subprocess-win32.cc

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// Copyright 2011 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "subprocess.h"

#include <stdio.h>
#include <windows.h>

#include <algorithm>

#include "util.h"

namespace {

void Win32Fatal(const char* function) {
  DWORD err = GetLastError();

  char* msg_buf;
  FormatMessageA(
        FORMAT_MESSAGE_ALLOCATE_BUFFER |
        FORMAT_MESSAGE_FROM_SYSTEM |
        FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        err,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (char*)&msg_buf,
        0,
        NULL);
  Fatal("%s: %s", function, msg_buf);
  LocalFree(msg_buf);
}

}  // anonymous namespace

Subprocess::Subprocess() : child_(NULL) , overlapped_() {
}

Subprocess::~Subprocess() {
  // Reap child if forgotten.
  if (child_)
    Finish();
}

HANDLE Subprocess::SetupPipe(HANDLE ioport) {
  char pipe_name[100];
  snprintf(pipe_name, sizeof(pipe_name),
           "\\\\.\\pipe\\ninja_pid%u_sp%p", GetProcessId(GetCurrentProcess()), this);

  pipe_ = ::CreateNamedPipeA(pipe_name,
                             PIPE_ACCESS_INBOUND | FILE_FLAG_OVERLAPPED,
                             PIPE_TYPE_BYTE,
                             PIPE_UNLIMITED_INSTANCES,
                             0, 0, INFINITE, NULL);
  if (pipe_ == INVALID_HANDLE_VALUE)
    Win32Fatal("CreateNamedPipe");

  if (!CreateIoCompletionPort(pipe_, ioport, (ULONG_PTR)this, 0))
    Win32Fatal("CreateIoCompletionPort");

  memset(&overlapped_, 0, sizeof(overlapped_));
  if (!ConnectNamedPipe(pipe_, &overlapped_) &&
      GetLastError() != ERROR_IO_PENDING) {
    Win32Fatal("ConnectNamedPipe");
  }

  // Get the write end of the pipe as a handle inheritable across processes.
  HANDLE output_write_handle = CreateFile(pipe_name, GENERIC_WRITE, 0,
                                          NULL, OPEN_EXISTING, 0, NULL);
  HANDLE output_write_child;
  if (!DuplicateHandle(GetCurrentProcess(), output_write_handle,
                       GetCurrentProcess(), &output_write_child,
                       0, TRUE, DUPLICATE_SAME_ACCESS)) {
    Win32Fatal("DuplicateHandle");
  }
  CloseHandle(output_write_handle);

  return output_write_child;
}

bool Subprocess::Start(SubprocessSet* set, const string& command) {
  HANDLE child_pipe = SetupPipe(set->ioport_);

  STARTUPINFOA startup_info = {};
  startup_info.cb = sizeof(STARTUPINFO);
  startup_info.dwFlags = STARTF_USESTDHANDLES;
  startup_info.hStdOutput = child_pipe;
  // TODO: what does this hook up stdin to?
  startup_info.hStdInput  = NULL;
  // TODO: is it ok to reuse pipe like this?
  startup_info.hStdError  = child_pipe;

  PROCESS_INFORMATION process_info;

  // Do not prepend 'cmd /c' on Windows, this breaks command
  // lines greater than 8,191 chars.
  if (!CreateProcessA(NULL, (char*)command.c_str(), NULL, NULL,
                      /* inherit handles */ TRUE, 0,
                      NULL, NULL,
                      &startup_info, &process_info)) {
    Win32Fatal("CreateProcess");
  }

  // Close pipe channel only used by the child.
  if (child_pipe)
    CloseHandle(child_pipe);

  CloseHandle(process_info.hThread);
  child_ = process_info.hProcess;

  return true;
}

void Subprocess::OnPipeReady() {
  DWORD bytes;
  if (!GetOverlappedResult(pipe_, &overlapped_, &bytes, TRUE)) {
    if (GetLastError() == ERROR_BROKEN_PIPE) {
      CloseHandle(pipe_);
      pipe_ = NULL;
      return;
    }
    Win32Fatal("GetOverlappedResult");
  }

  if (bytes)
    buf_.append(overlapped_buf_, bytes);

  memset(&overlapped_, 0, sizeof(overlapped_));
  if (!::ReadFile(pipe_, overlapped_buf_, sizeof(overlapped_buf_),
                  &bytes, &overlapped_)) {
    if (GetLastError() == ERROR_BROKEN_PIPE) {
      CloseHandle(pipe_);
      pipe_ = NULL;
      return;
    }
    if (GetLastError() != ERROR_IO_PENDING)
      Win32Fatal("ReadFile");
  }

  // Even if we read any bytes in the readfile call, we'll enter this
  // function again later and get them at that point.
}

bool Subprocess::Finish() {
  // TODO: add error handling for all of these.
  WaitForSingleObject(child_, INFINITE);

  DWORD exit_code = 0;
  GetExitCodeProcess(child_, &exit_code);

  CloseHandle(child_);
  child_ = NULL;

  return exit_code == 0;
}

bool Subprocess::Done() const {
  return pipe_ == NULL;
}

const string& Subprocess::GetOutput() const {
  return buf_;
}

SubprocessSet::SubprocessSet() {
  ioport_ = ::CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 1);
  if (!ioport_)
    Win32Fatal("CreateIoCompletionPort");
}

SubprocessSet::~SubprocessSet() {
  CloseHandle(ioport_);
}

void SubprocessSet::Add(Subprocess* subprocess) {
  running_.push_back(subprocess);
}

void SubprocessSet::DoWork() {
  DWORD bytes_read;
  Subprocess* subproc;
  OVERLAPPED* overlapped;

  if (!GetQueuedCompletionStatus(ioport_, &bytes_read, (PULONG_PTR)&subproc,
                                 &overlapped, INFINITE)) {
    if (GetLastError() != ERROR_BROKEN_PIPE)
      Win32Fatal("GetQueuedCompletionStatus");
  }

  subproc->OnPipeReady();

  if (subproc->Done()) {
    vector<Subprocess*>::iterator end =
        std::remove(running_.begin(), running_.end(), subproc);
    if (running_.end() != end) {
      finished_.push(subproc);
      running_.resize(end - running_.begin());
    }
  }
}

Subprocess* SubprocessSet::NextFinished() {
  if (finished_.empty())
    return NULL;
  Subprocess* subproc = finished_.front();
  finished_.pop();
  return subproc;
}