xdelta3-main.h

Linux下一个可以比较二进制文件的工具xdelta3.0u的源码。

static char* ext_tmpfile = NULL;

/* Like write(), but makes repeated calls to empty the buffer. */
static int
main_pipe_write (int outfd, uint8_t *exist_buf, usize_t remain)
{
  int ret;

  if ((ret = xd3_posix_io (outfd, exist_buf, remain,
			   (xd3_posix_func*) &write, NULL)))
    {
      XPR(NT "pipe write failed: %s", xd3_mainerror (ret));
      return ret;
    }

  return 0;
}

/* A simple error-reporting waitpid interface. */
static int
main_waitpid_check(pid_t pid)
{
  int status;
  int ret = 0;

  if (waitpid (pid, & status, 0) < 0)
    {
      ret = get_errno ();
      XPR(NT "compression subprocess: wait: %s\n", xd3_mainerror (ret));
    }
  else if (! WIFEXITED (status))
    {
      ret = ECHILD;
      XPR(NT "compression subprocess: signal %d\n",
	 WIFSIGNALED (status) ? WTERMSIG (status) : WSTOPSIG (status));
    }
  else if (WEXITSTATUS (status) != 0)
    {
      ret = ECHILD;
      XPR(NT "compression subprocess: exit %d\n", WEXITSTATUS (status));
    }

  return ret;
}

/* Wait for any existing child processes to check for abnormal exit. */
static int
main_external_compression_finish (void)
{
  int i;
  int ret;

  for (i = 0; i < 2; i += 1)
    {
      if (! ext_subprocs[i]) { continue; }

      if ((ret = main_waitpid_check (ext_subprocs[i])))
	{
	  return ret;
	}
    }

  return 0;
}

/* This runs as a forked process of main_input_decompress_setup() to
 * copy input to the decompression process.  First, the available
 * input is copied out of the existing buffer, then the buffer is
 * reused to continue reading from the compressed input file. */
static int
main_pipe_copier (uint8_t    *pipe_buf,
		  usize_t      pipe_bufsize,
		  usize_t      nread,
		  main_file   *ifile,
		  int         outfd)
{
  int ret;

  for (;;)
    {
      if (nread > 0 && (ret = main_pipe_write (outfd, pipe_buf, nread)))
	{
	  return ret;
	}

      if (nread < pipe_bufsize)
	{
	  break;
	}

      if ((ret = main_file_read (ifile, pipe_buf, pipe_bufsize,
				 & nread, "pipe read failed")) < 0)
	{
	  return ret;
	}
    }

  return 0;
}

/* This function is called after we have read some amount of data from
 * the input file and detected a compressed input.  Here we start a
 * decompression subprocess by forking twice.  The first process runs
 * the decompression command, the second process copies data to the
 * input of the first. */
static int
main_input_decompress_setup (const main_extcomp     *decomp,
			     main_file              *ifile,
			     uint8_t               *input_buf,
			     usize_t                 input_bufsize,
			     uint8_t               *pipe_buf,
			     usize_t                 pipe_bufsize,
			     usize_t                 pipe_avail,
			     usize_t                *nread)
{
  /* The two pipes: input and output file descriptors. */
  int outpipefd[2], inpipefd[2];
  int input_fd = -1;  /* The resulting input_fd (output of decompression). */
  pid_t decomp_id, copier_id;  /* The two subprocs. */
  int ret;

  outpipefd[0] = outpipefd[1] = -1;
  inpipefd[0]  = inpipefd[1]  = -1;

  if (pipe (outpipefd) || pipe (inpipefd))
    {
      XPR(NT "pipe failed: %s\n", xd3_mainerror (ret = get_errno ()));
      goto pipe_cleanup;
    }

  if ((decomp_id = fork ()) < 0)
    {
      XPR(NT "fork failed: %s\n", xd3_mainerror (ret = get_errno ()));
      goto pipe_cleanup;
    }

