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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
#ifndef nsScannerString_h___
#define nsScannerString_h___
#include "nsString.h"
#include "nsUnicharUtils.h" // for nsCaseInsensitiveStringComparator
#include "mozilla/LinkedList.h"
#include <algorithm>
/**
* NOTE: nsScannerString (and the other classes defined in this file) are
* not related to nsAString or any of the other xpcom/string classes.
*
* nsScannerString is based on the nsSlidingString implementation that used
* to live in xpcom/string. Now that nsAString is limited to representing
* only single fragment strings, nsSlidingString can no longer be used.
*
* An advantage to this design is that it does not employ any virtual
* functions.
*
* This file uses SCC-style indenting in deference to the nsSlidingString
* code from which this code is derived ;-)
*/
class nsScannerIterator;
class nsScannerSubstring;
class nsScannerString;
/**
* nsScannerBufferList
*
* This class maintains a list of heap-allocated Buffer objects. The buffers
* are maintained in a circular linked list. Each buffer has a usage count
* that is decremented by the owning nsScannerSubstring.
*
* The buffer list itself is reference counted. This allows the buffer list
* to be shared by multiple nsScannerSubstring objects. The reference
* counting is not threadsafe, which is not at all a requirement.
*
* When a nsScannerSubstring releases its reference to a buffer list, it
* decrements the usage count of the first buffer in the buffer list that it
* was referencing. It informs the buffer list that it can discard buffers
* starting at that prefix. The buffer list will do so if the usage count of
* that buffer is 0 and if it is the first buffer in the list. It will
* continue to prune buffers starting from the front of the buffer list until
* it finds a buffer that has a usage count that is non-zero.
*/
class nsScannerBufferList {
public:
/**
* Buffer objects are directly followed by a data segment. The start
* of the data segment is determined by increment the |this| pointer
* by 1 unit.
*/
class Buffer : public mozilla::LinkedListElement<Buffer> {
public:
void IncrementUsageCount() { ++mUsageCount; }
void DecrementUsageCount() { --mUsageCount; }
bool IsInUse() const { return mUsageCount != 0; }
const char16_t* DataStart() const { return (const char16_t*)(this + 1); }
char16_t* DataStart() { return (char16_t*)(this + 1); }
const char16_t* DataEnd() const { return mDataEnd; }
char16_t* DataEnd() { return mDataEnd; }
const Buffer* Next() const { return getNext(); }
Buffer* Next() { return getNext(); }
const Buffer* Prev() const { return getPrevious(); }
Buffer* Prev() { return getPrevious(); }
uint32_t DataLength() const { return mDataEnd - DataStart(); }
void SetDataLength(uint32_t len) { mDataEnd = DataStart() + len; }
private:
friend class nsScannerBufferList;
int32_t mUsageCount;
char16_t* mDataEnd;
};
/**
* Position objects serve as lightweight pointers into a buffer list.
* The mPosition member must be contained with mBuffer->DataStart()
* and mBuffer->DataEnd().
*/
class Position {
public:
Position() : mBuffer(nullptr), mPosition(nullptr) {}
Position(Buffer* buffer, char16_t* position)
: mBuffer(buffer), mPosition(position) {}
inline explicit Position(const nsScannerIterator& aIter);
inline Position& operator=(const nsScannerIterator& aIter);
static size_t Distance(const Position& p1, const Position& p2);
Buffer* mBuffer;
char16_t* mPosition;
};
static Buffer* AllocBufferFromString(const nsAString&);
static Buffer* AllocBuffer(uint32_t capacity); // capacity = number of chars
explicit nsScannerBufferList(Buffer* buf) : mRefCnt(0) {
mBuffers.insertBack(buf);
}
void AddRef() { ++mRefCnt; }
void Release() {
if (--mRefCnt == 0) delete this;
}
void Append(Buffer* buf) { mBuffers.insertBack(buf); }
void InsertAfter(Buffer* buf, Buffer* prev) { prev->setNext(buf); }
void SplitBuffer(const Position&);
void DiscardUnreferencedPrefix(Buffer*);
Buffer* Head() { return mBuffers.getFirst(); }
const Buffer* Head() const { return mBuffers.getFirst(); }
Buffer* Tail() { return mBuffers.getLast(); }
const Buffer* Tail() const { return mBuffers.getLast(); }
private:
friend class nsScannerSubstring;
~nsScannerBufferList() { ReleaseAll(); }
void ReleaseAll();
int32_t mRefCnt;
mozilla::LinkedList<Buffer> mBuffers;
};
/**
* nsScannerFragment represents a "slice" of a Buffer object.
