1 | //=== FileOutputBuffer.h - File Output Buffer -------------------*- C++ -*-===// |
2 | // |
3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
4 | // See https://llvm.org/LICENSE.txt for license information. |
5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
6 | // |
7 | //===----------------------------------------------------------------------===// |
8 | // |
9 | // Utility for creating a in-memory buffer that will be written to a file. |
10 | // |
11 | //===----------------------------------------------------------------------===// |
12 | |
13 | #ifndef LLVM_SUPPORT_FILEOUTPUTBUFFER_H |
14 | #define LLVM_SUPPORT_FILEOUTPUTBUFFER_H |
15 | |
16 | #include "llvm/ADT/StringRef.h" |
17 | #include "llvm/Support/DataTypes.h" |
18 | #include "llvm/Support/Error.h" |
19 | |
20 | namespace llvm { |
21 | /// FileOutputBuffer - This interface provides simple way to create an in-memory |
22 | /// buffer which will be written to a file. During the lifetime of these |
23 | /// objects, the content or existence of the specified file is undefined. That |
24 | /// is, creating an OutputBuffer for a file may immediately remove the file. |
25 | /// If the FileOutputBuffer is committed, the target file's content will become |
26 | /// the buffer content at the time of the commit. If the FileOutputBuffer is |
27 | /// not committed, the file will be deleted in the FileOutputBuffer destructor. |
28 | class FileOutputBuffer { |
29 | public: |
30 | enum { |
31 | /// Set the 'x' bit on the resulting file. |
32 | F_executable = 1, |
33 | |
34 | /// Don't use mmap and instead write an in-memory buffer to a file when this |
35 | /// buffer is closed. |
36 | F_no_mmap = 2, |
37 | }; |
38 | |
39 | /// Factory method to create an OutputBuffer object which manages a read/write |
40 | /// buffer of the specified size. When committed, the buffer will be written |
41 | /// to the file at the specified path. |
42 | /// |
43 | /// When F_modify is specified and \p FilePath refers to an existing on-disk |
44 | /// file \p Size may be set to -1, in which case the entire file is used. |
45 | /// Otherwise, the file shrinks or grows as necessary based on the value of |
46 | /// \p Size. It is an error to specify F_modify and Size=-1 if \p FilePath |
47 | /// does not exist. |
48 | static Expected<std::unique_ptr<FileOutputBuffer>> |
49 | create(StringRef FilePath, size_t Size, unsigned Flags = 0); |
50 | |
51 | /// Returns a pointer to the start of the buffer. |
52 | virtual uint8_t *getBufferStart() const = 0; |
53 | |
54 | /// Returns a pointer to the end of the buffer. |
55 | virtual uint8_t *getBufferEnd() const = 0; |
56 | |
57 | /// Returns size of the buffer. |
58 | virtual size_t getBufferSize() const = 0; |
59 | |
60 | /// Returns path where file will show up if buffer is committed. |
61 | StringRef getPath() const { return FinalPath; } |
62 | |
63 | /// Flushes the content of the buffer to its file and deallocates the |
64 | /// buffer. If commit() is not called before this object's destructor |
65 | /// is called, the file is deleted in the destructor. The optional parameter |
66 | /// is used if it turns out you want the file size to be smaller than |
67 | /// initially requested. |
68 | virtual Error commit() = 0; |
69 | |
70 | /// If this object was previously committed, the destructor just deletes |
71 | /// this object. If this object was not committed, the destructor |
72 | /// deallocates the buffer and the target file is never written. |
73 | virtual ~FileOutputBuffer() = default; |
74 | |
75 | /// This removes the temporary file (unless it already was committed) |
76 | /// but keeps the memory mapping alive. |
77 | virtual void discard() {} |
78 | |
79 | protected: |
80 | FileOutputBuffer(StringRef Path) : FinalPath(Path) {} |
81 | |
82 | std::string FinalPath; |
83 | }; |
84 | } // end namespace llvm |
85 | |
86 | #endif |
87 | |