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     F_executable = 1  /// 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   static Expected<std::unique_ptr<FileOutputBuffer>>
41   create(StringRef FilePath, size_t Size, unsigned Flags = 0);
42 
43   /// Returns a pointer to the start of the buffer.
44   virtual uint8_t *getBufferStart() const = 0;
45 
46   /// Returns a pointer to the end of the buffer.
47   virtual uint8_t *getBufferEnd() const = 0;
48 
49   /// Returns size of the buffer.
50   virtual size_t getBufferSize() const = 0;
51 
52   /// Returns path where file will show up if buffer is committed.
53   StringRef getPath() const { return FinalPath; }
54 
55   /// Flushes the content of the buffer to its file and deallocates the
56   /// buffer.  If commit() is not called before this object's destructor
57   /// is called, the file is deleted in the destructor. The optional parameter
58   /// is used if it turns out you want the file size to be smaller than
59   /// initially requested.
60   virtual Error commit() = 0;
61 
62   /// If this object was previously committed, the destructor just deletes
63   /// this object.  If this object was not committed, the destructor
64   /// deallocates the buffer and the target file is never written.
65   virtual ~FileOutputBuffer() {}
66 
67 protected:
68   FileOutputBuffer(StringRef Path) : FinalPath(Path) {}
69 
70   std::string FinalPath;
71 };
72 } // end namespace llvm
73 
74 #endif
75