range_map-inl.h

// Copyright (c) 2010 Google Inc.
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// range_map-inl.h: Range map implementation.
//
// See range_map.h for documentation.
//
// Author: Mark Mentovai

#ifndef PROCESSOR_RANGE_MAP_INL_H__
#define PROCESSOR_RANGE_MAP_INL_H__


#include <assert.h>

#include "processor/range_map.h"
#include "processor/linked_ptr.h"
#include "processor/logging.h"


namespace google_breakpad {

template<typename AddressType, typename EntryType>
void RangeMap<AddressType, EntryType>::SetEnableShrinkDown(
    bool enable_shrink_down) {
  enable_shrink_down_ = enable_shrink_down;
}

template<typename AddressType, typename EntryType>
bool RangeMap<AddressType, EntryType>::IsShrinkDownEnabled() const {
  return enable_shrink_down_;
}

template<typename AddressType, typename EntryType>
bool RangeMap<AddressType, EntryType>::StoreRange(const AddressType &base,
                                                  const AddressType &size,
                                                  const EntryType &entry) {
  return StoreRangeInternal(base, 0 /* delta */, size, entry);
}

template<typename AddressType, typename EntryType>
bool RangeMap<AddressType, EntryType>::StoreRangeInternal(
    const AddressType &base, const AddressType &delta,
    const AddressType &size, const EntryType &entry) {
  AddressType high = base + (size - 1);

  // Check for undersize or overflow.
  if (size <= 0 || high < base) {
    // The processor will hit this case too frequently with common symbol
    // files in the size == 0 case, which is more suited to a DEBUG channel.
    // Filter those out since there's no DEBUG channel at the moment.
    BPLOG_IF(INFO, size != 0) << "StoreRangeInternal failed, "
                              << HexString(base) << "+" << HexString(size)
                              << ", " << HexString(high)
                              << ", delta: " << HexString(delta);
    return false;
  }

  // Ensure that this range does not overlap with another one already in the
  // map.
  MapConstIterator iterator_base = map_.lower_bound(base);
  MapConstIterator iterator_high = map_.lower_bound(high);

  if (iterator_base != iterator_high) {
    // Some other range begins in the space used by this range.  It may be
    // contained within the space used by this range, or it may extend lower.
    // If enable_shrink_down_ is true, shrink the current range down, otherwise
    // this is an error.
    if (enable_shrink_down_) {
      AddressType additional_delta = iterator_base->first - base + 1;
      return StoreRangeInternal(base + additional_delta,
                                delta + additional_delta,
                                size - additional_delta, entry);
    } else {
      // The processor hits this case too frequently with common symbol files. 
      // This is most appropriate for a DEBUG channel, but since none exists
      // now simply comment out this logging.
      // AddressType other_base = iterator_base->second.base();
      // AddressType other_size = iterator_base->first - other_base + 1;
      // BPLOG(INFO) << "StoreRangeInternal failed, an existing range is "
      //             << "overlapping with the new range: new "
      //             << HexString(base) << "+" << HexString(size)
      //             << ", existing " << HexString(other_base) << "+"
      //             << HexString(other_size);
      return false;
    }
  }

  if (iterator_high != map_.end()) {
    if (iterator_high->second.base() <= high) {
      // The range above this one overlaps with this one.  It may fully
      // contain this range, or it may begin within this range and extend
      // higher.  If enable_shrink_down_ is true, shrink the other range down,
      // otherwise this is an error.
      if (enable_shrink_down_ && iterator_high->first > high) {
        // Shrink the other range down.
        AddressType other_high = iterator_high->first;
        AddressType additional_delta =
            high - iterator_high->second.base() + 1;
        EntryType other_entry;
        AddressType other_base = AddressType();
        AddressType other_size = AddressType();
        AddressType other_delta = AddressType();
        RetrieveRange(other_high, &other_entry, &other_base, &other_delta,
                      &other_size);
        map_.erase(iterator_high);
        map_.insert(MapValue(other_high,
                             Range(other_base + additional_delta,
                                   other_delta + additional_delta,
                                   other_entry)));
        // Retry to store this range.
        return StoreRangeInternal(base, delta, size, entry);
      } else {
        // The processor hits this case too frequently with common symbol files.
        // This is most appropriate for a DEBUG channel, but since none exists
        // now simply comment out this logging.
        //
        // AddressType other_base = iterator_high->second.base();
        // AddressType other_size = iterator_high->first - other_base + 1;
        // BPLOG(INFO) << "StoreRangeInternal failed, an existing range "
        //             << "contains or extends higher than the new range: new "
        //             << HexString(base) << "+" << HexString(size)
        //             << ", existing " << HexString(other_base) << "+"
        //             << HexString(other_size);
        return false;
      }
    }
  }

