gecko-dev/js/tamarin/core/AtomArray.cpp

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 *
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/////////////////////////////////////////////////////////
// AtomArray object
/////////////////////////////////////////////////////////
#include "avmplus.h"

namespace avmplus
{
	using namespace MMgc;

	AtomArray::AtomArray (int initialCapacity)
	{
		 m_length = 0; 
		 if (!initialCapacity)
		 {
			m_atoms = 0; 
		 }
		 else
		 {
			if (initialCapacity < kMinCapacity) 
				initialCapacity = kMinCapacity;
			GC *gc = GC::GetGC(this);
			setAtoms(gc, (Atom*) gc->Calloc(initialCapacity, sizeof(Atom), GC::kContainsPointers|GC::kZero));
		 }
	}

	AtomArray::~AtomArray()
	{
		clear();  
	}

	/////////////////////////////////////////////////////
	// Array AS API
	/////////////////////////////////////////////////////

	// Pop last element off the end of the array and shrink length
	Atom AtomArray::pop()
	{
		if (!m_length)
			return undefinedAtom;

		Atom retAtom = m_atoms[m_length - 1];
		setAtInternal(m_length - 1, 0); // so GC collects this item
		m_length--;
		return retAtom;
	}

	using namespace MMgc;

	// n arguments are pushed on the array
	uint32 AtomArray::push(Atom *args, int argc)
	{
		checkCapacity (m_length + argc);

		// slow path to trigger write barrier
		for(int i=0; i < argc; i++) {
			push(args[i]);
		}

		return argc;
	}

	// Reverse array elements
	void AtomArray::reverse()
	{
		if (m_length > 1)
		{
			for (uint32 k = 0; k < (m_length >> 1); k++)
			{
				Atom temp = m_atoms[k];
				m_atoms[k] = m_atoms[m_length - k - 1];
				m_atoms[m_length - k - 1] = temp;
			}
		}
	}

	// return 0th element, shift rest down
	Atom AtomArray::shift()
	{
		if (!m_length)
			return undefinedAtom;

		Atom *arr = m_atoms;
		Atom retAtom = arr[0];
		setAtInternal(0, 0);
		memmove (arr, arr + 1, (m_length - 1) * sizeof(Atom));
		arr[m_length - 1] = 0; // clear item so GC can collect it.
		m_length--;

		return retAtom;
	}

	// insertPoint arg - place to insert
	// insertCount arg - number to insert
	// deleteCount - number to delete
	// args - #insertCount args to insert
	void AtomArray::splice(uint32 insertPoint, uint32 insertCount, uint32 deleteCount, AtomArray *args, int offset)
	{
		long l_shiftAmount = (long)insertCount - (long) deleteCount; // long because result could be negative

		// Must be BEFORE arr = m_atoms since m_atoms might change
		checkCapacity (m_length + l_shiftAmount);

		Atom *arr = m_atoms;
		Atom *argsArr = args ? args->m_atoms : 0;

		if (l_shiftAmount < 0) 
		{
			int numberBeingDeleted = -l_shiftAmount;

			// whack deleted items so they're ref count goes down
			AvmCore::decrementAtomRegion(arr + insertPoint + insertCount, numberBeingDeleted);

			// shift elements down
			int toMove = m_length - insertPoint - deleteCount;
			memmove (arr + insertPoint + insertCount, arr + insertPoint + deleteCount, toMove * sizeof(Atom));

			// clear top part for RC purposes
			memset (arr + m_length - numberBeingDeleted, 0, numberBeingDeleted * sizeof(Atom));
		}
		else if (l_shiftAmount > 0)
		{
			memmove (arr + insertPoint + l_shiftAmount, arr + insertPoint, (m_length - insertPoint) * sizeof(Atom));
			// clear for RC purposes
			memset (arr + insertPoint, 0, l_shiftAmount * sizeof(Atom));
		}

