helpers.h

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/******************************************************************************
 *
 * File:         helpers.h
 * Description:  General utility functions
 * Author:       Daria Antonova
 *
 * (c) Copyright 2009, 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_HELPERS_H_
#define TESSERACT_CCUTIL_HELPERS_H_
 
#include <cassert>
#include <cstdio>
#include <cstring>
#include <functional>
#include <string>
 
// TODO(rays) Put the rest of the helpers in the namespace.
namespace tesseract {
 
// A simple linear congruential random number generator, using Knuth's
// constants from:
// http://en.wikipedia.org/wiki/Linear_congruential_generator.
class TRand {
 public:
  TRand() = default;
  // Sets the seed to the given value.
  void set_seed(uint64_t seed) {
    seed_ = seed;
  }
  // Sets the seed using a hash of a string.
  void set_seed(const std::string& str) {
    std::hash<std::string> hasher;
    set_seed(static_cast<uint64_t>(hasher(str)));
  }
 
  // Returns an integer in the range 0 to INT32_MAX.
  int32_t IntRand() {
    Iterate();
    return seed_ >> 33;
  }
  // Returns a floating point value in the range [-range, range].
  double SignedRand(double range) {
    return range * 2.0 * IntRand() / INT32_MAX - range;
  }
  // Returns a floating point value in the range [0, range].
  double UnsignedRand(double range) {
    return range * IntRand() / INT32_MAX;
  }
 
 private:
  // Steps the generator to the next value.
  void Iterate() {
    seed_ *= 6364136223846793005ULL;
    seed_ += 1442695040888963407ULL;
  }
 
  // The current value of the seed.
  uint64_t seed_{1};
};
 
}  // namespace tesseract
 
// Remove newline (if any) at the end of the string.
inline void chomp_string(char* str) {
  int last_index = static_cast<int>(strlen(str)) - 1;
  while (last_index >= 0 &&
         (str[last_index] == '\n' || str[last_index] == '\r')) {
    str[last_index--] = '\0';
  }
}
 
// Advance the current pointer of the file if it points to a newline character.
inline void SkipNewline(FILE* file) {
  if (fgetc(file) != '\n') {
    fseek(file, -1, SEEK_CUR);
  }
}
 
// Swaps the two args pointed to by the pointers.
// Operator= and copy constructor must work on T.
template <typename T>
inline void Swap(T* p1, T* p2) {
  T tmp(*p2);
  *p2 = *p1;
  *p1 = tmp;
}
 
// return the smallest multiple of block_size greater than or equal to n.
inline int RoundUp(int n, int block_size) {
  return block_size * ((n + block_size - 1) / block_size);
}
 
// Clip a numeric value to the interval [lower_bound, upper_bound].
template <typename T>
inline T ClipToRange(const T& x, const T& lower_bound, const T& upper_bound) {
  if (x < lower_bound) {
    return lower_bound;
  }
  if (x > upper_bound) {
    return upper_bound;
  }
  return x;
}
 
// Extend the range [lower_bound, upper_bound] to include x.
template <typename T1, typename T2>
inline void UpdateRange(const T1& x, T2* lower_bound, T2* upper_bound) {
  if (x < *lower_bound) {
    *lower_bound = x;
  }
  if (x > *upper_bound) {
    *upper_bound = x;
  }
}
 
// Decrease lower_bound to be <= x_lo AND increase upper_bound to be >= x_hi.
template <typename T1, typename T2>
inline void UpdateRange(const T1& x_lo, const T1& x_hi, T2* lower_bound,
                        T2* upper_bound) {
  if (x_lo < *lower_bound) {
    *lower_bound = x_lo;
  }
  if (x_hi > *upper_bound) {
    *upper_bound = x_hi;
  }
}
 
// Intersect the range [*lower2, *upper2] with the range [lower1, upper1],
// putting the result back in [*lower2, *upper2].
// If non-intersecting ranges are given, we end up with *lower2 > *upper2.
template <typename T>
inline void IntersectRange(const T& lower1, const T& upper1, T* lower2,
                           T* upper2) {
  if (lower1 > *lower2) {
    *lower2 = lower1;
  }
  if (upper1 < *upper2) {
    *upper2 = upper1;
  }
}
 
// Proper modulo arithmetic operator. Returns a mod b that works for -ve a.
// For any integer a and positive b, returns r : 0<=r<b and a=n*b + r for
// some integer n.
inline int Modulo(int a, int b) {
  return (a % b + b) % b;
}
 
// Integer division operator with rounding that works for negative input.
// Returns a divided by b, rounded to the nearest integer, without double
// counting at 0. With simple rounding 1/3 = 0, 0/3 = 0 -1/3 = 0, -2/3 = 0,
// -3/3 = 0 and -4/3 = -1.
// I want 1/3 = 0, 0/3 = 0, -1/3 = 0, -2/3 = -1, -3/3 = -1 and -4/3 = -1.
inline int DivRounded(int a, int b) {
  if (b < 0) {
    return -DivRounded(a, -b);
  }
  return a >= 0 ? (a + b / 2) / b : (a - b / 2) / b;
}
 
// Return a double cast to int with rounding.
inline int IntCastRounded(double x) {
  return x >= 0.0 ? static_cast<int>(x + 0.5) : -static_cast<int>(-x + 0.5);
}
 
// Return a float cast to int with rounding.
inline int IntCastRounded(float x) {
  return x >= 0.0F ? static_cast<int>(x + 0.5F) : -static_cast<int>(-x + 0.5F);
}
 
// Reverse the order of bytes in a n byte quantity for big/little-endian switch.
inline void ReverseN(void* ptr, int num_bytes) {
  assert(num_bytes == 1 || num_bytes == 2 || num_bytes == 4 || num_bytes == 8);
  char* cptr = static_cast<char*>(ptr);
  int halfsize = num_bytes / 2;
  for (int i = 0; i < halfsize; ++i) {
    char tmp = cptr[i];
    cptr[i] = cptr[num_bytes - 1 - i];
    cptr[num_bytes - 1 - i] = tmp;
  }
}
 
// Reverse the order of bytes in a 16 bit quantity for big/little-endian switch.
inline void Reverse16(void* ptr) {
  ReverseN(ptr, 2);
}
 
// Reverse the order of bytes in a 32 bit quantity for big/little-endian switch.
inline void Reverse32(void* ptr) {
  ReverseN(ptr, 4);
}
 
// Reverse the order of bytes in a 64 bit quantity for big/little-endian switch.
inline void Reverse64(void* ptr) {
  ReverseN(ptr, 8);
}
 
#endif  // TESSERACT_CCUTIL_HELPERS_H_