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-rw-r--r--xpcom/glue/nsDeque.cpp361
1 files changed, 361 insertions, 0 deletions
diff --git a/xpcom/glue/nsDeque.cpp b/xpcom/glue/nsDeque.cpp
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+/* -*- 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"
+
+#define modulus(x,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<size_t> newCapacity = mCapacity;
+ newCapacity *= 4;
+
+ NS_ASSERTION(newCapacity.isValid(), "Overflow");
+ if (!newCapacity.isValid()) {
+ return false;
+ }
+
+ // Sanity check the new byte size.
+ mozilla::CheckedInt<size_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&)
+{
+
+ if (mOrigin == 0) {
+ mOrigin = mCapacity - 1;
+ } else {
+ mOrigin--;
+ }
+
+ 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;
+ size_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() const
+{
+ 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() const
+{
+ 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(size_t aIndex) const
+{
+ void* result = 0;
+ if (aIndex < mSize) {
+ result = mData[modulus(mOrigin + aIndex, mCapacity)];
+ }
+ return result;
+}
+
+/**
+ * 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 (size_t i = 0; i < mSize; ++i) {
+ aFunctor(ObjectAt(i));
+ }
+}
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