LCOV - code coverage report
Current view: directory - xpcom/glue - nsTArray-inl.h (source / functions) Found Hit Coverage
Test: app.info Lines: 94 19 20.2 %
Date: 2012-06-02 Functions: 0 0 -

       1                 : /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2                 : /* vim:set ts=2 sw=2 sts=2 et cindent: */
       3                 : /* ***** BEGIN LICENSE BLOCK *****
       4                 :  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
       5                 :  *
       6                 :  * The contents of this file are subject to the Mozilla Public License Version
       7                 :  * 1.1 (the "License"); you may not use this file except in compliance with
       8                 :  * the License. You may obtain a copy of the License at
       9                 :  * http://www.mozilla.org/MPL/
      10                 :  *
      11                 :  * Software distributed under the License is distributed on an "AS IS" basis,
      12                 :  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
      13                 :  * for the specific language governing rights and limitations under the
      14                 :  * License.
      15                 :  *
      16                 :  * The Original Code is C++ array template.
      17                 :  *
      18                 :  * The Initial Developer of the Original Code is Google Inc.
      19                 :  * Portions created by the Initial Developer are Copyright (C) 2005
      20                 :  * the Initial Developer. All Rights Reserved.
      21                 :  *
      22                 :  * Contributor(s):
      23                 :  *  Darin Fisher <darin@meer.net>
      24                 :  *
      25                 :  * Alternatively, the contents of this file may be used under the terms of
      26                 :  * either the GNU General Public License Version 2 or later (the "GPL"), or
      27                 :  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
      28                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
      29                 :  * of those above. If you wish to allow use of your version of this file only
      30                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
      31                 :  * use your version of this file under the terms of the MPL, indicate your
      32                 :  * decision by deleting the provisions above and replace them with the notice
      33                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
      34                 :  * the provisions above, a recipient may use your version of this file under
      35                 :  * the terms of any one of the MPL, the GPL or the LGPL.
      36                 :  *
      37                 :  * ***** END LICENSE BLOCK ***** */
      38                 : 
      39                 : #ifndef nsTArray_h__
      40                 : #  error "Don't include this file directly"
      41                 : #endif
      42                 : 
      43                 : template<class Alloc>
      44                 : nsTArray_base<Alloc>::nsTArray_base()
      45              16 :   : mHdr(EmptyHdr()) {
      46              16 :   MOZ_COUNT_CTOR(nsTArray_base);
      47              16 : }
      48                 : 
      49                 : template<class Alloc>
      50                 : nsTArray_base<Alloc>::~nsTArray_base() {
      51               0 :   if (mHdr != EmptyHdr() && !UsesAutoArrayBuffer()) {
      52               0 :     Alloc::Free(mHdr);
      53                 :   }
      54               0 :   MOZ_COUNT_DTOR(nsTArray_base);
      55               0 : }
      56                 : 
      57                 : template<class Alloc>
      58                 : const nsTArrayHeader* nsTArray_base<Alloc>::GetAutoArrayBufferUnsafe(size_t elemAlign) const {
      59                 :   // Assuming |this| points to an nsAutoArray, we want to get a pointer to
      60                 :   // mAutoBuf.  So just cast |this| to nsAutoArray* and read &mAutoBuf!
      61                 : 
      62               0 :   const void* autoBuf = &reinterpret_cast<const nsAutoArrayBase<nsTArray<PRUint32>, 1>*>(this)->mAutoBuf;
      63                 : 
      64                 :   // If we're on a 32-bit system and elemAlign is 8, we need to adjust our
      65                 :   // pointer to take into account the extra alignment in the auto array.
      66                 : 
      67                 :   MOZ_STATIC_ASSERT(sizeof(void*) != 4 ||
      68                 :                     (MOZ_ALIGNOF(mozilla::AlignedElem<8>) == 8 &&
      69                 :                      sizeof(nsAutoTArray<mozilla::AlignedElem<8>, 1>) ==
      70                 :                        sizeof(void*) + sizeof(nsTArrayHeader) +
      71                 :                        4 + sizeof(mozilla::AlignedElem<8>)),
      72                 :                     "auto array padding wasn't what we expected");
      73                 : 
      74                 :   // We don't support alignments greater than 8 bytes.
