@@ -16,7 +16,6 @@
#include <string>
#include <string.h>
#include <sys/time.h>
-#include <utility>
#include <vector>
#ifndef __DOXYGEN__
@@ -237,12 +236,19 @@ 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>;
+
+private:
+ using base_reference = typename std::iterator_traits<Base>::reference;
+
+ struct result {
+ const difference_type index;
+ base_reference value;
+ };
+
+public:
+ using value_type = result;
using pointer = value_type *;
using reference = value_type &;
using iterator_category = std::input_iterator_tag;
@@ -481,20 +481,21 @@ std::string libcameraSourcePath()
* 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.
+ * whose value_type exposes both the element's value and its index.
*
* 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:
+ * The iterator's value_type is a structure that aggregates the index and value
+ * reference in two named members. The index is always const, and the value
+ * reference is conditionally const depending on the iterable. A typical usage
+ * pattern would be:
*
* \code{.cpp}
* std::vector<int> values = ...;
*
- * for (auto [index, value] : utils::enumerate(values)) {
- * ...
- * }
+ * for (const auto v : utils::enumerate(values))
+ * std::cout << "- index " << v.index << ", value " << v.value << std::endl;
* \endcode
*
* \return A value of unspecified type that, when used in a range-based for
@@ -79,16 +79,16 @@ protected:
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) {
+ for (const auto v : utils::enumerate(integers)) {
+ if (v.index != i || v.value != i + 1) {
cerr << "utils::enumerate(<vector>) test failed: i=" << i
- << ", index=" << index << ", value=" << value
- << std::endl;
+ << ", index=" << v.index << ", value=" << v.value
+ << endl;
return TestFail;
}
/* Verify that we can modify the value. */
- --value;
+ --v.value;
++i;
}
@@ -100,10 +100,10 @@ protected:
Span<const int> span{ integers };
i = 0;
- for (auto [index, value] : utils::enumerate(span)) {
- if (index != i || value != i) {
+ for (const auto v : utils::enumerate(span)) {
+ if (v.index != i || v.value != i) {
cerr << "utils::enumerate(<span>) test failed: i=" << i
- << ", index=" << index << ", value=" << value
+ << ", index=" << v.index << ", value=" << v.value
<< std::endl;
return TestFail;
}
@@ -114,11 +114,11 @@ protected:
const int array[] = { 0, 2, 4, 6, 8 };
i = 0;
- for (auto [index, value] : utils::enumerate(array)) {
- if (index != i || value != i * 2) {
+ for (const auto v : utils::enumerate(array)) {
+ if (v.index != i || v.value != i * 2) {
cerr << "utils::enumerate(<array>) test failed: i=" << i
- << ", index=" << index << ", value=" << value
- << std::endl;
+ << ", index=" << v.index << ", value=" << v.value
+ << endl;
return TestFail;
}
Returning a pair of { index, value } from container enumeration is error-prone, as the index and value can easily be swapped. Use a structure with named index and value fields instead. This will be squashed with "libcamera: utils: Add enumerate view for range-based for loops" if accepted. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> --- include/libcamera/internal/utils.h | 16 +++++++++++----- src/libcamera/utils.cpp | 13 +++++++------ test/utils.cpp | 24 ++++++++++++------------ 3 files changed, 30 insertions(+), 23 deletions(-)