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

/* Copyright (C) 1995,1996,1998,1999,2000,2001,2002, 2003 Free Software Foundation, Inc.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */


\f

#if HAVE_CONFIG_H
#  include <config.h>
#endif

#include "libguile/_scm.h"

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

#include "libguile/unif.h"
#include "libguile/eval.h"
#include "libguile/ports.h"
#include "libguile/read.h"
#include "libguile/root.h"
#include "libguile/strings.h"
#include "libguile/modules.h"
#include "libguile/validate.h"
#include "libguile/deprecation.h"

#include "libguile/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.
*/

scm_t_bits scm_tc16_strport;


static int
stfill_buffer (SCM port)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  
  if (pt->read_pos >= pt->read_end)
    return EOF;
  else
    return scm_return_first_int (*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_t_port *pt, off_t new_size)
{
  SCM old_stream = SCM_PACK (pt->stream);
  SCM new_stream = scm_allocate_string (new_size);
  unsigned long int old_size = SCM_STRING_LENGTH (old_stream);
  unsigned long int min_size = min (old_size, new_size);
  unsigned long int i;

  off_t index = pt->write_pos - pt->write_buf;

  pt->write_buf_size = new_size;

  for (i = 0; i != min_size; ++i)
    SCM_STRING_CHARS (new_stream) [i] = SCM_STRING_CHARS (old_stream) [i];

  /* reset buffer. */
  {
    pt->stream = SCM_UNPACK (new_stream);
    pt->read_buf = pt->write_buf = SCM_STRING_UCHARS (new_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_t_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, const void *data, size_t size)
{
  scm_t_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;
      
      memcpy ((char *) 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_t_port *pt = SCM_PTAB_ENTRY (port);
  
  if (pt->read_pos - pt->read_buf < offset)
    scm_misc_error ("st_end_input", "negative position", SCM_EOL);

  pt->write_pos = (unsigned char *) (pt->read_pos = pt->read_pos - offset);
  pt->rw_active = SCM_PORT_NEITHER;
}

static off_t
st_seek (SCM port, off_t offset, int whence)
{
  scm_t_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_CELL_WORD_0 (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_t_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 (SCM pos, SCM str, long modes, const char *caller)
{
  SCM z;
  scm_t_port *pt;
  size_t str_len, c_pos;

  SCM_ASSERT (SCM_I_STRINGP (str), str, SCM_ARG1, caller);
  str_len = SCM_I_STRING_LENGTH (str);
  c_pos = scm_to_unsigned_integer (pos, 0, str_len);

  if (!((modes & SCM_WRTNG) || (modes & SCM_RDNG)))
    scm_misc_error ("scm_mkstrport", "port must read or write", SCM_EOL);

  scm_mutex_lock (&scm_i_port_table_mutex);
  z = scm_new_port_table_entry (scm_tc16_strport);
  pt = SCM_PTAB_ENTRY(z);
  SCM_SETSTREAM (z, SCM_UNPACK (str));
  SCM_SET_CELL_TYPE(z, scm_tc16_strport|modes);
  pt->write_buf = pt->read_buf = SCM_I_STRING_UCHARS (str);
  pt->read_pos = pt->write_pos = pt->read_buf + c_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_mutex_unlock (&scm_i_port_table_mutex);

  /* 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_t_port *pt = SCM_PTAB_ENTRY (port);
  SCM str;

  if (pt->rw_active == SCM_PORT_WRITE)
    st_flush (port);

  str = scm_mem2string ((char *) pt->read_buf, pt->read_buf_size);
  scm_remember_upto_here_1 (port);
  return str;
}

SCM_DEFINE (scm_object_to_string, "object->string", 1, 1, 0,
	    (SCM obj, SCM printer),
	    "Return a Scheme string obtained by printing @var{obj}.\n"
	    "Printing function can be specified by the optional second\n"
	    "argument @var{printer} (default: @code{write}).")
#define FUNC_NAME s_scm_object_to_string
{
  SCM str, port;

  if (!SCM_UNBNDP (printer))
    SCM_VALIDATE_PROC (2, printer);

  str = scm_allocate_string (0);
  port = scm_mkstrport (SCM_INUM0, str, SCM_OPN | SCM_WRTNG, FUNC_NAME);

  if (SCM_UNBNDP (printer))
    scm_write (obj, port);
  else
    scm_call_2 (printer, obj, port);

