vendor/llvm/llvm-trunk-r338150

1 files changed, 66 insertions, 13 deletions

diff --git a/include/llvm/Support/MemoryBuffer.h b/include/llvm/Support/MemoryBuffer.h
index 7b849fdb8670..535579ecff53 100644
--- a/include/llvm/Support/MemoryBuffer.h
+++ b/include/llvm/Support/MemoryBuffer.h
@@ -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;
@@ -117,12 +119,6 @@ public:
   static std::unique_ptr<MemoryBuffer>
   getMemBufferCopy(StringRef InputData, const Twine &BufferName = "");
 
-  /// Allocate a new zero-initialized MemoryBuffer of the specified size. Note
-  /// that the caller need not initialize the memory allocated by this method.
-  /// The memory is owned by the MemoryBuffer object.
-  static std::unique_ptr<MemoryBuffer>
-  getNewMemBuffer(size_t Size, StringRef BufferName = "");
-
   /// Read all of stdin into a file buffer, and return it.
   static ErrorOr<std::unique_ptr<MemoryBuffer>> getSTDIN();
 
@@ -152,17 +148,21 @@ public:
   virtual BufferKind getBufferKind() const = 0;
 
   MemoryBufferRef getMemBufferRef() const;
+
+private:
+  virtual void anchor();
 };
 
-/// 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;
@@ -196,6 +196,60 @@ public:
   static std::unique_ptr<WritableMemoryBuffer>
   getNewUninitMemBuffer(size_t Size, const Twine &BufferName = "");
 
+  /// Allocate a new zero-initialized MemoryBuffer of the specified size. Note
+  /// that the caller need not initialize the memory allocated by this method.
+  /// The memory is owned by the MemoryBuffer object.
+  static std::unique_ptr<WritableMemoryBuffer>
+  getNewMemBuffer(size_t Size, const Twine &BufferName = "");
+
+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()
@@ -204,7 +258,6 @@ private:
   using MemoryBuffer::getFileOrSTDIN;
   using MemoryBuffer::getMemBuffer;
   using MemoryBuffer::getMemBufferCopy;
-  using MemoryBuffer::getNewMemBuffer;
   using MemoryBuffer::getOpenFile;
   using MemoryBuffer::getOpenFileSlice;
   using MemoryBuffer::getSTDIN;