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and outputs it when explicitly flushed. The intent is to use it in situations such as debug output logging where a signal handler can take care of flushing the buffer at program termination. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92001 91177308-0d34-0410-b5e6-96231b3b80d8
172 lines
5.1 KiB
C++
172 lines
5.1 KiB
C++
//===-- llvm/Support/circular_raw_ostream.h - Buffered streams --*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains raw_ostream implementations for streams to do circular
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// buffering of their output.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_CIRCULAR_RAW_OSTREAM_H
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#define LLVM_SUPPORT_CIRCULAR_RAW_OSTREAM_H
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#include "llvm/Support/raw_ostream.h"
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namespace llvm
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{
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/// circular_raw_ostream - A raw_ostream which *can* save its data
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/// to a circular buffer, or can pass it through directly to an
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/// underlying stream if specified with a buffer of zero.
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///
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class circular_raw_ostream : public raw_ostream {
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public:
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/// TAKE_OWNERSHIP - Tell this stream that it owns the underlying
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/// stream and is responsible for cleanup, memory management
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/// issues, etc.
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///
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static const bool TAKE_OWNERSHIP = true;
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/// REFERENCE_ONLY - Tell this stream it should not manage the
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/// held stream.
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///
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static const bool REFERENCE_ONLY = false;
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private:
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/// TheStream - The real stream we output to. We set it to be
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/// unbuffered, since we're already doing our own buffering.
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///
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raw_ostream *TheStream;
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/// OwnsStream - Are we responsible for managing the underlying
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/// stream?
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///
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bool OwnsStream;
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/// BufferSize - The size of the buffer in bytes.
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///
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size_t BufferSize;
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/// BufferArray - The actual buffer storage.
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///
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char *BufferArray;
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/// Cur - Pointer to the current output point in BufferArray.
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///
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char *Cur;
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/// Filled - Indicate whether the buffer has been completely
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/// filled. This helps avoid garbage output.
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///
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bool Filled;
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/// Banner - A pointer to a banner to print before dumping the
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/// log.
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///
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const char *Banner;
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/// flushBuffer - Dump the contents of the buffer to Stream.
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///
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void flushBuffer(void) {
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if (Filled)
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// Write the older portion of the buffer.
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TheStream->write(Cur, BufferArray + BufferSize - Cur);
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// Write the newer portion of the buffer.
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TheStream->write(BufferArray, Cur - BufferArray);
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Cur = BufferArray;
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Filled = false;
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}
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virtual void write_impl(const char *Ptr, size_t Size);
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/// current_pos - Return the current position within the stream,
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/// not counting the bytes currently in the buffer.
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///
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virtual uint64_t current_pos() const {
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// This has the same effect as calling TheStream.current_pos(),
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// but that interface is private.
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return TheStream->tell() - TheStream->GetNumBytesInBuffer();
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}
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public:
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/// circular_raw_ostream - Construct an optionally
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/// circular-buffered stream, handing it an underlying stream to
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/// do the "real" output.
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///
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/// As a side effect, if BuffSize is nonzero, the given Stream is
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/// set to be Unbuffered. This is because circular_raw_ostream
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/// does its own buffering, so it doesn't want another layer of
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/// buffering to be happening underneath it.
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///
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/// "Owns" tells the circular_raw_ostream whether it is
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/// responsible for managing the held stream, doing memory
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/// management of it, etc.
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///
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circular_raw_ostream(raw_ostream &Stream, const char *Header,
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size_t BuffSize = 0, bool Owns = REFERENCE_ONLY)
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: raw_ostream(/*unbuffered*/true),
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TheStream(0),
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OwnsStream(Owns),
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BufferSize(BuffSize),
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BufferArray(0),
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Filled(false),
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Banner(Header) {
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if (BufferSize != 0)
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BufferArray = new char[BufferSize];
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Cur = BufferArray;
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setStream(Stream, Owns);
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}
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explicit circular_raw_ostream()
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: raw_ostream(/*unbuffered*/true),
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TheStream(0),
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OwnsStream(REFERENCE_ONLY),
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BufferArray(0),
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Filled(false),
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Banner("") {
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Cur = BufferArray;
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}
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~circular_raw_ostream() {
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flush();
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flushBufferWithBanner();
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releaseStream();
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delete[] BufferArray;
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}
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/// setStream - Tell the circular_raw_ostream to output a
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/// different stream. "Owns" tells circular_raw_ostream whether
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/// it should take responsibility for managing the underlying
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/// stream.
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///
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void setStream(raw_ostream &Stream, bool Owns = REFERENCE_ONLY) {
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releaseStream();
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TheStream = &Stream;
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OwnsStream = Owns;
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}
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/// flushBufferWithBanner - Force output of the buffer along with
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/// a small header.
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///
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void flushBufferWithBanner(void);
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private:
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/// releaseStream - Delete the held stream if needed. Otherwise,
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/// transfer the buffer settings from this circular_raw_ostream
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/// back to the underlying stream.
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///
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void releaseStream() {
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if (!TheStream)
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return;
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if (OwnsStream)
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delete TheStream;
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}
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};
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} // end llvm namespace
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#endif
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