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/ErrorOr.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 
34   enum  {
35     F_executable = 1  /// set the 'x' bit on the resulting file
36   };
37 
38   /// Factory method to create an OutputBuffer object which manages a read/write
39   /// buffer of the specified size. When committed, the buffer will be written
40   /// to the file at the specified path.
41   static ErrorOr<std::unique_ptr<FileOutputBuffer>>
42   create(StringRef FilePath, size_t Size, unsigned Flags = 0);
43 
44   /// Returns a pointer to the start of the buffer.
getBufferStart()45   uint8_t *getBufferStart() {
46     return (uint8_t*)Region->data();
47   }
48 
49   /// Returns a pointer to the end of the buffer.
getBufferEnd()50   uint8_t *getBufferEnd() {
51     return (uint8_t*)Region->data() + Region->size();
52   }
53 
54   /// Returns size of the buffer.
getBufferSize()55   size_t getBufferSize() const {
56     return Region->size();
57   }
58 
59   /// Returns path where file will show up if buffer is committed.
getPath()60   StringRef getPath() const {
61     return FinalPath;
62   }
63 
64   /// Flushes the content of the buffer to its file and deallocates the
65   /// buffer.  If commit() is not called before this object's destructor
66   /// is called, the file is deleted in the destructor. The optional parameter
67   /// is used if it turns out you want the file size to be smaller than
68   /// initially requested.
69   std::error_code commit();
70 
71   /// If this object was previously committed, the destructor just deletes
72   /// this object.  If this object was not committed, the destructor
73   /// deallocates the buffer and the target file is never written.
74   ~FileOutputBuffer();
75 
76 private:
77   FileOutputBuffer(const FileOutputBuffer &) = delete;
78   FileOutputBuffer &operator=(const FileOutputBuffer &) = delete;
79 
80   FileOutputBuffer(std::unique_ptr<llvm::sys::fs::mapped_file_region> R,
81                    StringRef Path, StringRef TempPath);
82 
83   std::unique_ptr<llvm::sys::fs::mapped_file_region> Region;
84   SmallString<128>    FinalPath;
85   SmallString<128>    TempPath;
86 };
87 } // end namespace llvm
88 
89 #endif
90