tesseract/ccutil/genericvector.h

///////////////////////////////////////////////////////////////////////
// File:        genericvector.h
// Description: Generic vector class
// Author:      Daria Antonova
// Created:     Mon Jun 23 11:26:43 PDT 2008
//
// (C) Copyright 2007, Google Inc.
// Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
///////////////////////////////////////////////////////////////////////
//
#ifndef TESSERACT_CCUTIL_GENERICVECTOR_H_
#define TESSERACT_CCUTIL_GENERICVECTOR_H_

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>

#include "tesscallback.h"
#include "errcode.h"
#include "helpers.h"
#include "ndminx.h"
#include "strngs.h"

// Use PointerVector<T> below in preference to GenericVector<T*>, as that
// provides automatic deletion of pointers, [De]Serialize that works, and
// sort that works.
template <typename T>
class GenericVector {
 public:
  GenericVector() {
    init(kDefaultVectorSize);
  }
  GenericVector(int size, T init_val) {
    init(size);
    init_to_size(size, init_val);
  }

  // Copy
  GenericVector(const GenericVector& other) {
    this->init(other.size());
    this->operator+=(other);
  }
  GenericVector<T> &operator+=(const GenericVector& other);
  GenericVector<T> &operator=(const GenericVector& other);

  ~GenericVector();

  // Reserve some memory.
  void reserve(int size);
  // Double the size of the internal array.
  void double_the_size();

  // Resizes to size and sets all values to t.
  void init_to_size(int size, T t);

  // Return the size used.
  int size() const {
    return size_used_;
  }
  int size_reserved() const {
    return size_reserved_;
  }

  int length() const {
    return size_used_;
  }

  // Return true if empty.
  bool empty() const {
    return size_used_ == 0;
  }

  // Return the object from an index.
  T &get(int index) const;
  T &back() const;
  T &operator[](int index) const;
  // Returns the last object and removes it.
  T pop_back();

  // Return the index of the T object.
  // This method NEEDS a compare_callback to be passed to
  // set_compare_callback.
  int get_index(T object) const;

  // Return true if T is in the array
  bool contains(T object) const;

  // Return true if the index is valid
  T contains_index(int index) const;

  // Push an element in the end of the array
  int push_back(T object);
  void operator+=(T t);

  // Push an element in the end of the array if the same
  // element is not already contained in the array.
  int push_back_new(T object);

  // Push an element in the front of the array
  // Note: This function is O(n)
  int push_front(T object);

  // Set the value at the given index
  void set(T t, int index);

  // Insert t at the given index, push other elements to the right.
  void insert(T t, int index);

  // Removes an element at the given index and
  // shifts the remaining elements to the left.
  void remove(int index);

  // Truncates the array to the given size by removing the end.
  // If the current size is less, the array is not expanded.
  void truncate(int size) {
    if (size < size_used_)
      size_used_ = size;
  }

  // Add a callback to be called to delete the elements when the array took
  // their ownership.
  void set_clear_callback(TessCallback1<T>* cb);

  // Add a callback to be called to compare the elements when needed (contains,
  // get_id, ...)
  void set_compare_callback(TessResultCallback2<bool, T const &, T const &>* cb);

  // Clear the array, calling the clear callback function if any.
  // All the owned callbacks are also deleted.
  // If you don't want the callbacks to be deleted, before calling clear, set
  // the callback to NULL.
  void clear();

  // Delete objects pointed to by data_[i]
  void delete_data_pointers();

  // This method clears the current object, then, does a shallow copy of
  // its argument, and finally invalidates its argument.
  // Callbacks are moved to the current object;
  void move(GenericVector<T>* from);