		// Add the items to insert
		if (insertCount)
		{
			AvmAssert(args != 0);
			for (uint32 i=0; i<insertCount; i++)
			{
				setAtInternal(insertPoint+i, argsArr[i+offset]);
			}
		}

		m_length += l_shiftAmount;
		return;
	}

	// insert array of arguments at front of array
	Atom AtomArray::unshift(Atom *args, int argc)
	{
		// shift elements up by argc
		// inserts args into initial spots

		checkCapacity (m_length + argc);
		Atom *arr = m_atoms;
		memmove (arr + argc, arr, m_length * sizeof(Atom));
		// clear moved element for RC purposes
		memset (arr, 0, argc * sizeof(Atom));
		for(int i=0; i<argc; i++) {
			setAtInternal(i, args[i]);
		}

		m_length += argc;

		return nullObjectAtom;
	}

	/////////////////////////////////////////////////////
	/////////////////////////////////////////////////////
	/////////////////////////////////////////////////////

	void AtomArray::checkCapacity (int newLength)
	{
		AvmAssert(newLength >= 0);
		// !!@ handle case where capacity shrinks by 50% (resize buffer smaller)

		if (!m_atoms || newLength > int(capacity()))
		{
			// We oversize our buffer by 50% (is that the best algorithm?)
			int capacity = newLength + (newLength >> 2);
			if (capacity < kMinCapacity) capacity = kMinCapacity;
			GC* gc = GC::GetGC(this);
			Atom* newAtoms = (Atom*) gc->Calloc(capacity, sizeof(Atom), GC::kContainsPointers|GC::kZero);
			Atom* oldAtoms = m_atoms;
			setAtoms(gc, newAtoms);
			if(oldAtoms) {
				// use a memcpy to skip ref counting
				memcpy(m_atoms, oldAtoms, m_length*sizeof(Atom));
				memset(oldAtoms, 0, m_length*sizeof(Atom));
				gc->Free(oldAtoms);
			}
		}
	}

	void AtomArray::push (Atom a)
	{
		checkCapacity (m_length + 1);
		setAtInternal(m_length++, a);
	}

	void AtomArray::push (const AtomArray *a)
	{
		if (!a)
			return;

		push (a->m_atoms, a->getLength());
	}

	void AtomArray::removeAt (uint32 index)
	{
		AvmAssert (m_length > 0);
		AvmAssert (index >= 0);
		AvmAssert (index < uint32(m_length));
		if (!m_length)
			return;

		checkCapacity (m_length - 1);

		m_length--;
		// use setAt instead of direct access for proper ref count maintenance
		setAtInternal(index, 0);
		Atom *arr = m_atoms;
		if (m_length)
		{
			// shift down entries
			memmove (arr + index, arr + index + 1, (this->m_length - index) * sizeof(Atom));
		}
		arr[m_length] = 0; // clear our entry so GC can collect it
	}

	void AtomArray::insert (uint32 index, Atom a)
	{
		AvmAssert(index <= m_length);

		checkCapacity (m_length + 1);
		m_length++;

		Atom *arr = m_atoms;
		// shift entries up by one to make room
		memmove (arr + index + 1, arr + index, (m_length - index - 1) * sizeof(Atom));
		// this element is still in the array so don't let setAtInternal decrement its count
		m_atoms[index] = 0;
		setAtInternal(index, a);
	}

	void AtomArray::setAt (uint32 index, Atom a)
	{
		if (index > m_length)
		{
			AvmAssert(0);
			return;
		}

		setAtInternal(index, a);
	}

	Atom AtomArray::getAt (uint32 index) const
	{
		if (index > m_length)
		{
			AvmAssert(0);
			return nullObjectAtom;
		}

		return m_atoms[index];
	}

	void AtomArray::clear()
	{
#ifdef MMGC_DRC
		AvmCore::decrementAtomRegion(m_atoms, m_length);
#endif
		m_length = 0;
		if(m_atoms) {
			GC::GetGC(m_atoms)->Free(m_atoms);
			m_atoms = 0;
		}
	}
}