From: David Greene Date: Wed, 23 Dec 2009 16:08:15 +0000 (+0000) Subject: Add circular_raw_ostream, which buffers its output in a circular queue X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=e59011e7d913b59dd244b0295a984dcfe7976e72;p=oota-llvm.git Add circular_raw_ostream, which buffers its output in a circular queue 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 --- diff --git a/include/llvm/Support/circular_raw_ostream.h b/include/llvm/Support/circular_raw_ostream.h new file mode 100644 index 00000000000..2b3c329b586 --- /dev/null +++ b/include/llvm/Support/circular_raw_ostream.h @@ -0,0 +1,171 @@ +//===-- llvm/Support/circular_raw_ostream.h - Buffered streams --*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file contains raw_ostream implementations for streams to do circular +// buffering of their output. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_SUPPORT_CIRCULAR_RAW_OSTREAM_H +#define LLVM_SUPPORT_CIRCULAR_RAW_OSTREAM_H + +#include "llvm/Support/raw_ostream.h" + +namespace llvm +{ + /// 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. + /// + class circular_raw_ostream : public raw_ostream { + public: + /// TAKE_OWNERSHIP - Tell this stream that it owns the underlying + /// stream and is responsible for cleanup, memory management + /// issues, etc. + /// + static const bool TAKE_OWNERSHIP = true; + + /// REFERENCE_ONLY - Tell this stream it should not manage the + /// held stream. + /// + static const bool REFERENCE_ONLY = false; + + private: + /// TheStream - The real stream we output to. We set it to be + /// unbuffered, since we're already doing our own buffering. + /// + raw_ostream *TheStream; + + /// OwnsStream - Are we responsible for managing the underlying + /// stream? + /// + bool OwnsStream; + + /// BufferSize - The size of the buffer in bytes. + /// + size_t BufferSize; + + /// BufferArray - The actual buffer storage. + /// + char *BufferArray; + + /// Cur - Pointer to the current output point in BufferArray. + /// + char *Cur; + + /// Filled - Indicate whether the buffer has been completely + /// filled. This helps avoid garbage output. + /// + bool Filled; + + /// Banner - A pointer to a banner to print before dumping the + /// log. + /// + const char *Banner; + + /// flushBuffer - Dump the contents of the buffer to Stream. + /// + void flushBuffer(void) { + if (Filled) + // Write the older portion of the buffer. + TheStream->write(Cur, BufferArray + BufferSize - Cur); + // Write the newer portion of the buffer. + TheStream->write(BufferArray, Cur - BufferArray); + Cur = BufferArray; + Filled = false; + } + + virtual void write_impl(const char *Ptr, size_t Size); + + /// current_pos - Return the current position within the stream, + /// not counting the bytes currently in the buffer. + /// + virtual uint64_t current_pos() const { + // This has the same effect as calling TheStream.current_pos(), + // but that interface is private. + return TheStream->tell() - TheStream->GetNumBytesInBuffer(); + } + + public: + /// circular_raw_ostream - Construct an optionally + /// circular-buffered stream, handing it an underlying stream to + /// do the "real" output. + /// + /// As a side effect, if BuffSize is nonzero, the given Stream is + /// set to be Unbuffered. This is because circular_raw_ostream + /// does its own buffering, so it doesn't want another layer of + /// buffering to be happening underneath it. + /// + /// "Owns" tells the circular_raw_ostream whether it is + /// responsible for managing the held stream, doing memory + /// management of it, etc. + /// + circular_raw_ostream(raw_ostream &Stream, const char *Header, + size_t BuffSize = 0, bool Owns = REFERENCE_ONLY) + : raw_ostream(/*unbuffered*/true), + TheStream(0), + OwnsStream(Owns), + BufferSize(BuffSize), + BufferArray(0), + Filled(false), + Banner(Header) { + if (BufferSize != 0) + BufferArray = new char[BufferSize]; + Cur = BufferArray; + setStream(Stream, Owns); + } + explicit circular_raw_ostream() + : raw_ostream(/*unbuffered*/true), + TheStream(0), + OwnsStream(REFERENCE_ONLY), + BufferArray(0), + Filled(false), + Banner("") { + Cur = BufferArray; + } + + ~circular_raw_ostream() { + flush(); + flushBufferWithBanner(); + releaseStream(); + delete[] BufferArray; + } + + /// setStream - Tell the circular_raw_ostream to output a + /// different stream. "Owns" tells circular_raw_ostream whether + /// it should take responsibility for managing the underlying + /// stream. + /// + void setStream(raw_ostream &Stream, bool Owns = REFERENCE_ONLY) { + releaseStream(); + TheStream = &Stream; + OwnsStream = Owns; + } + + /// flushBufferWithBanner - Force output of the buffer along with + /// a small header. + /// + void flushBufferWithBanner(void); + + private: + /// releaseStream - Delete the held stream if needed. Otherwise, + /// transfer the buffer settings from this circular_raw_ostream + /// back to the underlying stream. + /// + void releaseStream() { + if (!TheStream) + return; + if (OwnsStream) + delete TheStream; + } + }; +} // end llvm namespace + + +#endif diff --git a/lib/Support/circular_raw_ostream.cpp b/lib/Support/circular_raw_ostream.cpp new file mode 100644 index 00000000000..e52996dc505 --- /dev/null +++ b/lib/Support/circular_raw_ostream.cpp @@ -0,0 +1,47 @@ +//===- circulat_raw_ostream.cpp - Implement the circular_raw_ostream class -===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This implements support for circular buffered streams. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Support/circular_raw_ostream.h" + +#include + +using namespace llvm; + +void circular_raw_ostream::write_impl(const char *Ptr, size_t Size) { + if (BufferSize == 0) { + TheStream->write(Ptr, Size); + return; + } + + // Write into the buffer, wrapping if necessary. + while (Size != 0) { + unsigned Bytes = std::min(Size, BufferSize - (Cur - BufferArray)); + memcpy(Cur, Ptr, Bytes); + Size -= Bytes; + Cur += Bytes; + if (Cur == BufferArray + BufferSize) { + // Reset the output pointer to the start of the buffer. + Cur = BufferArray; + Filled = true; + } + } +} + +void circular_raw_ostream::flushBufferWithBanner(void) { + if (BufferSize != 0) { + // Write out the buffer + int num = std::strlen(Banner); + TheStream->write(Banner, num); + flushBuffer(); + } +}