chromeos/process_proxy/process_output_watcher.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chromeos/process_proxy/process_output_watcher.h"
   6
   7 #include <algorithm>
   8 #include <cstdio>
   9 #include <cstring>
  10
  11 #include <sys/ioctl.h>
  12 #include <sys/select.h>
  13 #include <unistd.h>
  14
  15 #include "base/logging.h"
  16 #include "base/posix/eintr_wrapper.h"
  17
  18 namespace {
  19
  20 void InitReadFdSet(int out_fd, int stop_fd, fd_set* set) {
  21   FD_ZERO(set);
  22   if (out_fd != -1)
  23     FD_SET(out_fd, set);
  24   FD_SET(stop_fd, set);
  25 }
  26
  27 void CloseFd(int* fd) {
  28   if (*fd >= 0) {
  29     if (HANDLE_EINTR(close(*fd)) != 0)
  30       DPLOG(WARNING) << "close fd " << *fd << " failed.";
  31   }
  32   *fd = -1;
  33 }
  34
  35 }  // namespace
  36
  37 namespace chromeos {
  38
  39 ProcessOutputWatcher::ProcessOutputWatcher(int out_fd, int stop_fd,
  40     const ProcessOutputCallback& callback)
  41     : out_fd_(out_fd),
  42       stop_fd_(stop_fd),
  43       on_read_callback_(callback)  {
  44   VerifyFileDescriptor(out_fd_);
  45   VerifyFileDescriptor(stop_fd_);
  46   max_fd_ = std::max(out_fd_, stop_fd_);
  47   // We want to be sure we will be able to add 0 at the end of the input, so -1.
  48   read_buffer_size_ = arraysize(read_buffer_) - 1;
  49 }
  50
  51 void ProcessOutputWatcher::Start() {
  52   WatchProcessOutput();
  53   OnStop();
  54 }
  55
  56 ProcessOutputWatcher::~ProcessOutputWatcher() {
  57   CloseFd(&out_fd_);
  58   CloseFd(&stop_fd_);
  59 }
  60
  61 void ProcessOutputWatcher::WatchProcessOutput() {
  62   while (true) {
  63     // This has to be reset with every watch cycle.
  64     fd_set rfds;
  65     DCHECK(stop_fd_ >= 0);
  66     InitReadFdSet(out_fd_, stop_fd_, &rfds);
  67
  68     int select_result =
  69         HANDLE_EINTR(select(max_fd_ + 1, &rfds, NULL, NULL, NULL));
  70
  71     if (select_result < 0) {
  72       DPLOG(WARNING) << "select failed";
  73       return;
  74     }
  75
  76     // Check if we were stopped.
  77     if (FD_ISSET(stop_fd_, &rfds)) {
  78       return;
  79     }
  80
  81     if (out_fd_ != -1 && FD_ISSET(out_fd_, &rfds)) {
  82       ReadFromFd(PROCESS_OUTPUT_TYPE_OUT, &out_fd_);
  83     }
  84   }
  85 }
  86
  87 void ProcessOutputWatcher::VerifyFileDescriptor(int fd) {
  88   CHECK_LE(0, fd);
  89   CHECK_GT(FD_SETSIZE, fd);
  90 }
  91
  92 void ProcessOutputWatcher::ReadFromFd(ProcessOutputType type, int* fd) {
  93   // We don't want to necessary read pipe until it is empty so we don't starve
  94   // other streams in case data is written faster than we read it. If there is
  95   // more than read_buffer_size_ bytes in pipe, it will be read in the next
  96   // iteration.
  97   ssize_t bytes_read = HANDLE_EINTR(read(*fd, read_buffer_, read_buffer_size_));
  98   if (bytes_read < 0)
  99     DPLOG(WARNING) << "read from buffer failed";
 100
 101   if (bytes_read > 0) {
 102     on_read_callback_.Run(type, std::string(read_buffer_, bytes_read));
 103   }
 104
 105   // If there is nothing on the output the watched process has exited (slave end
 106   // of pty is closed).
 107   if (bytes_read <= 0) {
 108     // Slave pseudo terminal has been closed, we won't need master fd anymore.
 109     CloseFd(fd);
 110
 111     // We have lost contact with the process, so report it.
 112     on_read_callback_.Run(PROCESS_OUTPUT_TYPE_EXIT, "");
 113   }
 114 }
 115
 116 void ProcessOutputWatcher::OnStop() {
 117   delete this;
 118 }
 119
 120 }  // namespace chromeos