  return scm_strport_to_string (port);
}
#undef FUNC_NAME

SCM_DEFINE (scm_call_with_output_string, "call-with-output-string", 1, 0, 0, 
           (SCM proc),
	    "Calls the one-argument procedure @var{proc} with a newly created output\n"
	    "port.  When the function returns, the string composed of the characters\n"
	    "written into the port is returned.")
#define FUNC_NAME s_scm_call_with_output_string
{
  SCM p;

  p = scm_mkstrport (SCM_INUM0, 
		     scm_make_string (SCM_INUM0, SCM_UNDEFINED),
		     SCM_OPN | SCM_WRTNG,
                     FUNC_NAME);
  scm_call_1 (proc, p);

  return scm_get_output_string (p);
}
#undef FUNC_NAME

SCM_DEFINE (scm_call_with_input_string, "call-with-input-string", 2, 0, 0,
           (SCM string, SCM proc),
	    "Calls the one-argument procedure @var{proc} with a newly\n"
	    "created input port from which @var{string}'s contents may be\n"
	    "read.  The value yielded by the @var{proc} is returned.")
#define FUNC_NAME s_scm_call_with_input_string
{
  SCM p = scm_mkstrport(SCM_INUM0, string, SCM_OPN | SCM_RDNG, FUNC_NAME);
  return scm_call_1 (proc, p);
}
#undef FUNC_NAME

SCM_DEFINE (scm_open_input_string, "open-input-string", 1, 0, 0,
	    (SCM str),
	    "Take a string and return an input port that delivers characters\n"
	    "from the string. The port can be closed by\n"
	    "@code{close-input-port}, though its storage will be reclaimed\n"
	    "by the garbage collector if it becomes inaccessible.")
#define FUNC_NAME s_scm_open_input_string
{
  SCM p = scm_mkstrport(SCM_INUM0, str, SCM_OPN | SCM_RDNG, FUNC_NAME);
  return p;
}
#undef FUNC_NAME

SCM_DEFINE (scm_open_output_string, "open-output-string", 0, 0, 0, 
	    (void),
	    "Return an output port that will accumulate characters for\n"
	    "retrieval by @code{get-output-string}. The port can be closed\n"
	    "by the procedure @code{close-output-port}, though its storage\n"
	    "will be reclaimed by the garbage collector if it becomes\n"
	    "inaccessible.")
#define FUNC_NAME s_scm_open_output_string
{
  SCM p;

  p = scm_mkstrport (SCM_INUM0, 
		     scm_make_string (SCM_INUM0, SCM_UNDEFINED),
		     SCM_OPN | SCM_WRTNG,
                     FUNC_NAME);
  return p;
}
#undef FUNC_NAME

SCM_DEFINE (scm_get_output_string, "get-output-string", 1, 0, 0, 
	    (SCM port),
	    "Given an output port created by @code{open-output-string},\n"
	    "return a string consisting of the characters that have been\n"
	    "output to the port so far.")
#define FUNC_NAME s_scm_get_output_string
{
  SCM_VALIDATE_OPOUTSTRPORT (1, port);
  return scm_strport_to_string (port);
}
#undef FUNC_NAME


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

SCM
scm_c_eval_string_in_module (const char *expr, SCM module)
{
  return scm_eval_string_in_module (scm_makfrom0str (expr), module);
}


static SCM
inner_eval_string (void *data)
{
  SCM port = (SCM)data;
  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_primitive_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;
}

SCM_DEFINE (scm_eval_string_in_module, "eval-string", 1, 1, 0, 
            (SCM string, SCM module),
	    "Evaluate @var{string} as the text representation of a Scheme\n"
	    "form or forms, and return whatever value they produce.\n"
	    "Evaluation takes place in the given module, or the current\n"
            "module when no module is given.\n"
            "While the code is evaluated, the given module is made the\n"
	    "current one.  The current module is restored when this\n"
            "procedure returns.")
#define FUNC_NAME s_scm_eval_string_in_module
{
  SCM port = scm_mkstrport (SCM_INUM0, string, SCM_OPN | SCM_RDNG,
			    FUNC_NAME);
  if (SCM_UNBNDP (module))
    module = scm_current_module ();
  else
    SCM_VALIDATE_MODULE (2, module);
  return scm_c_call_with_current_module (module,
					 inner_eval_string, (void *)port);
}
#undef FUNC_NAME

SCM
scm_eval_string (SCM string)
{
  return scm_eval_string_in_module (string, SCM_UNDEFINED);
}

static scm_t_bits
scm_make_stptob ()
{
  scm_t_bits 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);

  return tc;
}

void
scm_init_strports ()
{
  scm_tc16_strport = scm_make_stptob ();

#include "libguile/strports.x"
}


/*
  Local Variables:
  c-file-style: "gnu"
  End:
*/