node/src/node_child_process.cc

// Copyright 2009 Ryan Dahl <ry@tinyclouds.org>
#include <node_child_process.h>

#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>

extern char **environ;

namespace node {

using namespace v8;

Persistent<FunctionTemplate> ChildProcess::constructor_template;

static Persistent<String> pid_symbol;
static Persistent<String> exit_symbol;
static Persistent<String> output_symbol;
static Persistent<String> error_symbol;

void ChildProcess::Initialize(Handle<Object> target) {
  HandleScope scope;

  Local<FunctionTemplate> t = FunctionTemplate::New(ChildProcess::New);
  constructor_template = Persistent<FunctionTemplate>::New(t);
  constructor_template->Inherit(EventEmitter::constructor_template);
  constructor_template->InstanceTemplate()->SetInternalFieldCount(1);
  constructor_template->SetClassName(String::NewSymbol("ChildProcess"));

  pid_symbol = NODE_PSYMBOL("pid");
  exit_symbol = NODE_PSYMBOL("exit");
  output_symbol = NODE_PSYMBOL("output");
  error_symbol = NODE_PSYMBOL("error");

  NODE_SET_PROTOTYPE_METHOD(constructor_template, "spawn", ChildProcess::Spawn);
  NODE_SET_PROTOTYPE_METHOD(constructor_template, "write", ChildProcess::Write);
  NODE_SET_PROTOTYPE_METHOD(constructor_template, "close", ChildProcess::Close);
  NODE_SET_PROTOTYPE_METHOD(constructor_template, "kill", ChildProcess::Kill);

  target->Set(String::NewSymbol("ChildProcess"),
      constructor_template->GetFunction());
}

Handle<Value> ChildProcess::New(const Arguments& args) {
  HandleScope scope;

  ChildProcess *p = new ChildProcess();
  p->Wrap(args.Holder());

  return args.This();
}

// This is an internal function. The third argument should be an array
// of key value pairs seperated with '='.
Handle<Value> ChildProcess::Spawn(const Arguments& args) {
  HandleScope scope;

  if ( args.Length() != 3
    || !args[0]->IsString()
    || !args[1]->IsArray()
    || !args[2]->IsArray()
     )
  {
    return ThrowException(Exception::Error(String::New("Bad argument.")));
  }

  ChildProcess *child = ObjectWrap::Unwrap<ChildProcess>(args.Holder());

  String::Utf8Value file(args[0]->ToString());

  int i;

  // Copy second argument args[1] into a c-string array called argv.
  // The array must be null terminated, and the first element must be
  // the name of the executable -- hence the complication.
  Local<Array> argv_handle = Local<Array>::Cast(args[1]);
  int argc = argv_handle->Length();
  int argv_length = argc + 1 + 1;
  char **argv = new char*[argv_length]; // heap allocated to detect errors
  argv[0] = strdup(*file); // + 1 for file
  argv[argv_length-1] = NULL;  // + 1 for NULL;
  for (i = 0; i < argc; i++) {
    String::Utf8Value arg(argv_handle->Get(Integer::New(i))->ToString());
    argv[i+1] = strdup(*arg);
  }

  // Copy third argument, args[2], into a c-string array called env.
  Local<Array> env_handle = Local<Array>::Cast(args[2]);
  int envc = env_handle->Length();
  char **env = new char*[envc+1]; // heap allocated to detect errors
  env[envc] = NULL;
  for (int i = 0; i < envc; i++) {
    String::Utf8Value pair(env_handle->Get(Integer::New(i))->ToString());
    env[i] = strdup(*pair);
  }

  int r = child->Spawn(argv[0], argv, env);

  for (i = 0; i < argv_length; i++) free(argv[i]);
  delete [] argv;

  for (i = 0; i < envc; i++) free(env[i]);
  delete [] env;

  if (r != 0) {
    return ThrowException(Exception::Error(String::New("Error spawning")));
  }

  child->handle_->Set(pid_symbol, Integer::New(child->pid_));

  return Undefined();
}

Handle<Value> ChildProcess::Write(const Arguments& args) {
  HandleScope scope;
  ChildProcess *child = ObjectWrap::Unwrap<ChildProcess>(args.Holder());
  assert(child);

  enum encoding enc = ParseEncoding(args[1]);
  ssize_t len = DecodeBytes(args[0], enc);

  if (len < 0) {
    Local<Value> exception = Exception::TypeError(String::New("Bad argument"));
    return ThrowException(exception);
  }

