1 files changed, 19 insertions, 20 deletions

diff --git a/src/libutil/archive.cc b/src/libutil/archive.cc
index ce7cf9754..ed0eb2fb5 100644
--- a/src/libutil/archive.cc
+++ b/src/libutil/archive.cc
@@ -27,11 +27,13 @@ struct ArchiveSettings : Config
         #endif
         "use-case-hack",
         "Whether to enable a Darwin-specific hack for dealing with file name collisions."};
+    Setting<bool> preallocateContents{this, false, "preallocate-contents",
+        "Whether to preallocate files when writing objects with known size."};
 };
 
 static ArchiveSettings archiveSettings;
 
-static GlobalConfig::Register r1(&archiveSettings);
+static GlobalConfig::Register rArchiveSettings(&archiveSettings);
 
 const std::string narVersionMagic1 = "nix-archive-1";
 
@@ -48,14 +50,14 @@ static void dumpContents(const Path & path, size_t size,
     AutoCloseFD fd = open(path.c_str(), O_RDONLY | O_CLOEXEC);
     if (!fd) throw SysError("opening file '%1%'", path);
 
-    std::vector<unsigned char> buf(65536);
+    std::vector<char> buf(65536);
     size_t left = size;
 
     while (left > 0) {
         auto n = std::min(left, buf.size());
         readFull(fd.get(), buf.data(), n);
         left -= n;
-        sink(buf.data(), n);
+        sink({buf.data(), n});
     }
 
     writePadding(size, sink);
@@ -66,9 +68,7 @@ static void dump(const Path & path, Sink & sink, PathFilter & filter)
 {
     checkInterrupt();
 
-    struct stat st;
-    if (lstat(path.c_str(), &st))
-        throw SysError("getting attributes of path '%1%'", path);
+    auto st = lstat(path);
 
     sink << "(";
 
@@ -155,14 +155,14 @@ static void parseContents(ParseSink & sink, Source & source, const Path & path)
     sink.preallocateContents(size);
 
     uint64_t left = size;
-    std::vector<unsigned char> buf(65536);
+    std::vector<char> buf(65536);
 
     while (left) {
         checkInterrupt();
         auto n = buf.size();
         if ((uint64_t)n > left) n = left;
         source(buf.data(), n);
-        sink.receiveContents(buf.data(), n);
+        sink.receiveContents({buf.data(), n});
         left -= n;
     }
 
@@ -300,21 +300,21 @@ struct RestoreSink : ParseSink
     Path dstPath;
     AutoCloseFD fd;
 
-    void createDirectory(const Path & path)
+    void createDirectory(const Path & path) override
     {
         Path p = dstPath + path;
         if (mkdir(p.c_str(), 0777) == -1)
             throw SysError("creating directory '%1%'", p);
     };
 
-    void createRegularFile(const Path & path)
+    void createRegularFile(const Path & path) override
     {
         Path p = dstPath + path;
         fd = open(p.c_str(), O_CREAT | O_EXCL | O_WRONLY | O_CLOEXEC, 0666);
         if (!fd) throw SysError("creating file '%1%'", p);
     }
 
-    void isExecutable()
+    void isExecutable() override
     {
         struct stat st;
         if (fstat(fd.get(), &st) == -1)
@@ -323,8 +323,11 @@ struct RestoreSink : ParseSink
             throw SysError("fchmod");
     }
 
-    void preallocateContents(uint64_t len)
+    void preallocateContents(uint64_t len) override
     {
+        if (!archiveSettings.preallocateContents)
+            return;
+
 #if HAVE_POSIX_FALLOCATE
         if (len) {
             errno = posix_fallocate(fd.get(), 0, len);
@@ -338,12 +341,12 @@ struct RestoreSink : ParseSink
 #endif
     }
 
-    void receiveContents(unsigned char * data, size_t len)
+    void receiveContents(std::string_view data) override
     {
-        writeFull(fd.get(), data, len);
+        writeFull(fd.get(), data);
     }
 
-    void createSymlink(const Path & path, const string & target)
+    void createSymlink(const Path & path, const string & target) override
     {
         Path p = dstPath + path;
         nix::createSymlink(target, p);
@@ -366,11 +369,7 @@ void copyNAR(Source & source, Sink & sink)
 
     ParseSink parseSink; /* null sink; just parse the NAR */
 
-    LambdaSource wrapper([&](unsigned char * data, size_t len) {
-        auto n = source.read(data, len);
-        sink(data, n);
-        return n;
-    });
+    TeeSource wrapper { source, sink };
 
     parseDump(parseSink, wrapper);
 }