  // Read/Write the array to a file. This does _NOT_ read/write the callbacks.
  // The callback given must be permanent since they will be called more than
  // once. The given callback will be deleted at the end.
  // If the callbacks are NULL, then the data is simply read/written using
  // fread (and swapping)/fwrite.
  // Returns false on error or if the callback returns false.
  // DEPRECATED. Use [De]Serialize[Classes] instead.
  bool write(FILE* f, TessResultCallback2<bool, FILE*, T const &>* cb) const;
  bool read(FILE* f, TessResultCallback3<bool, FILE*, T*, bool>* cb, bool swap);
  // Writes a vector of simple types to the given file. Assumes that bitwise
  // read/write of T will work. Returns false in case of error.
  bool Serialize(FILE* fp) const;
  // Reads a vector of simple types from the given file. Assumes that bitwise
  // read/write will work with ReverseN according to sizeof(T).
  // Returns false in case of error.
  // If swap is true, assumes a big/little-endian swap is needed.
  bool DeSerialize(bool swap, FILE* fp);
  // Writes a vector of classes to the given file. Assumes the existence of
  // bool T::Serialize(FILE* fp) const that returns false in case of error.
  // Returns false in case of error.
  bool SerializeClasses(FILE* fp) const;
  // Reads a vector of classes from the given file. Assumes the existence of
  // bool T::Deserialize(bool swap, FILE* fp) that returns false in case of
  // error. Also needs T::T() and T::T(constT&), as init_to_size is used in
  // this function. Returns false in case of error.
  // If swap is true, assumes a big/little-endian swap is needed.
  bool DeSerializeClasses(bool swap, FILE* fp);

  // Allocates a new array of double the current_size, copies over the
  // information from data to the new location, deletes data and returns
  // the pointed to the new larger array.
  // This function uses memcpy to copy the data, instead of invoking
  // operator=() for each element like double_the_size() does.
  static T *double_the_size_memcpy(int current_size, T *data) {
    T *data_new = new T[current_size * 2];
    memcpy(data_new, data, sizeof(T) * current_size);
    delete[] data;
    return data_new;
  }

  // Sorts the members of this vector using the less than comparator (cmp_lt),
  // which compares the values. Useful for GenericVectors to primitive types.
  // Will not work so great for pointers (unless you just want to sort some
  // pointers). You need to provide a specialization to sort_cmp to use
  // your type.
  void sort();

  // Sort the array into the order defined by the qsort function comparator.
  // The comparator function is as defined by qsort, ie. it receives pointers
  // to two Ts and returns negative if the first element is to appear earlier
  // in the result and positive if it is to appear later, with 0 for equal.
  void sort(int (*comparator)(const void*, const void*)) {
    qsort(data_, size_used_, sizeof(*data_), comparator);
  }

  // Searches the array (assuming sorted in ascending order, using sort()) for
  // an element equal to target and returns true if it is present.
  // Use binary_search to get the index of target, or its nearest candidate.
  bool bool_binary_search(const T& target) const {
    int index = binary_search(target);
    if (index >= size_used_)
      return false;
    return data_[index] == target;
  }
  // Searches the array (assuming sorted in ascending order, using sort()) for
  // an element equal to target and returns the index of the best candidate.
  // The return value is conceptually the largest index i such that
  // data_[i] <= target or 0 if target < the whole vector.
  // NOTE that this function uses operator> so really the return value is
  // the largest index i such that data_[i] > target is false.
  int binary_search(const T& target) const {
    int bottom = 0;
    int top = size_used_;
    do {
      int middle = (bottom + top) / 2;
      if (data_[middle] > target)
        top = middle;
      else
        bottom = middle;
    }
    while (top - bottom > 1);
    return bottom;
  }

  // Compact the vector by deleting elements using operator!= on basic types.
  // The vector must be sorted.
  void compact_sorted() {
    if (size_used_ == 0)
      return;

    // First element is in no matter what, hence the i = 1.
    int last_write = 0;
    for (int i = 1; i < size_used_; ++i) {
      // Finds next unique item and writes it.
      if (data_[last_write] != data_[i])
        data_[++last_write] = data_[i];
    }
    // last_write is the index of a valid data cell, so add 1.
    size_used_ = last_write + 1;
  }

  // Compact the vector by deleting elements for which delete_cb returns
  // true. delete_cb is a permanent callback and will be deleted.
  void compact(TessResultCallback1<bool, int>* delete_cb) {
    int new_size = 0;
    int old_index = 0;
    // Until the callback returns true, the elements stay the same.
    while (old_index < size_used_ && !delete_cb->Run(old_index++))
      ++new_size;
    // Now just copy anything else that gets false from delete_cb.
    for (; old_index < size_used_; ++old_index) {
      if (!delete_cb->Run(old_index)) {
        data_[new_size++] = data_[old_index];
      }
    }
    size_used_ = new_size;
    delete delete_cb;
  }

  T dot_product(const GenericVector<T>& other) const {
    T result = static_cast<T>(0);
    for (int i = MIN(size_used_, other.size_used_) - 1; i >= 0; --i)
      result += data_[i] * other.data_[i];
    return result;
  }

