gecko-dev/parser/htmlparser/nsScannerString.cpp at master · mozilla/gecko-dev · GitHub

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim:set ts=2 sw=2 sts=2 et cindent: */

/* 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 <stdlib.h>

#include "nsScannerString.h"

#include "mozilla/CheckedInt.h"

/**

* nsScannerBufferList

#define MAX_CAPACITY \

((UINT32_MAX / sizeof(char16_t)) - (sizeof(Buffer) + sizeof(char16_t)))

nsScannerBufferList::Buffer* nsScannerBufferList::AllocBufferFromString(

const nsAString& aString) {

uint32_t len = aString.Length();

Buffer* buf = AllocBuffer(len);

if (buf) {

nsAString::const_iterator source;

aString.BeginReading(source);

nsCharTraits<char16_t>::copy(buf->DataStart(), source.get(), len);

}

return buf;

}

nsScannerBufferList::Buffer* nsScannerBufferList::AllocBuffer(

uint32_t capacity) {

if (capacity > MAX_CAPACITY) return nullptr;

void* ptr = malloc(sizeof(Buffer) + (capacity + 1) * sizeof(char16_t));

if (!ptr) return nullptr;

Buffer* buf = new (ptr) Buffer();

buf->mUsageCount = 0;

buf->mDataEnd = buf->DataStart() + capacity;

// XXX null terminate. this shouldn't be required, but we do it because

// nsScanner erroneously thinks it can dereference DataEnd :-(

*buf->mDataEnd = char16_t(0);

return buf;

}

void nsScannerBufferList::ReleaseAll() {

while (!mBuffers.isEmpty()) {

Buffer* node = mBuffers.popFirst();

// printf(">>> freeing buffer @%p\n", node);

free(node);

}

void nsScannerBufferList::SplitBuffer(const Position& pos) {

// splitting to the right keeps the work string and any extant token

// pointing to and holding a reference count on the same buffer.

Buffer* bufferToSplit = pos.mBuffer;

NS_ASSERTION(bufferToSplit, "null pointer");

uint32_t splitOffset = pos.mPosition - bufferToSplit->DataStart();

NS_ASSERTION(pos.mPosition >= bufferToSplit->DataStart() &&

splitOffset <= bufferToSplit->DataLength(),

"split offset is outside buffer");

uint32_t len = bufferToSplit->DataLength() - splitOffset;

Buffer* new_buffer = AllocBuffer(len);

if (new_buffer) {

nsCharTraits<char16_t>::copy(new_buffer->DataStart(),

bufferToSplit->DataStart() + splitOffset, len);

InsertAfter(new_buffer, bufferToSplit);

bufferToSplit->SetDataLength(splitOffset);

}

void nsScannerBufferList::DiscardUnreferencedPrefix(Buffer* aBuf) {

if (aBuf == Head()) {

while (!mBuffers.isEmpty() && !Head()->IsInUse()) {

Buffer* buffer = Head();

buffer->remove();

free(buffer);

}

size_t nsScannerBufferList::Position::Distance(const Position& aStart,

const Position& aEnd) {

size_t result = 0;

if (aStart.mBuffer == aEnd.mBuffer) {

result = aEnd.mPosition - aStart.mPosition;

} else {

result = aStart.mBuffer->DataEnd() - aStart.mPosition;

for (Buffer* b = aStart.mBuffer->Next(); b != aEnd.mBuffer; b = b->Next())

result += b->DataLength();

result += aEnd.mPosition - aEnd.mBuffer->DataStart();

}

return result;

}

/**

* nsScannerSubstring

nsScannerSubstring::nsScannerSubstring()

: mStart(nullptr, nullptr),

mEnd(nullptr, nullptr),

mBufferList(nullptr),

mLength(0) {}

nsScannerSubstring::nsScannerSubstring(const nsAString& s)

: mBufferList(nullptr) {

Rebind(s);

}

nsScannerSubstring::~nsScannerSubstring() {

release_ownership_of_buffer_list();

}

void nsScannerSubstring::Rebind(const nsScannerSubstring& aString,

const nsScannerIterator& aStart,

const nsScannerIterator& aEnd) {

// allow for the case where &aString == this

aString.acquire_ownership_of_buffer_list();

release_ownership_of_buffer_list();

mStart = aStart;

mEnd = aEnd;

mBufferList = aString.mBufferList;

mLength = Distance(aStart, aEnd);

}

void nsScannerSubstring::Rebind(const nsAString& aString) {

release_ownership_of_buffer_list();

mBufferList = new nsScannerBufferList(AllocBufferFromString(aString));

init_range_from_buffer_list();

acquire_ownership_of_buffer_list();

}

nsScannerIterator& nsScannerSubstring::BeginReading(

nsScannerIterator& iter) const {

iter.mOwner = this;

iter.mFragment.mBuffer = mStart.mBuffer;

iter.mFragment.mFragmentStart = mStart.mPosition;

if (mStart.mBuffer == mEnd.mBuffer)

iter.mFragment.mFragmentEnd = mEnd.mPosition;

else

iter.mFragment.mFragmentEnd = mStart.mBuffer->DataEnd();

iter.mPosition = mStart.mPosition;

iter.normalize_forward();

return iter;

}

nsScannerIterator& nsScannerSubstring::EndReading(

nsScannerIterator& iter) const {

iter.mOwner = this;

iter.mFragment.mBuffer = mEnd.mBuffer;

iter.mFragment.mFragmentEnd = mEnd.mPosition;

if (mStart.mBuffer == mEnd.mBuffer)

iter.mFragment.mFragmentStart = mStart.mPosition;

else

iter.mFragment.mFragmentStart = mEnd.mBuffer->DataStart();

iter.mPosition = mEnd.mPosition;

