LLVM  9.0.0svn
FileOutputBuffer.h
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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/SmallString.h"
17 #include "llvm/ADT/StringRef.h"
18 #include "llvm/Support/DataTypes.h"
19 #include "llvm/Support/Error.h"
21 
22 namespace llvm {
23 /// FileOutputBuffer - This interface provides simple way to create an in-memory
24 /// buffer which will be written to a file. During the lifetime of these
25 /// objects, the content or existence of the specified file is undefined. That
26 /// is, creating an OutputBuffer for a file may immediately remove the file.
27 /// If the FileOutputBuffer is committed, the target file's content will become
28 /// the buffer content at the time of the commit. If the FileOutputBuffer is
29 /// not committed, the file will be deleted in the FileOutputBuffer destructor.
31 public:
32  enum {
33  /// set the 'x' bit on the resulting file
35  };
36 
37  /// Factory method to create an OutputBuffer object which manages a read/write
38  /// buffer of the specified size. When committed, the buffer will be written
39  /// to the file at the specified path.
40  ///
41  /// When F_modify is specified and \p FilePath refers to an existing on-disk
42  /// file \p Size may be set to -1, in which case the entire file is used.
43  /// Otherwise, the file shrinks or grows as necessary based on the value of
44  /// \p Size. It is an error to specify F_modify and Size=-1 if \p FilePath
45  /// does not exist.
47  create(StringRef FilePath, size_t Size, unsigned Flags = 0);
48 
49  /// Returns a pointer to the start of the buffer.
50  virtual uint8_t *getBufferStart() const = 0;
51 
52  /// Returns a pointer to the end of the buffer.
53  virtual uint8_t *getBufferEnd() const = 0;
54 
55  /// Returns size of the buffer.
56  virtual size_t getBufferSize() const = 0;
57 
58  /// Returns path where file will show up if buffer is committed.
59  StringRef getPath() const { return FinalPath; }
60 
61  /// Flushes the content of the buffer to its file and deallocates the
62  /// buffer. If commit() is not called before this object's destructor
63  /// is called, the file is deleted in the destructor. The optional parameter
64  /// is used if it turns out you want the file size to be smaller than
65  /// initially requested.
66  virtual Error commit() = 0;
67 
68  /// If this object was previously committed, the destructor just deletes
69  /// this object. If this object was not committed, the destructor
70  /// deallocates the buffer and the target file is never written.
71  virtual ~FileOutputBuffer() {}
72 
73  /// This removes the temporary file (unless it already was committed)
74  /// but keeps the memory mapping alive.
75  virtual void discard() {}
76 
77 protected:
79 
80  std::string FinalPath;
81 };
82 } // end namespace llvm
83 
84 #endif
virtual ~FileOutputBuffer()
If this object was previously committed, the destructor just deletes this object. ...
virtual uint8_t * getBufferEnd() const =0
Returns a pointer to the end of the buffer.
static Expected< std::unique_ptr< FileOutputBuffer > > create(StringRef FilePath, size_t Size, unsigned Flags=0)
Factory method to create an OutputBuffer object which manages a read/write buffer of the specified si...
This class represents lattice values for constants.
Definition: AllocatorList.h:23
StringRef getPath() const
Returns path where file will show up if buffer is committed.
FileOutputBuffer(StringRef Path)
virtual uint8_t * getBufferStart() const =0
Returns a pointer to the start of the buffer.
FileOutputBuffer - This interface provides simple way to create an in-memory buffer which will be wri...
Tagged union holding either a T or a Error.
Definition: CachePruning.h:22
virtual size_t getBufferSize() const =0
Returns size of the buffer.
uint32_t Size
Definition: Profile.cpp:46
virtual void discard()
This removes the temporary file (unless it already was committed) but keeps the memory mapping alive...
Lightweight error class with error context and mandatory checking.
Definition: Error.h:157
virtual Error commit()=0
Flushes the content of the buffer to its file and deallocates the buffer.
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48
set the &#39;x&#39; bit on the resulting file