      75               0 :   NS_ABORT_IF_FALSE(elemAlign <= 4 || elemAlign == 8, "unsupported alignment.");
      76               0 :   if (sizeof(void*) == 4 && elemAlign == 8) {
      77               0 :     autoBuf = reinterpret_cast<const char*>(autoBuf) + 4;
      78                 :   }
      79                 : 
      80               0 :   return reinterpret_cast<const Header*>(autoBuf);
      81                 : }
      82                 : 
      83                 : template<class Alloc>
      84                 : bool nsTArray_base<Alloc>::UsesAutoArrayBuffer() const {
      85               0 :   if (!mHdr->mIsAutoArray) {
      86               0 :     return false;
      87                 :   }
      88                 : 
      89                 :   // This is nuts.  If we were sane, we'd pass elemAlign as a parameter to
      90                 :   // this function.  Unfortunately this function is called in nsTArray_base's
      91                 :   // destructor, at which point we don't know elem_type's alignment.
      92                 :   //
      93                 :   // We'll fall on our face and return true when we should say false if
      94                 :   //
      95                 :   //   * we're not using our auto buffer,
      96                 :   //   * elemAlign == 4, and
      97                 :   //   * mHdr == GetAutoArrayBuffer(8).
      98                 :   //
      99                 :   // This could happen if |*this| lives on the heap and malloc allocated our
     100                 :   // buffer on the heap adjacent to |*this|.
     101                 :   //
     102                 :   // However, we can show that this can't happen.  If |this| is an auto array
     103                 :   // (as we ensured at the beginning of the method), GetAutoArrayBuffer(8)
     104                 :   // always points to memory owned by |*this|, because (as we assert below)
     105                 :   //
     106                 :   //   * GetAutoArrayBuffer(8) is at most 4 bytes past GetAutoArrayBuffer(4), and 
     107                 :   //   * sizeof(nsTArrayHeader) > 4.
     108                 :   //
     109                 :   // Since nsAutoTArray always contains an nsTArrayHeader,
     110                 :   // GetAutoArrayBuffer(8) will always point inside the auto array object,
     111                 :   // even if it doesn't point at the beginning of the header.
     112                 :   //
     113                 :   // Note that this means that we can't store elements with alignment 16 in an
     114                 :   // nsTArray, because GetAutoArrayBuffer(16) could lie outside the memory
     115                 :   // owned by this nsAutoTArray.  We statically assert that elem_type's
     116                 :   // alignment is 8 bytes or less in nsAutoArrayBase.
     117                 : 
     118                 :   MOZ_STATIC_ASSERT(sizeof(nsTArrayHeader) > 4,
     119                 :                     "see comment above");
     120                 : 
     121                 : #ifdef DEBUG
     122                 :   PRPtrdiff diff = reinterpret_cast<const char*>(GetAutoArrayBuffer(8)) -
     123               0 :                    reinterpret_cast<const char*>(GetAutoArrayBuffer(4));
     124               0 :   NS_ABORT_IF_FALSE(diff >= 0 && diff <= 4, "GetAutoArrayBuffer doesn't do what we expect.");
     125                 : #endif
     126                 : 
     127               0 :   return mHdr == GetAutoArrayBuffer(4) || mHdr == GetAutoArrayBuffer(8);
     128                 : }
     129                 : 
     130                 : 
     131                 : template<class Alloc>
     132                 : bool
     133                 : nsTArray_base<Alloc>::EnsureCapacity(size_type capacity, size_type elemSize) {
     134                 :   // This should be the most common case so test this first
     135               6 :   if (capacity <= mHdr->mCapacity)
     136               0 :     return true;
     137                 : 
     138                 :   // If the requested memory allocation exceeds size_type(-1)/2, then
     139                 :   // our doubling algorithm may not be able to allocate it.
