1 //=== FileOutputBuffer.h - File Output Buffer -------------------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // Utility for creating a in-memory buffer that will be written to a file. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_SUPPORT_FILEOUTPUTBUFFER_H 15 #define LLVM_SUPPORT_FILEOUTPUTBUFFER_H 16 17 #include "llvm/ADT/SmallString.h" 18 #include "llvm/ADT/StringRef.h" 19 #include "llvm/Support/DataTypes.h" 20 #include "llvm/Support/Error.h" 21 #include "llvm/Support/FileSystem.h" 22 23 namespace llvm { 24 /// FileOutputBuffer - This interface provides simple way to create an in-memory 25 /// buffer which will be written to a file. During the lifetime of these 26 /// objects, the content or existence of the specified file is undefined. That 27 /// is, creating an OutputBuffer for a file may immediately remove the file. 28 /// If the FileOutputBuffer is committed, the target file's content will become 29 /// the buffer content at the time of the commit. If the FileOutputBuffer is 30 /// not committed, the file will be deleted in the FileOutputBuffer destructor. 31 class FileOutputBuffer { 32 public: 33 enum { 34 /// set the 'x' bit on the resulting file 35 F_executable = 1, 36 37 /// the contents of the new file are initialized from the file that exists 38 /// at the location (if present). This allows in-place modification of an 39 /// existing file. 40 F_modify = 2 41 }; 42 43 /// Factory method to create an OutputBuffer object which manages a read/write 44 /// buffer of the specified size. When committed, the buffer will be written 45 /// to the file at the specified path. 46 /// 47 /// When F_modify is specified and \p FilePath refers to an existing on-disk 48 /// file \p Size may be set to -1, in which case the entire file is used. 49 /// Otherwise, the file shrinks or grows as necessary based on the value of 50 /// \p Size. It is an error to specify F_modify and Size=-1 if \p FilePath 51 /// does not exist. 52 static Expected<std::unique_ptr<FileOutputBuffer>> 53 create(StringRef FilePath, size_t Size, unsigned Flags = 0); 54 55 /// Returns a pointer to the start of the buffer. 56 virtual uint8_t *getBufferStart() const = 0; 57 58 /// Returns a pointer to the end of the buffer. 59 virtual uint8_t *getBufferEnd() const = 0; 60 61 /// Returns size of the buffer. 62 virtual size_t getBufferSize() const = 0; 63 64 /// Returns path where file will show up if buffer is committed. getPath()65 StringRef getPath() const { return FinalPath; } 66 67 /// Flushes the content of the buffer to its file and deallocates the 68 /// buffer. If commit() is not called before this object's destructor 69 /// is called, the file is deleted in the destructor. The optional parameter 70 /// is used if it turns out you want the file size to be smaller than 71 /// initially requested. 72 virtual Error commit() = 0; 73 74 /// If this object was previously committed, the destructor just deletes 75 /// this object. If this object was not committed, the destructor 76 /// deallocates the buffer and the target file is never written. ~FileOutputBuffer()77 virtual ~FileOutputBuffer() {} 78 79 protected: FileOutputBuffer(StringRef Path)80 FileOutputBuffer(StringRef Path) : FinalPath(Path) {} 81 82 std::string FinalPath; 83 }; 84 } // end namespace llvm 85 86 #endif 87