1 files changed, 130 insertions, 0 deletions
diff --git a/Source/cmFileTime.h b/Source/cmFileTime.h
new file mode 100644
index 000000000..d4de4e033
--- /dev/null
+++ b/Source/cmFileTime.h
@@ -0,0 +1,130 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#ifndef cmFileTime_h
+#define cmFileTime_h
+
+#include "cmConfigure.h" // IWYU pragma: keep
+
+#include <string>
+
+/** \class cmFileTime
+ * \brief Abstract file modification time with support for comparison with
+ *        other file modification times.
+ */
+class cmFileTime
+{
+public:
+  typedef long long NSC;
+  static constexpr NSC NsPerS = 1000000000;
+
+  cmFileTime() = default;
+  ~cmFileTime() = default;
+
+  /**
+   * @brief Loads the file time of fileName from the file system
+   * @return true on success
+   */
+  bool Load(std::string const& fileName);
+
+  /**
+   * @brief Return true if this is older than ftm
+   */
+  bool Older(cmFileTime const& ftm) const { return (this->NS - ftm.NS) < 0; }
+
+  /**
+   * @brief Return true if this is newer than ftm
+   */
+  bool Newer(cmFileTime const& ftm) const { return (ftm.NS - this->NS) < 0; }
+
+  /**
+   * @brief Return true if this is the same as ftm
+   */
+  bool Equal(cmFileTime const& ftm) const { return this->NS == ftm.NS; }
+
+  /**
+   * @brief Return true if this is not the same as ftm
+   */
+  bool Differ(cmFileTime const& ftm) const { return this->NS != ftm.NS; }
+
+  /**
+   * @brief Compare file modification times.
+   * @return -1, 0, +1 for this older, same, or newer than ftm.
+   */
+  int Compare(cmFileTime const& ftm) const
+  {
+    NSC const diff = this->NS - ftm.NS;
+    if (diff == 0) {
+      return 0;
+    }
+    return (diff < 0) ? -1 : 1;
+  }
+
+  // -- Comparison in second resolution
+
+  /**
+   * @brief Return true if this is at least a second older than ftm
+   */
+  bool OlderS(cmFileTime const& ftm) const
+  {
+    return (ftm.NS - this->NS) >= cmFileTime::NsPerS;
+  }
+
+  /**
+   * @brief Return true if this is at least a second newer than ftm
+   */
+  bool NewerS(cmFileTime const& ftm) const
+  {
+    return (this->NS - ftm.NS) >= cmFileTime::NsPerS;
+  }
+
+  /**
+   * @brief Return true if this is within the same second as ftm
+   */
+  bool EqualS(cmFileTime const& ftm) const
+  {
+    NSC diff = this->NS - ftm.NS;
+    if (diff < 0) {
+      diff = -diff;
+    }
+    return (diff < cmFileTime::NsPerS);
+  }
+
+  /**
+   * @brief Return true if this is older or newer than ftm by at least a second
+   */
+  bool DifferS(cmFileTime const& ftm) const
+  {
+    NSC diff = this->NS - ftm.NS;
+    if (diff < 0) {
+      diff = -diff;
+    }
+    return (diff >= cmFileTime::NsPerS);
+  }
+
+  /**
+   * @brief Compare file modification times.
+   * @return -1: this at least a second older, 0: this within the same second
+   *         as ftm, +1: this at least a second newer than ftm.
+   */
+  int CompareS(cmFileTime const& ftm) const
+  {
+    NSC const diff = this->NS - ftm.NS;
+    if (diff <= -cmFileTime::NsPerS) {
+      return -1;
+    }
+    if (diff >= cmFileTime::NsPerS) {
+      return 1;
+    }
+    return 0;
+  }
+
+  /**
+   * @brief The file modification time in nanoseconds
+   */
+  NSC GetNS() const { return this->NS; }
+
+private:
+  NSC NS = 0;
+};
+
+#endif