Technote 1122

Locking and Unlocking Handles

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static pascal OSErr Unsafe_DoSomethingToHandle (Handle h)
{
   OSErr err = noErr;

   HLock (h);
   if (!(err = MemError ())) {
      err = DoSomethingToPointer (*h);
      HUnlock (h);                      // äÎåØ!
      if (!err)
         err = MemError ();
   }
   return err;
}


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static pascal OSErr SafeOne_DoSomethingToHandle (Handle h)
{
   OSErr err = noErr;

   SInt8 hState = HGetState (h);
   if (!(err = MemError ())) {
      HLock (h);
      if (!(err = MemError ())) {
         err = DoSomethingToLockedHandle (h);
         HSetState (h,hState);
         if (!err)
            err = MemError ();
      }
   }
   return err;
}


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enum { kHandleLockMask = 0x80 }; // <MacMemory.h> 3.0.1Ç©ÇÁî≤ÇØǃǢÇÈÇΩÇfl

static pascal OSErr SafeTwo_DoSomethingToHandle (Handle h)
{
   OSErr err = noErr;

   SInt8 hState = HGetState (h);
   if (!(err = MemError ())) {
      Boolean handleWasLocked = (kHandleLockMask & hState) ? true : false;
      if (!handleWasLocked) {
         HLock (h);
         err = MemError ();
      }
      if (!err) {
         err = DoSomethingToLockedHandle (h);
         if (!handleWasLocked) {
            HUnlock (h);
            err = MemError ();
         }
      }
   }
   return err;
}


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static pascal OSErr UnnecessaryHandleLock (Handle h)
{
   OSErr err = noErr;

   SInt8 hState = HGetState (h);
   if (!(err = MemError ())) {
      HLock (h);
      if (!(err = MemError ())) {
         **h = 12;                 // ÇΩǩǙDZÇÃÇΩÇflÇ…ÉçÉbÉNÇ?
         HSetState (h, hState);
         if (!err)
            err = MemError ();
      }
   }
   return err;
}


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static pascal OSErr AvoidHandleLock (Handle h)
{
   OSErr err = noErr;

   char c = **h;
   err = DoSomethingToCharacter (&c);
   if (!err)
      **h = c;
   return err;
}


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ÉRÅ[ÉhÇÃàÍïîÇ™ìΔêËìIÇ…ÉnÉìÉhÉãÇóòópǵǃǢÇÈèÍçáÇÕÅAëºÇÃä÷êîǙǪÇÃÉnÉìÉhÉãÇ…óäÇÈêSîzǙǻǢÇÃÇ≈ÅAé©óRÇ…ÉçÉbÉNñîÇÕÉçÉbÉNÇÃâèúÇ™çsǶNjÇ∑ÅB

ó·Ç¶ÇŒÅAÉRÅ[ÉhÇÃàÍïîÇ™äOÇ…å©Ç¶Ç»Ç¢ì‡ïîÉoÉbÉtÉ@ÇÉnÉìÉhÉãÇΔǵǃéùǡǃǢÇÈèÍçáÇÕÅAǪÇÃÉRÅ[ÉhÇ™ÉnÉìÉhÉãÇÃê∂ê¨Ç©ÇÁâï˙Ç‹Ç≈ÇÇ∑Ç◊ǃä«óùÇ∑ÇÈÇΩÇflÅAìΔêËìIÇ…ÉnÉìÉhÉãÇóòópǵǃǢÇÈDZÇΔÇ…Ç»ÇËÇ‹Ç∑ÅB

LJǧàÍǬÇÃó·ÇÕàÍéûìIÇ…ÉoÉbÉtÉ@ÇäÑÇËìñǃǃÅAèIóπíºëOÇ…âï˙Ç∑ÇÈÉRÅ[ÉhÇ≈Ç∑ÅBNewHandle ()Ç™ê∂ê¨Ç∑ÇÈÉnÉìÉhÉãÇÕÉçÉbÉNÇ≥ÇÍÇ‹ÇπÇÒÇ™ÅADisposeHandle ()ÇÕÉçÉbÉNÇ≥ÇÍÇΩÉnÉìÉhÉãLJéÛÇØïtÇØÇ‹Ç∑ÇÃÇ≈à»â∫ÇÃÇÊǧǻÉAÉãÉSÉäÉYÉÄÇ™ê¨óßǵNjÇ∑ÅB

static pascal OSErr SafeThree_DoSomethingToHandle (void)
       {
           OSErr err = noErr;
        
           Handle h = NewHandle (12);
        
           if (!h)
               err = MemError ( );
           else
           {
               HLock (h);
               err = MemError ( );
        
               if (!err)
                   err = DoSomethingToLockedHandle (h);
        
               DisposeHandle (h);
        
               if (!err)
                   err = MemError ( );
           }
        
           return err;
       }


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Inside Macintosh: MemoryëÊ1èÕMemory Manager
Inside Macintosh: ProcessesëÊ7èÕSegment Manager