xpcom/string/nsStringIterator.h
author Kartikaya Gupta <kgupta@mozilla.com>
Tue, 23 May 2017 10:50:42 -0400
changeset 408330 fa1a20ec07bfb15ddb9101853ad0cedde28ad7a7
parent 395569 485e1632ef228d3dd621c5f4ae297795335a5dc1
child 428973 8b18f545fd6f7dd341010b041bd248a1e726bc13
permissions -rw-r--r--
Bug 1364525 - Update APIs to allow APZ to produce scrollbar transforms. r=pchang,botond This allows the APZCTreeManager::PushStateToWR function to also produce a set of transforms to be applied to scrollbar thumbs. The PushStateToWR function will be updated in the next patch to actually produce the transforms. This patch also rearranges code in WebRenderBridgeParent::CompositeToTarget so that either OMTA or APZ can produce animation updates. MozReview-Commit-ID: 1ghvVG32TC5

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */

#ifndef nsStringIterator_h___
#define nsStringIterator_h___

#include "nsCharTraits.h"
#include "nsAlgorithm.h"
#include "nsDebug.h"

/**
 * @see nsTAString
 */

template <class CharT>
class nsReadingIterator
{
public:
  typedef nsReadingIterator<CharT>    self_type;
  typedef ptrdiff_t                   difference_type;
  typedef size_t                      size_type;
  typedef CharT                       value_type;
  typedef const CharT*                pointer;
  typedef const CharT&                reference;

private:
  friend class mozilla::detail::nsStringRepr;
  friend class mozilla::detail::nsCStringRepr;

  // unfortunately, the API for nsReadingIterator requires that the
  // iterator know its start and end positions.  this was needed when
  // we supported multi-fragment strings, but now it is really just
  // extra baggage.  we should remove mStart and mEnd at some point.

  const CharT* mStart;
  const CharT* mEnd;
  const CharT* mPosition;

public:
  nsReadingIterator()
  {
  }
  // nsReadingIterator( const nsReadingIterator<CharT>& );                    // auto-generated copy-constructor OK
  // nsReadingIterator<CharT>& operator=( const nsReadingIterator<CharT>& );  // auto-generated copy-assignment operator OK

  pointer get() const
  {
    return mPosition;
  }

  CharT operator*() const
  {
    return *get();
  }

  self_type& operator++()
  {
    ++mPosition;
    return *this;
  }

  self_type operator++(int)
  {
    self_type result(*this);
    ++mPosition;
    return result;
  }

  self_type& operator--()
  {
    --mPosition;
    return *this;
  }

  self_type operator--(int)
  {
    self_type result(*this);
    --mPosition;
    return result;
  }

  self_type& advance(difference_type aN)
  {
    if (aN > 0) {
      difference_type step = XPCOM_MIN(aN, mEnd - mPosition);

      NS_ASSERTION(step > 0,
                   "can't advance a reading iterator beyond the end of a string");

      mPosition += step;
    } else if (aN < 0) {
      difference_type step = XPCOM_MAX(aN, -(mPosition - mStart));

      NS_ASSERTION(step < 0,
                   "can't advance (backward) a reading iterator beyond the end of a string");

      mPosition += step;
    }
    return *this;
  }

  // We return an unsigned type here (with corresponding assert) rather than
  // the more usual difference_type because we want to make this class go
  // away in favor of mozilla::RangedPtr.  Since RangedPtr has the same
  // requirement we are enforcing here, the transition ought to be much
  // smoother.
  size_type operator-(const self_type& aOther) const
  {
    MOZ_ASSERT(mPosition >= aOther.mPosition);
    return mPosition - aOther.mPosition;
  }
};

/**
 * @see nsTAString
 */

template <class CharT>
class nsWritingIterator
{
public:
  typedef nsWritingIterator<CharT>   self_type;
  typedef ptrdiff_t                  difference_type;
  typedef size_t                     size_type;
  typedef CharT                      value_type;
  typedef CharT*                     pointer;
  typedef CharT&                     reference;

private:
  friend class nsAString;
  friend class nsACString;

  // unfortunately, the API for nsWritingIterator requires that the
  // iterator know its start and end positions.  this was needed when
  // we supported multi-fragment strings, but now it is really just
  // extra baggage.  we should remove mStart and mEnd at some point.

  CharT* mStart;
  CharT* mEnd;
  CharT* mPosition;

public:
  nsWritingIterator()
  {
  }
  // nsWritingIterator( const nsWritingIterator<CharT>& );                    // auto-generated copy-constructor OK
  // nsWritingIterator<CharT>& operator=( const nsWritingIterator<CharT>& );  // auto-generated copy-assignment operator OK

  pointer get() const
  {
    return mPosition;
  }

  reference operator*() const
  {
    return *get();
  }

  self_type& operator++()
  {
    ++mPosition;
    return *this;
  }

  self_type operator++(int)
  {
    self_type result(*this);
    ++mPosition;
    return result;
  }

  self_type& operator--()
  {
    --mPosition;
    return *this;
  }

  self_type operator--(int)
  {
    self_type result(*this);
    --mPosition;
    return result;
  }

  self_type& advance(difference_type aN)
  {
    if (aN > 0) {
      difference_type step = XPCOM_MIN(aN, mEnd - mPosition);

      NS_ASSERTION(step > 0,
                   "can't advance a writing iterator beyond the end of a string");

      mPosition += step;
    } else if (aN < 0) {
      difference_type step = XPCOM_MAX(aN, -(mPosition - mStart));

      NS_ASSERTION(step < 0,
                   "can't advance (backward) a writing iterator beyond the end of a string");

      mPosition += step;
    }
    return *this;
  }

  // We return an unsigned type here (with corresponding assert) rather than
  // the more usual difference_type because we want to make this class go
  // away in favor of mozilla::RangedPtr.  Since RangedPtr has the same
  // requirement we are enforcing here, the transition ought to be much
  // smoother.
  size_type operator-(const self_type& aOther) const
  {
    MOZ_ASSERT(mPosition >= aOther.mPosition);
    return mPosition - aOther.mPosition;
  }
};

template <class CharT>
struct nsCharSinkTraits<nsWritingIterator<CharT>>
{
  static void
  write(nsWritingIterator<CharT>& aIter, const CharT* aStr, uint32_t aN)
  {
    nsCharTraits<CharT>::move(aIter.get(), aStr, aN);
    aIter.advance(aN);
  }
};

template <class CharT>
inline bool
operator==(const nsReadingIterator<CharT>& aLhs,
           const nsReadingIterator<CharT>& aRhs)
{
  return aLhs.get() == aRhs.get();
}

template <class CharT>
inline bool
operator!=(const nsReadingIterator<CharT>& aLhs,
           const nsReadingIterator<CharT>& aRhs)
{
  return aLhs.get() != aRhs.get();
}


//
// |nsWritingIterator|s
//

template <class CharT>
inline bool
operator==(const nsWritingIterator<CharT>& aLhs,
           const nsWritingIterator<CharT>& aRhs)
{
  return aLhs.get() == aRhs.get();
}

template <class CharT>
inline bool
operator!=(const nsWritingIterator<CharT>& aLhs,
           const nsWritingIterator<CharT>& aRhs)
{
  return aLhs.get() != aRhs.get();
}

#endif /* !defined(nsStringIterator_h___) */