include/o3tl/safeint.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #ifndef INCLUDED_O3TL_SAFEINT_HXX
  11 #define INCLUDED_O3TL_SAFEINT_HXX
  12
  13 #include <limits>
  14 #if defined(_MSC_VER)
  15 #include <safeint.h>
  16 #else
  17 #ifndef __has_builtin
  18 #   define __has_builtin(x) 0
  19 #endif
  20 #endif
  21
  22 namespace o3tl
  23 {
  24
  25 #if defined(_MSC_VER)
  26
  27 template<typename T> inline bool checked_multiply(T a, T b, T& result)
  28 {
  29     return !msl::utilities::SafeMultiply(a, b, result);
  30 }
  31
  32 template<typename T> inline bool checked_add(T a, T b, T& result)
  33 {
  34     return !msl::utilities::SafeAdd(a, b, result);
  35 }
  36
  37 #elif (defined __GNUC__ && __GNUC__ >= 5) || (__has_builtin(__builtin_mul_overflow) && !(defined ANDROID && defined __clang__))
  38
  39 template<typename T> inline bool checked_multiply(T a, T b, T& result)
  40 {
  41     return __builtin_mul_overflow(a, b, &result);
  42 }
  43
  44 template<typename T> inline bool checked_add(T a, T b, T& result)
  45 {
  46     return __builtin_add_overflow(a, b, &result);
  47 }
  48
  49 #else
  50
  51 //https://www.securecoding.cert.org/confluence/display/c/INT32-C.+Ensure+that+operations+on+signed+integers+do+not+result+in+overflow
  52 template<typename T> inline typename std::enable_if<std::is_signed<T>::value, bool>::type checked_multiply(T a, T b, T& result)
  53 {
  54   if (a > 0) {  /* a is positive */
  55     if (b > 0) {  /* a and b are positive */
  56       if (a > (std::numeric_limits<T>::max() / b)) {
  57         return true; /* Handle error */
  58       }
  59     } else { /* a positive, b nonpositive */
  60       if (b < (std::numeric_limits<T>::min() / a)) {
  61         return true; /* Handle error */
  62       }
  63     } /* a positive, b nonpositive */
  64   } else { /* a is nonpositive */
  65     if (b > 0) { /* a is nonpositive, b is positive */
  66       if (a < (std::numeric_limits<T>::min() / b)) {
  67         return true; /* Handle error */
  68       }
  69     } else { /* a and b are nonpositive */
  70       if ( (a != 0) && (b < (std::numeric_limits<T>::max() / a))) {
  71         return true; /* Handle error */
  72       }
  73     } /* End if a and b are nonpositive */
  74   } /* End if a is nonpositive */
  75
  76   result = a * b;
  77
  78   return false;
  79 }
  80
  81 //https://www.securecoding.cert.org/confluence/display/c/INT30-C.+Ensure+that+unsigned+integer+operations+do+not+wrap
  82 template<typename T> inline typename std::enable_if<std::is_unsigned<T>::value, bool>::type checked_multiply(T a, T b, T& result)
  83 {
  84     if (b && a > std::numeric_limits<T>::max() / b) {
  85         return true;/* Handle error */
  86     }
  87
  88     result = a * b;
  89
  90     return false;
  91 }
  92
  93 //https://www.securecoding.cert.org/confluence/display/c/INT32-C.+Ensure+that+operations+on+signed+integers+do+not+result+in+overflow
  94 template<typename T> inline typename std::enable_if<std::is_signed<T>::value, bool>::type checked_add(T a, T b, T& result)
  95 {
  96     if (((b > 0) && (a > (std::numeric_limits<T>::max() - b))) ||
  97         ((b < 0) && (a < (std::numeric_limits<T>::min() - b)))) {
  98         return true;
  99     }
 100
 101     result = a + b;
 102
 103     return false;
 104 }
 105
 106 //https://www.securecoding.cert.org/confluence/display/c/INT30-C.+Ensure+that+unsigned+integer+operations+do+not+wrap
 107 template<typename T> inline typename std::enable_if<std::is_unsigned<T>::value, bool>::type checked_add(T a, T b, T& result)
 108 {
 109     if (std::numeric_limits<T>::max() - a < b) {
 110         return true;/* Handle error */
 111     }
 112
 113     result = a + b;
 114
 115     return false;
 116 }
 117
 118 #endif
 119
 120 }
 121
 122 #endif
 123
 124 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */