[llvm] r327057 - [Support] Add WriteThroughMemoryBuffer.
Zachary Turner via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 8 12:34:47 PST 2018
Author: zturner
Date: Thu Mar 8 12:34:47 2018
New Revision: 327057
URL: http://llvm.org/viewvc/llvm-project?rev=327057&view=rev
Log:
[Support] Add WriteThroughMemoryBuffer.
This is like MemoryBuffer (read-only) and WritableMemoryBuffer
(writable private), but where the underlying file can be modified
after writing. This is useful when you want to open a file, make
some targeted edits, and then write it back out.
Differential Revision: https://reviews.llvm.org/D44230
Modified:
llvm/trunk/include/llvm/Support/FileSystem.h
llvm/trunk/include/llvm/Support/MemoryBuffer.h
llvm/trunk/lib/Support/MemoryBuffer.cpp
llvm/trunk/lib/Support/Unix/Path.inc
llvm/trunk/lib/Support/Windows/Path.inc
llvm/trunk/unittests/Support/MemoryBufferTest.cpp
Modified: llvm/trunk/include/llvm/Support/FileSystem.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/FileSystem.h?rev=327057&r1=327056&r2=327057&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/FileSystem.h (original)
+++ llvm/trunk/include/llvm/Support/FileSystem.h Thu Mar 8 12:34:47 2018
@@ -678,15 +678,20 @@ enum OpenFlags : unsigned {
/// with F_Excl.
F_Append = 2,
+ /// F_NoTrunc - When opening a file, if it already exists don't truncate
+ /// the file contents. F_Append implies F_NoTrunc, but F_Append seeks to
+ /// the end of the file, which F_NoTrunc doesn't.
+ F_NoTrunc = 4,
+
/// The file should be opened in text mode on platforms that make this
/// distinction.
- F_Text = 4,
+ F_Text = 8,
/// Open the file for read and write.
- F_RW = 8,
+ F_RW = 16,
/// Delete the file on close. Only makes a difference on windows.
- F_Delete = 16
+ F_Delete = 32
};
/// @brief Create a uniquely named file.
Modified: llvm/trunk/include/llvm/Support/MemoryBuffer.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/MemoryBuffer.h?rev=327057&r1=327056&r2=327057&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/MemoryBuffer.h (original)
+++ llvm/trunk/include/llvm/Support/MemoryBuffer.h Thu Mar 8 12:34:47 2018
@@ -20,6 +20,7 @@
#include "llvm/ADT/Twine.h"
#include "llvm/Support/CBindingWrapping.h"
#include "llvm/Support/ErrorOr.h"
+#include "llvm/Support/FileSystem.h"
#include <cstddef>
#include <cstdint>
#include <memory>
@@ -49,7 +50,8 @@ protected:
void init(const char *BufStart, const char *BufEnd,
bool RequiresNullTerminator);
- static constexpr bool Writable = false;
+ static constexpr sys::fs::mapped_file_region::mapmode Mapmode =
+ sys::fs::mapped_file_region::readonly;
public:
MemoryBuffer(const MemoryBuffer &) = delete;
@@ -148,15 +150,16 @@ public:
MemoryBufferRef getMemBufferRef() const;
};
-/// This class is an extension of MemoryBuffer, which allows writing to the
-/// underlying contents. It only supports creation methods that are guaranteed
-/// to produce a writable buffer. For example, mapping a file read-only is not
-/// supported.
+/// This class is an extension of MemoryBuffer, which allows copy-on-write
+/// access to the underlying contents. It only supports creation methods that
+/// are guaranteed to produce a writable buffer. For example, mapping a file
+/// read-only is not supported.
class WritableMemoryBuffer : public MemoryBuffer {
protected:
WritableMemoryBuffer() = default;
- static constexpr bool Writable = true;
+ static constexpr sys::fs::mapped_file_region::mapmode Mapmode =
+ sys::fs::mapped_file_region::priv;
public:
using MemoryBuffer::getBuffer;
@@ -198,6 +201,54 @@ public:
private:
// Hide these base class factory function so one can't write
+ // WritableMemoryBuffer::getXXX()
+ // and be surprised that he got a read-only Buffer.
