* tests/ports.test ("string ports"): test seeking/unreading from

[bpt/guile.git] / libguile / strports.c

/*	Copyright (C) 1995,1996,1998,1999 Free Software Foundation, Inc.
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 * 
 * You should have received a copy of the GNU General Public License
 * along with this software; see the file COPYING.  If not, write to
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 * Boston, MA 02111-1307 USA
 *
 * As a special exception, the Free Software Foundation gives permission
 * for additional uses of the text contained in its release of GUILE.
 *
 * The exception is that, if you link the GUILE library with other files
 * to produce an executable, this does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
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\f

#include "_scm.h"

#include <stdio.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "unif.h"
#include "eval.h"
#include "read.h"

#include "strports.h"

#ifdef HAVE_STRING_H
#include <string.h>
#endif

\f

/* {Ports - string ports}
 *
 */

/* NOTES:
   write_buf/write_end point to the ends of the allocated string.
   read_buf/read_end in principle point to the part of the string which
   has been written to, but this is only updated after a flush.
   read_pos and write_pos in principle should be equal, but this is only true
   when rw_active is SCM_PORT_NEITHER.
*/

static int
stfill_buffer (SCM port)
{
  scm_port *pt = SCM_PTAB_ENTRY (port);
  
  if (pt->read_pos >= pt->read_end)
    return EOF;
  else
    return scm_return_first (*pt->read_pos, port);
}

/* change the size of a port's string to new_size.  this doesn't
   change read_buf_size.  */
static void 
st_resize_port (scm_port *pt, off_t new_size)
{
  off_t index = pt->write_pos - pt->write_buf;

  pt->write_buf_size = new_size;

  scm_vector_set_length_x (pt->stream, SCM_MAKINUM (new_size));

  /* reset buffer in case reallocation moved the string. */
  {
    pt->read_buf = pt->write_buf = SCM_CHARS (pt->stream);
    pt->read_pos = pt->write_pos = pt->write_buf + index;
    pt->write_end = pt->write_buf + pt->write_buf_size;
    pt->read_end = pt->read_buf + pt->read_buf_size;
  }
}

/* amount by which write_buf is expanded.  */
#define SCM_WRITE_BLOCK 80

/* ensure that write_pos < write_end by enlarging the buffer when
   necessary.  update read_buf to account for written chars.  */
static void
st_flush (SCM port)
{
  scm_port *pt = SCM_PTAB_ENTRY (port);

  if (pt->write_pos == pt->write_end)
    {
      st_resize_port (pt, pt->write_buf_size + SCM_WRITE_BLOCK);
    }
  pt->read_pos = pt->write_pos;
  if (pt->read_pos > pt->read_end)
    {
      pt->read_end = (unsigned char *) pt->read_pos;
      pt->read_buf_size = pt->read_end - pt->read_buf;
    }
  pt->rw_active = SCM_PORT_NEITHER;
}

static void
st_write (SCM port, void *data, size_t size)
{
  scm_port *pt = SCM_PTAB_ENTRY (port);
  const char *input = (char *) data;

  while (size > 0)
    {
      int space = pt->write_end - pt->write_pos;
      int write_len = (size > space) ? space : size;
      
      strncpy (pt->write_pos, input, write_len);
      pt->write_pos += write_len;
      size -= write_len;
      input += write_len;
      if (write_len == space)
	st_flush (port);
    }
}

static void
st_end_input (SCM port, int offset)
{
  scm_port *pt = SCM_PTAB_ENTRY (port);
  const unsigned char *pos = pt->read_pos - offset;

  if (pos < pt->read_buf)
    scm_misc_error ("st_end_input", "negative position", SCM_EOL);
  
  pt->write_pos = (unsigned char *) pt->read_pos = pos;
  pt->rw_active = SCM_PORT_NEITHER;
}

static off_t
st_seek (SCM port, off_t offset, int whence)
{
  scm_port *pt = SCM_PTAB_ENTRY (port);
  off_t target;