  // Returns the index of what would be the target_index_th item in the array
  // if the members were sorted, without actually sorting. Members are
  // shuffled around, but it takes O(n) time.
  // NOTE: uses operator< and operator== on the members.
  int choose_nth_item(int target_index) {
    // Make sure target_index is legal.
    if (target_index < 0)
      target_index = 0;                   // ensure legal
    else if (target_index >= size_used_)
      target_index = size_used_ - 1;
    unsigned int seed = 1;
    return choose_nth_item(target_index, 0, size_used_, &seed);
  }

  // Swaps the elements with the given indices.
  void swap(int index1, int index2) {
    if (index1 != index2) {
      T tmp = data_[index1];
      data_[index1] = data_[index2];
      data_[index2] = tmp;
    }
  }

 protected:
  // Internal recursive version of choose_nth_item.
  int choose_nth_item(int target_index, int start, int end, unsigned int* seed);

  // Init the object, allocating size memory.
  void init(int size);

  // We are assuming that the object generally placed in thie
  // vector are small enough that for efficiency it makes sence
  // to start with a larger initial size.
  static const int kDefaultVectorSize = 4;
  inT32   size_used_;
  inT32   size_reserved_;
  T*    data_;
  TessCallback1<T>* clear_cb_;
  // Mutable because Run method is not const
  mutable TessResultCallback2<bool, T const &, T const &>* compare_cb_;
};

namespace tesseract {

// Function to read a GenericVector<char> from a whole file.
// Returns false on failure.
typedef bool (*FileReader)(const STRING& filename, GenericVector<char>* data);
// Function to write a GenericVector<char> to a whole file.
// Returns false on failure.
typedef bool (*FileWriter)(const GenericVector<char>& data,
                           const STRING& filename);
// The default FileReader loads the whole file into the vector of char,
// returning false on error.
inline bool LoadDataFromFile(const STRING& filename,
                             GenericVector<char>* data) {
  FILE* fp = fopen(filename.string(), "rb");
  if (fp == NULL) return false;
  fseek(fp, 0, SEEK_END);
  size_t size = ftell(fp);
  fseek(fp, 0, SEEK_SET);
  // Pad with a 0, just in case we treat the result as a string.
  data->init_to_size(size + 1, 0);
  bool result = fread(&(*data)[0], 1, size, fp) == size;
  fclose(fp);
  return result;
}
// The default FileWriter writes the vector of char to the filename file,
// returning false on error.
inline bool SaveDataToFile(const GenericVector<char>& data,
                          const STRING& filename) {
  FILE* fp = fopen(filename.string(), "wb");
  if (fp == NULL) return false;
  bool result = fwrite(&data[0], 1, data.size(), fp) == data.size();
  fclose(fp);
  return result;
}

template <typename T>
bool cmp_eq(T const & t1, T const & t2) {
  return t1 == t2;
}

// Used by sort()
// return < 0 if t1 < t2
// return 0 if t1 == t2
// return > 0 if t1 > t2
template <typename T>
int sort_cmp(const void* t1, const void* t2) {
  const T* a = static_cast<const T *> (t1);
  const T* b = static_cast<const T *> (t2);
  if (*a < *b) {
    return -1;
  } else if (*b < *a) {
    return 1;
  } else {
    return 0;
  }
}

// Used by PointerVector::sort()
// return < 0 if t1 < t2
// return 0 if t1 == t2
// return > 0 if t1 > t2
template <typename T>
int sort_ptr_cmp(const void* t1, const void* t2) {
  const T* a = *reinterpret_cast<T * const *>(t1);
  const T* b = *reinterpret_cast<T * const *>(t2);
  if (*a < *b) {
    return -1;
  } else if (*b < *a) {
    return 1;
  } else {
    return 0;
  }
}

// Subclass for a vector of pointers. Use in preference to GenericVector<T*>
// as it provides automatic deletion and correct serialization, with the
// corollary that all copy operations are deep copies of the pointed-to objects.
template<typename T>
class PointerVector : public GenericVector<T*> {
 public:
  PointerVector() : GenericVector<T*>() { }
  explicit PointerVector(int size) : GenericVector<T*>(size) { }
  ~PointerVector() {
    // Clear must be called here, even though it is called again by the base,
    // as the base will call the wrong clear.
    clear();
  }
  // Copy must be deep, as the pointers will be automatically deleted on
  // destruction.
  PointerVector(const PointerVector& other) {
    this->init(other.size());
    this->operator+=(other);
  }
  PointerVector<T>& operator+=(const PointerVector& other) {
    this->reserve(this->size_used_ + other.size_used_);
    for (int i = 0; i < other.size(); ++i) {
      this->push_back(new T(*other.data_[i]));
    }
    return *this;
  }

  PointerVector<T>& operator=(const PointerVector& other) {
    this->truncate(0);
    this->operator+=(other);
    return *this;
  }

  // Removes an element at the given index and
  // shifts the remaining elements to the left.
  void remove(int index) {
    delete GenericVector<T*>::data_[index];
    GenericVector<T*>::remove(index);
  }

  // Truncates the array to the given size by removing the end.
  // If the current size is less, the array is not expanded.
  void truncate(int size) {
    for (int i = size; i < GenericVector<T*>::size_used_; ++i)
      delete GenericVector<T*>::data_[i];
    GenericVector<T*>::truncate(size);
  }

  // Compact the vector by deleting elements for which delete_cb returns
  // true. delete_cb is a permanent callback and will be deleted.
  void compact(TessResultCallback1<bool, const T*>* delete_cb) {
    int new_size = 0;
    int old_index = 0;
    // Until the callback returns true, the elements stay the same.
    while (old_index < GenericVector<T*>::size_used_ &&
           !delete_cb->Run(GenericVector<T*>::data_[old_index++]))
      ++new_size;
    // Now just copy anything else that gets false from delete_cb.
    for (; old_index < GenericVector<T*>::size_used_; ++old_index) {
      if (!delete_cb->Run(GenericVector<T*>::data_[old_index])) {
        GenericVector<T*>::data_[new_size++] =
            GenericVector<T*>::data_[old_index];
      } else {
        delete GenericVector<T*>::data_[old_index];
      }
    }
    GenericVector<T*>::size_used_ = new_size;
    delete delete_cb;
  }

  // Clear the array, calling the clear callback function if any.
  // All the owned callbacks are also deleted.
  // If you don't want the callbacks to be deleted, before calling clear, set
  // the callback to NULL.
  void clear() {
    GenericVector<T*>::delete_data_pointers();
    GenericVector<T*>::clear();
  }

  // Writes a vector of simple types to the given file. Assumes that bitwise
  // read/write of T will work. Returns false in case of error.
  bool Serialize(FILE* fp) const {
    inT32 used = GenericVector<T*>::size_used_;
    if (fwrite(&used, sizeof(used), 1, fp) != 1) return false;
    for (int i = 0; i < used; ++i) {
      inT8 non_null = GenericVector<T*>::data_[i] != NULL;
      if (fwrite(&non_null, sizeof(non_null), 1, fp) != 1) return false;
      if (non_null && !GenericVector<T*>::data_[i]->Serialize(fp)) return false;
    }
    return true;
  }
  // Reads a vector of simple types from the given file. Assumes that bitwise
  // read/write will work with ReverseN according to sizeof(T).
  // Also needs T::T(), as new T is used in this function.
  // Returns false in case of error.
  // If swap is true, assumes a big/little-endian swap is needed.
  bool DeSerialize(bool swap, FILE* fp) {
    inT32 reserved;
    if (fread(&reserved, sizeof(reserved), 1, fp) != 1) return false;
    if (swap) Reverse32(&reserved);
    GenericVector<T*>::reserve(reserved);
    for (int i = 0; i < reserved; ++i) {
      inT8 non_null;
      if (fread(&non_null, sizeof(non_null), 1, fp) != 1) return false;
      T* item = NULL;
      if (non_null) {
        item = new T;
        if (!item->DeSerialize(swap, fp)) return false;
      }
      this->push_back(item);
    }
    return true;
  }

  // Sorts the items pointed to by the members of this vector using
  // t::operator<().
  void sort() {
    sort(&sort_ptr_cmp<T>);
  }
};

