gecko/toolkit/components/url-classifier/nsUrlClassifierPrefixSet.cpp

//* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=2 et sw=2 tw=80: */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Url Classifier code
 *
 * The Initial Developer of the Original Code is
 * the Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2011
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Gian-Carlo Pascutto <gpascutto@mozilla.com>
 *   Mehdi Mulani <mars.martian+bugmail@gmail.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "nsAutoPtr.h"
#include "nsCOMPtr.h"
#include "nsTArray.h"
#include "nsUrlClassifierPrefixSet.h"
#include "nsIUrlClassifierPrefixSet.h"
#include "nsToolkitCompsCID.h"
#include "nsTArray.h"
#include "nsThreadUtils.h"
#include "mozilla/Mutex.h"
#include "prlog.h"

// NSPR_LOG_MODULES=UrlClassifierPrefixSet:5
#if defined(PR_LOGGING)
static const PRLogModuleInfo *gUrlClassifierPrefixSetLog = nsnull;
#define LOG(args) PR_LOG(gUrlClassifierPrefixSetLog, PR_LOG_DEBUG, args)
#define LOG_ENABLED() PR_LOG_TEST(gUrlClassifierPrefixSetLog, 4)
#else
#define LOG(args)
#define LOG_ENABLED() (PR_FALSE)
#endif

NS_IMPL_THREADSAFE_ISUPPORTS1(nsUrlClassifierPrefixSet, nsIUrlClassifierPrefixSet);

nsUrlClassifierPrefixSet::nsUrlClassifierPrefixSet()
  : mHasPrefixes(PR_FALSE)
{
#if defined(PR_LOGGING)
  if (!gUrlClassifierPrefixSetLog)
    gUrlClassifierPrefixSetLog = PR_NewLogModule("UrlClassifierPrefixSet");
#endif
  LOG(("Instantiating PrefixSet"));
}

nsresult
nsUrlClassifierPrefixSet::SetPrefixes(const PRUint32 * aArray, PRUint32 aLength)
{
  if (mHasPrefixes) {
    mDeltas.Clear();
    mIndexPrefixes.Clear();
    mIndexStarts.Clear();
    mHasPrefixes = PR_FALSE;
  }
  if (aLength > 0) {
    // Ensure they are sorted before adding
    nsTArray<PRUint32> prefixes;
    prefixes.AppendElements(aArray, aLength);
    prefixes.Sort();
    AddPrefixes(prefixes.Elements(), prefixes.Length());
  }

  return NS_OK;
}

nsresult
nsUrlClassifierPrefixSet::AddPrefixes(const PRUint32 * prefixes, PRUint32 aLength)
{
  if (aLength == 0) {
    return NS_OK;
  }

  mIndexPrefixes.AppendElement(prefixes[0]);
  mIndexStarts.AppendElement(mDeltas.Length());

  PRUint32 numOfDeltas = 0;
  PRUint32 currentItem = prefixes[0];
  for (PRUint32 i = 1; i < aLength; i++) {
    if ((numOfDeltas >= DELTAS_LIMIT) ||
          (prefixes[i] - currentItem >= MAX_INDEX_DIFF)) {
      mIndexStarts.AppendElement(mDeltas.Length());
      mIndexPrefixes.AppendElement(prefixes[i]);
      numOfDeltas = 0;
    } else {
      PRUint16 delta = prefixes[i] - currentItem;
      mDeltas.AppendElement(delta);
      numOfDeltas++;
    }
    currentItem = prefixes[i];
  }

  mIndexPrefixes.Compact();
  mIndexStarts.Compact();
  mDeltas.Compact();

  LOG(("Total number of indices: %d", mIndexPrefixes.Length()));
  LOG(("Total number of deltas: %d", mDeltas.Length()));

  mHasPrefixes = PR_TRUE;

  return NS_OK;
}

PRUint32 nsUrlClassifierPrefixSet::BinSearch(PRUint32 start,
                                              PRUint32 end,
                                              PRUint32 target)
{
  while (start != end && end >= start) {
    int i = start + ((end - start) >> 1);
    int value = mIndexPrefixes[i];
    if (value < target) {
      start = i + 1;
    } else if (value > target) {
      end = i - 1;
    } else {
      return i;
    }
  }
  return end;
}

nsresult
nsUrlClassifierPrefixSet::Contains(PRUint32 aPrefix, PRBool * aFound)
{
  *aFound = PR_FALSE;

  if (!mHasPrefixes) {
    return NS_OK;
  }

  PRUint32 target = aPrefix;

  // We want to do a "Price is Right" binary search, that is, we want to find
  // the index of the value either equal to the target or the closest value
  // that is less than the target.
  //
  if (target < mIndexPrefixes[0]) {
    return NS_OK;
  }

  // |binsearch| does not necessarily return the correct index (when the
  // target is not found) but rather it returns an index at least one away
  // from the correct index.
  // Because of this, we need to check if the target lies before the beginning
  // of the indices.

  int i = BinSearch(0, mIndexPrefixes.Length() - 1, target);
  if (mIndexPrefixes[i] > target && i > 0) {
    i--;
  }

  // Now search through the deltas for the target.
  PRUint32 diff = target - mIndexPrefixes[i];
  PRUint32 deltaIndex = mIndexStarts[i];
  PRUint32 end = (i + 1 < mIndexStarts.Length()) ? mIndexStarts[i+1]
                                                 : mDeltas.Length();
  while (diff > 0 && deltaIndex < end) {
    diff -= mDeltas[deltaIndex];
    deltaIndex++;
  }

  if (diff == 0) {
    *aFound = PR_TRUE;
  }

  return NS_OK;
}

nsresult
nsUrlClassifierPrefixSet::EstimateSize(PRUint32 * aSize)
{
  *aSize = sizeof(PRBool);
  if (mHasPrefixes) {
    *aSize += sizeof(PRUint16) * mDeltas.Length();
    *aSize += sizeof(PRUint32) * mIndexPrefixes.Length();
    *aSize += sizeof(PRUint32) * mIndexStarts.Length();
  }
  return NS_OK;
}