1 files changed, 57 insertions, 0 deletions
diff --git a/Source/cmFileTimeCache.h b/Source/cmFileTimeCache.h
new file mode 100644
index 000000000..83b77b651
--- /dev/null
+++ b/Source/cmFileTimeCache.h
@@ -0,0 +1,57 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#ifndef cmFileTimeCache_h
+#define cmFileTimeCache_h
+
+#include "cmConfigure.h" // IWYU pragma: keep
+
+#include <string>
+#include <unordered_map>
+
+#include "cmFileTime.h" // IWYU pragma: keep
+
+/** \class cmFileTimeCache
+ * \brief Caches file modification times in an internal map for fast lookups.
+ */
+class cmFileTimeCache
+{
+public:
+  cmFileTimeCache();
+  ~cmFileTimeCache();
+
+  cmFileTimeCache(const cmFileTimeCache&) = delete;
+  cmFileTimeCache& operator=(const cmFileTimeCache&) = delete;
+
+  /**
+   * @brief Loads the file time from the cache or the file system.
+   * @return true on success
+   */
+  bool Load(std::string const& fileName, cmFileTime& fileTime);
+
+  /**
+   * @brief Removes a file time from the cache
+   * @return true if the file was found in the cache and removed
+   */
+  bool Remove(std::string const& fileName);
+
+  /**
+   * @brief Compare file modification times.
+   * @return true for successful comparison and false for error.
+   *
+   * When true is returned, result has -1, 0, +1 for
+   * f1 older, same, or newer than f2.
+   */
+  bool Compare(std::string const& f1, std::string const& f2, int* result);
+
+  /**
+   * @brief Compare file modification times.
+   * @return true unless both files exist and have modification times less
+   *         than 1 second apart.
+   */
+  bool DifferS(std::string const& f1, std::string const& f2);
+
+private:
+  std::unordered_map<std::string, cmFileTime> Cache;
+};
+
+#endif