1 files changed, 30 insertions, 12 deletions

diff --git a/lib/Support/TarWriter.cpp b/lib/Support/TarWriter.cpp
index 5fc17d2763776..f79b364dc1f7b 100644
--- a/lib/Support/TarWriter.cpp
+++ b/lib/Support/TarWriter.cpp
@@ -26,6 +26,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/Support/Path.h"
 
 using namespace llvm;
 
@@ -109,27 +110,44 @@ static void writePaxHeader(raw_fd_ostream &OS, StringRef Path) {
   pad(OS);
 }
 
+// In the Ustar header, a path can be split at any '/' to store
+// a path into UstarHeader::Name and UstarHeader::Prefix. This
+// function splits a given path for that purpose.
+static std::pair<StringRef, StringRef> splitPath(StringRef Path) {
+  if (Path.size() <= sizeof(UstarHeader::Name))
+    return {"", Path};
+  size_t Sep = Path.rfind('/', sizeof(UstarHeader::Name) + 1);
+  if (Sep == StringRef::npos)
+    return {"", Path};
+  return {Path.substr(0, Sep), Path.substr(Sep + 1)};
+}
+
+// Returns true if a given path can be stored to a Ustar header
+// without the PAX extension.
+static bool fitsInUstar(StringRef Path) {
+  StringRef Prefix;
+  StringRef Name;
+  std::tie(Prefix, Name) = splitPath(Path);
+  return Name.size() <= sizeof(UstarHeader::Name);
+}
+
 // The PAX header is an extended format, so a PAX header needs
 // to be followed by a "real" header.
 static void writeUstarHeader(raw_fd_ostream &OS, StringRef Path, size_t Size) {
+  StringRef Prefix;
+  StringRef Name;
+  std::tie(Prefix, Name) = splitPath(Path);
+
   UstarHeader Hdr = {};
-  memcpy(Hdr.Name, Path.data(), Path.size());
+  memcpy(Hdr.Name, Name.data(), Name.size());
   memcpy(Hdr.Mode, "0000664", 8);
   snprintf(Hdr.Size, sizeof(Hdr.Size), "%011zo", Size);
   memcpy(Hdr.Magic, "ustar", 6);
+  memcpy(Hdr.Prefix, Prefix.data(), Prefix.size());
   computeChecksum(Hdr);
   OS << StringRef(reinterpret_cast<char *>(&Hdr), sizeof(Hdr));
 }
 
-// We want to use '/' as a path separator even on Windows.
-// This function canonicalizes a given path.
-static std::string canonicalize(std::string S) {
-#ifdef LLVM_ON_WIN32
-  std::replace(S.begin(), S.end(), '\\', '/');
-#endif
-  return S;
-}
-
 // Creates a TarWriter instance and returns it.
 Expected<std::unique_ptr<TarWriter>> TarWriter::create(StringRef OutputPath,
                                                        StringRef BaseDir) {
@@ -145,8 +163,8 @@ TarWriter::TarWriter(int FD, StringRef BaseDir)
 // Append a given file to an archive.
 void TarWriter::append(StringRef Path, StringRef Data) {
   // Write Path and Data.
-  std::string S = BaseDir + "/" + canonicalize(Path) + "\0";
-  if (S.size() <= sizeof(UstarHeader::Name)) {
+  std::string S = BaseDir + "/" + sys::path::convert_to_slash(Path) + "\0";
+  if (fitsInUstar(S)) {
     writeUstarHeader(OS, S, Data.size());
   } else {
     writePaxHeader(OS, S);