1 //===-- llvm/Support/circular_raw_ostream.h - Buffered streams --*- 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 // This file contains raw_ostream implementations for streams to do circular 11 // buffering of their output. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_SUPPORT_CIRCULAR_RAW_OSTREAM_H 16 #define LLVM_SUPPORT_CIRCULAR_RAW_OSTREAM_H 17 18 #include "llvm/Support/raw_ostream.h" 19 20 namespace llvm 21 { 22 /// circular_raw_ostream - A raw_ostream which *can* save its data 23 /// to a circular buffer, or can pass it through directly to an 24 /// underlying stream if specified with a buffer of zero. 25 /// 26 class circular_raw_ostream : public raw_ostream { 27 public: 28 /// TAKE_OWNERSHIP - Tell this stream that it owns the underlying 29 /// stream and is responsible for cleanup, memory management 30 /// issues, etc. 31 /// 32 static const bool TAKE_OWNERSHIP = true; 33 34 /// REFERENCE_ONLY - Tell this stream it should not manage the 35 /// held stream. 36 /// 37 static const bool REFERENCE_ONLY = false; 38 39 private: 40 /// TheStream - The real stream we output to. We set it to be 41 /// unbuffered, since we're already doing our own buffering. 42 /// 43 raw_ostream *TheStream; 44 45 /// OwnsStream - Are we responsible for managing the underlying 46 /// stream? 47 /// 48 bool OwnsStream; 49 50 /// BufferSize - The size of the buffer in bytes. 51 /// 52 size_t BufferSize; 53 54 /// BufferArray - The actual buffer storage. 55 /// 56 char *BufferArray; 57 58 /// Cur - Pointer to the current output point in BufferArray. 59 /// 60 char *Cur; 61 62 /// Filled - Indicate whether the buffer has been completely 63 /// filled. This helps avoid garbage output. 64 /// 65 bool Filled; 66 67 /// Banner - A pointer to a banner to print before dumping the 68 /// log. 69 /// 70 const char *Banner; 71 72 /// flushBuffer - Dump the contents of the buffer to Stream. 73 /// 74 void flushBuffer() { 75 if (Filled) 76 // Write the older portion of the buffer. 77 TheStream->write(Cur, BufferArray + BufferSize - Cur); 78 // Write the newer portion of the buffer. 79 TheStream->write(BufferArray, Cur - BufferArray); 80 Cur = BufferArray; 81 Filled = false; 82 } 83 84 void write_impl(const char *Ptr, size_t Size) override; 85 86 /// current_pos - Return the current position within the stream, 87 /// not counting the bytes currently in the buffer. 88 /// 89 uint64_t current_pos() const override { 90 // This has the same effect as calling TheStream.current_pos(), 91 // but that interface is private. 92 return TheStream->tell() - TheStream->GetNumBytesInBuffer(); 93 } 94 95 public: 96 /// circular_raw_ostream - Construct an optionally 97 /// circular-buffered stream, handing it an underlying stream to 98 /// do the "real" output. 99 /// 100 /// As a side effect, if BuffSize is nonzero, the given Stream is 101 /// set to be Unbuffered. This is because circular_raw_ostream 102 /// does its own buffering, so it doesn't want another layer of 103 /// buffering to be happening underneath it. 104 /// 105 /// "Owns" tells the circular_raw_ostream whether it is 106 /// responsible for managing the held stream, doing memory 107 /// management of it, etc. 108 /// 109 circular_raw_ostream(raw_ostream &Stream, const char *Header, 110 size_t BuffSize = 0, bool Owns = REFERENCE_ONLY) 111 : raw_ostream(/*unbuffered*/ true), TheStream(nullptr), 112 OwnsStream(Owns), BufferSize(BuffSize), BufferArray(nullptr), 113 Filled(false), Banner(Header) { 114 if (BufferSize != 0) 115 BufferArray = new char[BufferSize]; 116 Cur = BufferArray; 117 setStream(Stream, Owns); 118 } 119 120 ~circular_raw_ostream() override { 121 flush(); 122 flushBufferWithBanner(); 123 releaseStream(); 124 delete[] BufferArray; 125 } 126 127 /// setStream - Tell the circular_raw_ostream to output a 128 /// different stream. "Owns" tells circular_raw_ostream whether 129 /// it should take responsibility for managing the underlying 130 /// stream. 131 /// 132 void setStream(raw_ostream &Stream, bool Owns = REFERENCE_ONLY) { 133 releaseStream(); 134 TheStream = &Stream; 135 OwnsStream = Owns; 136 } 137 138 /// flushBufferWithBanner - Force output of the buffer along with 139 /// a small header. 140 /// 141 void flushBufferWithBanner(); 142 143 private: 144 /// releaseStream - Delete the held stream if needed. Otherwise, 145 /// transfer the buffer settings from this circular_raw_ostream 146 /// back to the underlying stream. 147 /// 148 void releaseStream() { 149 if (!TheStream) 150 return; 151 if (OwnsStream) 152 delete TheStream; 153 } 154 }; 155 } // end llvm namespace 156 157 158 #endif 159