*/
struct nsScannerFragment {
typedef nsScannerBufferList::Buffer Buffer;
const Buffer* mBuffer;
const char16_t* mFragmentStart;
const char16_t* mFragmentEnd;
};
/**
* nsScannerSubstring is the base class for nsScannerString. It provides
* access to iterators and methods to bind the substring to another
* substring or nsAString instance.
*
* This class owns the buffer list.
*/
class nsScannerSubstring {
public:
typedef nsScannerBufferList::Buffer Buffer;
typedef nsScannerBufferList::Position Position;
typedef uint32_t size_type;
nsScannerSubstring();
explicit nsScannerSubstring(const nsAString& s);
~nsScannerSubstring();
nsScannerIterator& BeginReading(nsScannerIterator& iter) const;
nsScannerIterator& EndReading(nsScannerIterator& iter) const;
size_type Length() const { return mLength; }
void Rebind(const nsScannerSubstring&, const nsScannerIterator&,
const nsScannerIterator&);
void Rebind(const nsAString&);
bool GetNextFragment(nsScannerFragment&) const;
bool GetPrevFragment(nsScannerFragment&) const;
static inline Buffer* AllocBufferFromString(const nsAString& aStr) {
return nsScannerBufferList::AllocBufferFromString(aStr);
}
static inline Buffer* AllocBuffer(size_type aCapacity) {
return nsScannerBufferList::AllocBuffer(aCapacity);
}
protected:
void acquire_ownership_of_buffer_list() const {
mBufferList->AddRef();
mStart.mBuffer->IncrementUsageCount();
}
void release_ownership_of_buffer_list() {
if (mBufferList) {
mStart.mBuffer->DecrementUsageCount();
mBufferList->DiscardUnreferencedPrefix(mStart.mBuffer);
mBufferList->Release();
}
}
void init_range_from_buffer_list() {
mStart.mBuffer = mBufferList->Head();
mStart.mPosition = mStart.mBuffer->DataStart();
mEnd.mBuffer = mBufferList->Tail();
mEnd.mPosition = mEnd.mBuffer->DataEnd();
mLength = Position::Distance(mStart, mEnd);
}
Position mStart;
Position mEnd;
nsScannerBufferList* mBufferList;
size_type mLength;
friend class nsScannerSharedSubstring;
};
/**
* nsScannerString provides methods to grow and modify a buffer list.
*/
class nsScannerString : public nsScannerSubstring {
public:
explicit nsScannerString(Buffer*);
// you are giving ownership to the string, it takes and keeps your
// buffer, deleting it when done.
// Use AllocBuffer or AllocBufferFromString to create a Buffer object
// for use with this function.
void AppendBuffer(Buffer*);
void DiscardPrefix(const nsScannerIterator&);
// any other way you want to do this?
void UngetReadable(const nsAString& aReadable,
const nsScannerIterator& aCurrentPosition);
};
/**
* nsScannerSharedSubstring implements copy-on-write semantics for
* nsScannerSubstring. This class also manages releasing
* the reference to the scanner buffer when it is no longer needed.
*/
class nsScannerSharedSubstring {
public:
nsScannerSharedSubstring() : mBuffer(nullptr), mBufferList(nullptr) {}
~nsScannerSharedSubstring() {
if (mBufferList) ReleaseBuffer();
}
// Acquire a copy-on-write reference to the given substring.
void Rebind(const nsScannerIterator& aStart, const nsScannerIterator& aEnd);
// Get a const reference to this string
const nsAString& str() const { return mString; }
private:
typedef nsScannerBufferList::Buffer Buffer;
void ReleaseBuffer();
nsDependentSubstring mString;
Buffer* mBuffer;
nsScannerBufferList* mBufferList;
};
/**
* nsScannerIterator works just like nsReadingIterator<CharT> except that
* it knows how to iterate over a list of scanner buffers.
