/* Copyright (C) 1997, 2000 artofcode LLC.  All rights reserved.
  
  This program is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; either version 2 of the License, or (at your
  option) any later version.

  This program 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
  General Public License for more details.

  You should have received a copy of the GNU General Public License along
  with this program; if not, write to the Free Software Foundation, Inc.,
  59 Temple Place, Suite 330, Boston, MA, 02111-1307.

*/

/*$Id: gsdsrc.h,v 1.3.6.1.2.1 2003/01/17 00:49:02 giles Exp $ */
/* DataSource definitions */

#ifndef gsdsrc_INCLUDED
#  define gsdsrc_INCLUDED

#include "gsstruct.h"

/* ---------------- Types and structures ---------------- */

/*
 * A gs_data_source_t represents the data source for various constructs.  It
 * can be a string (either a gs_string or a byte-type object), a
 * positionable, non-procedure-based stream, or an array of floats.  An
 * ordinary positionable file stream will do, as long as the client doesn't
 * attempt to read past the EOF.
 *
 * The handling of floats is anomalous, but we don't see a good alternative
 * at the moment.
 */

#ifndef stream_DEFINED
#  define stream_DEFINED
typedef struct stream_s stream;
#endif

/*
 * Prepare to access a block of data from a source.  buf must be a client-
 * supplied buffer of at least length bytes.  If ptr == 0, always copy the
 * data into buf.  If ptr != 0, either copy the data into buf and set *ptr =
 * buf, or set *ptr to point to the data (which might be invalidated by the
 * next call).  Note that this procedure may or may not do bounds checking.
 */
#define data_source_proc_access(proc)\
  int proc(P5(const gs_data_source_t *psrc, ulong start, uint length,\
	      byte *buf, const byte **ptr))

typedef enum {
    data_source_type_string,
    data_source_type_bytes,
    data_source_type_floats,
    data_source_type_stream
} gs_data_source_type_t;
#ifndef gs_data_source_DEFINED
#  define gs_data_source_DEFINED
typedef struct gs_data_source_s gs_data_source_t;
#endif
struct gs_data_source_s {
    data_source_proc_access((*access));
    gs_data_source_type_t type;
    union d_ {
	gs_const_string str;	/* also used for byte objects */
	stream *strm;
    } data;
};

#define data_source_access_only(psrc, start, length, buf, ptr)\
  (*(psrc)->access)(psrc, (ulong)(start), length, buf, ptr)
#define data_source_access(psrc, start, length, buf, ptr)\
  BEGIN\
    int code_ = data_source_access_only(psrc, start, length, buf, ptr);\
    if ( code_ < 0 ) return code_;\
  END
#define data_source_copy_only(psrc, start, length, buf)\
  data_source_access_only(psrc, start, length, buf, (const byte **)0)
#define data_source_copy(psrc, start, length, buf)\
  data_source_access(psrc, start, length, buf, (const byte **)0)

/*
 * Data sources are always embedded in other structures, but they do have
 * pointers that need to be traced and relocated, so they do have a GC
 * structure type.
 */
extern_st(st_data_source);
#define public_st_data_source()	/* in gsdsrc.c */\
  gs_public_st_composite(st_data_source, gs_data_source_t, "gs_data_source_t",\
    data_source_enum_ptrs, data_source_reloc_ptrs)
#define st_data_source_max_ptrs 1

/* ---------------- Procedures ---------------- */

/* Initialize a data source of the various known types. */
data_source_proc_access(data_source_access_string);
#define data_source_init_string(psrc, strg)\
  ((psrc)->type = data_source_type_string,\
   (psrc)->data.str = strg, (psrc)->access = data_source_access_string)
#define data_source_init_string2(psrc, bytes, len)\
  ((psrc)->type = data_source_type_string,\
   (psrc)->data.str.data = bytes, (psrc)->data.str.size = len,\
   (psrc)->access = data_source_access_string)
data_source_proc_access(data_source_access_bytes);
#define data_source_init_bytes(psrc, bytes, len)\
  ((psrc)->type = data_source_type_bytes,\
   (psrc)->data.str.data = bytes, (psrc)->data.str.size = len,\
   (psrc)->access = data_source_access_bytes)
#define data_source_init_floats(psrc, floats, count)\
  ((psrc)->type = data_source_type_floats,\
   (psrc)->data.str.data = (byte *)floats,\
   (psrc)->data.str.size = (count) * sizeof(float),\
   (psrc)->access = data_source_access_bytes)
data_source_proc_access(data_source_access_stream);
#define data_source_init_stream(psrc, s)\
  ((psrc)->type = data_source_type_stream,\
   (psrc)->data.strm = s, (psrc)->access = data_source_access_stream)

#define data_source_is_stream(dsource)\
  ((dsource).type == data_source_type_stream)
#define data_source_is_array(dsource)\
  ((dsource).type == data_source_type_floats)

#endif /* gsdsrc_INCLUDED */