[libcamera-devel] [PATCH] libcamera: utils: Add map_keys() function

[Laurent Pinchart]

Add a map_keys() function to the utils namespace to extract keys from a
map.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 include/libcamera/internal/utils.h | 10 ++++++++++
 src/libcamera/utils.cpp            |  7 +++++++
 test/utils.cpp                     | 21 +++++++++++++++++++++
 3 files changed, 38 insertions(+)

diff --git a/include/libcamera/internal/utils.h b/include/libcamera/internal/utils.h
index 0953423ee8d0..4fe4843922a9 100644
--- a/include/libcamera/internal/utils.h
+++ b/include/libcamera/internal/utils.h
@@ -11,6 +11,7 @@
 #include <chrono>
 #include <memory>
 #include <ostream>
+#include <set>
 #include <sstream>
 #include <string>
 #include <string.h>
@@ -36,6 +37,15 @@ const char *basename(const char *path);
 char *secure_getenv(const char *name);
 std::string dirname(const std::string &path);
 
+template<typename T>
+std::set<typename T::key_type> map_keys(const T &map)
+{
+	std::set<typename T::key_type> keys;
+	std::transform(map.begin(), map.end(), std::inserter(keys, keys.end()),
+		       [](const auto &value) { return value.first; });
+	return keys;
+}
+
 template<class InputIt1, class InputIt2>
 unsigned int set_overlap(InputIt1 first1, InputIt1 last1,
 			 InputIt2 first2, InputIt2 last2)
diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
index d55338fe681a..1eb8970a5bbc 100644
--- a/src/libcamera/utils.cpp
+++ b/src/libcamera/utils.cpp
@@ -127,6 +127,13 @@ std::string dirname(const std::string &path)
 	return path.substr(0, pos + 1);
 }
 
+/**
+ * \fn std::set<typename T::key_type> map_keys(const T &map)
+ * \brief Retrieve the keys of a std::map<>
+ * \param[in] map The map whose keys to retrieve
+ * \return A std::set<> containing the keys of \a map
+ */
+
 /**
  * \fn libcamera::utils::set_overlap(InputIt1 first1, InputIt1 last1,
  *				     InputIt2 first2, InputIt2 last2)
diff --git a/test/utils.cpp b/test/utils.cpp
index 66b91f1203e1..a9d072030f1c 100644
--- a/test/utils.cpp
+++ b/test/utils.cpp
@@ -6,6 +6,8 @@
  */
 
 #include <iostream>
+#include <map>
+#include <set>
 #include <sstream>
 #include <string>
 #include <vector>
@@ -144,6 +146,25 @@ protected:
 		if (TestPass != testDirname())
 			return TestFail;
 
+
+		/* utils::map_keys() test. */
+		const std::map<std::string, unsigned int> map{
+			{ "zero", 0 },
+			{ "one", 1 },
+			{ "two", 2 },
+		};
+		const std::set<std::string> expectedKeys{
+			"zero",
+			"one",
+			"two",
+		};
+
+		const std::set<std::string> keys = utils::map_keys(map);
+		if (keys != expectedKeys) {
+			cerr << "utils::map_keys() test failed" << endl;
+			return TestFail;
+		}
+
 		return TestPass;
 	}
 };
-- 
Regards,

Laurent Pinchart