+ using MemoryBuffer::getFileAsStream;
+ using MemoryBuffer::getFileOrSTDIN;
+ using MemoryBuffer::getMemBuffer;
+ using MemoryBuffer::getMemBufferCopy;
+ using MemoryBuffer::getOpenFile;
+ using MemoryBuffer::getOpenFileSlice;
+ using MemoryBuffer::getSTDIN;
+};
+
+/// This class is an extension of MemoryBuffer, which allows write access to
+/// the underlying contents and committing those changes to the original source.
+/// It only supports creation methods that are guaranteed to produce a writable
+/// buffer. For example, mapping a file read-only is not supported.
+class WriteThroughMemoryBuffer : public MemoryBuffer {
+protected:
+ WriteThroughMemoryBuffer() = default;
+
+ static constexpr sys::fs::mapped_file_region::mapmode Mapmode =
+ sys::fs::mapped_file_region::readwrite;
+
+public:
+ using MemoryBuffer::getBuffer;
+ using MemoryBuffer::getBufferEnd;
+ using MemoryBuffer::getBufferStart;
+
+ // const_cast is well-defined here, because the underlying buffer is
+ // guaranteed to have been initialized with a mutable buffer.
+ char *getBufferStart() {
+ return const_cast<char *>(MemoryBuffer::getBufferStart());
+ }
+ char *getBufferEnd() {
+ return const_cast<char *>(MemoryBuffer::getBufferEnd());
+ }
+ MutableArrayRef<char> getBuffer() {
+ return {getBufferStart(), getBufferEnd()};
+ }
+
+ static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
+ getFile(const Twine &Filename, int64_t FileSize = -1);
+
+ /// Map a subrange of the specified file as a ReadWriteMemoryBuffer.
+ static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
+ getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset);
+
+private:
+ // Hide these base class factory function so one can't write
// WritableMemoryBuffer::getXXX()
// and be surprised that he got a read-only Buffer.
using MemoryBuffer::getFileAsStream;
Modified: llvm/trunk/lib/Support/MemoryBuffer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/MemoryBuffer.cpp?rev=327057&r1=327056&r2=327057&view=diff
==============================================================================
--- llvm/trunk/lib/Support/MemoryBuffer.cpp (original)
+++ llvm/trunk/lib/Support/MemoryBuffer.cpp Thu Mar 8 12:34:47 2018
@@ -184,10 +184,8 @@ class MemoryBufferMMapFile : public MB {
public:
MemoryBufferMMapFile(bool RequiresNullTerminator, int FD, uint64_t Len,
uint64_t Offset, std::error_code &EC)
- : MFR(FD,
- MB::Writable ? sys::fs::mapped_file_region::priv
- : sys::fs::mapped_file_region::readonly,
- getLegalMapSize(Len, Offset), getLegalMapOffset(Offset), EC) {
+ : MFR(FD, MB::Mapmode, getLegalMapSize(Len, Offset),
+ getLegalMapOffset(Offset), EC) {
if (!EC) {
const char *Start = getStart(Len, Offset);
MemoryBuffer::init(Start, Start + Len, RequiresNullTerminator);
@@ -361,6 +359,59 @@ static bool shouldUseMmap(int FD,
return true;
}
+static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
+getReadWriteFile(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
+ uint64_t Offset) {
+ int FD;
+ std::error_code EC = sys::fs::openFileForWrite(
+ Filename, FD, sys::fs::F_RW | sys::fs::F_NoTrunc);
+
+ if (EC)
+ return EC;
+
+ // Default is to map the full file.
+ if (MapSize == uint64_t(-1)) {
+ // If we don't know the file size, use fstat to find out. fstat on an open
+ // file descriptor is cheaper than stat on a random path.
+ if (FileSize == uint64_t(-1)) {
+ sys::fs::file_status Status;
+ std::error_code EC = sys::fs::status(FD, Status);
+ if (EC)
+ return EC;
+
+ // If this not a file or a block device (e.g. it's a named pipe
+ // or character device), we can't mmap it, so error out.
