diff options
| -rw-r--r-- | include/libcamera/internal/utils.h | 86 | ||||
| -rw-r--r-- | src/libcamera/utils.cpp | 34 | ||||
| -rw-r--r-- | test/utils.cpp | 59 |
3 files changed, 179 insertions, 0 deletions
diff --git a/include/libcamera/internal/utils.h b/include/libcamera/internal/utils.h index d0146b71..83dada7c 100644 --- a/include/libcamera/internal/utils.h +++ b/include/libcamera/internal/utils.h @@ -9,12 +9,14 @@ #include <algorithm> #include <chrono> +#include <iterator> #include <memory> #include <ostream> #include <sstream> #include <string> #include <string.h> #include <sys/time.h> +#include <utility> #include <vector> #ifndef __DOXYGEN__ @@ -230,6 +232,90 @@ details::reverse_adapter<T> reverse(T &&iterable) return { iterable }; } +namespace details { + +template<typename Base> +class enumerate_iterator +{ +private: + using base_reference = typename std::iterator_traits<Base>::reference; + +public: + using difference_type = typename std::iterator_traits<Base>::difference_type; + using value_type = std::pair<const difference_type, base_reference>; + using pointer = value_type *; + using reference = value_type &; + using iterator_category = std::input_iterator_tag; + + explicit enumerate_iterator(Base iter) + : current_(iter), pos_(0) + { + } + + enumerate_iterator &operator++() + { + ++current_; + ++pos_; + return *this; + } + + bool operator!=(const enumerate_iterator &other) const + { + return current_ != other.current_; + } + + value_type operator*() const + { + return { pos_, *current_ }; + } + +private: + Base current_; + difference_type pos_; +}; + +template<typename Base> +class enumerate_adapter +{ +public: + using iterator = enumerate_iterator<Base>; + + enumerate_adapter(Base begin, Base end) + : begin_(begin), end_(end) + { + } + + iterator begin() const + { + return iterator{ begin_ }; + } + + iterator end() const + { + return iterator{ end_ }; + } + +private: + const Base begin_; + const Base end_; +}; + +} /* namespace details */ + +template<typename T> +auto enumerate(T &iterable) -> details::enumerate_adapter<decltype(iterable.begin())> +{ + return { std::begin(iterable), std::end(iterable) }; +} + +#ifndef __DOXYGEN__ +template<typename T, size_t N> +auto enumerate(T (&iterable)[N]) -> details::enumerate_adapter<T *> +{ + return { std::begin(iterable), std::end(iterable) }; +} +#endif + } /* namespace utils */ } /* namespace libcamera */ diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp index c4098a74..826144d3 100644 --- a/src/libcamera/utils.cpp +++ b/src/libcamera/utils.cpp @@ -472,6 +472,40 @@ std::string libcameraSourcePath() * loop, will cause the loop to iterate over the \a iterable in reverse order */ +/** + * \fn enumerate(T &iterable) + * \brief Wrap an iterable to enumerate index and value in a range-based loop + * \param[in] iterable The iterable + * + * Range-based for loops are handy and widely preferred in C++, but are limited + * in their ability to replace for loops that require access to a loop counter. + * The enumerate() function solves this problem by wrapping the \a iterable in + * an adapter that, when used as a range-expression, will provide iterators + * whose value_type is a pair of index and value reference. + * + * The iterable must support std::begin() and std::end(). This includes all + * containers provided by the standard C++ library, as well as C-style arrays. + * + * A typical usage pattern would use structured binding to store the index and + * value in two separate variables: + * + * \code{.cpp} + * std::vector<int> values = ...; + * + * for (auto [index, value] : utils::enumerate(values)) { + * ... + * } + * \endcode + * + * Note that the argument to enumerate() has to be an lvalue, as the lifetime + * of any rvalue would not be extended to the whole for loop. The compiler will + * complain if an rvalue is passed to the function, in which case it should be + * stored in a local variable before the loop. + * + * \return A value of unspecified type that, when used in a range-based for + * loop, iterates over an indexed view of the \a iterable + */ + } /* namespace utils */ } /* namespace libcamera */ diff --git a/test/utils.cpp b/test/utils.cpp index 08f29389..7e24c71e 100644 --- a/test/utils.cpp +++ b/test/utils.cpp @@ -12,6 +12,7 @@ #include <vector> #include <libcamera/geometry.h> +#include <libcamera/span.h> #include "libcamera/internal/utils.h" @@ -73,6 +74,60 @@ protected: return TestPass; } + int testEnumerate() + { + std::vector<int> integers{ 1, 2, 3, 4, 5 }; + int i = 0; + + for (auto [index, value] : utils::enumerate(integers)) { + if (index != i || value != i + 1) { + cerr << "utils::enumerate(<vector>) test failed: i=" << i + << ", index=" << index << ", value=" << value + << std::endl; + return TestFail; + } + + /* Verify that we can modify the value. */ + --value; + ++i; + } + + if (integers != std::vector<int>{ 0, 1, 2, 3, 4 }) { + cerr << "Failed to modify container in enumerated range loop" << endl; + return TestFail; + } + + Span<const int> span{ integers }; + i = 0; + + for (auto [index, value] : utils::enumerate(span)) { + if (index != i || value != i) { + cerr << "utils::enumerate(<span>) test failed: i=" << i + << ", index=" << index << ", value=" << value + << std::endl; + return TestFail; + } + + ++i; + } + + const int array[] = { 0, 2, 4, 6, 8 }; + i = 0; + + for (auto [index, value] : utils::enumerate(array)) { + if (index != i || value != i * 2) { + cerr << "utils::enumerate(<array>) test failed: i=" << i + << ", index=" << index << ", value=" << value + << std::endl; + return TestFail; + } + + ++i; + } + + return TestPass; + } + int run() { /* utils::hex() test. */ @@ -177,6 +232,10 @@ protected: return TestFail; } + /* utils::enumerate() test. */ + if (testEnumerate() != TestPass) + return TestFail; + return TestPass; } }; |