  /* The first child runs the decompression process: */
  if (decomp_id == 0)
    {
      /* Setup pipes: write to the outpipe, read from the inpipe. */
      if (dup2 (outpipefd[PIPE_WRITE_FD], STDOUT_FILENO) < 0 ||
	  dup2 (inpipefd[PIPE_READ_FD], STDIN_FILENO) < 0 ||
	  close (outpipefd[PIPE_READ_FD]) ||
	  close (outpipefd[PIPE_WRITE_FD]) ||
	  close (inpipefd[PIPE_READ_FD]) ||
	  close (inpipefd[PIPE_WRITE_FD]) ||
	  execlp (decomp->decomp_cmdname, decomp->decomp_cmdname,
		  decomp->decomp_options, NULL))
	{
	  XPR(NT "child process %s failed to execute: %s\n",
	      decomp->decomp_cmdname, xd3_mainerror (get_errno ()));
	}

      _exit (127);
    }

  ext_subprocs[0] = decomp_id;

  if ((copier_id = fork ()) < 0)
    {
      XPR(NT "fork failed: %s\n", xd3_mainerror (ret = get_errno ()));
      goto pipe_cleanup;
    }

  /* The second child runs the copier process: */
  if (copier_id == 0)
    {
      int exitval = 0;

      if (close (inpipefd[PIPE_READ_FD]) ||
	  main_pipe_copier (pipe_buf, pipe_bufsize, pipe_avail,
			    ifile, inpipefd[PIPE_WRITE_FD]) ||
	  close (inpipefd[PIPE_WRITE_FD]))
	{
	  XPR(NT "child copier process failed: %s\n",
	      xd3_mainerror (get_errno ()));
	  exitval = 1;
	}

      _exit (exitval);
    }

  ext_subprocs[1] = copier_id;

  /* The parent closes both pipes after duplicating the output of
   * compression. */
  input_fd = dup (outpipefd[PIPE_READ_FD]);

  if (input_fd < 0 ||
      main_file_close (ifile) ||
      close (outpipefd[PIPE_READ_FD]) ||
      close (outpipefd[PIPE_WRITE_FD]) ||
      close (inpipefd[PIPE_READ_FD]) ||
      close (inpipefd[PIPE_WRITE_FD]))
    {
      XPR(NT "dup/close failed: %s\n", xd3_mainerror (ret = get_errno ()));
      goto pipe_cleanup;
    }

#if XD3_STDIO
  /* Note: fdopen() acquires the fd, closes it when finished. */
  if ((ifile->file = fdopen (input_fd, "r")) == NULL)
    {
      XPR(NT "fdopen failed: %s\n", xd3_mainerror (ret = get_errno ()));
      goto pipe_cleanup;
    }

#elif XD3_POSIX
  ifile->file = input_fd;
#endif

  ifile->compressor = decomp;

  /* Now the input file is decompressed. */
  return main_file_read (ifile, input_buf, input_bufsize,
			 nread, "input decompression failed");

 pipe_cleanup:
  close (input_fd);
  close (outpipefd[PIPE_READ_FD]);
  close (outpipefd[PIPE_WRITE_FD]);
  close (inpipefd[PIPE_READ_FD]);
  close (inpipefd[PIPE_WRITE_FD]);
  return ret;
}


/* This routine is called when the first buffer of input data is read
 * by the main program (unless input decompression is disabled by
 * command-line option).  If it recognizes the magic number of a known
 * input type it invokes decompression.
 *
 * Skips decompression if the decompression type or the file type is
 * RD_NONEXTERNAL.
 *
 * Behaves exactly like main_file_read, otherwise.
 *
 * This function uses a separate buffer to read the first small block
 * of input.  If a compressed input is detected, the separate buffer
 * is passed to the pipe copier.  This avoids using the same size
 * buffer in both cases. */
static int
main_decompress_input_check (main_file   *ifile,
			    uint8_t    *input_buf,
			    usize_t      input_size,
			    usize_t     *nread)
{
  int ret;
  usize_t i;
  usize_t check_nread;
  uint8_t check_buf[XD3_ALLOCSIZE];

  if ((ret = main_file_read (ifile, check_buf,
			     min (input_size, XD3_ALLOCSIZE),
			     & check_nread, "input read failed")))
    {
      return ret;
    }

