BinaryCacheStore::readFile(): Return a shared_ptr to a string

This allows readFile() to indicate that a file doesn't exist, and
might eliminate some large string copying.

1 files changed, 8 insertions, 3 deletions

diff --git a/src/libstore/local-binary-cache-store.cc b/src/libstore/local-binary-cache-store.cc
index efd6d47254f2..7968c98b9558 100644
--- a/src/libstore/local-binary-cache-store.cc
+++ b/src/libstore/local-binary-cache-store.cc
@@ -22,7 +22,7 @@ protected:
 
     void upsertFile(const std::string & path, const std::string & data) override;
 
-    std::string getFile(const std::string & path) override;
+    std::shared_ptr<std::string> getFile(const std::string & path) override;
 
 };
 
@@ -59,9 +59,14 @@ void LocalBinaryCacheStore::upsertFile(const std::string & path, const std::stri
     atomicWrite(binaryCacheDir + "/" + path, data);
 }
 
-std::string LocalBinaryCacheStore::getFile(const std::string & path)
+std::shared_ptr<std::string> LocalBinaryCacheStore::getFile(const std::string & path)
 {
-    return readFile(binaryCacheDir + "/" + path);
+    try {
+        return std::make_shared<std::string>(readFile(binaryCacheDir + "/" + path));
+    } catch (SysError & e) {
+        if (e.errNo == ENOENT) return 0;
+        throw;
+    }
 }
 
 ref<Store> openLocalBinaryCacheStore(std::shared_ptr<Store> localStore,