  char * buf = new char[len];
  ssize_t written = DecodeWrite(buf, len, args[0], enc);
  assert(written == len);
  int r = child->Write(buf, len);
  delete [] buf;

  return r == 0 ? True() : False();
}

Handle<Value> ChildProcess::Kill(const Arguments& args) {
  HandleScope scope;
  ChildProcess *child = ObjectWrap::Unwrap<ChildProcess>(args.Holder());
  assert(child);

  int sig = SIGTERM;

  if (args.Length() > 0) {
    if (args[0]->IsNumber()) {
      sig = args[0]->Int32Value();
    } else if (args[0]->IsString()) {
      Local<String> signame = args[0]->ToString();
      Local<Object> process = Context::GetCurrent()->Global();
      Local<Object> node_obj = process->Get(String::NewSymbol("process"))->ToObject();

      Local<Value> sig_v = node_obj->Get(signame);
      if (!sig_v->IsNumber()) {
        return ThrowException(Exception::Error(String::New("Unknown signal")));
      }
      sig = sig_v->Int32Value();
    }
  }

  if (child->Kill(sig) != 0) {
    return ThrowException(Exception::Error(String::New(strerror(errno))));
  }

  return Undefined();
}

Handle<Value> ChildProcess::Close(const Arguments& args) {
  HandleScope scope;
  ChildProcess *child = ObjectWrap::Unwrap<ChildProcess>(args.Holder());
  assert(child);
  return child->Close() == 0 ? True() : False();
}

void ChildProcess::reader_closed(evcom_reader *r) {
  ChildProcess *child = static_cast<ChildProcess*>(r->data);
  if (r == &child->stdout_reader_) {
    child->stdout_fd_ = -1;
  } else {
    assert(r == &child->stderr_reader_);
    child->stderr_fd_ = -1;
  }
  evcom_reader_detach(r);
  child->MaybeShutdown();
}

void ChildProcess::stdin_closed(evcom_writer *w) {
  ChildProcess *child = static_cast<ChildProcess*>(w->data);
  assert(w == &child->stdin_writer_);
  child->stdin_fd_ = -1;
  evcom_writer_detach(w);
  child->MaybeShutdown();
}

void ChildProcess::on_read(evcom_reader *r, const void *buf, size_t len) {
  ChildProcess *child = static_cast<ChildProcess*>(r->data);
  HandleScope scope;

  bool isSTDOUT = (r == &child->stdout_reader_);
  enum encoding encoding = isSTDOUT ?
    child->stdout_encoding_ : child->stderr_encoding_;

  // TODO emit 'end' event instead of null.

  Local<Value> data = len ? Encode(buf, len, encoding) : Local<Value>::New(Null());
  child->Emit(isSTDOUT ? output_symbol : error_symbol, 1, &data);
  child->MaybeShutdown();
}

ChildProcess::ChildProcess() : EventEmitter() {
  evcom_reader_init(&stdout_reader_);
  stdout_reader_.data     = this;
  stdout_reader_.on_read  = on_read;
  stdout_reader_.on_close = reader_closed;

  evcom_reader_init(&stderr_reader_);
  stderr_reader_.data     = this;
  stderr_reader_.on_read  = on_read;
  stderr_reader_.on_close = reader_closed;

  evcom_writer_init(&stdin_writer_);
  stdin_writer_.data      = this;
  stdin_writer_.on_close  = stdin_closed;

  ev_init(&child_watcher_, ChildProcess::OnCHLD);
  child_watcher_.data = this;

  stdout_fd_ = -1;
  stderr_fd_ = -1;
  stdin_fd_ = -1;

  stdout_encoding_ = UTF8;
  stderr_encoding_ = UTF8;

  got_chld_ = false;
  exit_code_ = 0;

  pid_ = 0;
}

ChildProcess::~ChildProcess() {
  Shutdown();
}

void ChildProcess::Shutdown() {
  if (stdin_fd_ >= 0) {
    evcom_writer_close(&stdin_writer_);
  }

  if (stdin_fd_  >= 0) close(stdin_fd_);
  if (stdout_fd_ >= 0) close(stdout_fd_);
  if (stderr_fd_ >= 0) close(stderr_fd_);

  stdin_fd_ = -1;
  stdout_fd_ = -1;
  stderr_fd_ = -1;

  evcom_writer_detach(&stdin_writer_);
  evcom_reader_detach(&stdout_reader_);
  evcom_reader_detach(&stderr_reader_);

  ev_child_stop(EV_DEFAULT_UC_ &child_watcher_);