     140                 :   // Additionally we couldn't fit in the Header::mCapacity
     141                 :   // member. Just bail out in cases like that.  We don't want to be
     142                 :   // allocating 2 GB+ arrays anyway.
     143               6 :   if ((PRUint64)capacity * elemSize > size_type(-1)/2) {
     144               0 :     NS_ERROR("Attempting to allocate excessively large array");
     145               0 :     return false;
     146                 :   }
     147                 : 
     148               6 :   if (mHdr == EmptyHdr()) {
     149                 :     // Malloc() new data
     150                 :     Header *header = static_cast<Header*>
     151               6 :                      (Alloc::Malloc(sizeof(Header) + capacity * elemSize));
     152               6 :     if (!header)
     153               0 :       return false;
     154               6 :     header->mLength = 0;
     155               6 :     header->mCapacity = capacity;
     156               6 :     header->mIsAutoArray = 0;
     157               6 :     mHdr = header;
     158                 : 
     159               6 :     return true;
     160                 :   }
     161                 : 
     162                 :   // We increase our capacity so |capacity * elemSize + sizeof(Header)| is the
     163                 :   // next power of two, if this value is less than pageSize bytes, or otherwise
     164                 :   // so it's the next multiple of pageSize.
     165               0 :   const PRUint32 pageSizeBytes = 12;
     166               0 :   const PRUint32 pageSize = 1 << pageSizeBytes;
     167                 : 
     168               0 :   PRUint32 minBytes = capacity * elemSize + sizeof(Header);
     169                 :   PRUint32 bytesToAlloc;
     170               0 :   if (minBytes >= pageSize) {
     171                 :     // Round up to the next multiple of pageSize.
     172               0 :     bytesToAlloc = pageSize * ((minBytes + pageSize - 1) / pageSize);
     173                 :   }
     174                 :   else {
     175                 :     // Round up to the next power of two.  See
     176                 :     // http://graphics.stanford.edu/~seander/bithacks.html
     177               0 :     bytesToAlloc = minBytes - 1;
     178               0 :     bytesToAlloc |= bytesToAlloc >> 1;
     179               0 :     bytesToAlloc |= bytesToAlloc >> 2;
     180               0 :     bytesToAlloc |= bytesToAlloc >> 4;
     181               0 :     bytesToAlloc |= bytesToAlloc >> 8;
     182               0 :     bytesToAlloc |= bytesToAlloc >> 16;
     183               0 :     bytesToAlloc++;
     184                 : 
     185               0 :     MOZ_ASSERT((bytesToAlloc & (bytesToAlloc - 1)) == 0,
     186                 :                "nsTArray's allocation size should be a power of two!");
     187                 :   }
     188                 : 
     189                 :   Header *header;
     190               0 :   if (UsesAutoArrayBuffer()) {
     191                 :     // Malloc() and copy
     192               0 :     header = static_cast<Header*>(Alloc::Malloc(bytesToAlloc));
     193               0 :     if (!header)
     194               0 :       return false;
     195                 : 
     196               0 :     memcpy(header, mHdr, sizeof(Header) + Length() * elemSize);
     197                 :   } else {
     198                 :     // Realloc() existing data
     199               0 :     header = static_cast<Header*>(Alloc::Realloc(mHdr, bytesToAlloc));
     200               0 :     if (!header)
     201               0 :       return false;
     202                 :   }
     203                 : 
     204                 :   // How many elements can we fit in bytesToAlloc?
     205               0 :   PRUint32 newCapacity = (bytesToAlloc - sizeof(Header)) / elemSize;
     206               0 :   MOZ_ASSERT(newCapacity >= capacity, "Didn't enlarge the array enough!");
     207               0 :   header->mCapacity = newCapacity;
     208                 : 
     209               0 :   mHdr = header;
     210                 : 
     211               0 :   return true;
     212                 : }
     213                 : 
     214                 : template<class Alloc>
     215                 : void
     216                 : nsTArray_base<Alloc>::ShrinkCapacity(size_type elemSize, size_t elemAlign) {
     217               0 :   if (mHdr == EmptyHdr() || UsesAutoArrayBuffer())
     218               0 :     return;
     219                 : 
     220               0 :   if (mHdr->mLength >= mHdr->mCapacity)  // should never be greater than...
