diff options
| author | Laurent Pinchart <laurent.pinchart@ideasonboard.com> | 2021-12-06 16:21:19 +0200 |
|---|---|---|
| committer | Laurent Pinchart <laurent.pinchart@ideasonboard.com> | 2021-12-07 19:09:31 +0200 |
| commit | f413f944d789911c9ded831ac45a7674c129ceba (patch) | |
| tree | c09d9d0e96e9e504d3a35c7d02e5c31d33908b1b | |
| parent | 72679c682eb0b9f03948f258a26f78c037d33c48 (diff) | |
libcamera: base: utils: Add abs_diff() utility function
The abs_diff() function computes the absolute difference of two
elements. This may seem trivial at first, but can lead to unexpected
results when operating on unsigned operands. A common implementation
of the absolute difference of two unsigned int (used through the
libcamera code base) is
std::abs(static_cast<int>(a - b))
but doesn't return the expected result when either a or b is larger than
UINT_MAX / 2 due to overflows. The abs_diff() function offers a safe
alternative.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
| -rw-r--r-- | include/libcamera/base/utils.h | 9 | ||||
| -rw-r--r-- | src/libcamera/base/utils.cpp | 17 |
2 files changed, 26 insertions, 0 deletions
diff --git a/include/libcamera/base/utils.h b/include/libcamera/base/utils.h index 3a803176..9ab18101 100644 --- a/include/libcamera/base/utils.h +++ b/include/libcamera/base/utils.h @@ -346,6 +346,15 @@ public: } }; +template<typename T> +decltype(auto) abs_diff(const T &a, const T &b) +{ + if (a < b) + return b - a; + else + return a - b; +} + } /* namespace utils */ #ifndef __DOXYGEN__ diff --git a/src/libcamera/base/utils.cpp b/src/libcamera/base/utils.cpp index 45b92b67..8cf8a5b2 100644 --- a/src/libcamera/base/utils.cpp +++ b/src/libcamera/base/utils.cpp @@ -437,6 +437,23 @@ std::string toAscii(const std::string &str) * \return True if \a Duration is a non-zero time value, False otherwise */ +/** + * \fn abs_diff(const T& a, const T& b) + * \brief Calculates the absolute value of the difference between two elements + * \param[in] a The first element + * \param[in] b The second element + * + * This function calculates the absolute value of the difference between two + * elements of the same type, in such a way that a negative value will never + * occur during the calculation. + * + * This is inspired by the std::abs_diff() candidate proposed in N4318 + * (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4318.pdf). + * + * \return The absolute value of the difference of the two parameters \a a and + * \a b + */ + } /* namespace utils */ #ifndef __DOXYGEN__ |