}  // namespace tesseract

// A useful vector that uses operator== to do comparisons.
template <typename T>
class GenericVectorEqEq : public GenericVector<T> {
 public:
  GenericVectorEqEq() {
    GenericVector<T>::set_compare_callback(
        NewPermanentTessCallback(tesseract::cmp_eq<T>));
  }
  GenericVectorEqEq(int size) : GenericVector<T>(size) {
    GenericVector<T>::set_compare_callback(
        NewPermanentTessCallback(tesseract::cmp_eq<T>));
  }
};

template <typename T>
void GenericVector<T>::init(int size) {
  size_used_ = 0;
  size_reserved_ = 0;
  data_ = 0;
  clear_cb_ = 0;
  compare_cb_ = 0;
  reserve(size);
}

template <typename T>
GenericVector<T>::~GenericVector() {
  clear();
}

// Reserve some memory. If the internal array contains elements, they are
// copied.
template <typename T>
void GenericVector<T>::reserve(int size) {
  if (size_reserved_ >= size || size <= 0)
    return;
  T* new_array = new T[size];
  for (int i = 0; i < size_used_; ++i)
    new_array[i] = data_[i];
  if (data_ != NULL) delete[] data_;
  data_ = new_array;
  size_reserved_ = size;
}

template <typename T>
void GenericVector<T>::double_the_size() {
  if (size_reserved_ == 0) {
    reserve(kDefaultVectorSize);
  }
  else {
    reserve(2 * size_reserved_);
  }
}

// Resizes to size and sets all values to t.
template <typename T>
void GenericVector<T>::init_to_size(int size, T t) {
  reserve(size);
  size_used_ = size;
  for (int i = 0; i < size; ++i)
    data_[i] = t;
}


// Return the object from an index.
template <typename T>
T &GenericVector<T>::get(int index) const {
  ASSERT_HOST(index >= 0 && index < size_used_);
  return data_[index];
}

template <typename T>
T &GenericVector<T>::operator[](int index) const {
  assert(index >= 0 && index < size_used_);
  return data_[index];
}

template <typename T>
T &GenericVector<T>::back() const {
  ASSERT_HOST(size_used_ > 0);
  return data_[size_used_ - 1];
}
// Returns the last object and removes it.
template <typename T>
T GenericVector<T>::pop_back() {
  ASSERT_HOST(size_used_ > 0);
  return data_[--size_used_];
}

// Return the object from an index.
template <typename T>
void GenericVector<T>::set(T t, int index) {
  ASSERT_HOST(index >= 0 && index < size_used_);
  data_[index] = t;
}

// Shifts the rest of the elements to the right to make
// space for the new elements and inserts the given element
// at the specified index.
template <typename T>
void GenericVector<T>::insert(T t, int index) {
  ASSERT_HOST(index >= 0 && index <= size_used_);
  if (size_reserved_ == size_used_)
    double_the_size();
  for (int i = size_used_; i > index; --i) {
    data_[i] = data_[i-1];
  }
  data_[index] = t;
  size_used_++;
}

// Removes an element at the given index and
// shifts the remaining elements to the left.
template <typename T>
void GenericVector<T>::remove(int index) {
  ASSERT_HOST(index >= 0 && index < size_used_);
  for (int i = index; i < size_used_ - 1; ++i) {
    data_[i] = data_[i+1];
  }
  size_used_--;
}

// Return true if the index is valindex
template <typename T>
T GenericVector<T>::contains_index(int index) const {
  return index >= 0 && index < size_used_;
}

// Return the index of the T object.
template <typename T>
int GenericVector<T>::get_index(T object) const {
  for (int i = 0; i < size_used_; ++i) {
    ASSERT_HOST(compare_cb_ != NULL);
    if (compare_cb_->Run(object, data_[i]))
      return i;
  }
  return -1;
}

// Return true if T is in the array
template <typename T>
bool GenericVector<T>::contains(T object) const {
  return get_index(object) != -1;
}

// Add an element in the array
template <typename T>
int GenericVector<T>::push_back(T object) {
  int index = 0;
  if (size_used_ == size_reserved_)
    double_the_size();
  index = size_used_++;
  data_[index] = object;
  return index;
}

template <typename T>
int GenericVector<T>::push_back_new(T object) {
  int index = get_index(object);
  if (index >= 0)
    return index;
  return push_back(object);
}

// Add an element in the array (front)
template <typename T>
int GenericVector<T>::push_front(T object) {
  if (size_used_ == size_reserved_)
    double_the_size();
  for (int i = size_used_; i > 0; --i)
    data_[i] = data_[i-1];
  data_[0] = object;
  ++size_used_;
  return 0;
}

template <typename T>
void GenericVector<T>::operator+=(T t) {
  push_back(t);
}

template <typename T>
GenericVector<T> &GenericVector<T>::operator+=(const GenericVector& other) {
  this->reserve(size_used_ + other.size_used_);
  for (int i = 0; i < other.size(); ++i) {
    this->operator+=(other.data_[i]);
  }
  return *this;
}

template <typename T>
GenericVector<T> &GenericVector<T>::operator=(const GenericVector& other) {
  this->truncate(0);
  this->operator+=(other);
  return *this;
}