  /* XXX Kill the PID? */
  pid_ = 0;
}

static inline int SetNonBlocking(int fd) {
  int flags = fcntl(fd, F_GETFL, 0);
  int r = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
  if (r != 0) {
    perror("SetNonBlocking()");
  }
  return r;
}

// Note that args[0] must be the same as the "file" param.  This is an
// execvp() requirement.
int ChildProcess::Spawn(const char *file, char *const args[], char **env) {
  assert(pid_ == 0);
  assert(stdout_fd_ == -1);
  assert(stderr_fd_ == -1);
  assert(stdin_fd_ == -1);

  int stdout_pipe[2], stdin_pipe[2], stderr_pipe[2];

  /* An implementation of popen(), basically */
  if (pipe(stdout_pipe) < 0) {
    perror("pipe()");
    return -1;
  }

  if (pipe(stderr_pipe) < 0) {
    perror("pipe()");
    return -2;
  }

  if (pipe(stdin_pipe) < 0) {
    perror("pipe()");
    return -3;
  }

  // Save environ in the case that we get it clobbered
  // by the child process.
  char **save_our_env = environ;

  switch (pid_ = vfork()) {
    case -1:  // Error.
      Shutdown();
      return -4;

    case 0:  // Child.
      close(stdout_pipe[0]);  // close read end
      dup2(stdout_pipe[1], STDOUT_FILENO);

      close(stderr_pipe[0]);  // close read end
      dup2(stderr_pipe[1], STDERR_FILENO);

      close(stdin_pipe[1]);  // close write end
      dup2(stdin_pipe[0],  STDIN_FILENO);

      environ = env;

      execvp(file, args);
      perror("execvp()");
      _exit(127);
  }

  // Restore environment.
  environ = save_our_env;

  // Parent.

  ev_child_set(&child_watcher_, pid_, 0);
  ev_child_start(EV_DEFAULT_UC_ &child_watcher_);

  close(stdout_pipe[1]);
  stdout_fd_ = stdout_pipe[0];
  SetNonBlocking(stdout_fd_);

  close(stderr_pipe[1]);
  stderr_fd_ = stderr_pipe[0];
  SetNonBlocking(stderr_fd_);

  close(stdin_pipe[0]);
  stdin_fd_ = stdin_pipe[1];
  SetNonBlocking(stdin_fd_);

  evcom_reader_set(&stdout_reader_, stdout_fd_);
  evcom_reader_attach(EV_DEFAULT_UC_ &stdout_reader_);

  evcom_reader_set(&stderr_reader_, stderr_fd_);
  evcom_reader_attach(EV_DEFAULT_UC_ &stderr_reader_);

  evcom_writer_set(&stdin_writer_, stdin_fd_);
  evcom_writer_attach(EV_DEFAULT_UC_ &stdin_writer_);

  Ref();

  return 0;
}

void ChildProcess::OnCHLD(EV_P_ ev_child *watcher, int revents) {
  ev_child_stop(EV_A_ watcher);
  ChildProcess *child = static_cast<ChildProcess*>(watcher->data);

  assert(revents == EV_CHILD);
  assert(child->pid_ == watcher->rpid);
  assert(&child->child_watcher_ == watcher);

  child->got_chld_ = true;
  child->exit_code_ = watcher->rstatus;

  if (child->stdin_fd_  >= 0) evcom_writer_close(&child->stdin_writer_);

  child->MaybeShutdown();
}

int ChildProcess::Write(const char *str, size_t len) {
  if (stdin_fd_ < 0 || got_chld_) return -1;
  evcom_writer_write(&stdin_writer_, str, len);
  return 0;
}

int ChildProcess::Close(void) {
  if (stdin_fd_ < 0 || got_chld_) return -1;
  evcom_writer_close(&stdin_writer_);
  return 0;
}

int ChildProcess::Kill(int sig) {
  if (got_chld_ || pid_ == 0) return -1;
  return kill(pid_, sig);
}

void ChildProcess::MaybeShutdown(void) {
  if (stdout_fd_ < 0 && stderr_fd_ < 0 && got_chld_) {
    HandleScope scope;
    Handle<Value> argv[1] = { Integer::New(exit_code_) };
    Emit(exit_symbol, 1, argv);
    Shutdown();
    Unref();
  }
}

}  // namespace node