checkpoint

src/clone_source.hpp

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+/*
+  ISC License
+
+  Copyright (c) 2026, Antonio SJ Musumeci <trapexit@spawn.link>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#pragma once
+
+#include "branches.hpp"
+#include "fs_exists.hpp"
+#include "fs_lstat.hpp"
+#include "fs_path.hpp"
+
+
+namespace CloneSource
+{
+  // Look up a clone source for path_ across branches_, honoring the
+  // configured func.getattr.policy when it has observable side-effects
+  // ("newest" picks branch with the newest mtime; "cdco"/"cdfo"/"ff"
+  // all degenerate to first-found which matches the cheap path).
+  // If policy_name_ is "newest", picks the branch holding the newest
+  // copy of path_; otherwise returns the first branch where path_ exists.
+  static
+  inline
+  const Branch*
+  find(const Branches::Impl &branches_,
+       const fs::path       &path_,
+       const std::string    &policy_name_)
+  {
+    if(policy_name_ == "newest")
+      {
+        const Branch *best = nullptr;
+        struct timespec newest = {0,0};
+        struct stat st;
+        for(const auto &b : branches_)
+          {
+            if(!fs::exists(b.path,path_,&st))
+              continue;
+            if(best
+               && ((st.st_mtim.tv_sec  <  newest.tv_sec)
+                   || ((st.st_mtim.tv_sec == newest.tv_sec)
+                       && (st.st_mtim.tv_nsec < newest.tv_nsec))))
+              continue;
+            newest = st.st_mtim;
+            best = &b;
+          }
+        return best;
+      }
+
+    for(const auto &b : branches_)
+      {
+        if(fs::exists(b.path,path_))
+          return &b;
+      }
+    return nullptr;
+  }
+}