  for (i = 0; i < SIZEOF_ARRAY (extcomp_types); i += 1)
    {
      const main_extcomp *decomp = & extcomp_types[i];

      if ((check_nread > decomp->magic_size) &&
	  /* The following expr skips decompression if we are trying
	   * to read a VCDIFF input and that is the magic number. */
	  !((decomp->flags & RD_NONEXTERNAL) &&
	    (ifile->flags & RD_NONEXTERNAL)) &&
	  memcmp (check_buf, decomp->magic, decomp->magic_size) == 0)
	{
	  if (! option_quiet)
	    {
	      XPR(NT "%s | %s %s\n",
		 ifile->filename,
		 decomp->decomp_cmdname,
		 decomp->decomp_options);
	    }

	  return main_input_decompress_setup (decomp, ifile,
					      input_buf, input_size,
					      check_buf, XD3_ALLOCSIZE,
					      check_nread, nread);
	}
    }

  /* Now read the rest of the input block. */
  (*nread) = 0;

  if (check_nread == XD3_ALLOCSIZE)
    {
      ret = main_file_read (ifile, input_buf + XD3_ALLOCSIZE,
			    input_size - XD3_ALLOCSIZE, nread,
			    "input read failed");
    }

  memcpy (input_buf, check_buf, check_nread);

  (*nread) += check_nread;

  return 0;
}

/* This is called when the source file needs to be decompressed.  We
 * fork/exec a decompression command with the proper input and output
 * to a temporary file. */
static int
main_decompress_source (main_file *sfile, xd3_source *source)
{
  const main_extcomp *decomp = sfile->compressor;
  pid_t decomp_id;  /* One subproc. */
  int   input_fd  = -1;
  int   output_fd = -1;
  int   ret;
  char *tmpname = NULL;
  char *tmpdir  = getenv ("TMPDIR");
  static const char tmpl[] = "/xd3src.XXXXXX";

  /* Make a template for mkstmp() */
  if (tmpdir == NULL) { tmpdir = "/tmp"; }
  if ((tmpname =
       (char*) main_malloc (strlen (tmpdir) + sizeof (tmpl) + 1)) == NULL)
    {
      return ENOMEM;
    }
  sprintf (tmpname, "%s%s", tmpdir, tmpl);

  XD3_ASSERT (ext_tmpfile == NULL);
  ext_tmpfile = tmpname;

  /* Open the output FD. */
  if ((output_fd = mkstemp (tmpname)) < 0)
    {
      XPR(NT "mkstemp failed: %s: %s",
	  tmpname, xd3_mainerror (ret = get_errno ()));
      goto cleanup;
    }

  /* Copy the input FD, reset file position. */
  XD3_ASSERT (main_file_isopen (sfile));
#if XD3_STDIO
  if ((input_fd = dup (fileno (sfile->file))) < 0)
    {
      XPR(NT "dup failed: %s", xd3_mainerror (ret = get_errno ()));
      goto cleanup;
    }
  main_file_close (sfile);
  sfile->file = NULL;
#elif XD3_POSIX
  input_fd = sfile->file;
  sfile->file = -1;
#endif

  if ((ret = lseek (input_fd, SEEK_SET, 0)) != 0)
    {
      XPR(NT "lseek failed: : %s", xd3_mainerror (ret = get_errno ()));
      goto cleanup;
    }

  if ((decomp_id = fork ()) < 0)
    {
      XPR(NT "fork failed: %s", xd3_mainerror (ret = get_errno ()));
      goto cleanup;
    }

  /* The child runs the decompression process: */
  if (decomp_id == 0)
    {
      /* Setup pipes: write to the output file, read from the pipe. */
      if (dup2 (input_fd, STDIN_FILENO) < 0 ||
	  dup2 (output_fd, STDOUT_FILENO) < 0 ||
	  execlp (decomp->decomp_cmdname, decomp->decomp_cmdname,
		  decomp->decomp_options, NULL))
	{
	  XPR(NT "child process %s failed to execute: %s\n",
		   decomp->decomp_cmdname, xd3_mainerror (get_errno ()));
	}

