//===-- PipePosix.cpp -------------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "lldb/Host/posix/PipePosix.h"
#include "lldb/Host/FileSystem.h"
#include "lldb/Host/HostInfo.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/FileSystem.h"

#include <functional>
#include <thread>

#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>

using namespace lldb;
using namespace lldb_private;

int PipePosix::kInvalidDescriptor = -1;

enum PIPES { READ, WRITE }; // Constants 0 and 1 for READ and WRITE

// pipe2 is supported by Linux, FreeBSD v10 and higher.
// TODO: Add more platforms that support pipe2.
#if defined(__linux__) || (defined(__FreeBSD__) && __FreeBSD__ >= 10)
#define PIPE2_SUPPORTED 1
#else
#define PIPE2_SUPPORTED 0
#endif

namespace
{

constexpr auto OPEN_WRITER_SLEEP_TIMEOUT_MSECS = 100;

#if defined(FD_CLOEXEC) && !PIPE2_SUPPORTED
bool SetCloexecFlag(int fd)
{
    int flags = ::fcntl(fd, F_GETFD);
    if (flags == -1)
        return false;
    return (::fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == 0);
}
#endif

std::chrono::time_point<std::chrono::steady_clock>
Now()
{
    return std::chrono::steady_clock::now();
}

Error
SelectIO(int handle, bool is_read, const std::function<Error(bool&)> &io_handler, const std::chrono::microseconds &timeout)
{
    Error error;
    fd_set fds;
    bool done = false;

    using namespace std::chrono;

    const auto finish_time = Now() + timeout;

    while (!done)
    {
        struct timeval tv = {0, 0};
        if (timeout != microseconds::zero())
        {
            const auto remaining_dur = duration_cast<microseconds>(finish_time - Now());
            if (remaining_dur.count() <= 0)
            {
                error.SetErrorString("timeout exceeded");
                break;
            }
            const auto dur_secs = duration_cast<seconds>(remaining_dur);
            const auto dur_usecs = remaining_dur % seconds(1);

            tv.tv_sec = dur_secs.count();
            tv.tv_usec = dur_usecs.count();
        }
        else
            tv.tv_sec = 1;

        FD_ZERO(&fds);
        FD_SET(handle, &fds);

        const auto retval = ::select(handle + 1,
                                     (is_read) ? &fds : nullptr,
                                     (is_read) ? nullptr : &fds,
                                     nullptr, &tv);
        if (retval == -1)
        {
            if (errno == EINTR)
                continue;
            error.SetErrorToErrno();
            break;
        }
        if (retval == 0)
        {
            error.SetErrorString("timeout exceeded");
            break;
        }
        if (!FD_ISSET(handle, &fds))
        {
            error.SetErrorString("invalid state");
            break;
        }

        error = io_handler(done);
        if (error.Fail())
        {
          if (error.GetError() == EINTR)
              continue;
            break;
        }
    }
    return error;
}

}

PipePosix::PipePosix()
{
    m_fds[READ] = PipePosix::kInvalidDescriptor;
    m_fds[WRITE] = PipePosix::kInvalidDescriptor;
}

PipePosix::~PipePosix()
{
    Close();
}

Error
PipePosix::CreateNew(bool child_processes_inherit)
{
    if (CanRead() || CanWrite())
        return Error(EINVAL, eErrorTypePOSIX);

    Error error;
#if PIPE2_SUPPORTED
    if (::pipe2(m_fds, (child_processes_inherit) ? 0 : O_CLOEXEC) == 0)
        return error;
#else
    if (::pipe(m_fds) == 0)
    {
#ifdef FD_CLOEXEC
        if (!child_processes_inherit)
        {
            if (!SetCloexecFlag(m_fds[0]) || !SetCloexecFlag(m_fds[1]))
            {
                error.SetErrorToErrno();
                Close();
                return error;
            }
        }
#endif
        return error;
    }
#endif

    error.SetErrorToErrno();
    m_fds[READ] = PipePosix::kInvalidDescriptor;
    m_fds[WRITE] = PipePosix::kInvalidDescriptor;
    return error;
}

Error
PipePosix::CreateNew(llvm::StringRef name, bool child_process_inherit)
{
    if (CanRead() || CanWrite())
        return Error("Pipe is already opened");

    Error error;
    if (::mkfifo(name.data(), 0660) != 0)
        error.SetErrorToErrno();

    return error;
}

Error
PipePosix::CreateWithUniqueName(llvm::StringRef prefix, bool child_process_inherit, llvm::SmallVectorImpl<char>& name)
{
    llvm::SmallString<PATH_MAX> named_pipe_path;
    llvm::SmallString<PATH_MAX> pipe_spec((prefix + ".%%%%%%").str());
    FileSpec tmpdir_file_spec;
    tmpdir_file_spec.Clear();
    if (HostInfo::GetLLDBPath(ePathTypeLLDBTempSystemDir, tmpdir_file_spec))
    {
        tmpdir_file_spec.AppendPathComponent(pipe_spec.c_str());
    }
    else
    {
        tmpdir_file_spec.AppendPathComponent("/tmp");
        tmpdir_file_spec.AppendPathComponent(pipe_spec.c_str());
    }

