log.c

wget (command line browser) source code

struct logvprintf_state {
  char *bigmsg;
  int expected_size;
  int allocated;
};

/* Print a message to the log.  A copy of message will be saved to
   saved_log, for later reusal by log_dump_context().

   It is not possible to code this function in a "natural" way, using
   a loop, because of the braindeadness of the varargs API.
   Specifically, each call to vsnprintf() must be preceded by va_start
   and followed by va_end.  And this is possible only in the function
   that contains the `...' declaration.  The alternative would be to
   use va_copy, but that's not portable.  */

static int
logvprintf (struct logvprintf_state *state, const char *fmt, va_list args)
{
  char smallmsg[128];
  char *write_ptr = smallmsg;
  int available_size = sizeof (smallmsg);
  int numwritten;
  FILE *fp = get_log_fp ();

  if (!save_context_p)
    {
      /* In the simple case just call vfprintf(), to avoid needless
         allocation and games with vsnprintf(). */
      vfprintf (fp, fmt, args);
      goto flush;
    }

  if (state->allocated != 0)
    {
      write_ptr = state->bigmsg;
      available_size = state->allocated;
    }

  /* The GNU coding standards advise not to rely on the return value
     of sprintf().  However, vsnprintf() is a relatively new function
     missing from legacy systems.  Therefore I consider it safe to
     assume that its return value is meaningful.  On the systems where
     vsnprintf() is not available, we use the implementation from
     snprintf.c which does return the correct value.  */
  numwritten = vsnprintf (write_ptr, available_size, fmt, args);

  /* vsnprintf() will not step over the limit given by available_size.
     If it fails, it will return either -1 (POSIX?) or the number of
     characters that *would have* been written, if there had been
     enough room (C99).  In the former case, we double the
     available_size and malloc to get a larger buffer, and try again.
     In the latter case, we use the returned information to build a
     buffer of the correct size.  */

  if (numwritten == -1)
    {
      /* Writing failed, and we don't know the needed size.  Try
	 again with doubled size. */
      int newsize = available_size << 1;
      state->bigmsg = xrealloc (state->bigmsg, newsize);
      state->allocated = newsize;
      return 0;
    }
  else if (numwritten >= available_size)
    {
      /* Writing failed, but we know exactly how much space we
	 need. */
      int newsize = numwritten + 1;
      state->bigmsg = xrealloc (state->bigmsg, newsize);
      state->allocated = newsize;
      return 0;
    }

  /* Writing succeeded. */
  saved_append (write_ptr);
  fputs (write_ptr, fp);
  if (state->bigmsg)
    xfree (state->bigmsg);

 flush:
  if (flush_log_p)
    logflush ();
  else
    needs_flushing = 1;

  return 1;
}

/* Flush LOGFP.  Useful while flushing is disabled.  */
void
logflush (void)
{
  FILE *fp = get_log_fp ();
  if (fp)
    fflush (fp);
  needs_flushing = 0;
}

/* Enable or disable log flushing. */
void
log_set_flush (int flush)
{
  if (flush == flush_log_p)
    return;

  if (flush == 0)
    {
      /* Disable flushing by setting flush_log_p to 0. */
      flush_log_p = 0;
    }
  else
    {
      /* Reenable flushing.  If anything was printed in no-flush mode,
	 flush the log now.  */
      if (needs_flushing)
	logflush ();
      flush_log_p = 1;
    }
}

/* (Temporarily) disable storing log to memory.  Returns the old
   status of storing, with which this function can be called again to
   reestablish storing. */

int
log_set_save_context (int savep)
{
  int old = save_context_p;
  save_context_p = savep;
  return old;
}

/* Handle difference in va_start between pre-ANSI and ANSI C.  Note
   that we always use `...' in function definitions and let ansi2knr
   convert it for us.  */

#ifdef WGET_USE_STDARG
# define VA_START(args, arg1) va_start (args, arg1)
#else
# define VA_START(args, ignored) va_start (args)
#endif

/* Print a message to the screen or to the log.  The first argument
   defines the verbosity of the message, and the rest are as in
   printf(3).  */

void
logprintf (enum log_options o, const char *fmt, ...)
{
  va_list args;
  struct logvprintf_state lpstate;
  int done;

  check_redirect_output ();
  if (inhibit_logging)
    return;
  CHECK_VERBOSE (o);

  memset (&lpstate, '\0', sizeof (lpstate));
  do
    {
      VA_START (args, fmt);
      done = logvprintf (&lpstate, fmt, args);
      va_end (args);
    }
  while (!done);
}

