TarWriter: Fix a bug in Ustar header.

If we split a filename into `Name` and `Prefix`, `Prefix` is at most
145 bytes. We had a bug that didn't split a path correctly. This bug
was pointed out by Rafael in the post commit review.

This patch adds a unit test for TarWriter to verify the fix.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291494 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/TarWriter.cpp

@@ -122,7 +122,7 @@ static void writePaxHeader(raw_fd_ostream &OS, StringRef Path) {
 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);
+  size_t Sep = Path.rfind('/', sizeof(UstarHeader::Prefix) + 1);
   if (Sep == StringRef::npos)
     return {"", Path};
   return {Path.substr(0, Sep), Path.substr(Sep + 1)};

unittests/Support/CMakeLists.txt

@@ -43,10 +43,11 @@ add_llvm_unittest(SupportTests
   SpecialCaseListTest.cpp
   StringPool.cpp
   SwapByteOrderTest.cpp
+  TarWriterTest.cpp
   TargetParserTest.cpp
-  Threading.cpp
   ThreadLocalTest.cpp
   ThreadPool.cpp
+  Threading.cpp
   TimerTest.cpp
   TypeNameTest.cpp
   TrailingObjectsTest.cpp

unittests/Support/TarWriterTest.cpp

@@ -0,0 +1,88 @@
+//===- llvm/unittest/Support/TarWriterTest.cpp ----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/TarWriter.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+namespace {
+
+struct UstarHeader {
+  char Name[100];
+  char Mode[8];
+  char Uid[8];
+  char Gid[8];
+  char Size[12];
+  char Mtime[12];
+  char Checksum[8];
+  char TypeFlag;
+  char Linkname[100];
+  char Magic[6];
+  char Version[2];
+  char Uname[32];
+  char Gname[32];
+  char DevMajor[8];
+  char DevMinor[8];
+  char Prefix[155];
+  char Pad[12];
+};
+
+class TarWriterTest : public ::testing::Test {};
+
+static UstarHeader create(StringRef Base, StringRef Filename) {
+  // Create a temporary file.
+  SmallString<128> Path;
+  std::error_code EC =
+      sys::fs::createTemporaryFile("TarWriterTest", "tar", Path);
+  EXPECT_FALSE((bool)EC);
+
+  // Create a tar file.
+  Expected<std::unique_ptr<TarWriter>> TarOrErr = TarWriter::create(Path, Base);
+  EXPECT_TRUE((bool)TarOrErr);
+  std::unique_ptr<TarWriter> Tar = std::move(*TarOrErr);
+  Tar->append(Filename, "contents");
+  Tar.release();
+
+  // Read the tar file.
+  ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = MemoryBuffer::getFile(Path);
+  EXPECT_TRUE((bool)MBOrErr);
+  std::unique_ptr<MemoryBuffer> MB = std::move(*MBOrErr);
+  sys::fs::remove(Path);
+  return *reinterpret_cast<const UstarHeader *>(MB->getBufferStart());
+}
+
+TEST_F(TarWriterTest, Basics) {
+  UstarHeader Hdr = create("base", "file");
+  ASSERT_EQ("ustar", StringRef(Hdr.Magic));
+  ASSERT_EQ("00", StringRef(Hdr.Version, 2));
+  ASSERT_EQ("base/file", StringRef(Hdr.Name));
+  ASSERT_EQ("00000000010", StringRef(Hdr.Size));
+}
+
+TEST_F(TarWriterTest, LongFilename) {
+  UstarHeader Hdr1 = create(
+      "012345678", std::string(99, 'x') + "/" + std::string(44, 'x') + "/foo");
+  ASSERT_EQ("foo", StringRef(Hdr1.Name));
+  ASSERT_EQ("012345678/" + std::string(99, 'x') + "/" + std::string(44, 'x'),
+            StringRef(Hdr1.Prefix));
+
+  UstarHeader Hdr2 = create(
+      "012345678", std::string(99, 'x') + "/" + std::string(45, 'x') + "/foo");
+  ASSERT_EQ("foo", StringRef(Hdr2.Name));
+  ASSERT_EQ("012345678/" + std::string(99, 'x') + "/" + std::string(45, 'x'),
+            StringRef(Hdr2.Prefix));
+
+  UstarHeader Hdr3 = create(
+      "012345678", std::string(99, 'x') + "/" + std::string(46, 'x') + "/foo");
+  ASSERT_EQ(std::string(46, 'x') + "/foo", StringRef(Hdr3.Name));
+  ASSERT_EQ("012345678/" + std::string(99, 'x'), StringRef(Hdr3.Prefix));
+}
+}