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 //===- llvm/Support/Memory.h - Memory Support -------------------*- 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
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares the llvm::sys::Memory class.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_SUPPORT_MEMORY_H
 #define LLVM_SUPPORT_MEMORY_H
 
 #include "llvm/Support/DataTypes.h"
 #include <system_error>
 #include <utility>
 
 namespace llvm {
 
 // Forward declare raw_ostream: it is used for debug dumping below.
 class raw_ostream;
 
 namespace sys {
 
   /// This class encapsulates the notion of a memory block which has an address
   /// and a size. It is used by the Memory class (a friend) as the result of
   /// various memory allocation operations.
   /// @see Memory
   /// Memory block abstraction.
   class MemoryBlock {
   public:
     MemoryBlock() : Address(nullptr), AllocatedSize(0) {}
     MemoryBlock(void *addr, size_t allocatedSize)
         : Address(addr), AllocatedSize(allocatedSize) {}
     void *base() const { return Address; }
     /// The size as it was allocated. This is always greater or equal to the
     /// size that was originally requested.
     size_t allocatedSize() const { return AllocatedSize; }
 
   private:
     void *Address;    ///< Address of first byte of memory area
     size_t AllocatedSize; ///< Size, in bytes of the memory area
     unsigned Flags = 0;
     friend class Memory;
   };
 
   /// This class provides various memory handling functions that manipulate
   /// MemoryBlock instances.
   /// @since 1.4
   /// An abstraction for memory operations.
   class Memory {
   public:
     enum ProtectionFlags {
       MF_READ = 0x1000000,
       MF_WRITE = 0x2000000,
       MF_EXEC = 0x4000000,
       MF_RWE_MASK = 0x7000000,
 
       /// The \p MF_HUGE_HINT flag is used to indicate that the request for
       /// a memory block should be satisfied with large pages if possible.
       /// This is only a hint and small pages will be used as fallback.
       ///
       /// The presence or absence of this flag in the returned memory block
       /// is (at least currently) *not* a reliable indicator that the memory
       /// block will use or will not use large pages. On some systems a request
       /// without this flag can be backed by large pages without this flag being
       /// set, and on some other systems a request with this flag can fallback
       /// to small pages without this flag being cleared.
       MF_HUGE_HINT = 0x0000001
     };
 
     /// This method allocates a block of memory that is suitable for loading
     /// dynamically generated code (e.g. JIT). An attempt to allocate
     /// \p NumBytes bytes of virtual memory is made.
     /// \p NearBlock may point to an existing allocation in which case
     /// an attempt is made to allocate more memory near the existing block.
     /// The actual allocated address is not guaranteed to be near the requested
     /// address.
     /// \p Flags is used to set the initial protection flags for the block
     /// of the memory.
     /// \p EC [out] returns an object describing any error that occurs.
     ///
     /// This method may allocate more than the number of bytes requested.  The
     /// actual number of bytes allocated is indicated in the returned
     /// MemoryBlock.
     ///
     /// The start of the allocated block must be aligned with the
     /// system allocation granularity (64K on Windows, page size on Linux).
     /// If the address following \p NearBlock is not so aligned, it will be
     /// rounded up to the next allocation granularity boundary.
     ///
     /// \r a non-null MemoryBlock if the function was successful,
     /// otherwise a null MemoryBlock is with \p EC describing the error.
     ///
     /// Allocate mapped memory.
     static MemoryBlock allocateMappedMemory(size_t NumBytes,
                                             const MemoryBlock *const NearBlock,
                                             unsigned Flags,
                                             std::error_code &EC);
 
     /// This method releases a block of memory that was allocated with the
     /// allocateMappedMemory method. It should not be used to release any
     /// memory block allocated any other way.
     /// \p Block describes the memory to be released.
     ///
     /// \r error_success if the function was successful, or an error_code
     /// describing the failure if an error occurred.
     ///
     /// Release mapped memory.
     static std::error_code releaseMappedMemory(MemoryBlock &Block);
 
     /// This method sets the protection flags for a block of memory to the
     /// state specified by /p Flags.  The behavior is not specified if the
     /// memory was not allocated using the allocateMappedMemory method.
     /// \p Block describes the memory block to be protected.
     /// \p Flags specifies the new protection state to be assigned to the block.
     ///
     /// If \p Flags is MF_WRITE, the actual behavior varies
     /// with the operating system (i.e. MF_READ | MF_WRITE on Windows) and the
     /// target architecture (i.e. MF_WRITE -> MF_READ | MF_WRITE on i386).
     ///
     /// \r error_success if the function was successful, or an error_code
     /// describing the failure if an error occurred.
     ///
     /// Set memory protection state.
     static std::error_code protectMappedMemory(const MemoryBlock &Block,
                                                unsigned Flags);
 
     /// InvalidateInstructionCache - Before the JIT can run a block of code
     /// that has been emitted it must invalidate the instruction cache on some
     /// platforms.
     static void InvalidateInstructionCache(const void *Addr, size_t Len);
   };
 
   /// Owning version of MemoryBlock.
   class OwningMemoryBlock {
   public:
     OwningMemoryBlock() = default;
     explicit OwningMemoryBlock(MemoryBlock M) : M(std::move(M)) {}
     OwningMemoryBlock(OwningMemoryBlock &&Other) {
       M = Other.M;
       Other.M = MemoryBlock();
     }
     OwningMemoryBlock& operator=(OwningMemoryBlock &&Other) {
       M = Other.M;
       Other.M = MemoryBlock();
       return *this;
     }
     ~OwningMemoryBlock() {
       if (M.base())
         Memory::releaseMappedMemory(M);
     }
     void *base() const { return M.base(); }
     /// The size as it was allocated. This is always greater or equal to the
     /// size that was originally requested.
     size_t allocatedSize() const { return M.allocatedSize(); }
     MemoryBlock getMemoryBlock() const { return M; }
     std::error_code release() {
       std::error_code EC;
       if (M.base()) {
         EC = Memory::releaseMappedMemory(M);
         M = MemoryBlock();
       }
       return EC;
     }
   private:
     MemoryBlock M;
   };
 
 #ifndef NDEBUG
   /// Debugging output for Memory::ProtectionFlags.
   raw_ostream &operator<<(raw_ostream &OS, const Memory::ProtectionFlags &PF);
 
   /// Debugging output for MemoryBlock.
   raw_ostream &operator<<(raw_ostream &OS, const MemoryBlock &MB);
 #endif // ifndef NDEBUG
   }    // end namespace sys
   }    // end namespace llvm
 
 #endif

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