gecko-dev/xpcom/glue/nsDeque.cpp

433 строки
10 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "nsDeque.h"
#include "nsISupportsImpl.h"
#include <string.h>
#ifdef DEBUG_rickg
#include <stdio.h>
#endif
#include "mozilla/CheckedInt.h"
/**
* 07/02/2001 09:17p 509,104 clangref.pdf from openwatcom's site
* Watcom C Language Reference Edition 11.0c
* page 118 of 297
*
* The % symbol yields the remainder from the division of the first operand
* by the second operand. The operands of % must have integral type.
*
* When both operands of % are positive, the result is a positive value
* smaller than the second operand. When one or both operands is negative,
* whether the result is positive or negative is implementation-defined.
*
*/
/* Ok, so first of all, C is underspecified. joy.
* The following functions do not provide a correct implementation of modulus
* They provide functionality for x>-y.
* There are risks of 2*y being greater than max int, which is part of the
* reason no multiplication is used and other operations are avoided.
*
* modasgn
* @param x variable
* @param y expression
* approximately equivalent to x %= y
*
* modulus
* @param x expression
* @param y expression
* approximately equivalent to x % y
*/
#define modasgn(x,y) if (x<0) x+=y; x%=y
#define modulus(x,y) ((x<0)?(x+y)%(y):(x)%(y))
/**
* Standard constructor
* @param deallocator, called by Erase and ~nsDeque
*/
nsDeque::nsDeque(nsDequeFunctor* aDeallocator)
{
MOZ_COUNT_CTOR(nsDeque);
mDeallocator = aDeallocator;
mOrigin = mSize = 0;
mData = mBuffer; // don't allocate space until you must
mCapacity = sizeof(mBuffer) / sizeof(mBuffer[0]);
memset(mData, 0, mCapacity * sizeof(mBuffer[0]));
}
/**
* Destructor
*/
nsDeque::~nsDeque()
{
MOZ_COUNT_DTOR(nsDeque);
#ifdef DEBUG_rickg
char buffer[30];
printf("Capacity: %i\n", mCapacity);
static int mCaps[15] = {0};
switch (mCapacity) {
case 4: mCaps[0]++; break;
case 8: mCaps[1]++; break;
case 16: mCaps[2]++; break;
case 32: mCaps[3]++; break;
case 64: mCaps[4]++; break;
case 128: mCaps[5]++; break;
case 256: mCaps[6]++; break;
case 512: mCaps[7]++; break;
case 1024: mCaps[8]++; break;
case 2048: mCaps[9]++; break;
case 4096: mCaps[10]++; break;
default:
break;
}
#endif
Erase();
if (mData && mData != mBuffer) {
free(mData);
}
mData = 0;
SetDeallocator(0);
}
size_t
nsDeque::SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
{
size_t size = 0;
if (mData != mBuffer) {
size += aMallocSizeOf(mData);
}
if (mDeallocator) {
size += aMallocSizeOf(mDeallocator);
}
return size;
}
size_t
nsDeque::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
{
return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
}
/**
* Set the functor to be called by Erase()
* The deque owns the functor.
*
* @param aDeallocator functor object for use by Erase()
*/
void
nsDeque::SetDeallocator(nsDequeFunctor* aDeallocator)
{
delete mDeallocator;
mDeallocator = aDeallocator;
}
/**
* Remove all items from container without destroying them.
*/
void
nsDeque::Empty()
{
if (mSize && mData) {
memset(mData, 0, mCapacity * sizeof(*mData));
}
mSize = 0;
mOrigin = 0;
}
/**
* Remove and delete all items from container
*/
void
nsDeque::Erase()
{
if (mDeallocator && mSize) {
ForEach(*mDeallocator);
}
Empty();
}
/**
* This method quadruples the size of the deque
* Elements in the deque are resequenced so that elements
* in the deque are stored sequentially
*
* @return whether growing succeeded
*/
bool
nsDeque::GrowCapacity()
{
mozilla::CheckedInt<int32_t> newCapacity = mCapacity;
newCapacity *= 4;
NS_ASSERTION(newCapacity.isValid(), "Overflow");
if (!newCapacity.isValid()) {
return false;
}
// Sanity check the new byte size.
mozilla::CheckedInt<int32_t> newByteSize = newCapacity;
newByteSize *= sizeof(void*);
NS_ASSERTION(newByteSize.isValid(), "Overflow");
if (!newByteSize.isValid()) {
return false;
}
void** temp = (void**)malloc(newByteSize.value());
if (!temp) {
return false;
}
//Here's the interesting part: You can't just move the elements
//directly (in situ) from the old buffer to the new one.
//Since capacity has changed, the old origin doesn't make
//sense anymore. It's better to resequence the elements now.
memcpy(temp, mData + mOrigin, sizeof(void*) * (mCapacity - mOrigin));
memcpy(temp + (mCapacity - mOrigin), mData, sizeof(void*) * mOrigin);
if (mData != mBuffer) {
free(mData);
}
mCapacity = newCapacity.value();
mOrigin = 0; //now realign the origin...
mData = temp;
return true;
}
/**
* This method adds an item to the end of the deque.
* This operation has the potential to cause the
* underlying buffer to resize.