     221               0 :     return;
     222                 : 
     223               0 :   size_type length = Length();
     224                 : 
     225               0 :   if (IsAutoArray() && GetAutoArrayBuffer(elemAlign)->mCapacity >= length) {
     226               0 :     Header* header = GetAutoArrayBuffer(elemAlign);
     227                 : 
     228                 :     // Copy data, but don't copy the header to avoid overwriting mCapacity
     229               0 :     header->mLength = length;
     230               0 :     memcpy(header + 1, mHdr + 1, length * elemSize);
     231                 : 
     232               0 :     Alloc::Free(mHdr);
     233               0 :     mHdr = header;
     234               0 :     return;
     235                 :   }
     236                 : 
     237               0 :   if (length == 0) {
     238               0 :     MOZ_ASSERT(!IsAutoArray(), "autoarray should have fit 0 elements");
     239               0 :     Alloc::Free(mHdr);
     240               0 :     mHdr = EmptyHdr();
     241               0 :     return;
     242                 :   }
     243                 : 
     244               0 :   size_type size = sizeof(Header) + length * elemSize;
     245               0 :   void *ptr = Alloc::Realloc(mHdr, size);
     246               0 :   if (!ptr)
     247               0 :     return;
     248               0 :   mHdr = static_cast<Header*>(ptr);
     249               0 :   mHdr->mCapacity = length;
     250                 : }
     251                 : 
     252                 : template<class Alloc>
     253                 : void
     254                 : nsTArray_base<Alloc>::ShiftData(index_type start,
     255                 :                                 size_type oldLen, size_type newLen,
     256                 :                                 size_type elemSize, size_t elemAlign) {
     257               6 :   if (oldLen == newLen)
     258               0 :     return;
     259                 : 
     260                 :   // Determine how many elements need to be shifted
     261               6 :   size_type num = mHdr->mLength - (start + oldLen);
     262                 : 
     263                 :   // Compute the resulting length of the array
     264               6 :   mHdr->mLength += newLen - oldLen;
     265               6 :   if (mHdr->mLength == 0) {
     266               0 :     ShrinkCapacity(elemSize, elemAlign);
     267                 :   } else {
     268                 :     // Maybe nothing needs to be shifted
     269               6 :     if (num == 0)
     270               6 :       return;
     271                 :     // Perform shift (change units to bytes first)
     272               0 :     start *= elemSize;
     273               0 :     newLen *= elemSize;
     274               0 :     oldLen *= elemSize;
     275               0 :     num *= elemSize;
     276               0 :     char *base = reinterpret_cast<char*>(mHdr + 1) + start;
     277               0 :     memmove(base + newLen, base + oldLen, num);
     278                 :   }
     279                 : }
     280                 : 
     281                 : template<class Alloc>
     282                 : bool
     283                 : nsTArray_base<Alloc>::InsertSlotsAt(index_type index, size_type count,
     284                 :                                     size_type elementSize, size_t elemAlign)  {
     285                 :   MOZ_ASSERT(index <= Length(), "Bogus insertion index");
     286                 :   size_type newLen = Length() + count;
     287                 : 
     288                 :   EnsureCapacity(newLen, elementSize);
     289                 : 
     290                 :   // Check for out of memory conditions
     291                 :   if (Capacity() < newLen)
     292                 :     return false;
     293                 : 
     294                 :   // Move the existing elements as needed.  Note that this will
     295                 :   // change our mLength, so no need to call IncrementLength.
     296                 :   ShiftData(index, 0, count, elementSize, elemAlign);
     297                 :       
     298                 :   return true;
     299                 : }
     300                 : 
     301                 : // nsTArray_base::IsAutoArrayRestorer is an RAII class which takes
     302                 : // |nsTArray_base &array| in its constructor.  When it's destructed, it ensures
     303                 : // that
     304                 : //
     305                 : //   * array.mIsAutoArray has the same value as it did when we started, and
     306                 : //   * if array has an auto buffer and mHdr would otherwise point to sEmptyHdr,
     307                 : //     array.mHdr points to array's auto buffer.