// must not |normalize_backward| as that would likely invalidate tests like

// |while ( first != last )|

return iter;

}

bool nsScannerSubstring::GetNextFragment(nsScannerFragment& frag) const {

// check to see if we are at the end of the buffer list

if (frag.mBuffer == mEnd.mBuffer) return false;

frag.mBuffer = frag.mBuffer->getNext();

if (frag.mBuffer == mStart.mBuffer)

frag.mFragmentStart = mStart.mPosition;

else

frag.mFragmentStart = frag.mBuffer->DataStart();

if (frag.mBuffer == mEnd.mBuffer)

frag.mFragmentEnd = mEnd.mPosition;

else

frag.mFragmentEnd = frag.mBuffer->DataEnd();

return true;

}

bool nsScannerSubstring::GetPrevFragment(nsScannerFragment& frag) const {

// check to see if we are at the beginning of the buffer list

if (frag.mBuffer == mStart.mBuffer) return false;

frag.mBuffer = frag.mBuffer->getPrevious();

if (frag.mBuffer == mStart.mBuffer)

frag.mFragmentStart = mStart.mPosition;

else

frag.mFragmentStart = frag.mBuffer->DataStart();

if (frag.mBuffer == mEnd.mBuffer)

frag.mFragmentEnd = mEnd.mPosition;

else

frag.mFragmentEnd = frag.mBuffer->DataEnd();

return true;

}

/**

* nsScannerString

nsScannerString::nsScannerString(Buffer* aBuf) {

mBufferList = new nsScannerBufferList(aBuf);

init_range_from_buffer_list();

acquire_ownership_of_buffer_list();

}

void nsScannerString::AppendBuffer(Buffer* aBuf) {

mBufferList->Append(aBuf);

mLength += aBuf->DataLength();

mEnd.mBuffer = aBuf;

mEnd.mPosition = aBuf->DataEnd();

}

void nsScannerString::DiscardPrefix(const nsScannerIterator& aIter) {

Position old_start(mStart);

mStart = aIter;

mLength -= Position::Distance(old_start, mStart);

mStart.mBuffer->IncrementUsageCount();

old_start.mBuffer->DecrementUsageCount();

mBufferList->DiscardUnreferencedPrefix(old_start.mBuffer);

}

void nsScannerString::UngetReadable(const nsAString& aReadable,

const nsScannerIterator& aInsertPoint)

* Warning: this routine manipulates the shared buffer list in an

* unexpected way. The original design did not really allow for

* insertions, but this call promises that if called for a point after the

* end of all extant token strings, that no token string or the work string

* will be invalidated.

* This routine is protected because it is the responsibility of the

* derived class to keep those promises.

{

Position insertPos(aInsertPoint);

mBufferList->SplitBuffer(insertPos);

// splitting to the right keeps the work string and any extant token

// pointing to and holding a reference count on the same buffer

Buffer* new_buffer = AllocBufferFromString(aReadable);

// make a new buffer with all the data to insert...

// ALERT: we may have empty space to re-use in the split buffer,

// measure the cost of this and decide if we should do the work to fill

// it

Buffer* buffer_to_split = insertPos.mBuffer;

mBufferList->InsertAfter(new_buffer, buffer_to_split);

mLength += aReadable.Length();

mEnd.mBuffer = mBufferList->Tail();

mEnd.mPosition = mEnd.mBuffer->DataEnd();

}

/**

* 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 = const_cast<Buffer*>(aStart.buffer());

bool 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 = nullptr;

mBufferList = nullptr;

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();

}

/**

* utils -- based on code from nsReadableUtils.cpp

// private helper function

static inline nsAString::iterator& copy_multifragment_string(

nsScannerIterator& first, const nsScannerIterator& last,

nsAString::iterator& result) {

typedef nsCharSourceTraits<nsScannerIterator> source_traits;

typedef nsCharSinkTraits<nsAString::iterator> sink_traits;

while (first != last) {

uint32_t distance = source_traits::readable_distance(first, last);

sink_traits::write(result, source_traits::read(first), distance);

NS_ASSERTION(distance > 0,

"|copy_multifragment_string| will never terminate");

source_traits::advance(first, distance);

}

return result;

}

bool CopyUnicodeTo(const nsScannerIterator& aSrcStart,

const nsScannerIterator& aSrcEnd, nsAString& aDest) {

mozilla::CheckedInt<nsAString::size_type> distance(

Distance(aSrcStart, aSrcEnd));

if (!distance.isValid()) {

return false; // overflow detected

}

if (!aDest.SetLength(distance.value(), mozilla::fallible)) {

aDest.Truncate();

return false; // out of memory

}

auto writer = aDest.BeginWriting();

nsScannerIterator fromBegin(aSrcStart);

copy_multifragment_string(fromBegin, aSrcEnd, writer);

return true;

}

bool AppendUnicodeTo(const nsScannerIterator& aSrcStart,

const nsScannerIterator& aSrcEnd, nsAString& aDest) {

const nsAString::size_type oldLength = aDest.Length();

mozilla::CheckedInt<nsAString::size_type> newLen(

Distance(aSrcStart, aSrcEnd));

newLen += oldLength;

if (!newLen.isValid()) {

return false; // overflow detected

}

if (!aDest.SetLength(newLen.value(), mozilla::fallible))

return false; // out of memory

auto writer = aDest.BeginWriting();

std::advance(writer, oldLength);

nsScannerIterator fromBegin(aSrcStart);

copy_multifragment_string(fromBegin, aSrcEnd, writer);

return true;

}

gecko-dev/parser/htmlparser/nsScannerString.cpp at master · mozilla/gecko-dev · GitHub

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