*
* @param aItem: new item to be added to deque
*/
bool
nsDeque::Push(void* aItem, const fallible_t&)
{
if (mSize == mCapacity && !GrowCapacity()) {
return false;
}
mData[modulus(mOrigin + mSize, mCapacity)] = aItem;
mSize++;
return true;
}
/**
* This method adds an item to the front of the deque.
* This operation has the potential to cause the
* underlying buffer to resize.
*
* --Commments for GrowCapacity() case
* We've grown and shifted which means that the old
* final element in the deque is now the first element
* in the deque. This is temporary.
* We haven't inserted the new element at the front.
*
* To continue with the idea of having the front at zero
* after a grow, we move the old final item (which through
* the voodoo of mOrigin-- is now the first) to its final
* position which is conveniently the old length.
*
* Note that this case only happens when the deque is full.
* [And that pieces of this magic only work if the deque is full.]
* picture:
* [ABCDEFGH] @[mOrigin:3]:D.
* Task: PushFront("Z")
* shift mOrigin so, @[mOrigin:2]:C
* stretch and rearrange: (mOrigin:0)
* [CDEFGHAB ________ ________ ________]
* copy: (The second C is currently out of bounds)
* [CDEFGHAB C_______ ________ ________]
* later we will insert Z:
* [ZDEFGHAB C_______ ________ ________]
* and increment size: 9. (C is no longer out of bounds)
* --
* @param aItem: new item to be added to deque
*/
bool
nsDeque::PushFront(void* aItem, const fallible_t&)
{
mOrigin--;
modasgn(mOrigin, mCapacity);
if (mSize == mCapacity) {
if (!GrowCapacity()) {
return false;
}
/* Comments explaining this are above*/
mData[mSize] = mData[mOrigin];
}
mData[mOrigin] = aItem;
mSize++;
return true;
}
/**
* Remove and return the last item in the container.
*
* @return ptr to last item in container
*/
void*
nsDeque::Pop()
{
void* result = 0;
if (mSize > 0) {
--mSize;
int32_t offset = modulus(mSize + mOrigin, mCapacity);
result = mData[offset];
mData[offset] = 0;
if (!mSize) {
mOrigin = 0;
}
}
return result;
}
/**
* This method gets called you want to remove and return
* the first member in the container.
*
* @return last item in container
*/
void*
nsDeque::PopFront()
{
void* result = 0;
if (mSize > 0) {
NS_ASSERTION(mOrigin < mCapacity, "Error: Bad origin");
result = mData[mOrigin];
mData[mOrigin++] = 0; //zero it out for debugging purposes.
mSize--;
// Cycle around if we pop off the end
// and reset origin if when we pop the last element
if (mCapacity == mOrigin || !mSize) {
mOrigin = 0;
}
}
return result;
}
/**
* This method gets called you want to peek at the bottom
* member without removing it.
*
* @return last item in container
*/
void*
nsDeque::Peek()
{
void* result = 0;
if (mSize > 0) {
result = mData[modulus(mSize - 1 + mOrigin, mCapacity)];
}
return result;
}
/**
* This method gets called you want to peek at the topmost
* member without removing it.
*
* @return last item in container
*/
void*
nsDeque::PeekFront()
{
void* result = 0;
if (mSize > 0) {
result = mData[mOrigin];
}
return result;
}
/**
* Call this to retrieve the ith element from this container.
* Keep in mind that accessing the underlying elements is
* done in a relative fashion. Object 0 is not necessarily
* the first element (the first element is at mOrigin).
*
* @param aIndex : 0 relative offset of item you want
* @return void* or null
*/
void*
nsDeque::ObjectAt(int32_t aIndex) const
{
void* result = 0;
if (aIndex >= 0 && aIndex < mSize) {
result = mData[modulus(mOrigin + aIndex, mCapacity)];
}
return result;
}
void*
nsDeque::RemoveObjectAt(int32_t aIndex)
{
if (aIndex < 0 || aIndex >= mSize) {
return 0;
}
void* result = mData[modulus(mOrigin + aIndex, mCapacity)];
// "Shuffle down" all elements in the array by 1, overwritting the element
// being removed.
for (int32_t i = aIndex; i < mSize; ++i) {
mData[modulus(mOrigin + i, mCapacity)] =
mData[modulus(mOrigin + i + 1, mCapacity)];
}
mSize--;
return result;
}
void*
nsDeque::Last() const
{
return ObjectAt(mSize - 1);
}
/**
* Call this method when you want to iterate all the
* members of the container, passing a functor along
* to call your code.
*
* @param aFunctor object to call for each member
* @return *this
*/
void
nsDeque::ForEach(nsDequeFunctor& aFunctor) const
{
for (int32_t i = 0; i < mSize; ++i) {
aFunctor(ObjectAt(i));
}
}
/**
* Call this method when you want to iterate all the
* members of the container, calling the functor you
* passed with each member. This process will interrupt
* if your function returns non 0 to this method.
*
* @param aFunctor object to call for each member
* @return first nonzero result of aFunctor or 0.
*/
const void*
nsDeque::FirstThat(nsDequeFunctor& aFunctor) const
{
for (int32_t i = 0; i < mSize; ++i) {
void* obj = aFunctor(ObjectAt(i));
if (obj) {
return obj;
}
}
return 0;
}