     308                 : 
     309                 : template<class Alloc>
     310                 : nsTArray_base<Alloc>::IsAutoArrayRestorer::IsAutoArrayRestorer(
     311                 :   nsTArray_base<Alloc> &array,
     312                 :   size_t elemAlign) 
     313                 :   : mArray(array),
     314                 :     mElemAlign(elemAlign),
     315                 :     mIsAuto(array.IsAutoArray())
     316                 : {
     317                 : }
     318                 : 
     319                 : template<class Alloc>
     320                 : nsTArray_base<Alloc>::IsAutoArrayRestorer::~IsAutoArrayRestorer() {
     321                 :   // Careful: We don't want to set mIsAutoArray = 1 on sEmptyHdr.
     322                 :   if (mIsAuto && mArray.mHdr == mArray.EmptyHdr()) {
     323                 :     // Call GetAutoArrayBufferUnsafe() because GetAutoArrayBuffer() asserts
     324                 :     // that mHdr->mIsAutoArray is true, which surely isn't the case here.
     325                 :     mArray.mHdr = mArray.GetAutoArrayBufferUnsafe(mElemAlign);
     326                 :     mArray.mHdr->mLength = 0;
     327                 :   }
     328                 :   else {
     329                 :     mArray.mHdr->mIsAutoArray = mIsAuto;
     330                 :   }
     331                 : }
     332                 : 
     333                 : template<class Alloc>
     334                 : template<class Allocator>
     335                 : bool
     336                 : nsTArray_base<Alloc>::SwapArrayElements(nsTArray_base<Allocator>& other,
     337                 :                                         size_type elemSize,
     338                 :                                         size_t elemAlign) {
     339                 : 
     340                 :   // EnsureNotUsingAutoArrayBuffer will set mHdr = sEmptyHdr even if we have an
     341                 :   // auto buffer.  We need to point mHdr back to our auto buffer before we
     342                 :   // return, otherwise we'll forget that we have an auto buffer at all!
     343                 :   // IsAutoArrayRestorer takes care of this for us.
     344                 : 
     345                 :   IsAutoArrayRestorer ourAutoRestorer(*this, elemAlign);
     346                 :   typename nsTArray_base<Allocator>::IsAutoArrayRestorer otherAutoRestorer(other, elemAlign);
     347                 : 
     348                 :   // If neither array uses an auto buffer which is big enough to store the
     349                 :   // other array's elements, then ensure that both arrays use malloc'ed storage
     350                 :   // and swap their mHdr pointers.
     351                 :   if ((!UsesAutoArrayBuffer() || Capacity() < other.Length()) &&
     352                 :       (!other.UsesAutoArrayBuffer() || other.Capacity() < Length())) {
     353                 : 
     354                 :     if (!EnsureNotUsingAutoArrayBuffer(elemSize) ||
     355                 :         !other.EnsureNotUsingAutoArrayBuffer(elemSize)) {
     356                 :       return false;
     357                 :     }
     358                 : 
     359                 :     Header *temp = mHdr;
     360                 :     mHdr = other.mHdr;
     361                 :     other.mHdr = temp;
     362                 : 
     363                 :     return true;
     364                 :   }
     365                 : 
     366                 :   // Swap the two arrays using memcpy, since at least one is using an auto
     367                 :   // buffer which is large enough to hold all of the other's elements.  We'll
     368                 :   // copy the shorter array into temporary storage.
     369                 :   //
     370                 :   // (We could do better than this in some circumstances.  Suppose we're
     371                 :   // swapping arrays X and Y.  X has space for 2 elements in its auto buffer,
     372                 :   // but currently has length 4, so it's using malloc'ed storage.  Y has length
     373                 :   // 2.  When we swap X and Y, we don't need to use a temporary buffer; we can
     374                 :   // write Y straight into X's auto buffer, write X's malloc'ed buffer on top
     375                 :   // of Y, and then switch X to using its auto buffer.)
