Bommels05/Mozilla
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Reduce string copying and allocation in the parser by only copying the scanner buffer when we need to mutate the string. Allow a nsDependentString / nsDependentSubstring to be created without being bound to anything. Move StripChar() onto nsSubstring from nsString. Bug 269853, r=jst, sr=darin.

Browse Source 
git-svn-id: svn://10.0.0.236/trunk@165773 18797224-902f-48f8-a5cc-f745e15eee43
This commit is contained in:
bryner%brianryner.com
2004-11-25 07:03:20 +00:00
parent 2e6bee01c4
commit 7a461c49a4
17 changed files with 458 additions and 138 deletions
Download Patch File Download Diff File Expand all files Collapse all files

86
mozilla/parser/htmlparser/src/nsScannerString.cpp
View File

@@ -244,16 +244,8 @@ nsScannerSubstring::AsString() const
if (mStart.mBuffer == mEnd.mBuffer) {
// We only have a single fragment to deal with, so just return it
// as a substring. We take advantage of the fact that |nsString| and
// |nsDependentSubstring| don't have any members that aren't on
// |nsSubstring|, so that have same same layout. Furthermore,
// we know that the implementation of ~nsString() will not try
// to free the data if the string was constructed as a
// |nsDependentSubstring|.
mFlattenedRep.~nsString(); // in case we have a buffer currently
new (&mutable_this->mFlattenedRep)
nsDependentSubstring(mStart.mPosition, mEnd.mPosition);
// as a substring.
mutable_this->mFlattenedRep.Rebind(mStart.mPosition, mEnd.mPosition);
} else {
// Otherwise, we need to copy the data into a flattened buffer.
nsScannerIterator start, end;
@@ -429,6 +421,64 @@ nsScannerString::ReplaceCharacter(nsScannerIterator& aPosition, PRUnichar aChar)
}
/**
* nsScannerSharedSubstring
*/
void
nsScannerSharedSubstring::Rebind(const nsScannerIterator &aStart,
const nsScannerIterator &aEnd)
{
// If the start and end positions are inside the same buffer, we must
// acquire ownership of the buffer. If not, we can optimize by not holding
// onto it.
Buffer *buffer = NS_CONST_CAST(Buffer*, aStart.buffer());
PRBool sameBuffer = buffer == aEnd.buffer();
nsScannerBufferList *bufferList;
if (sameBuffer) {
bufferList = aStart.mOwner->mBufferList;
bufferList->AddRef();
buffer->IncrementUsageCount();
}
if (mBufferList)
ReleaseBuffer();
if (sameBuffer) {
mBuffer = buffer;
mBufferList = bufferList;
mString.Rebind(aStart.mPosition, aEnd.mPosition);
} else {
mBuffer = nsnull;
mBufferList = nsnull;
CopyUnicodeTo(aStart, aEnd, mString);
}
}
void
nsScannerSharedSubstring::ReleaseBuffer()
{
NS_ASSERTION(mBufferList, "Should only be called with non-null mBufferList");
mBuffer->DecrementUsageCount();
mBufferList->DiscardUnreferencedPrefix(mBuffer);
mBufferList->Release();
}
void
nsScannerSharedSubstring::MakeMutable()
{
nsString temp(mString); // this will force a copy of the data
mString.Assign(temp); // mString will now share the just-allocated buffer
ReleaseBuffer();
mBuffer = nsnull;
mBufferList = nsnull;
}
/**
* utils -- based on code from nsReadableUtils.cpp
*/
@@ -446,6 +496,22 @@ CopyUnicodeTo( const nsScannerIterator& aSrcStart,
copy_string(fromBegin, aSrcEnd, writer);
}
void
AppendUnicodeTo( const nsScannerIterator& aSrcStart,
const nsScannerIterator& aSrcEnd,
nsScannerSharedSubstring& aDest )
{
// Check whether we can just create a dependent string.
if (aDest.str().IsEmpty()) {
// We can just make |aDest| point to the buffer.
// This will take care of copying if the buffer spans fragments.
aDest.Rebind(aSrcStart, aSrcEnd);
} else {
// The dest string is not empty, so it can't be a dependent substring.
AppendUnicodeTo(aSrcStart, aSrcEnd, aDest.writable());
}
}
void
AppendUnicodeTo( const nsScannerIterator& aSrcStart,
const nsScannerIterator& aSrcEnd,