// Add a callback to be called to delete the elements when the array took
// their ownership.
template <typename T>
void GenericVector<T>::set_clear_callback(TessCallback1<T>* cb) {
  clear_cb_ = cb;
}

// Add a callback to be called to delete the elements when the array took
// their ownership.
template <typename T>
void GenericVector<T>::set_compare_callback(
    TessResultCallback2<bool, T const &, T const &>* cb) {
  compare_cb_ = cb;
}

// Clear the array, calling the callback function if any.
template <typename T>
void GenericVector<T>::clear() {
  if (size_reserved_ > 0) {
    if (clear_cb_ != NULL)
      for (int i = 0; i < size_used_; ++i)
        clear_cb_->Run(data_[i]);
    delete[] data_;
    data_ = NULL;
    size_used_ = 0;
    size_reserved_ = 0;
  }
  if (clear_cb_ != NULL) {
    delete clear_cb_;
    clear_cb_ = NULL;
  }
  if (compare_cb_ != NULL) {
    delete compare_cb_;
    compare_cb_ = NULL;
  }
}

template <typename T>
void GenericVector<T>::delete_data_pointers() {
  for (int i = 0; i < size_used_; ++i)
    if (data_[i]) {
      delete data_[i];
    }
}


template <typename T>
bool GenericVector<T>::write(
    FILE* f, TessResultCallback2<bool, FILE*, T const &>* cb) const {
  if (fwrite(&size_reserved_, sizeof(size_reserved_), 1, f) != 1) return false;
  if (fwrite(&size_used_, sizeof(size_used_), 1, f) != 1) return false;
  if (cb != NULL) {
    for (int i = 0; i < size_used_; ++i) {
      if (!cb->Run(f, data_[i])) {
        delete cb;
        return false;
      }
    }
    delete cb;
  } else {
    if (fwrite(data_, sizeof(T), size_used_, f) != size_used_) return false;
  }
  return true;
}

template <typename T>
bool GenericVector<T>::read(FILE* f,
                            TessResultCallback3<bool, FILE*, T*, bool>* cb,
                            bool swap) {
  inT32 reserved;
  if (fread(&reserved, sizeof(reserved), 1, f) != 1) return false;
  if (swap) Reverse32(&reserved);
  reserve(reserved);
  if (fread(&size_used_, sizeof(size_used_), 1, f) != 1) return false;
  if (swap) Reverse32(&size_used_);
  if (cb != NULL) {
    for (int i = 0; i < size_used_; ++i) {
      if (!cb->Run(f, data_ + i, swap)) {
        delete cb;
        return false;
      }
    }
    delete cb;
  } else {
    if (fread(data_, sizeof(T), size_used_, f) != size_used_) return false;
    if (swap) {
      for (int i = 0; i < size_used_; ++i)
        ReverseN(&data_[i], sizeof(T));
    }
  }
  return true;
}

// Writes a vector of simple types to the given file. Assumes that bitwise
// read/write of T will work. Returns false in case of error.
template <typename T>
bool GenericVector<T>::Serialize(FILE* fp) const {
  if (fwrite(&size_used_, sizeof(size_used_), 1, fp) != 1) return false;
  if (fwrite(data_, sizeof(*data_), size_used_, fp) != size_used_) return false;
  return true;
}

// Reads a vector of simple types from the given file. Assumes that bitwise
// read/write will work with ReverseN according to sizeof(T).
// Returns false in case of error.
// If swap is true, assumes a big/little-endian swap is needed.
template <typename T>
bool GenericVector<T>::DeSerialize(bool swap, FILE* fp) {
  inT32 reserved;
  if (fread(&reserved, sizeof(reserved), 1, fp) != 1) return false;
  if (swap) Reverse32(&reserved);
  reserve(reserved);
  size_used_ = reserved;
  if (fread(data_, sizeof(T), size_used_, fp) != size_used_) return false;
  if (swap) {
    for (int i = 0; i < size_used_; ++i)
      ReverseN(&data_[i], sizeof(data_[i]));
  }
  return true;
}

