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//===- MemoryBufferCache.h - Cache for loaded memory buffers ----*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
#include "llvm/ADT/IntrusiveRefCntPtr.h"
#include "llvm/ADT/StringMap.h"
#include <memory>
namespace llvm {
class MemoryBuffer;
} // end namespace llvm
namespace clang {
/// Manage memory buffers across multiple users.
/// Ensures that multiple users have a consistent view of each buffer. This is
/// used by \a CompilerInstance when building PCMs to ensure that each \a
/// ModuleManager sees the same files.
/// \a finalizeCurrentBuffers() should be called before creating a new user.
/// This locks in the current buffers, ensuring that no buffer that has already
/// been accessed can be purged, preventing use-after-frees.
class MemoryBufferCache : public llvm::RefCountedBase<MemoryBufferCache> {
struct BufferEntry {
std::unique_ptr<llvm::MemoryBuffer> Buffer;
/// Track the timeline of when this was added to the cache.
unsigned Index;
/// Cache of buffers.
llvm::StringMap<BufferEntry> Buffers;
/// Monotonically increasing index.
unsigned NextIndex = 0;
/// Bumped to prevent "older" buffers from being removed.
unsigned FirstRemovableIndex = 0;
/// Store the Buffer under the Filename.
/// \pre There is not already buffer is not already in the cache.
/// \return a reference to the buffer as a convenience.
llvm::MemoryBuffer &addBuffer(llvm::StringRef Filename,
std::unique_ptr<llvm::MemoryBuffer> Buffer);
/// Try to remove a buffer from the cache.
/// \return false on success, iff \c !isBufferFinal().
bool tryToRemoveBuffer(llvm::StringRef Filename);
/// Get a pointer to the buffer if it exists; else nullptr.
llvm::MemoryBuffer *lookupBuffer(llvm::StringRef Filename);
/// Check whether the buffer is final.
/// \return true iff \a finalizeCurrentBuffers() has been called since the
/// buffer was added. This prevents buffers from being removed.
bool isBufferFinal(llvm::StringRef Filename);
/// Finalize the current buffers in the cache.
/// Should be called when creating a new user to ensure previous uses aren't
/// invalidated.
void finalizeCurrentBuffers();
} // end namespace clang