StreamTee.h

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//===-- StreamTee.h ------------------------------------------*- 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
//
//===----------------------------------------------------------------------===//

#ifndef LLDB_UTILITY_STREAMTEE_H
#define LLDB_UTILITY_STREAMTEE_H

#include <limits.h>

#include <mutex>

#include "lldb/Utility/Stream.h"

namespace lldb_private {

class StreamTee : public Stream {
public:
  StreamTee() : Stream(), m_streams_mutex(), m_streams() {}

  StreamTee(lldb::StreamSP &stream_sp)
      : Stream(), m_streams_mutex(), m_streams() {
    // No need to lock mutex during construction
    if (stream_sp)
      m_streams.push_back(stream_sp);
  }

  StreamTee(lldb::StreamSP &stream_sp, lldb::StreamSP &stream_2_sp)
      : Stream(), m_streams_mutex(), m_streams() {
    // No need to lock mutex during construction
    if (stream_sp)
      m_streams.push_back(stream_sp);
    if (stream_2_sp)
      m_streams.push_back(stream_2_sp);
  }

  StreamTee(const StreamTee &rhs)
      : Stream(rhs), m_streams_mutex(), m_streams() {
    // Don't copy until we lock down "rhs"
    std::lock_guard<std::recursive_mutex> guard(rhs.m_streams_mutex);
    m_streams = rhs.m_streams;
  }

  ~StreamTee() override {}

  StreamTee &operator=(const StreamTee &rhs) {
    if (this != &rhs) {
      Stream::operator=(rhs);
      std::lock(m_streams_mutex, rhs.m_streams_mutex);
      std::lock_guard<std::recursive_mutex> lhs_locker(m_streams_mutex,
                                                       std::adopt_lock);
      std::lock_guard<std::recursive_mutex> rhs_locker(rhs.m_streams_mutex,
                                                       std::adopt_lock);
      m_streams = rhs.m_streams;
    }
    return *this;
  }

  void Flush() override {
    std::lock_guard<std::recursive_mutex> guard(m_streams_mutex);
    collection::iterator pos, end;
    for (pos = m_streams.begin(), end = m_streams.end(); pos != end; ++pos) {
      // Allow for our collection to contain NULL streams. This allows the
      // StreamTee to be used with hard coded indexes for clients that might
      // want N total streams with only a few that are set to valid values.
      Stream *strm = pos->get();
      if (strm)
        strm->Flush();
    }
  }

  size_t AppendStream(const lldb::StreamSP &stream_sp) {
    size_t new_idx = m_streams.size();
    std::lock_guard<std::recursive_mutex> guard(m_streams_mutex);
    m_streams.push_back(stream_sp);
    return new_idx;
  }

  size_t GetNumStreams() const {
    size_t result = 0;
    {
      std::lock_guard<std::recursive_mutex> guard(m_streams_mutex);
      result = m_streams.size();
    }
    return result;
  }

  lldb::StreamSP GetStreamAtIndex(uint32_t idx) {
    lldb::StreamSP stream_sp;
    std::lock_guard<std::recursive_mutex> guard(m_streams_mutex);
    if (idx < m_streams.size())
      stream_sp = m_streams[idx];
    return stream_sp;
  }

  void SetStreamAtIndex(uint32_t idx, const lldb::StreamSP &stream_sp) {
    std::lock_guard<std::recursive_mutex> guard(m_streams_mutex);
    // Resize our stream vector as necessary to fit as many streams as needed.
    // This also allows this class to be used with hard coded indexes that can
    // be used contain many streams, not all of which are valid.
    if (idx >= m_streams.size())
      m_streams.resize(idx + 1);
    m_streams[idx] = stream_sp;
  }

protected:
  typedef std::vector<lldb::StreamSP> collection;
  mutable std::recursive_mutex m_streams_mutex;
  collection m_streams;

  size_t WriteImpl(const void *s, size_t length) override {
    std::lock_guard<std::recursive_mutex> guard(m_streams_mutex);
    if (m_streams.empty())
      return 0;

    size_t min_bytes_written = SIZE_MAX;
    collection::iterator pos, end;
    for (pos = m_streams.begin(), end = m_streams.end(); pos != end; ++pos) {
      // Allow for our collection to contain NULL streams. This allows the
      // StreamTee to be used with hard coded indexes for clients that might
      // want N total streams with only a few that are set to valid values.
      Stream *strm = pos->get();
      if (strm) {
        const size_t bytes_written = strm->Write(s, length);
        if (min_bytes_written > bytes_written)
          min_bytes_written = bytes_written;
      }
    }
    if (min_bytes_written == SIZE_MAX)
      return 0;
    return min_bytes_written;
  }
};

} // namespace lldb_private

#endif // LLDB_UTILITY_STREAMTEE_H