1 files changed, 93 insertions, 0 deletions
diff --git a/src/libutil/source-path.cc b/src/libutil/source-path.cc
new file mode 100644
index 000000000..b6563ee90
--- /dev/null
+++ b/src/libutil/source-path.cc
@@ -0,0 +1,93 @@
+#include "source-path.hh"
+
+namespace nix {
+
+std::ostream & operator << (std::ostream & str, const SourcePath & path)
+{
+    str << path.to_string();
+    return str;
+}
+
+std::string_view SourcePath::baseName() const
+{
+    return path.baseName().value_or("source");
+}
+
+SourcePath SourcePath::parent() const
+{
+    auto p = path.parent();
+    assert(p);
+    return std::move(*p);
+}
+
+InputAccessor::Stat SourcePath::lstat() const
+{
+    auto st = nix::lstat(path.abs());
+    return InputAccessor::Stat {
+        .type =
+            S_ISREG(st.st_mode) ? InputAccessor::tRegular :
+            S_ISDIR(st.st_mode) ? InputAccessor::tDirectory :
+            S_ISLNK(st.st_mode) ? InputAccessor::tSymlink :
+            InputAccessor::tMisc,
+        .isExecutable = S_ISREG(st.st_mode) && st.st_mode & S_IXUSR
+    };
+}
+
+std::optional<InputAccessor::Stat> SourcePath::maybeLstat() const
+{
+    // FIXME: merge these into one operation.
+    if (!pathExists())
+        return {};
+    return lstat();
+}
+
+InputAccessor::DirEntries SourcePath::readDirectory() const
+{
+    InputAccessor::DirEntries res;
+    for (auto & entry : nix::readDirectory(path.abs())) {
+        std::optional<InputAccessor::Type> type;
+        switch (entry.type) {
+        case DT_REG: type = InputAccessor::Type::tRegular; break;
+        case DT_LNK: type = InputAccessor::Type::tSymlink; break;
+        case DT_DIR: type = InputAccessor::Type::tDirectory; break;
+        }
+        res.emplace(entry.name, type);
+    }
+    return res;
+}
+
+SourcePath SourcePath::resolveSymlinks() const
+{
+    SourcePath res(CanonPath::root);
+
+    int linksAllowed = 1024;
+
+    std::list<std::string> todo;
+    for (auto & c : path)
+        todo.push_back(std::string(c));
+
+    while (!todo.empty()) {
+        auto c = *todo.begin();
+        todo.pop_front();
+        if (c == "" || c == ".")
+            ;
+        else if (c == "..")
+            res.path.pop();
+        else {
+            res.path.push(c);
+            if (auto st = res.maybeLstat(); st && st->type == InputAccessor::tSymlink) {
+                if (!linksAllowed--)
+                    throw Error("infinite symlink recursion in path '%s'", path);
+                auto target = res.readLink();
+                res.path.pop();
+                if (hasPrefix(target, "/"))
+                    res.path = CanonPath::root;
+                todo.splice(todo.begin(), tokenizeString<std::list<std::string>>(target, "/"));
+            }
+        }
+    }
+
+    return res;
+}
+
+}