// Writes a vector of classes to the given file. Assumes the existence of
// bool T::Serialize(FILE* fp) const that returns false in case of error.
// Returns false in case of error.
template <typename T>
bool GenericVector<T>::SerializeClasses(FILE* fp) const {
  if (fwrite(&size_used_, sizeof(size_used_), 1, fp) != 1) return false;
  for (int i = 0; i < size_used_; ++i) {
    if (!data_[i].Serialize(fp)) return false;
  }
  return true;
}

// Reads a vector of classes from the given file. Assumes the existence of
// bool T::Deserialize(bool swap, FILE* fp) that returns false in case of
// error. Alse needs T::T() and T::T(constT&), as init_to_size is used in
// this function. Returns false in case of error.
// If swap is true, assumes a big/little-endian swap is needed.
template <typename T>
bool GenericVector<T>::DeSerializeClasses(bool swap, FILE* fp) {
  uinT32 reserved;
  if (fread(&reserved, sizeof(reserved), 1, fp) != 1) return false;
  if (swap) Reverse32(&reserved);
  T empty;
  init_to_size(reserved, empty);
  for (int i = 0; i < reserved; ++i) {
    if (!data_[i].DeSerialize(swap, fp)) return false;
  }
  return true;
}

// This method clear the current object, then, does a shallow copy of
// its argument, and finally invalidates its argument.
template <typename T>
void GenericVector<T>::move(GenericVector<T>* from) {
  this->clear();
  this->data_ = from->data_;
  this->size_reserved_ = from->size_reserved_;
  this->size_used_ = from->size_used_;
  this->compare_cb_ = from->compare_cb_;
  this->clear_cb_ = from->clear_cb_;
  from->data_ = NULL;
  from->clear_cb_ = NULL;
  from->compare_cb_ = NULL;
  from->size_used_ = 0;
  from->size_reserved_ = 0;
}

template <typename T>
void GenericVector<T>::sort() {
  sort(&tesseract::sort_cmp<T>);
}

// Internal recursive version of choose_nth_item.
// The algorithm used comes from "Algorithms" by Sedgewick:
// http://books.google.com/books/about/Algorithms.html?id=idUdqdDXqnAC
// The principle is to choose a random pivot, and move everything less than
// the pivot to its left, and everything greater than the pivot to the end
// of the array, then recurse on the part that contains the desired index, or
// just return the answer if it is in the equal section in the middle.
// The random pivot guarantees average linear time for the same reason that
// n times vector::push_back takes linear time on average.
// target_index, start and and end are all indices into the full array.
// Seed is a seed for rand_r for thread safety purposes. Its value is
// unimportant as the random numbers do not affect the result except
// between equal answers.
template <typename T>
int GenericVector<T>::choose_nth_item(int target_index, int start, int end,
                                      unsigned int* seed) {
  // Number of elements to process.
  int num_elements = end - start;
  // Trivial cases.
  if (num_elements <= 1)
    return start;
  if (num_elements == 2) {
    if (data_[start] < data_[start + 1]) {
      return target_index > start ? start + 1 : start;
    } else {
      return target_index > start ? start : start + 1;
    }
  }
  // Place the pivot at start.
  #ifdef _MSC_VER  // TODO(zdenop): check this
  srand(*seed);
  #define rand_r(seed) rand()
  #endif  // _MSC_VER
  int pivot = rand_r(seed) % num_elements + start;
  swap(pivot, start);
  // The invariant condition here is that items [start, next_lesser) are less
  // than the pivot (which is at index next_lesser) and items
  // [prev_greater, end) are greater than the pivot, with items
  // [next_lesser, prev_greater) being equal to the pivot.
  int next_lesser = start;
  int prev_greater = end;
  for (int next_sample = start + 1; next_sample < prev_greater;) {
    if (data_[next_sample] < data_[next_lesser]) {
      swap(next_lesser++, next_sample++);
    } else if (data_[next_sample] == data_[next_lesser]) {
      ++next_sample;
    } else {
      swap(--prev_greater, next_sample);
    }
  }
  // Now the invariant is set up, we recurse on just the section that contains
  // the desired index.
  if (target_index < next_lesser)
    return choose_nth_item(target_index, start, next_lesser, seed);
  else if (target_index < prev_greater)
    return next_lesser;          // In equal bracket.
  else
    return choose_nth_item(target_index, prev_greater, end, seed);
}


#endif  // TESSERACT_CCUTIL_GENERICVECTOR_H_