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[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.

llvm-svn: 219260
This commit is contained in:
Nick Kledzik 2014-10-08 00:22:18 +00:00
parent 8cd4c9d947
commit 7c3f6ac57e
3 changed files with 69 additions and 8 deletions
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4
llvm/include/llvm/Support/MemoryBuffer.h
View File

@ -126,6 +126,10 @@ public:
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getFileOrSTDIN(const Twine &Filename, int64_t FileSize = -1);
/// Map a subrange of the the specified file as a MemoryBuffer.
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset);
//===--------------------------------------------------------------------===//
// Provided for performance analysis.
//===--------------------------------------------------------------------===//

23
llvm/lib/Support/MemoryBuffer.cpp
View File

@ -97,6 +97,10 @@ public:
};
}
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
uint64_t Offset, bool RequiresNullTerminator, bool IsVolatileSize);
std::unique_ptr<MemoryBuffer>
MemoryBuffer::getMemBuffer(StringRef InputData, StringRef BufferName,
bool RequiresNullTerminator) {
@ -167,6 +171,12 @@ MemoryBuffer::getFileOrSTDIN(const Twine &Filename, int64_t FileSize) {
return getFile(Filename, FileSize);
}
ErrorOr<std::unique_ptr<MemoryBuffer>>
MemoryBuffer::getFileSlice(const Twine &FilePath, uint64_t MapSize,
uint64_t Offset) {
return getFileAux(FilePath, -1, MapSize, Offset, false, false);
}
//===----------------------------------------------------------------------===//
// MemoryBuffer::getFile implementation.
@ -232,15 +242,12 @@ getMemoryBufferForStream(int FD, const Twine &BufferName) {
return MemoryBuffer::getMemBufferCopy(Buffer, BufferName);
}
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getFileAux(const Twine &Filename, int64_t FileSize, bool RequiresNullTerminator,
bool IsVolatileSize);
ErrorOr<std::unique_ptr<MemoryBuffer>>
MemoryBuffer::getFile(const Twine &Filename, int64_t FileSize,
bool RequiresNullTerminator, bool IsVolatileSize) {
return getFileAux(Filename, FileSize, RequiresNullTerminator,
IsVolatileSize);
return getFileAux(Filename, FileSize, FileSize, 0,
RequiresNullTerminator, IsVolatileSize);
}
static ErrorOr<std::unique_ptr<MemoryBuffer>>
@ -249,15 +256,15 @@ getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,
bool IsVolatileSize);
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getFileAux(const Twine &Filename, int64_t FileSize, bool RequiresNullTerminator,
bool IsVolatileSize) {
getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
uint64_t Offset, bool RequiresNullTerminator, bool IsVolatileSize) {
int FD;
std::error_code EC = sys::fs::openFileForRead(Filename, FD);
if (EC)
return EC;
ErrorOr<std::unique_ptr<MemoryBuffer>> Ret =
getOpenFileImpl(FD, Filename, FileSize, FileSize, 0,
getOpenFileImpl(FD, Filename, FileSize, MapSize, Offset,
RequiresNullTerminator, IsVolatileSize);
close(FD);
return Ret;

50
llvm/unittests/Support/MemoryBufferTest.cpp
View File

@ -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"));
}
}