Report text output and exit code for command-line operations.

apps/app_host/operation_launcher.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Creates an anonymous pipe for communicating an exit code from an operation
+// implemented by one or more subprocesses. If the original subprocess exits
+// without writing its result and without duplicating its output HANDLE into
+// some other process a failure is assumed to have occurred. Otherwise the
+// client closes its copy of the output HANDLE and the operation is considered
+// to be in progress until either its result has been read or no more valid
+// output HANDLEs remain.
+
+#include "operation_launcher.h"
+
+#include "base/command_line.h"
+#include "base/compiler_specific.h"
+#include "base/logging.h"
+#include "base/process_util.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/synchronization/lock.h"
+#include "base/threading/platform_thread.h"
+#include "base/win/scoped_handle.h"
+#include "chrome/common/chrome_switches.h"
+
+namespace app_host {
+
+namespace {
+
+// Implements a background thread to read the exit code of the child process.
+class ExitCodeReader : public base::PlatformThread::Delegate {
+ public:
+  ExitCodeReader(base::win::ScopedHandle exit_code_read)
+      : success_(false), exit_code_(0) {
+    exit_code_read_ = exit_code_read.Pass();
+  }
+
+  virtual void ThreadMain() OVERRIDE {
+    DWORD bytes_read = 0;
+    BOOL read_success = ::ReadFile(
+        exit_code_read_, &exit_code_, sizeof(exit_code_), &bytes_read, NULL);
+    if (!read_success || bytes_read != sizeof(exit_code_)) {
+        DLOG(ERROR) << "Failed to read exit code.";
+    } else {
+      success_ = true;
+    }
+  }
+
+  // Only call these accessors after the ExitCodeReader thread has completed.
+  DWORD exit_code() { return exit_code_; }
+  bool success() { return success_; }
+
+ private:
+  bool success_;
+  DWORD exit_code_;
+
+  base::win::ScopedHandle exit_code_read_;
+};
+
+}  // namespace
+
+bool LaunchOperation(const CommandLine& command_line,
+                     HANDLE output_write,
+                     DWORD* exit_code) {
+  base::win::ScopedHandle exit_code_read;
+  base::win::ScopedHandle exit_code_write;
+
+  if (::CreatePipe(exit_code_read.Receive(), exit_code_write.Receive(),
+                   NULL, 0) == 0) {
+    DPLOG(ERROR) << "CreatePipe failed.";
+    return false;
+  }
+
+  CommandLine full_command_line(command_line);
+  full_command_line.AppendSwitchASCII(
+      switches::kTaskOutputHandle,
+      base::UintToString(reinterpret_cast<int>(output_write)));
+  full_command_line.AppendSwitchASCII(
+      switches::kTaskResultHandle,
+      base::UintToString(reinterpret_cast<int>(exit_code_write.Get())));
+  full_command_line.AppendSwitchASCII(
+      switches::kTaskRemoteProcessId,
+      base::UintToString(::GetCurrentProcessId()));
+
+  base::win::ScopedHandle child_process;
+  base::win::ScopedHandle background_thread;
+
+  bool launch_result = base::LaunchProcess(full_command_line,
+                                           base::LaunchOptions(),
+                                           child_process.Receive());
+  if (!launch_result) {
+    DLOG(INFO) << "Failed to execute "
+               << full_command_line.GetCommandLineString();
+    return false;
+  }
+
+  DLOG(INFO) << "Executed " << full_command_line.GetCommandLineString();
+
+  ExitCodeReader exit_code_reader(exit_code_read.Pass());
+  base::PlatformThread::Create(
+      0, &exit_code_reader, background_thread.Receive());
+
+  HANDLE handles[] = {child_process.Get(), background_thread.Get()};
+  DWORD wait_result = WaitForMultipleObjects(2, handles, FALSE, INFINITE);
+  switch (wait_result) {
+    case WAIT_FAILED:
+      DLOG(ERROR) << "Wait for operation failed.";
+      break;
+    case WAIT_OBJECT_0:
+      // The child process exited. If the operation is still in progress
+      // (delegated to a tertiary process) that process is required to have
+      // duplicated the write handles by now; the closing of all outstanding
+      // handles to exit_code_write will be our signal that the operation has
+      // completed.
+      exit_code_write.Close();
+      break;
+    case WAIT_OBJECT_0 + 1:
+      // The reader thread has completed. We have read (or permanently failed to
+      // read) the operation exit code. The child process may or may not exit at
+      // this point, but we already have everything we need.
+      break;
+    default:
+      NOTREACHED();
+      return false;
+  }
+
+  // Whether or not the thread is still running, allow Join to do whatever
+  // cleanup is required.
+  base::PlatformThread::Join(background_thread.Take());
+
+  if (exit_code_reader.success())
+    *exit_code = exit_code_reader.exit_code();
+  return exit_code_reader.success();
+}
+
+}  // namespace app_host