//===-- llvm/Support/circular_raw_ostream.h - Buffered streams --*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// 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 constexpr bool TAKE_OWNERSHIP = true;
/// REFERENCE_ONLY - Tell this stream it should not manage the
/// held stream.
///
static constexpr 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 = nullptr;
/// 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 = nullptr;
/// 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 = false;
/// 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() {
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;
}
void write_impl(const char *Ptr, size_t Size) override;
/// current_pos - Return the current position within the stream,
/// not counting the bytes currently in the buffer.
///
uint64_t current_pos() const override {
// 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), OwnsStream(Owns),
BufferSize(BuffSize), Banner(Header) {
if (BufferSize != 0)
BufferArray = new char[BufferSize];
Cur = BufferArray;
setStream(Stream, Owns);
}
~circular_raw_ostream() override {
flush();
flushBufferWithBanner();
releaseStream();
delete[] BufferArray;
}
bool is_displayed() const override {
return TheStream->is_displayed();
}
/// 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();
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