gecko-dev/xpcom/ds/nsAtomTable.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
// vim:cindent:ts=2:et:sw=2:
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* The Original Code is mozilla.org code.
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*
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#include "nsAtomTable.h"
#include "nsString.h"
#include "nsCRT.h"
#include "pldhash.h"
#include "prenv.h"
#include "nsISizeOfHandler.h"
/**
* The shared hash table for atom lookups.
*
* XXX This should be manipulated in a threadsafe way or we should make
* sure it's only manipulated from the main thread. Probably the latter
* is better, since the former would hurt performance.
*
* If |gAtomTable.entryCount| is 0, then the table is uninitialized.
*/
static PLDHashTable gAtomTable;
struct AtomTableEntry : public PLDHashEntryHdr {
AtomImpl *mAtom;
};
PR_STATIC_CALLBACK(const void *)
AtomTableGetKey(PLDHashTable *table, PLDHashEntryHdr *entry)
{
AtomTableEntry *he = NS_STATIC_CAST(AtomTableEntry*, entry);
return he->mAtom->mString;
}
PR_STATIC_CALLBACK(PLDHashNumber)
AtomTableHashKey(PLDHashTable *table, const void *key)
{
const PRUnichar *str = NS_STATIC_CAST(const PRUnichar*, key);
if (!str) {
static const PRUnichar empty_buffer[] = {0};
str = empty_buffer;
}
return nsCRT::HashCode(str);
}
PR_STATIC_CALLBACK(PRBool)
AtomTableMatchKey(PLDHashTable *table,
const PLDHashEntryHdr *entry,
const void *key)
{
const AtomTableEntry *he = NS_STATIC_CAST(const AtomTableEntry*, entry);
const PRUnichar* keyStr = NS_STATIC_CAST(const PRUnichar*, key);
return nsCRT::strcmp(keyStr, he->mAtom->mString) == 0;
}
PR_STATIC_CALLBACK(void)
AtomTableClearEntry(PLDHashTable *table, PLDHashEntryHdr *entry)
{
AtomTableEntry *he = NS_STATIC_CAST(AtomTableEntry*, entry);
AtomImpl *atom = he->mAtom;
he->mAtom = 0;
he->keyHash = 0;
// Normal |AtomImpl| atoms are deleted when their refcount hits 0, and
// they then remove themselves from the table. In other words, they
// are owned by the callers who own references to them.
// |PermanentAtomImpl| permanent atoms ignore their refcount and are
// deleted when they are removed from the table at table destruction.
// In other words, they are owned by the atom table.
if (atom->IsPermanent())
delete atom;
}
static PLDHashTableOps AtomTableOps = {
PL_DHashAllocTable,
PL_DHashFreeTable,
AtomTableGetKey,
AtomTableHashKey,
AtomTableMatchKey,
PL_DHashMoveEntryStub,
AtomTableClearEntry,
PL_DHashFinalizeStub,
NULL
};
#ifdef DEBUG
PR_STATIC_CALLBACK(PLDHashOperator)
DumpAtomLeaks(PLDHashTable *table, PLDHashEntryHdr *he,
PRUint32 index, void *arg)
{
AtomTableEntry *entry = NS_STATIC_CAST(AtomTableEntry*, he);
AtomImpl* atom = entry->mAtom;
if (!atom->IsPermanent()) {
++*NS_STATIC_CAST(PRUint32*, arg);
const PRUnichar *str;
atom->GetUnicode(&str);
fputs(NS_LossyConvertUCS2toASCII(str).get(), stdout);
fputs("\n", stdout);
}
return PL_DHASH_NEXT;
}
#endif
void NS_PurgeAtomTable()
{
if (gAtomTable.entryCount) {
#ifdef DEBUG
if (PR_GetEnv("MOZ_DUMP_ATOM_LEAKS")) {
PRUint32 leaked = 0;
printf("*** %d atoms still exist (including permanent):\n",
gAtomTable.entryCount);
PL_DHashTableEnumerate(&gAtomTable, DumpAtomLeaks, &leaked);
printf("*** %u non-permanent atoms leaked\n", leaked);
}
#endif
PL_DHashTableFinish(&gAtomTable);
gAtomTable.entryCount = 0;
}
}
AtomImpl::AtomImpl()
{
NS_INIT_ISUPPORTS();
}
AtomImpl::~AtomImpl()
{
NS_PRECONDITION(gAtomTable.entryCount, "uninitialized atom hashtable");
// Permanent atoms are removed from the hashtable at shutdown, and we
// don't want to remove them twice. See comment above in
// |AtomTableClearEntry|.
if (!IsPermanent()) {
PL_DHashTableOperate(&gAtomTable, mString, PL_DHASH_REMOVE);
if (gAtomTable.entryCount == 0) {
PL_DHashTableFinish(&gAtomTable);
NS_ASSERTION(gAtomTable.entryCount == 0,
"PL_DHashTableFinish changed the entry count");
}
}
}
NS_IMPL_THREADSAFE_ISUPPORTS1(AtomImpl, nsIAtom)
NS_IMETHODIMP_(nsrefcnt) PermanentAtomImpl::AddRef()
{
return 2;
}
NS_IMETHODIMP_(nsrefcnt) PermanentAtomImpl::Release()
{
return 1;
}
/* virtual */ PRBool
AtomImpl::IsPermanent()
{
return PR_FALSE;
}
/* virtual */ PRBool
PermanentAtomImpl::IsPermanent()
{
return PR_TRUE;
}
void* AtomImpl::operator new ( size_t size, const nsAString& aString )
{
/*
Note: since the |size| will initially also include the |PRUnichar| member
|mString|, our size calculation will give us one character too many.
