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//===- InMemoryModuleCache.h - In-memory cache for modules ------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_SERIALIZATION_INMEMORYMODULECACHE_H
#define LLVM_CLANG_SERIALIZATION_INMEMORYMODULECACHE_H
#include "llvm/ADT/IntrusiveRefCntPtr.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/Support/MemoryBuffer.h"
#include <memory>
namespace clang {
/// In-memory cache for modules.
///
/// This is a cache for modules for use across a compilation, sharing state
/// between the CompilerInstances in an implicit modules build. It must be
/// shared by each CompilerInstance, ASTReader, ASTWriter, and ModuleManager
/// that are coordinating.
///
/// Critically, it ensures that a single process has a consistent view of each
/// PCM. This is used by \a CompilerInstance when building PCMs to ensure that
/// each \a ModuleManager sees the same files.
class InMemoryModuleCache : public llvm::RefCountedBase<InMemoryModuleCache> {
struct PCM {
std::unique_ptr<llvm::MemoryBuffer> Buffer;
/// Track whether this PCM is known to be good (either built or
/// successfully imported by a CompilerInstance/ASTReader using this
/// cache).
bool IsFinal = false;
PCM() = default;
PCM(std::unique_ptr<llvm::MemoryBuffer> Buffer)
: Buffer(std::move(Buffer)) {}
};
/// Cache of buffers.
llvm::StringMap<PCM> PCMs;
public:
/// There are four states for a PCM. It must monotonically increase.
///
/// 1. Unknown: the PCM has neither been read from disk nor built.
/// 2. Tentative: the PCM has been read from disk but not yet imported or
/// built. It might work.
/// 3. ToBuild: the PCM read from disk did not work but a new one has not
/// been built yet.
/// 4. Final: indicating that the current PCM was either built in this
/// process or has been successfully imported.
enum State { Unknown, Tentative, ToBuild, Final };
/// Get the state of the PCM.
State getPCMState(llvm::StringRef Filename) const;
/// Store the PCM under the Filename.
///
/// \pre state is Unknown
/// \post state is Tentative
/// \return a reference to the buffer as a convenience.
llvm::MemoryBuffer &addPCM(llvm::StringRef Filename,
std::unique_ptr<llvm::MemoryBuffer> Buffer);
/// Store a just-built PCM under the Filename.
///
/// \pre state is Unknown or ToBuild.
/// \pre state is not Tentative.
/// \return a reference to the buffer as a convenience.
llvm::MemoryBuffer &addBuiltPCM(llvm::StringRef Filename,
std::unique_ptr<llvm::MemoryBuffer> Buffer);
/// Try to remove a buffer from the cache. No effect if state is Final.
///
/// \pre state is Tentative/Final.
/// \post Tentative => ToBuild or Final => Final.
/// \return false on success, i.e. if Tentative => ToBuild.
bool tryToDropPCM(llvm::StringRef Filename);
/// Mark a PCM as final.
///
/// \pre state is Tentative or Final.
/// \post state is Final.
void finalizePCM(llvm::StringRef Filename);
/// Get a pointer to the pCM if it exists; else nullptr.
llvm::MemoryBuffer *lookupPCM(llvm::StringRef Filename) const;
/// Check whether the PCM is final and has been shown to work.
///
/// \return true iff state is Final.
bool isPCMFinal(llvm::StringRef Filename) const;
/// Check whether the PCM is waiting to be built.
///
/// \return true iff state is ToBuild.
bool shouldBuildPCM(llvm::StringRef Filename) const;
};
} // end namespace clang
#endif // LLVM_CLANG_SERIALIZATION_INMEMORYMODULECACHE_H
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