gecko-dev/xpcom/glue/nsTArray.cpp

135 lines
4.4 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"
const nsTArray_base::Header nsTArray_base::sEmptyHdr = { 0, 0 };
PRBool
nsTArray_base::EnsureCapacity(size_type capacity, size_type elemSize) {
// If the requested memory allocation exceeds size_type(-1)/2, then our
// doubling algorithm may not be able to allocate it. Just bail out in
// cases like that. We don't want to be allocating 2 GB+ arrays anyway.
if (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 = NS_STATIC_CAST(Header*,
NS_Alloc(sizeof(Header) + capacity * elemSize));
if (!header)
return PR_FALSE;
header->mLength = 0;
header->mCapacity = capacity;
mHdr = header;
} else {
// NS_Realloc existing data
if (capacity <= mHdr->mCapacity)
return PR_TRUE;
// Use doubling algorithm when forced to increase available capacity.
if (mHdr->mCapacity > 0) {
size_type temp = mHdr->mCapacity;
while (temp < capacity)
temp <<= 1;
capacity = temp;
}
size_type size = sizeof(Header) + capacity * elemSize;
void *ptr = NS_Realloc(mHdr, size);
if (!ptr)
return PR_FALSE;
mHdr = NS_STATIC_CAST(Header*, ptr);
mHdr->mCapacity = capacity;
}
return PR_TRUE;
}
void
nsTArray_base::ShrinkCapacity(size_type elemSize) {
if (mHdr == &sEmptyHdr)
return;
if (mHdr->mLength >= mHdr->mCapacity) // should never be greater than...
return;
if (mHdr->mLength == 0) {
NS_Free(mHdr);
mHdr = NS_CONST_CAST(Header *, &sEmptyHdr);
return;
}
size_type size = sizeof(Header) + mHdr->mLength * elemSize;
void *ptr = NS_Realloc(mHdr, size);
if (!ptr)
return;
mHdr = NS_STATIC_CAST(Header*, ptr);
mHdr->mCapacity = mHdr->mLength;
}
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 = NS_REINTERPRET_CAST(char*, mHdr + 1) + start;
memmove(base + newLen, base + oldLen, num);
}
}