     376                 : 
     377                 :   if (!EnsureCapacity(other.Length(), elemSize) ||
     378                 :       !other.EnsureCapacity(Length(), elemSize)) {
     379                 :     return false;
     380                 :   }
     381                 : 
     382                 :   // The EnsureCapacity calls above shouldn't have caused *both* arrays to
     383                 :   // switch from their auto buffers to malloc'ed space.
     384                 :   NS_ABORT_IF_FALSE(UsesAutoArrayBuffer() ||
     385                 :                     other.UsesAutoArrayBuffer(),
     386                 :                     "One of the arrays should be using its auto buffer.");
     387                 : 
     388                 :   size_type smallerLength = NS_MIN(Length(), other.Length());
     389                 :   size_type largerLength = NS_MAX(Length(), other.Length());
     390                 :   void *smallerElements, *largerElements;
     391                 :   if (Length() <= other.Length()) {
     392                 :     smallerElements = Hdr() + 1;
     393                 :     largerElements = other.Hdr() + 1;
     394                 :   }
     395                 :   else {
     396                 :     smallerElements = other.Hdr() + 1;
     397                 :     largerElements = Hdr() + 1;
     398                 :   }
     399                 : 
     400                 :   // Allocate temporary storage for the smaller of the two arrays.  We want to
     401                 :   // allocate this space on the stack, if it's not too large.  Sounds like a
     402                 :   // job for AutoTArray!  (One of the two arrays we're swapping is using an
     403                 :   // auto buffer, so we're likely not allocating a lot of space here.  But one
     404                 :   // could, in theory, allocate a huge AutoTArray on the heap.)
     405                 :   nsAutoTArray<PRUint8, 64, Alloc> temp;
     406                 :   if (!temp.SetCapacity(smallerLength * elemSize)) {
     407                 :     return false;
     408                 :   }
     409                 : 
     410                 :   memcpy(temp.Elements(), smallerElements, smallerLength * elemSize);
     411                 :   memcpy(smallerElements, largerElements, largerLength * elemSize);
     412                 :   memcpy(largerElements, temp.Elements(), smallerLength * elemSize);
     413                 : 
     414                 :   // Swap the arrays' lengths.
     415                 :   NS_ABORT_IF_FALSE((other.Length() == 0 || mHdr != EmptyHdr()) &&
     416                 :                     (Length() == 0 || other.mHdr != EmptyHdr()),
     417                 :                     "Don't set sEmptyHdr's length.");
     418                 :   size_type tempLength = Length();
     419                 :   mHdr->mLength = other.Length();
     420                 :   other.mHdr->mLength = tempLength;
     421                 : 
     422                 :   return true;
     423                 : }
     424                 : 
     425                 : template<class Alloc>
     426                 : bool
     427                 : nsTArray_base<Alloc>::EnsureNotUsingAutoArrayBuffer(size_type elemSize) {
     428                 :   if (UsesAutoArrayBuffer()) {
     429                 : 
     430                 :     // If you call this on a 0-length array, we'll set that array's mHdr to
     431                 :     // sEmptyHdr, in flagrant violation of the nsAutoTArray invariants.  It's
     432                 :     // up to you to set it back!  (If you don't, the nsAutoTArray will forget
     433                 :     // that it has an auto buffer.)
     434                 :     if (Length() == 0) {
     435                 :       mHdr = EmptyHdr();
     436                 :       return true;
     437                 :     }
     438                 : 
     439                 :     size_type size = sizeof(Header) + Length() * elemSize;
     440                 : 
     441                 :     Header* header = static_cast<Header*>(Alloc::Malloc(size));
     442                 :     if (!header)
     443                 :       return false;
     444                 : 
     445                 :     memcpy(header, mHdr, size);
     446                 :     header->mCapacity = Length();
     447                 :     mHdr = header;
     448                 :   }
     449                 :   
     450                 :   return true;
     451                 : }

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