tesseract  4.1.1
helpers.h
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1 /* -*-C-*-
2  ********************************************************************************
3  *
4  * File: helpers.h
5  * Description: General utility functions
6  * Author: Daria Antonova
7  *
8  * (c) Copyright 2009, Google Inc.
9  ** Licensed under the Apache License, Version 2.0 (the "License");
10  ** you may not use this file except in compliance with the License.
11  ** You may obtain a copy of the License at
12  ** http://www.apache.org/licenses/LICENSE-2.0
13  ** Unless required by applicable law or agreed to in writing, software
14  ** distributed under the License is distributed on an "AS IS" BASIS,
15  ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16  ** See the License for the specific language governing permissions and
17  ** limitations under the License.
18  *
19  ********************************************************************************/
20 
21 #ifndef TESSERACT_CCUTIL_HELPERS_H_
22 #define TESSERACT_CCUTIL_HELPERS_H_
23 
24 #include <cassert>
25 #include <cstdio>
26 #include <cstring>
27 #include <functional>
28 #include <string>
29 
30 // TODO(rays) Put the rest of the helpers in the namespace.
31 namespace tesseract {
32 
33 // A simple linear congruential random number generator, using Knuth's
34 // constants from:
35 // http://en.wikipedia.org/wiki/Linear_congruential_generator.
36 class TRand {
37  public:
38  TRand() = default;
39  // Sets the seed to the given value.
40  void set_seed(uint64_t seed) {
41  seed_ = seed;
42  }
43  // Sets the seed using a hash of a string.
44  void set_seed(const std::string& str) {
45  std::hash<std::string> hasher;
46  set_seed(static_cast<uint64_t>(hasher(str)));
47  }
48 
49  // Returns an integer in the range 0 to INT32_MAX.
50  int32_t IntRand() {
51  Iterate();
52  return seed_ >> 33;
53  }
54  // Returns a floating point value in the range [-range, range].
55  double SignedRand(double range) {
56  return range * 2.0 * IntRand() / INT32_MAX - range;
57  }
58  // Returns a floating point value in the range [0, range].
59  double UnsignedRand(double range) {
60  return range * IntRand() / INT32_MAX;
61  }
62 
63  private:
64  // Steps the generator to the next value.
65  void Iterate() {
66  seed_ *= 6364136223846793005ULL;
67  seed_ += 1442695040888963407ULL;
68  }
69 
70  // The current value of the seed.
71  uint64_t seed_{1};
72 };
73 
74 } // namespace tesseract
75 
76 // Remove newline (if any) at the end of the string.
77 inline void chomp_string(char* str) {
78  int last_index = static_cast<int>(strlen(str)) - 1;
79  while (last_index >= 0 &&
80  (str[last_index] == '\n' || str[last_index] == '\r')) {
81  str[last_index--] = '\0';
82  }
83 }
84 
85 // Advance the current pointer of the file if it points to a newline character.
86 inline void SkipNewline(FILE* file) {
87  if (fgetc(file) != '\n') {
88  fseek(file, -1, SEEK_CUR);
89  }
90 }
91 
92 // Swaps the two args pointed to by the pointers.
93 // Operator= and copy constructor must work on T.
94 template <typename T>
95 inline void Swap(T* p1, T* p2) {
96  T tmp(*p2);
97  *p2 = *p1;
98  *p1 = tmp;
99 }
100 
101 // return the smallest multiple of block_size greater than or equal to n.
102 inline int RoundUp(int n, int block_size) {
103  return block_size * ((n + block_size - 1) / block_size);
104 }
105 
106 // Clip a numeric value to the interval [lower_bound, upper_bound].
107 template <typename T>
108 inline T ClipToRange(const T& x, const T& lower_bound, const T& upper_bound) {
109  if (x < lower_bound) {
110  return lower_bound;
111  }
112  if (x > upper_bound) {
113  return upper_bound;
114  }
115  return x;
116 }
117 
118 // Extend the range [lower_bound, upper_bound] to include x.
119 template <typename T1, typename T2>
120 inline void UpdateRange(const T1& x, T2* lower_bound, T2* upper_bound) {
121  if (x < *lower_bound) {
122  *lower_bound = x;
123  }
124  if (x > *upper_bound) {
125  *upper_bound = x;
126  }
127 }
128 
129 // Decrease lower_bound to be <= x_lo AND increase upper_bound to be >= x_hi.
130 template <typename T1, typename T2>
131 inline void UpdateRange(const T1& x_lo, const T1& x_hi, T2* lower_bound,
132  T2* upper_bound) {
133  if (x_lo < *lower_bound) {
134  *lower_bound = x_lo;
135  }
136  if (x_hi > *upper_bound) {
137  *upper_bound = x_hi;
138  }
139 }
140 
141 // Intersect the range [*lower2, *upper2] with the range [lower1, upper1],
142 // putting the result back in [*lower2, *upper2].
143 // If non-intersecting ranges are given, we end up with *lower2 > *upper2.
