//=== FileOutputBuffer.h - File Output Buffer -------------------*- 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 // //===----------------------------------------------------------------------===// // // Utility for creating a in-memory buffer that will be written to a file. // //===----------------------------------------------------------------------===// #ifndef LLVM_SUPPORT_FILEOUTPUTBUFFER_H #define LLVM_SUPPORT_FILEOUTPUTBUFFER_H #include "llvm/ADT/SmallString.h" #include "llvm/ADT/StringRef.h" #include "llvm/Support/DataTypes.h" #include "llvm/Support/Error.h" #include "llvm/Support/FileSystem.h" namespace llvm { /// FileOutputBuffer - This interface provides simple way to create an in-memory /// buffer which will be written to a file. During the lifetime of these /// objects, the content or existence of the specified file is undefined. That /// is, creating an OutputBuffer for a file may immediately remove the file. /// If the FileOutputBuffer is committed, the target file's content will become /// the buffer content at the time of the commit. If the FileOutputBuffer is /// not committed, the file will be deleted in the FileOutputBuffer destructor. class FileOutputBuffer { public: enum { /// set the 'x' bit on the resulting file F_executable = 1, /// Don't use mmap and instead write an in-memory buffer to a file when this /// buffer is closed. F_no_mmap = 2, }; /// Factory method to create an OutputBuffer object which manages a read/write /// buffer of the specified size. When committed, the buffer will be written /// to the file at the specified path. /// /// When F_modify is specified and \p FilePath refers to an existing on-disk /// file \p Size may be set to -1, in which case the entire file is used. /// Otherwise, the file shrinks or grows as necessary based on the value of /// \p Size. It is an error to specify F_modify and Size=-1 if \p FilePath /// does not exist. static Expected> create(StringRef FilePath, size_t Size, unsigned Flags = 0); /// Returns a pointer to the start of the buffer. virtual uint8_t *getBufferStart() const = 0; /// Returns a pointer to the end of the buffer. virtual uint8_t *getBufferEnd() const = 0; /// Returns size of the buffer. virtual size_t getBufferSize() const = 0; /// Returns path where file will show up if buffer is committed. StringRef getPath() const { return FinalPath; } /// Flushes the content of the buffer to its file and deallocates the /// buffer. If commit() is not called before this object's destructor /// is called, the file is deleted in the destructor. The optional parameter /// is used if it turns out you want the file size to be smaller than /// initially requested. virtual Error commit() = 0; /// If this object was previously committed, the destructor just deletes /// this object. If this object was not committed, the destructor /// deallocates the buffer and the target file is never written. virtual ~FileOutputBuffer() {} /// This removes the temporary file (unless it already was committed) /// but keeps the memory mapping alive. virtual void discard() {} protected: FileOutputBuffer(StringRef Path) : FinalPath(Path) {} std::string FinalPath; }; } // end namespace llvm #endif