  if (pt->rw_active == SCM_PORT_READ && offset == 0 && whence == SEEK_CUR)
    /* special case to avoid disturbing the unread-char buffer.  */
    {
      if (pt->read_buf == pt->putback_buf)
	{
	  target = pt->saved_read_pos - pt->saved_read_buf
	    - (pt->read_end - pt->read_pos);
	}
      else
	{
	  target = pt->read_pos - pt->read_buf;
	}
    }
  else
    /* all other cases.  */
    {
      if (pt->rw_active == SCM_PORT_WRITE)
	st_flush (port);
  
      if (pt->rw_active == SCM_PORT_READ)
	scm_end_input (port);

      switch (whence)
	{
	case SEEK_CUR:
	  target = pt->read_pos - pt->read_buf + offset;
	  break;
	case SEEK_END:
	  target = pt->read_end - pt->read_buf + offset;
	  break;
	default: /* SEEK_SET */
	  target = offset;
	  break;
	}

      if (target < 0)
	scm_misc_error ("st_seek", "negative offset", SCM_EOL);
  
      if (target >= pt->write_buf_size)
	{
	  if (!(SCM_CAR (port) & SCM_WRTNG))
	    {
	      if (target > pt->write_buf_size)
		{
		  scm_misc_error ("st_seek", 
				  "seek past end of read-only strport",
				  SCM_EOL);
		}
	    }
	  else
	    {
	      st_resize_port (pt, target + (target == pt->write_buf_size
					    ? SCM_WRITE_BLOCK
					    : 0));
	    }
	}
      pt->read_pos = pt->write_pos = pt->read_buf + target;
      if (pt->read_pos > pt->read_end)
	{
	  pt->read_end = (unsigned char *) pt->read_pos;
	  pt->read_buf_size = pt->read_end - pt->read_buf;
	}
    }
  return target;
}

static void
st_truncate (SCM port, off_t length)
{
  scm_port *pt = SCM_PTAB_ENTRY (port);

  if (length > pt->write_buf_size)
    st_resize_port (pt, length);

  pt->read_buf_size = length;
  pt->read_end = pt->read_buf + length;
  if (pt->read_pos > pt->read_end)
    pt->read_pos = pt->read_end;
  
  if (pt->write_pos > pt->read_end)
    pt->write_pos = pt->read_end;
}

SCM 
scm_mkstrport (pos, str, modes, caller)
     SCM pos;
     SCM str;
     long modes;
     const char * caller;
{
  SCM z;
  scm_port *pt;
  int str_len;

  SCM_ASSERT (SCM_INUMP(pos) && SCM_INUM(pos) >= 0, pos, SCM_ARG1, caller);
  SCM_ASSERT (SCM_NIMP(str) && SCM_ROSTRINGP(str), str, SCM_ARG1, caller);
  str_len = SCM_ROLENGTH (str);
  if (SCM_INUM (pos) > str_len)
    scm_out_of_range (caller, pos);
  if (!((modes & SCM_WRTNG) || (modes & SCM_RDNG)))
    scm_misc_error ("scm_mkstrport", "port must read or write", SCM_EOL);
  SCM_NEWCELL (z);
  SCM_DEFER_INTS;
  pt = scm_add_to_port_table (z);
  SCM_SETCAR (z, scm_tc16_strport | modes);
  SCM_SETPTAB_ENTRY (z, pt);
  SCM_SETSTREAM (z, str);
  pt->write_buf = pt->read_buf = SCM_ROCHARS (str);
  pt->read_pos = pt->write_pos = pt->read_buf + SCM_INUM (pos);
  pt->write_buf_size = pt->read_buf_size = str_len;
  pt->write_end = pt->read_end = pt->read_buf + pt->read_buf_size;

  pt->rw_random = 1;

  SCM_ALLOW_INTS;