#ifdef ENABLE_DEBUG
/* The same as logprintf(), but does anything only if opt.debug is
   non-zero.  */
void
debug_logprintf (const char *fmt, ...)
{
  if (opt.debug)
    {
      va_list args;
      struct logvprintf_state lpstate;
      int done;

      check_redirect_output ();
      if (inhibit_logging)
	return;

      memset (&lpstate, '\0', sizeof (lpstate));
      do
	{
	  VA_START (args, fmt);
	  done = logvprintf (&lpstate, fmt, args);
	  va_end (args);
	}
      while (!done);
    }
}
#endif /* ENABLE_DEBUG */

/* Open FILE and set up a logging stream.  If FILE cannot be opened,
   exit with status of 1.  */
void
log_init (const char *file, int appendp)
{
  if (file)
    {
      logfp = fopen (file, appendp ? "a" : "w");
      if (!logfp)
	{
	  perror (opt.lfilename);
	  exit (1);
	}
    }
  else
    {
      /* The log goes to stderr to avoid collisions with the output if
         the user specifies `-O -'.  #### Francois Pinard suggests
         that it's a better idea to print to stdout by default, and to
         stderr only if the user actually specifies `-O -'.  He says
         this inconsistency is harder to document, but is overall
         easier on the user.  */
      logfp = stderr;

      /* If the output is a TTY, enable storing, which will make Wget
         remember the last several printed messages, to be able to
         dump them to a log file in case SIGHUP or SIGUSR1 is received
         (or Ctrl+Break is pressed under Windows).  */
      if (1
#ifdef HAVE_ISATTY
	  && isatty (fileno (logfp))
#endif
	  )
	{
	  save_context_p = 1;
	}
    }
}

/* Close LOGFP, inhibit further logging and free the memory associated
   with it.  */
void
log_close (void)
{
  int i;

  if (logfp)
    fclose (logfp);
  logfp = NULL;
  inhibit_logging = 1;
  save_context_p = 0;

  for (i = 0; i < SAVED_LOG_LINES; i++)
    free_log_line (i);
  log_line_current = -1;
  trailing_line = 0;
}

/* Dump saved lines to logfp. */
static void
log_dump_context (void)
{
  int num = log_line_current;
  FILE *fp = get_log_fp ();
  if (!fp)
    return;

  if (num == -1)
    return;
  if (trailing_line)
    ROT_ADVANCE (num);
  do
    {
      struct log_ln *ln = log_lines + num;
      if (ln->content)
	fputs (ln->content, fp);
      ROT_ADVANCE (num);
    }
  while (num != log_line_current);
  if (trailing_line)
    if (log_lines[log_line_current].content)
      fputs (log_lines[log_line_current].content, fp);
  fflush (fp);
}

/* When SIGHUP or SIGUSR1 are received, the output is redirected
   elsewhere.  Such redirection is only allowed once. */
enum { RR_NONE, RR_REQUESTED, RR_DONE } redirect_request = RR_NONE;
static const char *redirect_request_signal_name;

/* Redirect output to `wget-log'.  */

static void
redirect_output (void)
{
  char *logfile = unique_name (DEFAULT_LOGFILE, 0);
  fprintf (stderr, _("\n%s received, redirecting output to `%s'.\n"),
	   redirect_request_signal_name, logfile);
  logfp = fopen (logfile, "w");
  if (!logfp)
    {
      /* Eek!  Opening the alternate log file has failed.  Nothing we
         can do but disable printing completely. */
      fprintf (stderr, _("%s: %s; disabling logging.\n"),
	       logfile, strerror (errno));
      inhibit_logging = 1;
    }
  else
    {
      /* Dump the context output to the newly opened log.  */
      log_dump_context ();
    }
  xfree (logfile);
  save_context_p = 0;
}

/* Check whether a signal handler requested the output to be
   redirected. */

static void
check_redirect_output (void)
{
  if (redirect_request == RR_REQUESTED)
    {
      redirect_request = RR_DONE;
      redirect_output ();
    }
}

/* Request redirection at a convenient time.  This may be called from
   a signal handler. */

void
log_request_redirect_output (const char *signal_name)
{
  if (redirect_request == RR_NONE && save_context_p)
    /* Request output redirection.  The request will be processed by
       check_redirect_output(), which is called from entry point log
       functions. */
    redirect_request = RR_REQUESTED;
  redirect_request_signal_name = signal_name;
}