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circular_raw_ostream.h
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1 //===-- llvm/Support/circular_raw_ostream.h - Buffered streams --*- 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 // This file contains raw_ostream implementations for streams to do circular
10 // buffering of their output.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_SUPPORT_CIRCULAR_RAW_OSTREAM_H
15 #define LLVM_SUPPORT_CIRCULAR_RAW_OSTREAM_H
16 
18 
19 namespace llvm {
20  /// circular_raw_ostream - A raw_ostream which *can* save its data
21  /// to a circular buffer, or can pass it through directly to an
22  /// underlying stream if specified with a buffer of zero.
23  ///
25  public:
26  /// TAKE_OWNERSHIP - Tell this stream that it owns the underlying
27  /// stream and is responsible for cleanup, memory management
28  /// issues, etc.
29  ///
30  static const bool TAKE_OWNERSHIP = true;
31 
32  /// REFERENCE_ONLY - Tell this stream it should not manage the
33  /// held stream.
34  ///
35  static const bool REFERENCE_ONLY = false;
36 
37  private:
38  /// TheStream - The real stream we output to. We set it to be
39  /// unbuffered, since we're already doing our own buffering.
40  ///
41  raw_ostream *TheStream;
42 
43  /// OwnsStream - Are we responsible for managing the underlying
44  /// stream?
45  ///
46  bool OwnsStream;
47 
48  /// BufferSize - The size of the buffer in bytes.
49  ///
50  size_t BufferSize;
51 
52  /// BufferArray - The actual buffer storage.
53  ///
54  char *BufferArray;
55 
56  /// Cur - Pointer to the current output point in BufferArray.
57  ///
58  char *Cur;
59 
60  /// Filled - Indicate whether the buffer has been completely
61  /// filled. This helps avoid garbage output.
62  ///
63  bool Filled;
64 
65  /// Banner - A pointer to a banner to print before dumping the
66  /// log.
67  ///
68  const char *Banner;
69 
70  /// flushBuffer - Dump the contents of the buffer to Stream.
71  ///
72  void flushBuffer() {
73  if (Filled)
74  // Write the older portion of the buffer.
75  TheStream->write(Cur, BufferArray + BufferSize - Cur);
76  // Write the newer portion of the buffer.
77  TheStream->write(BufferArray, Cur - BufferArray);
78  Cur = BufferArray;
79  Filled = false;
80  }
81 
82  void write_impl(const char *Ptr, size_t Size) override;
83 
84  /// current_pos - Return the current position within the stream,
85  /// not counting the bytes currently in the buffer.
86  ///
87  uint64_t current_pos() const override {
88  // This has the same effect as calling TheStream.current_pos(),
89  // but that interface is private.
90  return TheStream->tell() - TheStream->GetNumBytesInBuffer();
91  }
92 
93  public:
94  /// circular_raw_ostream - Construct an optionally
95  /// circular-buffered stream, handing it an underlying stream to
96  /// do the "real" output.
97  ///
98  /// As a side effect, if BuffSize is nonzero, the given Stream is
99  /// set to be Unbuffered. This is because circular_raw_ostream
100  /// does its own buffering, so it doesn't want another layer of
101  /// buffering to be happening underneath it.
102  ///
103  /// "Owns" tells the circular_raw_ostream whether it is
104  /// responsible for managing the held stream, doing memory
105  /// management of it, etc.
106  ///
107  circular_raw_ostream(raw_ostream &Stream, const char *Header,
108  size_t BuffSize = 0, bool Owns = REFERENCE_ONLY)
109  : raw_ostream(/*unbuffered*/ true), TheStream(nullptr),
110  OwnsStream(Owns), BufferSize(BuffSize), BufferArray(nullptr),
111  Filled(false), Banner(Header) {
112  if (BufferSize != 0)
113  BufferArray = new char[BufferSize];
114  Cur = BufferArray;
115  setStream(Stream, Owns);
116  }
117 
119  flush();
121  releaseStream();
122  delete[] BufferArray;
123  }
124 
125  /// setStream - Tell the circular_raw_ostream to output a
126  /// different stream. "Owns" tells circular_raw_ostream whether
127  /// it should take responsibility for managing the underlying
128  /// stream.
129  ///
130  void setStream(raw_ostream &Stream, bool Owns = REFERENCE_ONLY) {
131  releaseStream();
132  TheStream = &Stream;
133  OwnsStream = Owns;
134  }
135 
136  /// flushBufferWithBanner - Force output of the buffer along with
137  /// a small header.
138  ///
139  void flushBufferWithBanner();
140 
141  private:
142  /// releaseStream - Delete the held stream if needed. Otherwise,
143  /// transfer the buffer settings from this circular_raw_ostream
144  /// back to the underlying stream.
145  ///
146  void releaseStream() {
147  if (!TheStream)
148  return;
149  if (OwnsStream)
150  delete TheStream;
151  }
152  };
153 } // end llvm namespace
154 
155 #endif
This class represents lattice values for constants.
Definition: AllocatorList.h:23
block Block Frequency true
circular_raw_ostream(raw_ostream &Stream, const char *Header, size_t BuffSize=0, bool Owns=REFERENCE_ONLY)
circular_raw_ostream - Construct an optionally circular-buffered stream, handing it an underlying str...
circular_raw_ostream - A raw_ostream which can save its data to a circular buffer, or can pass it through directly to an underlying stream if specified with a buffer of zero.
void setStream(raw_ostream &Stream, bool Owns=REFERENCE_ONLY)
setStream - Tell the circular_raw_ostream to output a different stream.
raw_ostream & write(unsigned char C)
void flushBufferWithBanner()
flushBufferWithBanner - Force output of the buffer along with a small header.
static const bool REFERENCE_ONLY
REFERENCE_ONLY - Tell this stream it should not manage the held stream.
size_t GetNumBytesInBuffer() const
Definition: raw_ostream.h:133
uint32_t Size
Definition: Profile.cpp:46
static const bool TAKE_OWNERSHIP
TAKE_OWNERSHIP - Tell this stream that it owns the underlying stream and is responsible for cleanup...
uint64_t tell() const
tell - Return the current offset with the file.
Definition: raw_ostream.h:99
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:45