+ sys::fs::file_type Type = Status.type();
+ if (Type != sys::fs::file_type::regular_file &&
+ Type != sys::fs::file_type::block_file)
+ return make_error_code(errc::invalid_argument);
+
+ FileSize = Status.getSize();
+ }
+ MapSize = FileSize;
+ }
+
+ std::unique_ptr<WriteThroughMemoryBuffer> Result(
+ new (NamedBufferAlloc(Filename))
+ MemoryBufferMMapFile<WriteThroughMemoryBuffer>(false, FD, MapSize,
+ Offset, EC));
+ if (EC)
+ return EC;
+ return std::move(Result);
+}
+
+ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
+WriteThroughMemoryBuffer::getFile(const Twine &Filename, int64_t FileSize) {
+ return getReadWriteFile(Filename, FileSize, FileSize, 0);
+}
+
+/// Map a subrange of the specified file as a WritableMemoryBuffer.
+ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
+WriteThroughMemoryBuffer::getFileSlice(const Twine &Filename, uint64_t MapSize,
+ uint64_t Offset) {
+ return getReadWriteFile(Filename, -1, MapSize, Offset);
+}
+
template <typename MB>
static ErrorOr<std::unique_ptr<MB>>
getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,
Modified: llvm/trunk/lib/Support/Unix/Path.inc
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Unix/Path.inc?rev=327057&r1=327056&r2=327057&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Unix/Path.inc (original)
+++ llvm/trunk/lib/Support/Unix/Path.inc Thu Mar 8 12:34:47 2018
@@ -792,7 +792,7 @@ std::error_code openFileForWrite(const T
if (Flags & F_Append)
OpenFlags |= O_APPEND;
- else
+ else if (!(Flags & F_NoTrunc))
OpenFlags |= O_TRUNC;
if (Flags & F_Excl)
Modified: llvm/trunk/lib/Support/Windows/Path.inc
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Windows/Path.inc?rev=327057&r1=327056&r2=327057&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Windows/Path.inc (original)
+++ llvm/trunk/lib/Support/Windows/Path.inc Thu Mar 8 12:34:47 2018
@@ -1101,7 +1101,7 @@ std::error_code openFileForWrite(const T
DWORD CreationDisposition;
if (Flags & F_Excl)
CreationDisposition = CREATE_NEW;
- else if (Flags & F_Append)
+ else if ((Flags & F_Append) || (Flags & F_NoTrunc))
CreationDisposition = OPEN_ALWAYS;
else
CreationDisposition = CREATE_ALWAYS;
Modified: llvm/trunk/unittests/Support/MemoryBufferTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/MemoryBufferTest.cpp?rev=327057&r1=327056&r2=327057&view=diff
==============================================================================
--- llvm/trunk/unittests/Support/MemoryBufferTest.cpp (original)
+++ llvm/trunk/unittests/Support/MemoryBufferTest.cpp Thu Mar 8 12:34:47 2018
@@ -260,4 +260,33 @@ TEST_F(MemoryBufferTest, writableSlice)
for (size_t i = 0; i < MB.getBufferSize(); i += 0x10)
EXPECT_EQ("0123456789abcdef", MB.getBuffer().substr(i, 0x10)) << "i: " << i;
}
+
+TEST_F(MemoryBufferTest, writeThroughFile) {
+ // Create a file initialized with some data
+ int FD;
+ SmallString<64> TestPath;
+ sys::fs::createTemporaryFile("MemoryBufferTest_WriteThrough", "temp", FD,
+ TestPath);
+ FileRemover Cleanup(TestPath);
+ raw_fd_ostream OF(FD, true);
+ OF << "0123456789abcdef";
+ OF.close();
+ {
+ auto MBOrError = WriteThroughMemoryBuffer::getFile(TestPath);
+ ASSERT_FALSE(MBOrError.getError());
+ // Write some data. It should be mapped readwrite, so that upon completion
+ // the original file contents are modified.
+ WriteThroughMemoryBuffer &MB = **MBOrError;
+ ASSERT_EQ(16, MB.getBufferSize());
+ char *Start = MB.getBufferStart();
+ ASSERT_EQ(MB.getBufferEnd(), MB.getBufferStart() + MB.getBufferSize());
+ ::memset(Start, 'x', MB.getBufferSize());
+ }
+
+ auto MBOrError = MemoryBuffer::getFile(TestPath);
+ ASSERT_FALSE(MBOrError.getError());
+ auto &MB = **MBOrError;
+ ASSERT_EQ(16, MB.getBufferSize());
+ EXPECT_EQ("xxxxxxxxxxxxxxxx", MB.getBuffer());
+}
}
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