    // It's possible that another process creates the target path after we've
    // verified it's available but before we create it, in which case we
    // should try again.
    Error error;
    do {
        llvm::sys::fs::createUniqueFile(tmpdir_file_spec.GetPath().c_str(), named_pipe_path);
        error = CreateNew(named_pipe_path, child_process_inherit);
    } while (error.GetError() == EEXIST);

    if (error.Success())
        name = named_pipe_path;
    return error;
}

Error
PipePosix::OpenAsReader(llvm::StringRef name, bool child_process_inherit)
{
    if (CanRead() || CanWrite())
        return Error("Pipe is already opened");

    int flags = O_RDONLY | O_NONBLOCK;
    if (!child_process_inherit)
        flags |= O_CLOEXEC;

    Error error;
    int fd = ::open(name.data(), flags);
    if (fd != -1)
        m_fds[READ] = fd;
    else
        error.SetErrorToErrno();

    return error;
}

Error
PipePosix::OpenAsWriterWithTimeout(llvm::StringRef name, bool child_process_inherit, const std::chrono::microseconds &timeout)
{
    if (CanRead() || CanWrite())
        return Error("Pipe is already opened");

    int flags = O_WRONLY | O_NONBLOCK;
    if (!child_process_inherit)
        flags |= O_CLOEXEC;

    using namespace std::chrono;
    const auto finish_time = Now() + timeout;

    while (!CanWrite())
    {
        if (timeout != microseconds::zero())
        {
            const auto dur = duration_cast<microseconds>(finish_time - Now()).count();
            if (dur <= 0)
                return Error("timeout exceeded - reader hasn't opened so far");
        }

        errno = 0;
        int fd = ::open(name.data(), flags);
        if (fd == -1)
        {
            const auto errno_copy = errno;
            // We may get ENXIO if a reader side of the pipe hasn't opened yet.
            if (errno_copy != ENXIO)
                return Error(errno_copy, eErrorTypePOSIX);

            std::this_thread::sleep_for(milliseconds(OPEN_WRITER_SLEEP_TIMEOUT_MSECS));
        }
        else
        {
            m_fds[WRITE] = fd;
        }
    }

    return Error();
}

int
PipePosix::GetReadFileDescriptor() const
{
    return m_fds[READ];
}

int
PipePosix::GetWriteFileDescriptor() const
{
    return m_fds[WRITE];
}

int
PipePosix::ReleaseReadFileDescriptor()
{
    const int fd = m_fds[READ];
    m_fds[READ] = PipePosix::kInvalidDescriptor;
    return fd;
}

int
PipePosix::ReleaseWriteFileDescriptor()
{
    const int fd = m_fds[WRITE];
    m_fds[WRITE] = PipePosix::kInvalidDescriptor;
    return fd;
}

void
PipePosix::Close()
{
    CloseReadFileDescriptor();
    CloseWriteFileDescriptor();
}

Error
PipePosix::Delete(llvm::StringRef name)
{
    return FileSystem::Unlink(name.data());
}

bool
PipePosix::CanRead() const
{
    return m_fds[READ] != PipePosix::kInvalidDescriptor;
}

bool
PipePosix::CanWrite() const
{
    return m_fds[WRITE] != PipePosix::kInvalidDescriptor;
}

void
PipePosix::CloseReadFileDescriptor()
{
    if (CanRead())
    {
        close(m_fds[READ]);
        m_fds[READ] = PipePosix::kInvalidDescriptor;
    }
}

void
PipePosix::CloseWriteFileDescriptor()
{
    if (CanWrite())
    {
        close(m_fds[WRITE]);
        m_fds[WRITE] = PipePosix::kInvalidDescriptor;
    }
}

Error
PipePosix::ReadWithTimeout(void *buf, size_t size, const std::chrono::microseconds &timeout, size_t &bytes_read)
{
    bytes_read = 0;
    if (!CanRead())
        return Error(EINVAL, eErrorTypePOSIX);

    auto handle = GetReadFileDescriptor();
    return SelectIO(handle,
                    true,
                    [=, &bytes_read](bool &done)
                    {
                      Error error;
                      auto result = ::read(handle,
                                           reinterpret_cast<char*>(buf) + bytes_read,
                                           size - bytes_read);
                      if (result != -1)
                      {
                          bytes_read += result;
                          if (bytes_read == size || result == 0)
                              done = true;
                      }
                      else
                          error.SetErrorToErrno();

                      return error;
                  },
                  timeout);
}

Error
PipePosix::Write(const void *buf, size_t size, size_t &bytes_written)
{
    bytes_written = 0;
    if (!CanWrite())
        return Error(EINVAL, eErrorTypePOSIX);

    auto handle = GetWriteFileDescriptor();
    return SelectIO(handle,
                    false,
                    [=, &bytes_written](bool &done)
                    {
                        Error error;
                        auto result = ::write(handle,
                                              reinterpret_cast<const char*>(buf) + bytes_written,
                                              size - bytes_written);
                        if (result != -1)
                        {
                            bytes_written += result;
                            if (bytes_written == size)
                                done = true;
                        }
                        else
                            error.SetErrorToErrno();

                        return error;
                    },
                    std::chrono::microseconds::zero());
}