or on an unspecified background thread.
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*
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* NOTE: it is the responsibility of the implementor of this method
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* to handle the callback in a thread safe manner.
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*
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* @param resolver
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* nsHostResolver object associated with this result
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* @param record
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* the host record containing the results of the lookup
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* @param status
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* if successful, |record| contains non-null results
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*/
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virtual void OnLookupComplete(nsHostResolver *resolver,
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nsHostRecord *record,
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nsresult status) = 0;
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};
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/**
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* nsHostResolver - an asynchronous host name resolver.
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*/
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class nsHostResolver
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{
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public:
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/**
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* host resolver instances are reference counted.
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*/
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NS_DECL_REFCOUNTED_THREADSAFE(nsHostResolver)
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/**
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* creates an addref'd instance of a nsHostResolver object.
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*/
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static nsresult Create(PRUint32 maxCacheEntries, // zero disables cache
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PRUint32 maxCacheLifetime, // minutes
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nsHostResolver **resolver);
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/**
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* puts the resolver in the shutdown state, which will cause any pending
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* callbacks to be detached. any future calls to ResolveHost will fail.
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*/
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void Shutdown();
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/**
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* resolve the given hostname asynchronously. the caller can synthesize
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* a synchronous host lookup using a lock and a cvar. as noted above
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* the callback will occur re-entrantly from an unspecified thread. the
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* host lookup cannot be canceled (cancelation can be layered above this
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* by having the callback implementation return without doing anything).
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*/
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nsresult ResolveHost(const char *hostname,
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PRUint16 flags,
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PRUint16 af,
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nsResolveHostCallback *callback);
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/**
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* removes the specified callback from the nsHostRecord for the given
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* hostname, flags, and address family. these parameters should correspond
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* to the parameters passed to ResolveHost. this function executes the
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* callback if the callback is still pending with the given status.
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*/
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void DetachCallback(const char *hostname,
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PRUint16 flags,
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PRUint16 af,
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nsResolveHostCallback *callback,
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nsresult status);
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/**
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* values for the flags parameter passed to ResolveHost and DetachCallback
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* that may be bitwise OR'd together.
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*
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* NOTE: in this implementation, these flags correspond exactly in value
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* to the flags defined on nsIDNSService.
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*/
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enum {
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RES_BYPASS_CACHE = 1 << 0,
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RES_CANON_NAME = 1 << 1,
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RES_PRIORITY_MEDIUM = 1 << 2,
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RES_PRIORITY_LOW = 1 << 3,
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RES_SPECULATE = 1 << 4
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};
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private:
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nsHostResolver(PRUint32 maxCacheEntries=50, PRUint32 maxCacheLifetime=1);
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~nsHostResolver();
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nsresult Init();
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nsresult IssueLookup(nsHostRecord *);
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PRBool GetHostToLookup(nsHostRecord **m);
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void OnLookupComplete(nsHostRecord *, nsresult, PRAddrInfo *);
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void DeQueue(PRCList &aQ, nsHostRecord **aResult);
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void ClearPendingQueue(PRCList *aPendingQueue);
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nsresult ConditionallyCreateThread(nsHostRecord *rec);
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static void MoveQueue(nsHostRecord *aRec, PRCList &aDestQ);
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static void ThreadFunc(void *);
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PRUint32 mMaxCacheEntries;
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PRUint32 mMaxCacheLifetime;
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PRLock *mLock;
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PRCondVar *mIdleThreadCV; // non-null if idle thread
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PRUint32 mNumIdleThreads;
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PRUint32 mThreadCount;
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PRUint32 mActiveAnyThreadCount;
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PLDHashTable mDB;
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PRCList mHighQ;
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PRCList mMediumQ;
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PRCList mLowQ;
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PRCList mEvictionQ;
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PRUint32 mEvictionQSize;
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PRUint32 mPendingCount;
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PRTime mCreationTime;
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PRBool mShutdown;
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PRIntervalTime mLongIdleTimeout;
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PRIntervalTime mShortIdleTimeout;
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};
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#endif // nsHostResolver_h__
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