gecko-dev/xpcom/glue/nsDeque.cpp
Andrew McCreight 41063b6447 Bug 875557 - Make nsDeque infallible by default. r=bsmedberg
Also remove some unused return values.
2013-05-28 16:57:54 -07:00

593 lines
15 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 "nsCRT.h"
#ifdef DEBUG_rickg
#include <stdio.h>
#endif
/**
* 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] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
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);
}
/**
* 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() {
int32_t theNewSize=mCapacity<<2;
NS_ASSERTION(theNewSize>mCapacity, "Overflow");
if (theNewSize<=mCapacity)
return false;
void** temp=(void**)malloc(theNewSize * sizeof(void*));
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=theNewSize;
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;
}
/**
* Create and return an iterator pointing to
* the beginning of the queue. Note that this
* takes the circular buffer semantics into account.
*
* @return new deque iterator, init'ed to 1st item
*/
nsDequeIterator nsDeque::Begin() const{
return nsDequeIterator(*this, 0);
}
/**
* Create and return an iterator pointing to
* the last item in the deque.
* Note that this takes the circular buffer semantics
* into account.
*
* @return new deque iterator, init'ed to the last item
*/
nsDequeIterator nsDeque::End() const{
return nsDequeIterator(*this, mSize - 1);
}
void* nsDeque::Last() const {
return End().GetCurrent();
}
/**
* 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;
}
/******************************************************
* Here comes the nsDequeIterator class...
******************************************************/
/**
* DequeIterator is an object that knows how to iterate (forward and backward)
* through a Deque. Normally, you don't need to do this, but there are some special
* cases where it is pretty handy, so here you go.
*
* This is a standard dequeiterator constructor
*
* @param aQueue is the deque object to be iterated
* @param aIndex is the starting position for your iteration
*/
nsDequeIterator::nsDequeIterator(const nsDeque& aQueue, int aIndex)
: mIndex(aIndex),
mDeque(aQueue)
{
}
/**
* Create a copy of a DequeIterator
*
* @param aCopy is another iterator to copy from
*/
nsDequeIterator::nsDequeIterator(const nsDequeIterator& aCopy)
: mIndex(aCopy.mIndex),
mDeque(aCopy.mDeque)
{
}
/**
* Moves iterator to first element in deque
* @return *this
*/
nsDequeIterator& nsDequeIterator::First(){
mIndex=0;
return *this;
}
/**
* Standard assignment operator for dequeiterator
*
* @param aCopy is an iterator to be copied from
* @return *this
*/
nsDequeIterator& nsDequeIterator::operator=(const nsDequeIterator& aCopy) {
NS_ASSERTION(&mDeque==&aCopy.mDeque,"you can't change the deque that an interator is iterating over, sorry.");
mIndex=aCopy.mIndex;
return *this;
}
/**
* preform ! operation against to iterators to test for equivalence
* (or lack thereof)!
*
* @param aIter is the object to be compared to
* @return TRUE if NOT equal.
*/
bool nsDequeIterator::operator!=(nsDequeIterator& aIter) {
return bool(!this->operator==(aIter));
}
/**
* Compare two iterators for increasing order.
*
* @param aIter is the other iterator to be compared to
* @return TRUE if this object points to an element before
* the element pointed to by aIter.
* FALSE if this and aIter are not iterating over the same deque.
*/
bool nsDequeIterator::operator<(nsDequeIterator& aIter) {
return bool(((mIndex<aIter.mIndex) && (&mDeque==&aIter.mDeque)));
}
/**
* Compare two iterators for equivalence.
*
* @param aIter is the other iterator to be compared to
* @return TRUE if EQUAL
*/
bool nsDequeIterator::operator==(nsDequeIterator& aIter) {
return bool(((mIndex==aIter.mIndex) && (&mDeque==&aIter.mDeque)));
}
/**
* Compare two iterators for non strict decreasing order.
*
* @param aIter is the other iterator to be compared to
* @return TRUE if this object points to the same element, or
* an element after the element pointed to by aIter.
* FALSE if this and aIter are not iterating over the same deque.
*/
bool nsDequeIterator::operator>=(nsDequeIterator& aIter) {
return bool(((mIndex>=aIter.mIndex) && (&mDeque==&aIter.mDeque)));
}
/**
* Pre-increment operator
*
* @return object at post-incremented index
*/
void* nsDequeIterator::operator++() {
NS_ASSERTION(mIndex<mDeque.mSize,
"You have reached the end of the Internet."\
"You have seen everything there is to see. Please go back. Now."
);
#ifndef TIMELESS_LIGHTWEIGHT
if (mIndex>=mDeque.mSize) return 0;
#endif
return mDeque.ObjectAt(++mIndex);
}
/**
* Post-increment operator
*
* @param param is ignored
* @return object at pre-incremented index
*/
void* nsDequeIterator::operator++(int) {
NS_ASSERTION(mIndex<=mDeque.mSize,
"You have already reached the end of the Internet."\
"You have seen everything there is to see. Please go back. Now."
);
#ifndef TIMELESS_LIGHTWEIGHT
if (mIndex>mDeque.mSize) return 0;
#endif
return mDeque.ObjectAt(mIndex++);
}
/**
* Pre-decrement operator
*
* @return object at pre-decremented index
*/
void* nsDequeIterator::operator--() {
NS_ASSERTION(mIndex>=0,
"You have reached the beginning of the Internet."\
"You have seen everything there is to see. Please go forward. Now."
);
#ifndef TIMELESS_LIGHTWEIGHT
if (mIndex<0) return 0;
#endif
return mDeque.ObjectAt(--mIndex);
}
/**
* Post-decrement operator
*
* @param param is ignored
* @return object at post-decremented index
*/
void* nsDequeIterator::operator--(int) {
NS_ASSERTION(mIndex>=0,
"You have already reached the beginning of the Internet."\
"You have seen everything there is to see. Please go forward. Now."
);
#ifndef TIMELESS_LIGHTWEIGHT
if (mIndex<0) return 0;
#endif
return mDeque.ObjectAt(mIndex--);
}
/**
* Dereference operator
* Note that the iterator floats, so you don't need to do:
* <code>++iter; aDeque.PopFront();</code>
* Unless you actually want your iterator to jump 2 spaces.
*
* Picture: [1 2I 3 4]
* PopFront()
* Picture: [2 3I 4]
* Note that I still happily points to object at the second index
*
* @return object at ith index
*/
void* nsDequeIterator::GetCurrent() {
NS_ASSERTION(mIndex<mDeque.mSize&&mIndex>=0,"Current is out of bounds");
#ifndef TIMELESS_LIGHTWEIGHT
if (mIndex>=mDeque.mSize||mIndex<0) return 0;
#endif
return mDeque.ObjectAt(mIndex);
}
/**
* 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 nsDequeIterator::ForEach(nsDequeFunctor& aFunctor) const{
mDeque.ForEach(aFunctor);
}
/**
* 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* nsDequeIterator::FirstThat(nsDequeFunctor& aFunctor) const{
return mDeque.FirstThat(aFunctor);
}