  /* ensure write_pos is writable. */
  if ((modes & SCM_WRTNG) && pt->write_pos == pt->write_end)
    st_flush (z);
  return z;
}

/* create a new string from a string port's buffer.  */
SCM scm_strport_to_string (SCM port)
{
  scm_port *pt = SCM_PTAB_ENTRY (port);

  if (pt->rw_active == SCM_PORT_WRITE)
    st_flush (port);
  return scm_makfromstr (pt->read_buf, pt->read_buf_size, 0);
}

SCM_PROC(s_call_with_output_string, "call-with-output-string", 1, 0, 0, scm_call_with_output_string);

SCM 
scm_call_with_output_string (proc)
     SCM proc;
{
  SCM p;

  p = scm_mkstrport (SCM_INUM0, 
		     scm_make_string (SCM_INUM0, SCM_UNDEFINED),
		     SCM_OPN | SCM_WRTNG,
		     s_call_with_output_string);
  scm_apply (proc, p, scm_listofnull);

  return scm_strport_to_string (p);
}



/* Return a Scheme string obtained by printing a given object.
 */


SCM
scm_strprint_obj (obj)
     SCM obj;
{
  SCM str;
  SCM port;

  str = scm_makstr (0, 0);
  port = scm_mkstrport (SCM_INUM0, str, SCM_OPN | SCM_WRTNG, "scm_strprint_obj");
  scm_prin1 (obj, port, 1);
  {
    return scm_strport_to_string (port);
  }
}




SCM_PROC(s_call_with_input_string, "call-with-input-string", 2, 0, 0, scm_call_with_input_string);

SCM 
scm_call_with_input_string (str, proc)
     SCM str;
     SCM proc;
{
  SCM p = scm_mkstrport(SCM_INUM0, str, SCM_OPN | SCM_RDNG, s_call_with_input_string);
  return scm_apply (proc, p, scm_listofnull);
}



/* Given a null-terminated string EXPR containing a Scheme expression
   read it, and return it as an SCM value. */
SCM
scm_read_0str (expr)
     char *expr;
{
  SCM port = scm_mkstrport (SCM_INUM0,
			    scm_makfrom0str (expr),
			    SCM_OPN | SCM_RDNG,
			    "scm_eval_0str");
  SCM form;

  /* Read expressions from that port; ignore the values.  */
  form = scm_read (port);

  scm_close_port (port);
  return form;
}

/* Given a null-terminated string EXPR containing Scheme program text,
   evaluate it, and return the result of the last expression evaluated.  */
SCM
scm_eval_0str (expr)
     char *expr;
{
  return scm_eval_string (scm_makfrom0str (expr));
}


SCM_PROC (s_eval_string, "eval-string", 1, 0, 0, scm_eval_string);

SCM
scm_eval_string (string)
     SCM string;
{
  SCM port = scm_mkstrport (SCM_INUM0, string, SCM_OPN | SCM_RDNG,
			    "scm_eval_0str");
  SCM form;
  SCM ans = SCM_UNSPECIFIED;

  /* Read expressions from that port; ignore the values.  */
  while (!SCM_EOF_OBJECT_P (form = scm_read (port)))
    ans = scm_eval_x (form);

  /* Don't close the port here; if we re-enter this function via a
     continuation, then the next time we enter it, we'll get an error.
     It's a string port anyway, so there's no advantage to closing it
     early.  */

  return ans;
}

void scm_make_stptob (void); /* Called from ports.c */

void
scm_make_stptob ()
{
  long tc = scm_make_port_type ("string", stfill_buffer, st_write);
  scm_set_port_mark        (tc, scm_markstream);
  scm_set_port_end_input   (tc, st_end_input);
  scm_set_port_flush       (tc, st_flush);
  scm_set_port_seek        (tc, st_seek);
  scm_set_port_truncate    (tc, st_truncate);
}

void
scm_init_strports ()
{
#include "strports.x"
}