log.c

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logflush (void)
{
  FILE *fp = get_log_fp ();
  if (fp)
    fflush (fp);
  needs_flushing = false;
}

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

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

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

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

/* 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;
  bool done;

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

  xzero (lpstate);
  do
    {
      va_start (args, fmt);
      done = log_vprintf_internal (&lpstate, fmt, args);
      va_end (args);
    }
  while (!done);
}

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

      check_redirect_output ();
      if (inhibit_logging)
        return;

      xzero (lpstate);
      do
        {
          va_start (args, fmt);
          done = log_vprintf_internal (&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, bool appendp)
{
  if (file)
    {
      logfp = fopen (file, appendp ? "a" : "w");
      if (!logfp)
        {
          fprintf (stderr, "%s: %s: %s\n", exec_name, file, strerror (errno));
          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 (1
#ifdef HAVE_ISATTY
          && isatty (fileno (logfp))
#endif
          )
        {
          /* If the output is a TTY, enable save context, i.e. store
             the most recent several messages ("context") and dump
             them to a log file in case SIGHUP or SIGUSR1 is received
             (or Ctrl+Break is pressed under Windows).  */
          save_context_p = true;
        }
    }
}

/* 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 = true;
  save_context_p = false;

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

/* 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);
}

/* String escape functions. */

/* Return the number of non-printable characters in SOURCE.
   Non-printable characters are determined as per safe-ctype.c.  */

static int
count_nonprint (const char *source)
{
  const char *p;
  int cnt;
  for (p = source, cnt = 0; *p; p++)
    if (!ISPRINT (*p))
      ++cnt;
  return cnt;
}

/* Copy SOURCE to DEST, escaping non-printable characters.

   Non-printable refers to anything outside the non-control ASCII
   range (32-126) which means that, for example, CR, LF, and TAB are
   considered non-printable along with ESC, BS, and other control
   chars.  This is by design: it makes sure that messages from remote
   servers cannot be easily used to deceive the users by mimicking
   Wget's output.  Disallowing non-ASCII characters is another
   necessary security measure, which makes sure that remote servers
   cannot garble the screen or guess the local charset and perform
   homographic attacks.

   Of course, the above mandates that escnonprint only be used in
   contexts expected to be ASCII, such as when printing host names,
   URL components, HTTP headers, FTP server messages, and the like.

   ESCAPE is the leading character of the escape sequence.  BASE
   should be the base of the escape sequence, and must be either 8 for
   octal or 16 for hex.

   DEST must point to a location with sufficient room to store an
   encoded version of SOURCE.  */

static void
copy_and_escape (const char *source, char *dest, char escape, int base)
{
  const char *from = source;
  char *to = dest;
  unsigned char c;

  /* Copy chars from SOURCE to DEST, escaping non-printable ones. */
  switch (base)
    {
    case 8:
      while ((c = *from++) != '\0')
        if (ISPRINT (c))
          *to++ = c;
        else
          {
            *to++ = escape;
            *to++ = '0' + (c >> 6);
            *to++ = '0' + ((c >> 3) & 7);
            *to++ = '0' + (c & 7);
          }
      break;
    case 16:
      while ((c = *from++) != '\0')
        if (ISPRINT (c))
          *to++ = c;
        else
          {
            *to++ = escape;
            *to++ = XNUM_TO_DIGIT (c >> 4);
            *to++ = XNUM_TO_DIGIT (c & 0xf);
          }
      break;
    default:
      abort ();
    }
  *to = '\0';
}

#define RING_SIZE 3
struct ringel {
  char *buffer;
  int size;
};
static struct ringel ring[RING_SIZE];   /* ring data */

static const char *
escnonprint_internal (const char *str, char escape, int base)
{
  static int ringpos;                   /* current ring position */
  int nprcnt;

  assert (base == 8 || base == 16);

  nprcnt = count_nonprint (str);
  if (nprcnt == 0)
    /* If there are no non-printable chars in STR, don't bother
       copying anything, just return STR.  */
    return str;

  {
    /* Set up a pointer to the current ring position, so we can write
       simply r->X instead of ring[ringpos].X. */
    struct ringel *r = ring + ringpos;

    /* Every non-printable character is replaced with the escape char
       and three (or two, depending on BASE) *additional* chars.  Size
       must also include the length of the original string and one
       additional char for the terminating \0. */
    int needed_size = strlen (str) + 1 + (base == 8 ? 3 * nprcnt : 2 * nprcnt);

    /* If the current buffer is uninitialized or too small,
       (re)allocate it.  */
    if (r->buffer == NULL || r->size < needed_size)
      {
        r->buffer = xrealloc (r->buffer, needed_size);
        r->size = needed_size;
      }

    copy_and_escape (str, r->buffer, escape, base);
    ringpos = (ringpos + 1) % RING_SIZE;
    return r->buffer;
  }
}

/* Return a pointer to a static copy of STR with the non-printable
   characters escaped as \ooo.  If there are no non-printable
   characters in STR, STR is returned.  See copy_and_escape for more
   information on which characters are considered non-printable.

   DON'T call this function on translated strings because escaping
   will break them.  Don't call it on literal strings from the source,
   which are by definition trusted.  If newlines are allowed in the
   string, escape and print it line by line because escaping the whole
   string will convert newlines to \012.  (This is so that expectedly
   single-line messages cannot use embedded newlines to mimic Wget's
   output and deceive the user.)

   escnonprint doesn't quote its escape character because it is notf
   meant as a general and reversible quoting mechanism, but as a quick
   way to defang binary junk sent by malicious or buggy servers.

   NOTE: since this function can return a pointer to static data, be
   careful to copy its result before calling it again.  However, to be
   more useful with printf, it maintains an internal ring of static
   buffers to return.  Currently the ring size is 3, which means you
   can print up to three values in the same printf; if more is needed,
   bump RING_SIZE.  */

const char *
escnonprint (const char *str)
{
  return escnonprint_internal (str, '\\', 8);
}

/* Return a pointer to a static copy of STR with the non-printable
   characters escaped as %XX.  If there are no non-printable
   characters in STR, STR is returned.

   See escnonprint for usage details.  */

const char *
escnonprint_uri (const char *str)
{
  return escnonprint_internal (str, '%', 16);
}

void
log_cleanup (void)
{
  int i;
  for (i = 0; i < countof (ring); i++)
    xfree_null (ring[i].buffer);
}

/* When SIGHUP or SIGUSR1 are received, the output is redirected
   elsewhere.  Such redirection is only allowed once. */
static 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;
  logfp = unique_create (DEFAULT_LOGFILE, false, &logfile);
  if (logfp)
    {
      fprintf (stderr, _("\n%s received, redirecting output to `%s'.\n"),
               redirect_request_signal_name, logfile);
      xfree (logfile);
      /* Dump the context output to the newly opened log.  */
      log_dump_context ();
    }
  else
    {
      /* Eek!  Opening the alternate log file has failed.  Nothing we
         can do but disable printing completely. */
      fprintf (stderr, _("\n%s received.\n"), redirect_request_signal_name);
      fprintf (stderr, _("%s: %s; disabling logging.\n"),
               logfile, strerror (errno));
      inhibit_logging = true;
    }
  save_context_p = false;
}

/* 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;
}