[Support] Add MemoryBuffer::getFileSlice()

mach-o supports "fat" files which are a header/table-of-contents followed by a
concatenation of mach-o files built for different architectures. Currently, 
MemoryBuffer has no easy way to map a subrange (slice) of a file which lld
will need to select a mach-o slice of a fat file. The new function provides 
an easy way to map a slice of a file into a MemoryBuffer. Test case included.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219260 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 50 insertions, 0 deletions

diff --git a/unittests/Support/MemoryBufferTest.cpp b/unittests/Support/MemoryBufferTest.cpp
index 93bf301267ea..1cdd6adbf8ba 100644
--- a/unittests/Support/MemoryBufferTest.cpp
+++ b/unittests/Support/MemoryBufferTest.cpp
@@ -169,4 +169,54 @@ TEST_F(MemoryBufferTest, getOpenFileReopened) {
   testGetOpenFileSlice(true);
 }
 
+
+TEST_F(MemoryBufferTest, slice) {
+  // Create a file that is six pages long with different data on each page.
+  int FD;
+  SmallString<64> TestPath;
+  sys::fs::createTemporaryFile("MemoryBufferTest_Slice", "temp", FD, TestPath);
+  raw_fd_ostream OF(FD, true, /*unbuffered=*/true);
+  for (unsigned i = 0; i < 0x2000 / 8; ++i) {
+    OF << "12345678";
+  }
+  for (unsigned i = 0; i < 0x2000 / 8; ++i) {
+    OF << "abcdefgh";
+  }
+  for (unsigned i = 0; i < 0x2000 / 8; ++i) {
+    OF << "ABCDEFGH";
+  }
+  OF.close();
+
+  // Try offset of one page.
+  ErrorOr<OwningBuffer> MB = MemoryBuffer::getFileSlice(TestPath.str(),
+                                                        0x4000, 0x1000);
+  std::error_code EC = MB.getError();
+  ASSERT_FALSE(EC);
+  EXPECT_EQ(0x4000UL, MB.get()->getBufferSize());
+ 
+  StringRef BufData = MB.get()->getBuffer();
+  EXPECT_TRUE(BufData.substr(0x0000,8).equals("12345678"));
+  EXPECT_TRUE(BufData.substr(0x0FF8,8).equals("12345678"));
+  EXPECT_TRUE(BufData.substr(0x1000,8).equals("abcdefgh"));
+  EXPECT_TRUE(BufData.substr(0x2FF8,8).equals("abcdefgh"));
+  EXPECT_TRUE(BufData.substr(0x3000,8).equals("ABCDEFGH"));
+  EXPECT_TRUE(BufData.substr(0x3FF8,8).equals("ABCDEFGH"));
+   
+  // Try non-page aligned.
+  ErrorOr<OwningBuffer> MB2 = MemoryBuffer::getFileSlice(TestPath.str(),
+                                                         0x3000, 0x0800);
+  EC = MB2.getError();
+  ASSERT_FALSE(EC);
+  EXPECT_EQ(0x3000UL, MB2.get()->getBufferSize());
+  
+  StringRef BufData2 = MB2.get()->getBuffer();
+  EXPECT_TRUE(BufData2.substr(0x0000,8).equals("12345678"));
+  EXPECT_TRUE(BufData2.substr(0x17F8,8).equals("12345678"));
+  EXPECT_TRUE(BufData2.substr(0x1800,8).equals("abcdefgh"));
+  EXPECT_TRUE(BufData2.substr(0x2FF8,8).equals("abcdefgh"));
+ 
+}
+
+
+
 }