144 template <typename T>
145 inline void IntersectRange(const T& lower1, const T& upper1, T* lower2,
146  T* upper2) {
147  if (lower1 > *lower2) {
148  *lower2 = lower1;
149  }
150  if (upper1 < *upper2) {
151  *upper2 = upper1;
152  }
153 }
154 
155 // Proper modulo arithmetic operator. Returns a mod b that works for -ve a.
156 // For any integer a and positive b, returns r : 0<=r<b and a=n*b + r for
157 // some integer n.
158 inline int Modulo(int a, int b) {
159  return (a % b + b) % b;
160 }
161 
162 // Integer division operator with rounding that works for negative input.
163 // Returns a divided by b, rounded to the nearest integer, without double
164 // counting at 0. With simple rounding 1/3 = 0, 0/3 = 0 -1/3 = 0, -2/3 = 0,
165 // -3/3 = 0 and -4/3 = -1.
166 // I want 1/3 = 0, 0/3 = 0, -1/3 = 0, -2/3 = -1, -3/3 = -1 and -4/3 = -1.
167 inline int DivRounded(int a, int b) {
168  if (b < 0) {
169  return -DivRounded(a, -b);
170  }
171  return a >= 0 ? (a + b / 2) / b : (a - b / 2) / b;
172 }
173 
174 // Return a double cast to int with rounding.
175 inline int IntCastRounded(double x) {
176  return x >= 0.0 ? static_cast<int>(x + 0.5) : -static_cast<int>(-x + 0.5);
177 }
178 
179 // Return a float cast to int with rounding.
180 inline int IntCastRounded(float x) {
181  return x >= 0.0F ? static_cast<int>(x + 0.5F) : -static_cast<int>(-x + 0.5F);
182 }
183 
184 // Reverse the order of bytes in a n byte quantity for big/little-endian switch.
185 inline void ReverseN(void* ptr, int num_bytes) {
186  assert(num_bytes == 1 || num_bytes == 2 || num_bytes == 4 || num_bytes == 8);
187  char* cptr = static_cast<char*>(ptr);
188  int halfsize = num_bytes / 2;
189  for (int i = 0; i < halfsize; ++i) {
190  char tmp = cptr[i];
191  cptr[i] = cptr[num_bytes - 1 - i];
192  cptr[num_bytes - 1 - i] = tmp;
193  }
194 }
195 
196 // Reverse the order of bytes in a 16 bit quantity for big/little-endian switch.
197 inline void Reverse16(void* ptr) {
198  ReverseN(ptr, 2);
199 }
200 
201 // Reverse the order of bytes in a 32 bit quantity for big/little-endian switch.
202 inline void Reverse32(void* ptr) {
203  ReverseN(ptr, 4);
204 }
205 
206 // Reverse the order of bytes in a 64 bit quantity for big/little-endian switch.
207 inline void Reverse64(void* ptr) {
208  ReverseN(ptr, 8);
209 }
210 
211 #endif // TESSERACT_CCUTIL_HELPERS_H_
IntCastRounded
int IntCastRounded(double x)
Definition: helpers.h:175
chomp_string
void chomp_string(char *str)
Definition: helpers.h:77
RoundUp
int RoundUp(int n, int block_size)
Definition: helpers.h:102
Reverse32
void Reverse32(void *ptr)
Definition: helpers.h:202
tesseract
Definition: altorenderer.cpp:25
ClipToRange
T ClipToRange(const T &x, const T &lower_bound, const T &upper_bound)
Definition: helpers.h:108
IntersectRange
void IntersectRange(const T &lower1, const T &upper1, T *lower2, T *upper2)
Definition: helpers.h:145
tesseract::TRand::set_seed
void set_seed(const std::string &str)
Definition: helpers.h:44
DivRounded
int DivRounded(int a, int b)
Definition: helpers.h:167
UpdateRange
void UpdateRange(const T1 &x, T2 *lower_bound, T2 *upper_bound)
Definition: helpers.h:120
tesseract::TRand::IntRand
int32_t IntRand()
Definition: helpers.h:50
SkipNewline
void SkipNewline(FILE *file)
Definition: helpers.h:86
Swap
void Swap(T *p1, T *p2)
Definition: helpers.h:95
Reverse64
void Reverse64(void *ptr)
Definition: helpers.h:207
Reverse16
void Reverse16(void *ptr)
Definition: helpers.h:197
tesseract::TRand::SignedRand
double SignedRand(double range)
Definition: helpers.h:55
tesseract::TRand::UnsignedRand
double UnsignedRand(double range)
Definition: helpers.h:59
Modulo
int Modulo(int a, int b)
Definition: helpers.h:158
tesseract::TRand::set_seed
void set_seed(uint64_t seed)
Definition: helpers.h:40
tesseract::TRand::TRand
TRand()=default
ReverseN
void ReverseN(void *ptr, int num_bytes)
Definition: helpers.h:185
tesseract::TRand
Definition: helpers.h:36