gecko-dev/xpcom/glue/nsTArray.cpp

278 lines
8.5 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is C++ array template.
*
* The Initial Developer of the Original Code is Google Inc.
* Portions created by the Initial Developer are Copyright (C) 2005
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Darin Fisher <darin@meer.net>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#include <string.h>
#include "nsTArray.h"
#include "nsXPCOM.h"
#include "nsDebug.h"
nsTArray_base::Header nsTArray_base::sEmptyHdr = { 0, 0, 0 };
nsTArray_base::nsTArray_base()
: mHdr(&sEmptyHdr) {
MOZ_COUNT_CTOR(nsTArray_base);
}
nsTArray_base::~nsTArray_base() {
if (mHdr != &sEmptyHdr && !UsesAutoArrayBuffer()) {
NS_Free(mHdr);
}
MOZ_COUNT_DTOR(nsTArray_base);
}
PRBool
nsTArray_base::EnsureCapacity(size_type capacity, size_type elemSize) {
// This should be the most common case so test this first
if (capacity <= mHdr->mCapacity)
return PR_TRUE;
// If the requested memory allocation exceeds size_type(-1)/2, then our
// doubling algorithm may not be able to allocate it. Additionally we
// couldn't fit in the Header::mCapacity member. Just bail out in cases
// like that. We don't want to be allocating 2 GB+ arrays anyway.
if ((PRUint64)capacity * elemSize > size_type(-1)/2) {
NS_ERROR("Attempting to allocate excessively large array");
return PR_FALSE;
}
if (mHdr == &sEmptyHdr) {
// NS_Alloc new data
Header *header = static_cast<Header*>
(NS_Alloc(sizeof(Header) + capacity * elemSize));
if (!header)
return PR_FALSE;
header->mLength = 0;
header->mCapacity = capacity;
header->mIsAutoArray = 0;
mHdr = header;
return PR_TRUE;
}
// Use doubling algorithm when forced to increase available capacity.
capacity = PR_MAX(capacity, mHdr->mCapacity << 1);
Header *header;
if (UsesAutoArrayBuffer()) {
// NS_Alloc and copy
header = static_cast<Header*>
(NS_Alloc(sizeof(Header) + capacity * elemSize));
if (!header)
return PR_FALSE;
memcpy(header, mHdr, sizeof(Header) + Length() * elemSize);
} else {
// NS_Realloc existing data
size_type size = sizeof(Header) + capacity * elemSize;
header = static_cast<Header*>(NS_Realloc(mHdr, size));
if (!header)
return PR_FALSE;
}
header->mCapacity = capacity;
mHdr = header;
return PR_TRUE;
}
void
nsTArray_base::ShrinkCapacity(size_type elemSize) {
if (mHdr == &sEmptyHdr || UsesAutoArrayBuffer())
return;
if (mHdr->mLength >= mHdr->mCapacity) // should never be greater than...
return;
size_type length = Length();
if (IsAutoArray() && GetAutoArrayBuffer()->mCapacity >= length) {
Header* header = GetAutoArrayBuffer();
// Copy data, but don't copy the header to avoid overwriting mCapacity
header->mLength = length;
memcpy(header + 1, mHdr + 1, length * elemSize);
NS_Free(mHdr);
mHdr = header;
return;
}
if (length == 0) {
NS_ASSERTION(!IsAutoArray(), "autoarray should have fit 0 elements");
NS_Free(mHdr);
mHdr = &sEmptyHdr;
return;
}
size_type size = sizeof(Header) + length * elemSize;
void *ptr = NS_Realloc(mHdr, size);
if (!ptr)
return;
mHdr = static_cast<Header*>(ptr);
mHdr->mCapacity = length;
}
void
nsTArray_base::ShiftData(index_type start, size_type oldLen, size_type newLen,
size_type elemSize) {
if (oldLen == newLen)
return;
// Determine how many elements need to be shifted
size_type num = mHdr->mLength - (start + oldLen);
// Compute the resulting length of the array
mHdr->mLength += newLen - oldLen;
if (mHdr->mLength == 0) {
ShrinkCapacity(elemSize);
} else {
// Maybe nothing needs to be shifted
if (num == 0)
return;
// Perform shift (change units to bytes first)
start *= elemSize;
newLen *= elemSize;
oldLen *= elemSize;
num *= elemSize;
char *base = reinterpret_cast<char*>(mHdr + 1) + start;
memmove(base + newLen, base + oldLen, num);
}
}
PRBool
nsTArray_base::InsertSlotsAt(index_type index, size_type count,
size_type elementSize) {
NS_ASSERTION(index <= Length(), "Bogus insertion index");
size_type newLen = Length() + count;
EnsureCapacity(newLen, elementSize);
// Check for out of memory conditions
if (Capacity() < newLen)
return PR_FALSE;
// Move the existing elements as needed. Note that this will
// change our mLength, so no need to call IncrementLength.
