From 384f7c422acca2f3658393abfc16ea57cd74caa6 Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@mit.edu>
Date: Sun, 21 Feb 2016 19:22:26 -0500
Subject: Implement utimens

---
 src/operations.cc   | 23 +++++++++++++++++++++++
 src/posix_extras.cc | 13 +++++++++++++
 src/posix_extras.h  |  7 +++++++
 3 files changed, 43 insertions(+)

diff --git a/src/operations.cc b/src/operations.cc
index df12738..355ffc3 100644
--- a/src/operations.cc
+++ b/src/operations.cc
@@ -30,6 +30,7 @@
 #include <glog/logging.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <time.h>
 
 #include "fuse.h"
 #include "posix_extras.h"
@@ -130,6 +131,27 @@ int Open(const char* const path, fuse_file_info* const file_info) noexcept {
   return OpenResource<File>(path, file_info->flags, &file_info->fh);
 }
 
+int Utimens(const char* const path, const timespec times[2]) noexcept {
+  try {
+    root_->UTimeNs(
+        std::strcmp(path, "/") == 0
+            ?
+            // Update the times on the mount point.
+            "."
+            :
+            // Trim the leading slash so UTimeNs will treat it relative to
+            // root_.
+            path + 1,
+        times[0], times[1]);
+    return 0;
+  } catch (const std::system_error& e) {
+    return -e.code().value();
+  } catch (...) {
+    LOG(ERROR) << "utimens: caught unexpected value";
+    return -ENOTRECOVERABLE;
+  }
+}
+
 int Release(const char*, fuse_file_info* const file_info) noexcept {
   return ReleaseResource<File>(file_info->fh);
 }
@@ -211,6 +233,7 @@ fuse_operations FuseOperations(File* const root) {
 
   result.mknod = &Mknod;
   result.open = &Open;
+  result.utimens = &Utimens;
   result.release = &Release;
   result.unlink = &Unlink;
 
diff --git a/src/posix_extras.cc b/src/posix_extras.cc
index f8274fb..7529251 100644
--- a/src/posix_extras.cc
+++ b/src/posix_extras.cc
@@ -14,6 +14,7 @@
 
 #include "posix_extras.h"
 
+#include <array>
 #include <cerrno>
 #include <experimental/optional>
 #include <stdexcept>
@@ -110,6 +111,18 @@ void File::UnlinkAt(const char* const path) const {
   }
 }
 
+void File::UTimeNs(const char* const path, const timespec& access,
+                   const timespec& modification) const {
+  if (path[0] == '/') {
+    throw std::invalid_argument("absolute path");
+  }
+
+  std::array<const timespec, 2> times{{access, modification}};
+  if (utimensat(fd_, path, times.data(), AT_SYMLINK_NOFOLLOW) == -1) {
+    throw SystemError();
+  }
+}
+
 int File::Duplicate() const {
   int result;
   if ((result = dup(fd_)) == -1) {
diff --git a/src/posix_extras.h b/src/posix_extras.h
index 60b2284..a73f9fe 100644
--- a/src/posix_extras.h
+++ b/src/posix_extras.h
@@ -21,6 +21,7 @@
 #include <dirent.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <time.h>
 
 namespace scoville {
 
@@ -81,6 +82,12 @@ class File {
   // must indeed be relative (i.e., it must not start with '/').
   void UnlinkAt(const char* path) const;
 
+  // Sets the access and modification times of the file at the path relative to
+  // the file descriptor.  The path must indeed be relative (i.e., it must not
+  // start with '/').  Does not follow symbolic links.
+  void UTimeNs(const char* path, const timespec& access,
+               const timespec& modification) const;
+
  private:
   File() {}
 
-- 
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