  // Store the range in the map by its high address, so that lower_bound can
  // be used to quickly locate a range by address.
  map_.insert(MapValue(high, Range(base, delta, entry)));
  return true;
}


template<typename AddressType, typename EntryType>
bool RangeMap<AddressType, EntryType>::RetrieveRange(
    const AddressType &address, EntryType *entry, AddressType *entry_base,
    AddressType *entry_delta, AddressType *entry_size) const {
  BPLOG_IF(ERROR, !entry) << "RangeMap::RetrieveRange requires |entry|";
  assert(entry);

  MapConstIterator iterator = map_.lower_bound(address);
  if (iterator == map_.end())
    return false;

  // The map is keyed by the high address of each range, so |address| is
  // guaranteed to be lower than the range's high address.  If |range| is
  // not directly preceded by another range, it's possible for address to
  // be below the range's low address, though.  When that happens, address
  // references something not within any range, so return false.
  if (address < iterator->second.base())
    return false;

  *entry = iterator->second.entry();
  if (entry_base)
    *entry_base = iterator->second.base();
  if (entry_delta)
    *entry_delta = iterator->second.delta();
  if (entry_size)
    *entry_size = iterator->first - iterator->second.base() + 1;

  return true;
}


template<typename AddressType, typename EntryType>
bool RangeMap<AddressType, EntryType>::RetrieveNearestRange(
    const AddressType &address, EntryType *entry, AddressType *entry_base,
    AddressType *entry_delta, AddressType *entry_size) const {
  BPLOG_IF(ERROR, !entry) << "RangeMap::RetrieveNearestRange requires |entry|";
  assert(entry);

  // If address is within a range, RetrieveRange can handle it.
  if (RetrieveRange(address, entry, entry_base, entry_delta, entry_size))
    return true;

  // upper_bound gives the first element whose key is greater than address,
  // but we want the first element whose key is less than or equal to address.
  // Decrement the iterator to get there, but not if the upper_bound already
  // points to the beginning of the map - in that case, address is lower than
  // the lowest stored key, so return false.
  MapConstIterator iterator = map_.upper_bound(address);
  if (iterator == map_.begin())
    return false;
  --iterator;

  *entry = iterator->second.entry();
  if (entry_base)
    *entry_base = iterator->second.base();
  if (entry_delta)
    *entry_delta = iterator->second.delta();
  if (entry_size)
    *entry_size = iterator->first - iterator->second.base() + 1;

  return true;
}


template<typename AddressType, typename EntryType>
bool RangeMap<AddressType, EntryType>::RetrieveRangeAtIndex(
    int index, EntryType *entry, AddressType *entry_base,
    AddressType *entry_delta, AddressType *entry_size) const {
  BPLOG_IF(ERROR, !entry) << "RangeMap::RetrieveRangeAtIndex requires |entry|";
  assert(entry);

  if (index >= GetCount()) {
    BPLOG(ERROR) << "Index out of range: " << index << "/" << GetCount();
    return false;
  }

  // Walk through the map.  Although it's ordered, it's not a vector, so it
  // can't be addressed directly by index.
  MapConstIterator iterator = map_.begin();
  for (int this_index = 0; this_index < index; ++this_index)
    ++iterator;

  *entry = iterator->second.entry();
  if (entry_base)
    *entry_base = iterator->second.base();
  if (entry_delta)
    *entry_delta = iterator->second.delta();
  if (entry_size)
    *entry_size = iterator->first - iterator->second.base() + 1;

  return true;
}


template<typename AddressType, typename EntryType>
int RangeMap<AddressType, EntryType>::GetCount() const {
  return map_.size();
}


template<typename AddressType, typename EntryType>
void RangeMap<AddressType, EntryType>::Clear() {
  map_.clear();
}


}  // namespace google_breakpad


#endif  // PROCESSOR_RANGE_MAP_INL_H__