ShiftData(index, 0, count, elementSize);
return PR_TRUE;
}
PRBool
nsTArray_base::SwapArrayElements(nsTArray_base& other, size_type elemSize)
{
#ifdef DEBUG
PRBool isAuto = IsAutoArray();
PRBool otherIsAuto = other.IsAutoArray();
#endif
if (!EnsureNotUsingAutoArrayBuffer(elemSize) ||
!other.EnsureNotUsingAutoArrayBuffer(elemSize)) {
return PR_FALSE;
}
NS_ASSERTION(isAuto == IsAutoArray(), "lost auto info");
NS_ASSERTION(otherIsAuto == other.IsAutoArray(), "lost auto info");
NS_ASSERTION(!UsesAutoArrayBuffer() && !other.UsesAutoArrayBuffer(),
"both should be using an alloced buffer now");
// If the two arrays have different mIsAutoArray values (i.e. one is an
// autoarray and one is not) then simply switching the buffers is going to
// make that bit wrong. We therefore adjust these mIsAutoArray bits before
// switching the buffers so that once the buffers are switched the
// mIsAutoArray bits are right again.
// However, we have to watch out so that we don't set the bit on
// sEmptyHeader. If an array (A) uses the empty header (and the other (B)
// therefore must be an nsAutoTArray) we make A point to the B's autobuffer
// so that when the buffers are switched B points to its own autobuffer.
// Adjust mIsAutoArray flags before swapping the buffers
if (IsAutoArray() && !other.IsAutoArray()) {
if (other.mHdr == &sEmptyHdr) {
// Set other to use our built-in buffer so that we use it
// after the swap below.
other.mHdr = GetAutoArrayBuffer();
other.mHdr->mLength = 0;
}
else {
other.mHdr->mIsAutoArray = 1;
}
mHdr->mIsAutoArray = 0;
}
else if (!IsAutoArray() && other.IsAutoArray()) {
if (mHdr == &sEmptyHdr) {
// Set us to use other's built-in buffer so that other use it
// after the swap below.
mHdr = other.GetAutoArrayBuffer();
mHdr->mLength = 0;
}
else {
mHdr->mIsAutoArray = 1;
}
other.mHdr->mIsAutoArray = 0;
}
// Swap the buffers
Header *h = other.mHdr;
other.mHdr = mHdr;
mHdr = h;
NS_ASSERTION(isAuto == IsAutoArray(), "lost auto info");
NS_ASSERTION(otherIsAuto == other.IsAutoArray(), "lost auto info");
return PR_TRUE;
}
PRBool
nsTArray_base::EnsureNotUsingAutoArrayBuffer(size_type elemSize)
{
if (UsesAutoArrayBuffer()) {
size_type size = sizeof(Header) + Length() * elemSize;
Header* header = static_cast<Header*>(NS_Alloc(size));
if (!header)
return PR_FALSE;
memcpy(header, mHdr, size);
header->mCapacity = Length();
mHdr = header;
}
return PR_TRUE;
}