      _exit (127);
    }

  close (input_fd);
  close (output_fd);
  input_fd  = -1;
  output_fd = -1;

  /* Then wait for completion. */
  if ((ret = main_waitpid_check (decomp_id)))
    {
      goto cleanup;
    }

  /* Open/stat the decompressed source file. */
  if ((ret = main_file_open (sfile, tmpname, XO_READ))) { goto cleanup; }
  if ((ret = main_file_stat (sfile, & source->size, 1))) { goto cleanup; }
  return 0;

 cleanup:
  close (input_fd);
  close (output_fd);
  if (tmpname) { free (tmpname); }
  ext_tmpfile = NULL;
  return ret;
}

/* Initiate re-compression of the output stream.  This is easier than
 * input decompression because we know beforehand that the stream will
 * be compressed, whereas the input has already been read when we
 * decide it should be decompressed.  Thus, it only requires one
 * subprocess and one pipe. */
static int
main_recompress_output (main_file *ofile)
{
  pid_t recomp_id;  /* One subproc. */
  int   pipefd[2];  /* One pipe. */
  int   output_fd = -1;
  int   ret;
  const main_extcomp *recomp = ofile->compressor;

  pipefd[0] = pipefd[1] = -1;

  if (pipe (pipefd))
    {
      XPR(NT "pipe failed: %s\n", xd3_mainerror (ret = get_errno ()));
      goto pipe_cleanup;
    }

  if ((recomp_id = fork ()) < 0)
    {
      XPR(NT "fork failed: %s\n", xd3_mainerror (ret = get_errno ()));
      goto pipe_cleanup;
    }

  /* The child runs the recompression process: */
  if (recomp_id == 0)
    {
      /* Setup pipes: write to the output file, read from the pipe. */
      if (dup2 (XFNO (ofile), STDOUT_FILENO) < 0 ||
	  dup2 (pipefd[PIPE_READ_FD], STDIN_FILENO) < 0 ||
	  close (pipefd[PIPE_READ_FD]) ||
	  close (pipefd[PIPE_WRITE_FD]) ||
	  execlp (recomp->recomp_cmdname, recomp->recomp_cmdname,
		  recomp->recomp_options, NULL))
	{
	  XPR(NT "child process %s failed to execute: %s\n",
	      recomp->recomp_cmdname, xd3_mainerror (get_errno ()));
	}

      _exit (127);
    }

  ext_subprocs[0] = recomp_id;

  /* The parent closes both pipes after duplicating the output-fd for
   * writing to the compression pipe. */
  output_fd = dup (pipefd[PIPE_WRITE_FD]);

  if (output_fd < 0 ||
      main_file_close (ofile) ||
      close (pipefd[PIPE_READ_FD]) ||
      close (pipefd[PIPE_WRITE_FD]))
    {
      XPR(NT "close failed: %s\n", xd3_mainerror (ret = get_errno ()));
      goto pipe_cleanup;
    }

#if XD3_STDIO
  /* Note: fdopen() acquires the fd, closes it when finished. */
  if ((ofile->file = fdopen (output_fd, "w")) == NULL)
    {
      XPR(NT "fdopen failed: %s\n", xd3_mainerror (ret = get_errno ()));
      goto pipe_cleanup;
    }

#elif XD3_POSIX
  ofile->file = output_fd;
#endif

  /* Now the output file will be compressed. */
  return 0;

 pipe_cleanup:
  close (output_fd);
  close (pipefd[PIPE_READ_FD]);
  close (pipefd[PIPE_WRITE_FD]);
  return ret;
}
#endif /* EXTERNAL_COMPRESSION */

/* Identify the compressor that was used based on its ident string,
 * which is passed in the application header. */
static const main_extcomp*
main_ident_compressor (const char *ident)
{
  usize_t i;

  for (i = 0; i < SIZEOF_ARRAY (extcomp_types); i += 1)
    {
      if (strcmp (extcomp_types[i].ident, ident) == 0)
	{
	  return & extcomp_types[i];
	}
    }

  return NULL;
}

/* Return the main_ex