gecko-dev/xpcom/glue/nsVoidArray.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; c-file-offsets: ((substatement-open . 0)) -*- */
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*
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*
* The Original Code is mozilla.org code.
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* The Initial Developer of the Original Code is
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* the Initial Developer. All Rights Reserved.
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#ifndef nsVoidArray_h___
#define nsVoidArray_h___
//#define DEBUG_VOIDARRAY 1
#include "nsDebug.h"
// Comparator callback function for sorting array values.
typedef int (* nsVoidArrayComparatorFunc)
(const void* aElement1, const void* aElement2, void* aData);
// Enumerator callback function. Return false to stop
typedef bool (* nsVoidArrayEnumFunc)(void* aElement, void *aData);
/// A basic zero-based array of void*'s that manages its own memory
class NS_COM_GLUE nsVoidArray {
public:
nsVoidArray();
nsVoidArray(PRInt32 aCount); // initial count of aCount elements set to nsnull
~nsVoidArray();
nsVoidArray& operator=(const nsVoidArray& other);
inline PRInt32 Count() const {
return mImpl ? mImpl->mCount : 0;
}
// If the array grows, the newly created entries will all be null
bool SetCount(PRInt32 aNewCount);
// returns the max number that can be held without allocating
inline PRInt32 GetArraySize() const {
return mImpl ? (PRInt32(mImpl->mBits) & kArraySizeMask) : 0;
}
void* FastElementAt(PRInt32 aIndex) const
{
NS_ASSERTION(0 <= aIndex && aIndex < Count(), "nsVoidArray::FastElementAt: index out of range");
return mImpl->mArray[aIndex];
}
// This both asserts and bounds-checks, because (1) we don't want
// people to write bad code, but (2) we don't want to change it to
// crashing for backwards compatibility. See bug 96108.
void* ElementAt(PRInt32 aIndex) const
{
NS_ASSERTION(0 <= aIndex && aIndex < Count(), "nsVoidArray::ElementAt: index out of range");
return SafeElementAt(aIndex);
}
// bounds-checked version
void* SafeElementAt(PRInt32 aIndex) const
{
if (PRUint32(aIndex) >= PRUint32(Count())) // handles aIndex < 0 too
{
return nsnull;
}
// The bounds check ensures mImpl is non-null.
return mImpl->mArray[aIndex];
}
void* operator[](PRInt32 aIndex) const { return ElementAt(aIndex); }
PRInt32 IndexOf(void* aPossibleElement) const;
bool InsertElementAt(void* aElement, PRInt32 aIndex);
bool InsertElementsAt(const nsVoidArray &other, PRInt32 aIndex);
bool ReplaceElementAt(void* aElement, PRInt32 aIndex);
// useful for doing LRU arrays, sorting, etc
bool MoveElement(PRInt32 aFrom, PRInt32 aTo);
bool AppendElement(void* aElement) {
return InsertElementAt(aElement, Count());
}
bool AppendElements(nsVoidArray& aElements) {
return InsertElementsAt(aElements, Count());
}
bool RemoveElement(void* aElement);
bool RemoveElementsAt(PRInt32 aIndex, PRInt32 aCount);
bool RemoveElementAt(PRInt32 aIndex) { return RemoveElementsAt(aIndex,1); }
void Clear();
bool SizeTo(PRInt32 aMin);
// Subtly different - Compact() tries to be smart about whether we
// should reallocate the array; SizeTo() always reallocates.
void Compact();
void Sort(nsVoidArrayComparatorFunc aFunc, void* aData);
bool EnumerateForwards(nsVoidArrayEnumFunc aFunc, void* aData);
bool EnumerateBackwards(nsVoidArrayEnumFunc aFunc, void* aData);
protected:
bool GrowArrayBy(PRInt32 aGrowBy);
struct Impl {
/**
* Packed bits. The low 30 bits are the array's size.
* The two highest bits indicate whether or not we "own" mImpl and
* must free() it when destroyed, and whether we have a preallocated
* nsAutoVoidArray buffer.
*/
PRUint32 mBits;
/**
* The number of elements in the array
*/
PRInt32 mCount;
/**
* Array data, padded out to the actual size of the array.
*/
void* mArray[1];
};
Impl* mImpl;
#if DEBUG_VOIDARRAY
PRInt32 mMaxCount;
PRInt32 mMaxSize;
bool mIsAuto;
#endif
enum {
kArrayOwnerMask = 1 << 31,
kArrayHasAutoBufferMask = 1 << 30,
kArraySizeMask = ~(kArrayOwnerMask | kArrayHasAutoBufferMask)
};
enum { kAutoBufSize = 8 };
// bit twiddlers
void SetArray(Impl *newImpl, PRInt32 aSize, PRInt32 aCount, bool aOwner,
bool aHasAuto);
inline bool IsArrayOwner() const {
return mImpl && (mImpl->mBits & kArrayOwnerMask);
}
inline bool HasAutoBuffer() const {
return mImpl && (mImpl->mBits & kArrayHasAutoBufferMask);
}
private:
/// Copy constructors are not allowed
nsVoidArray(const nsVoidArray& other);
};
// A zero-based array with a bit of automatic internal storage
class NS_COM_GLUE nsAutoVoidArray : public nsVoidArray {
public:
nsAutoVoidArray();
void ResetToAutoBuffer()
{
SetArray(reinterpret_cast<Impl*>(mAutoBuf), kAutoBufSize, 0, false,
true);
}
nsAutoVoidArray& operator=(const nsVoidArray& other)
{
nsVoidArray::operator=(other);
return *this;
}
protected:
// The internal storage
char mAutoBuf[sizeof(Impl) + (kAutoBufSize - 1) * sizeof(void*)];
};
//===================================================================
// nsSmallVoidArray is not a general-purpose replacement for
// ns(Auto)VoidArray because there is (some) extra CPU overhead for arrays
// larger than 1 element, though not a lot. It is appropriate for
// space-sensitive uses where sizes of 0 or 1 are moderately common or
// more, and where we're NOT storing arbitrary integers or arbitrary
// pointers.
// NOTE: nsSmallVoidArray can ONLY be used for holding items that always
// have the low bit as a 0 - i.e. element & 1 == 0. This happens to be
// true for allocated and object pointers for all the architectures we run
// on, but conceivably there might be some architectures/compilers for
// which it is NOT true. We know this works for all existing architectures
// because if it didn't then nsCheapVoidArray would have failed. Also note
// that we will ASSERT if this assumption is violated in DEBUG builds.
// XXX we're really re-implementing the whole nsVoidArray interface here -
// some form of abstract class would be useful
// I disagree on the abstraction here. If the point of this class is to be
// as small as possible, and no one will ever derive from it, as I found
// today, there should not be any virtualness to it to avoid the vtable
// ptr overhead.
class NS_COM_GLUE nsSmallVoidArray : private nsVoidArray
{
public:
~nsSmallVoidArray();
nsSmallVoidArray& operator=(nsSmallVoidArray& other);
void* operator[](PRInt32 aIndex) const { return ElementAt(aIndex); }
PRInt32 GetArraySize() const;
PRInt32 Count() const;
void* FastElementAt(PRInt32 aIndex) const;
// This both asserts and bounds-checks, because (1) we don't want
// people to write bad code, but (2) we don't want to change it to
// crashing for backwards compatibility. See bug 96108.
void* ElementAt(PRInt32 aIndex) const
{
NS_ASSERTION(0 <= aIndex && aIndex < Count(), "nsSmallVoidArray::ElementAt: index out of range");
return SafeElementAt(aIndex);
}
void* SafeElementAt(PRInt32 aIndex) const {
// let compiler inline; it may be able to remove these checks
if (PRUint32(aIndex) >= PRUint32(Count())) // handles aIndex < 0 too
{
return nsnull;
}
return FastElementAt(aIndex);
}
PRInt32 IndexOf(void* aPossibleElement) const;
bool InsertElementAt(void* aElement, PRInt32 aIndex);
bool InsertElementsAt(const nsVoidArray &other, PRInt32 aIndex);
bool ReplaceElementAt(void* aElement, PRInt32 aIndex);
bool MoveElement(PRInt32 aFrom, PRInt32 aTo);
bool AppendElement(void* aElement);
bool AppendElements(nsVoidArray& aElements) {
return InsertElementsAt(aElements, Count());
}
bool RemoveElement(void* aElement);
bool RemoveElementsAt(PRInt32 aIndex, PRInt32 aCount);
bool RemoveElementAt(PRInt32 aIndex);
void Clear();
bool SizeTo(PRInt32 aMin);
void Compact();
void Sort(nsVoidArrayComparatorFunc aFunc, void* aData);
bool EnumerateForwards(nsVoidArrayEnumFunc aFunc, void* aData);
bool EnumerateBackwards(nsVoidArrayEnumFunc aFunc, void* aData);
private:
bool HasSingle() const
{
return !!(reinterpret_cast<PRWord>(mImpl) & 0x1);
}
void* GetSingle() const
{
NS_ASSERTION(HasSingle(), "wrong type");
return reinterpret_cast<void*>
(reinterpret_cast<PRWord>(mImpl) & ~0x1);
}
void SetSingle(void *aChild)
{
NS_ASSERTION(HasSingle() || !mImpl, "overwriting array");
mImpl = reinterpret_cast<Impl*>
(reinterpret_cast<PRWord>(aChild) | 0x1);
}
bool IsEmpty() const
{
// Note that this isn't the same as Count()==0
return !mImpl;
}
const nsVoidArray* AsArray() const
{
NS_ASSERTION(!HasSingle(), "This is a single");
return this;
}
nsVoidArray* AsArray()
{
NS_ASSERTION(!HasSingle(), "This is a single");
return this;
}
bool EnsureArray();
};
#endif /* nsVoidArray_h___ */