Move some fs-related functions to their own file

Unclutter `util.cc` a bit

1 files changed, 44 insertions, 0 deletions

diff --git a/src/libutil/filesystem.cc b/src/libutil/filesystem.cc
new file mode 100644
index 000000000..e67383e6f
--- /dev/null
+++ b/src/libutil/filesystem.cc
@@ -0,0 +1,44 @@
+#include <sys/time.h>
+
+#include "util.hh"
+#include "types.hh"
+
+namespace nix {
+
+void createSymlink(const Path & target, const Path & link,
+    std::optional<time_t> mtime)
+{
+    if (symlink(target.c_str(), link.c_str()))
+        throw SysError("creating symlink from '%1%' to '%2%'", link, target);
+    if (mtime) {
+        struct timeval times[2];
+        times[0].tv_sec = *mtime;
+        times[0].tv_usec = 0;
+        times[1].tv_sec = *mtime;
+        times[1].tv_usec = 0;
+        if (lutimes(link.c_str(), times))
+            throw SysError("setting time of symlink '%s'", link);
+    }
+}
+
+void replaceSymlink(const Path & target, const Path & link,
+    std::optional<time_t> mtime)
+{
+    for (unsigned int n = 0; true; n++) {
+        Path tmp = canonPath(fmt("%s/.%d_%s", dirOf(link), n, baseNameOf(link)));
+
+        try {
+            createSymlink(target, tmp, mtime);
+        } catch (SysError & e) {
+            if (e.errNo == EEXIST) continue;
+            throw;
+        }
+
+        if (rename(tmp.c_str(), link.c_str()) != 0)
+            throw SysError("renaming '%1%' to '%2%'", tmp, link);
+
+        break;
+    }
+}
+
+}