We use that extra character for a zero-terminator.
Note: this construction is not guaranteed to be possible by the C++
compiler. A more reliable scheme is used by |nsShared[C]String|s, see
http://lxr.mozilla.org/seamonkey/source/xpcom/ds/nsSharedString.h#174
*/
size += aString.Length() * sizeof(PRUnichar);
AtomImpl* ii = NS_STATIC_CAST(AtomImpl*, ::operator new(size));
PRUnichar* toBegin = &ii->mString[0];
nsReadingIterator<PRUnichar> fromBegin, fromEnd;
*copy_string(aString.BeginReading(fromBegin), aString.EndReading(fromEnd), toBegin) = PRUnichar(0);
return ii;
}
void* PermanentAtomImpl::operator new ( size_t size, AtomImpl* aAtom ) {
NS_ASSERTION(!aAtom->IsPermanent(),
"converting atom that's already permanent");
// Just let the constructor overwrite the vtable pointer.
return aAtom;
}
NS_IMETHODIMP
AtomImpl::ToString(nsAString& aBuf) /*FIX: const */
{
aBuf.Assign(mString);
return NS_OK;
}
NS_IMETHODIMP
AtomImpl::GetUnicode(const PRUnichar **aResult) /*FIX: const */
{
NS_PRECONDITION(aResult, "null out param");
*aResult = mString;
return NS_OK;
}
NS_IMETHODIMP
AtomImpl::SizeOf(nsISizeOfHandler* aHandler, PRUint32* _retval) /*FIX: const */
{
#ifdef DEBUG
NS_PRECONDITION(_retval, "null out param");
*_retval = sizeof(*this) + nsCRT::strlen(mString) * sizeof(PRUnichar);
#endif
return NS_OK;
}
//----------------------------------------------------------------------
NS_COM nsIAtom* NS_NewAtom(const char* isolatin1)
{
return NS_NewAtom(NS_ConvertASCIItoUCS2(isolatin1));
}
NS_COM nsIAtom* NS_NewPermanentAtom(const char* isolatin1)
{
return NS_NewPermanentAtom(NS_ConvertASCIItoUCS2(isolatin1));
}
static AtomTableEntry* GetAtomHashEntry(const nsAString& aString)
{
if ( !gAtomTable.entryCount )
PL_DHashTableInit(&gAtomTable, &AtomTableOps, 0,
sizeof(AtomTableEntry), 2048);
return NS_STATIC_CAST(AtomTableEntry*,
PL_DHashTableOperate(&gAtomTable,
PromiseFlatString(aString).get(),
PL_DHASH_ADD));
}
NS_COM nsIAtom* NS_NewAtom( const nsAString& aString )
{
AtomTableEntry *he = GetAtomHashEntry(aString);
AtomImpl* atom = he->mAtom;
if (!atom) {
atom = new (aString) AtomImpl();
he->mAtom = atom;
if (!atom) {
PL_DHashTableRawRemove(&gAtomTable, he);
return nsnull;
}
}
NS_ADDREF(atom);
return atom;
}
NS_COM nsIAtom* NS_NewPermanentAtom( const nsAString& aString )
{
AtomTableEntry *he = GetAtomHashEntry(aString);
AtomImpl* atom = he->mAtom;
if (atom) {
// ensure that it's permanent
if (!atom->IsPermanent()) {
#ifdef NS_BUILD_REFCNT_LOGGING
{
nsrefcnt refcount = atom->GetRefCount();
do {
NS_LOG_RELEASE(atom, --refcount, "AtomImpl");
} while (refcount);
}
#endif
atom = new (atom) PermanentAtomImpl();
}
} else {
// otherwise, make a new atom
atom = new (aString) PermanentAtomImpl();
he->mAtom = atom;
if ( !atom ) {
PL_DHashTableRawRemove(&gAtomTable, he);
return nsnull;
}
}
NS_ADDREF(atom);
return atom;
}
NS_COM nsIAtom* NS_NewAtom( const PRUnichar* str )
{
return NS_NewAtom(nsDependentString(str));
}
NS_COM nsIAtom* NS_NewPermanentAtom( const PRUnichar* str )
{
return NS_NewPermanentAtom(nsDependentString(str));
}
NS_COM nsrefcnt NS_GetNumberOfAtoms(void)
{
return gAtomTable.entryCount;
}