/usr/include/hphp/util/overflow.h is in hhvm-dev 3.11.1+dfsg-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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+----------------------------------------------------------------------+
| HipHop for PHP |
+----------------------------------------------------------------------+
| Copyright (c) 2010-2015 Facebook, Inc. (http://www.facebook.com) |
+----------------------------------------------------------------------+
| This source file is subject to version 3.01 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| http://www.php.net/license/3_01.txt |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
*/
#ifndef incl_HPHP_UTIL_OVERFLOW_H
#define incl_HPHP_UTIL_OVERFLOW_H
namespace HPHP {
template<typename T>
typename std::enable_if<std::is_integral<T>::value, bool>::type
add_overflow(T a, T b) {
// Cast to unsigned so that ua + ub isn't undefined.
auto const ua = static_cast<typename std::make_unsigned<T>::type>(a);
auto const ub = static_cast<typename std::make_unsigned<T>::type>(b);
// Overflow if the inputs have the same sign, and the result of addition has
// the opposite sign.
return (~(ua ^ ub) & (ua ^ (ua + ub))) >> std::numeric_limits<T>::digits;
}
template<typename T>
typename std::enable_if<std::is_integral<T>::value, bool>::type
sub_overflow(T a, T b) {
if (b == std::numeric_limits<T>::min()) {
// a - (INT_MIN) --> a - (-huge) --> a + huge
return a >= 0;
}
return add_overflow(a, -b);
}
template<typename T>
typename std::enable_if<std::is_integral<T>::value, bool>::type
mul_overflow(T a, T b) {
auto max = std::numeric_limits<T>::max();
auto min = std::numeric_limits<T>::min();
// Handle bad div cases first.
if (a == 0 || b == 0) {
return false;
}
if ((a == min && b == -1) || (b == min && a == -1)) {
return true;
}
if (a > 0) {
if (b > 0) {
return a > max / b;
} else {
return b < min / a;
}
} else {
if (b < 0) {
return a < max / b;
} else {
return a < min / b;
}
}
}
}
#endif
|