1 //=== FileOutputBuffer.h - File Output Buffer -------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Utility for creating a in-memory buffer that will be written to a file.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_SUPPORT_FILEOUTPUTBUFFER_H
15 #define LLVM_SUPPORT_FILEOUTPUTBUFFER_H
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"
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 {
34 /// set the 'x' bit on the resulting file
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
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.
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
52 static Expected<std::unique_ptr<FileOutputBuffer>>
53 create(StringRef FilePath, size_t Size, unsigned Flags = 0);
55 /// Returns a pointer to the start of the buffer.
56 virtual uint8_t *getBufferStart() const = 0;
58 /// Returns a pointer to the end of the buffer.
59 virtual uint8_t *getBufferEnd() const = 0;
61 /// Returns size of the buffer.
62 virtual size_t getBufferSize() const = 0;
64 /// Returns path where file will show up if buffer is committed.
65 StringRef getPath() const { return FinalPath; }
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;
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.
77 virtual ~FileOutputBuffer() {}
80 FileOutputBuffer(StringRef Path) : FinalPath(Path) {}
82 std::string FinalPath;
84 } // end namespace llvm