*/
class nsScannerIterator {
public:
typedef nsScannerIterator self_type;
typedef ptrdiff_t difference_type;
typedef char16_t value_type;
typedef const char16_t* pointer;
typedef const char16_t& reference;
typedef nsScannerSubstring::Buffer Buffer;
protected:
nsScannerFragment mFragment;
const char16_t* mPosition;
const nsScannerSubstring* mOwner;
friend class nsScannerSubstring;
friend class nsScannerSharedSubstring;
public:
// nsScannerIterator(); // auto-generate
// default constructor is OK nsScannerIterator( const nsScannerIterator& ); //
// auto-generated copy-constructor OK nsScannerIterator& operator=( const
// nsScannerIterator& ); // auto-generated copy-assignment operator OK
inline void normalize_forward();
inline void normalize_backward();
pointer get() const { return mPosition; }
char16_t operator*() const { return *get(); }
const nsScannerFragment& fragment() const { return mFragment; }
const Buffer* buffer() const { return mFragment.mBuffer; }
self_type& operator++() {
++mPosition;
normalize_forward();
return *this;
}
self_type operator++(int) {
self_type result(*this);
++mPosition;
normalize_forward();
return result;
}
self_type& operator--() {
normalize_backward();
--mPosition;
return *this;
}
self_type operator--(int) {
self_type result(*this);
normalize_backward();
--mPosition;
return result;
}
difference_type size_forward() const {
return mFragment.mFragmentEnd - mPosition;
}
difference_type size_backward() const {
return mPosition - mFragment.mFragmentStart;
}
self_type& advance(difference_type n) {
while (n > 0) {
difference_type one_hop = std::min(n, size_forward());
NS_ASSERTION(one_hop > 0,
"Infinite loop: can't advance a reading iterator beyond the "
"end of a string");
// perhaps I should |break| if |!one_hop|?
mPosition += one_hop;
normalize_forward();
n -= one_hop;
}
while (n < 0) {
normalize_backward();
difference_type one_hop = std::max(n, -size_backward());
NS_ASSERTION(one_hop < 0,
"Infinite loop: can't advance (backward) a reading iterator "
"beyond the end of a string");
// perhaps I should |break| if |!one_hop|?
mPosition += one_hop;
n -= one_hop;
}
return *this;
}
};
inline bool SameFragment(const nsScannerIterator& a,
const nsScannerIterator& b) {
return a.fragment().mFragmentStart == b.fragment().mFragmentStart;
}
template <>
struct nsCharSourceTraits<nsScannerIterator> {
typedef nsScannerIterator::difference_type difference_type;
static uint32_t readable_distance(const nsScannerIterator& first,
const nsScannerIterator& last) {
return uint32_t(SameFragment(first, last) ? last.get() - first.get()
: first.size_forward());
}
static const nsScannerIterator::value_type* read(
const nsScannerIterator& iter) {
return iter.get();
}
static void advance(nsScannerIterator& s, difference_type n) { s.advance(n); }
};
/**
* inline methods follow
*/
inline void nsScannerIterator::normalize_forward() {
while (mPosition == mFragment.mFragmentEnd &&
mOwner->GetNextFragment(mFragment))
mPosition = mFragment.mFragmentStart;
}
inline void nsScannerIterator::normalize_backward() {
while (mPosition == mFragment.mFragmentStart &&
mOwner->GetPrevFragment(mFragment))
mPosition = mFragment.mFragmentEnd;
}
inline bool operator==(const nsScannerIterator& lhs,
const nsScannerIterator& rhs) {
return lhs.get() == rhs.get();
}
inline bool operator!=(const nsScannerIterator& lhs,
const nsScannerIterator& rhs) {
return lhs.get() != rhs.get();
}
inline nsScannerBufferList::Position::Position(const nsScannerIterator& aIter)
: mBuffer(const_cast<Buffer*>(aIter.buffer())),
mPosition(const_cast<char16_t*>(aIter.get())) {}
inline nsScannerBufferList::Position& nsScannerBufferList::Position::operator=(
const nsScannerIterator& aIter) {
mBuffer = const_cast<Buffer*>(aIter.buffer());
mPosition = const_cast<char16_t*>(aIter.get());
return *this;
}
/**
* scanner string utils
*
* These methods mimic the API provided by nsReadableUtils in xpcom/string.
* Here we provide only the methods that the htmlparser module needs.
*/
inline size_t Distance(const nsScannerIterator& aStart,
const nsScannerIterator& aEnd) {
typedef nsScannerBufferList::Position Position;
return Position::Distance(Position(aStart), Position(aEnd));
}
bool CopyUnicodeTo(const nsScannerIterator& aSrcStart,
const nsScannerIterator& aSrcEnd, nsAString& aDest);
bool AppendUnicodeTo(const nsScannerIterator& aSrcStart,
const nsScannerIterator& aSrcEnd, nsAString& aDest);
#endif // !defined(nsScannerString_h___)