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/*$Id: scommon.h,v 1.2.2.1 2000/11/02 15:05:08 igorm Exp $ */
/* Definitions common to stream clients and implementors */

#ifndef scommon_DEFINED
#  define scommon_DEFINED

#include "gsmemory.h"
#include "gstypes.h"		/* for gs_string */
#include "gsstype.h"		/* for extern_st */

/*
 * There are three major structures involved in the stream package.
 *
 * A stream is an "object" that owns a buffer, which it uses to implement
 * byte-oriented sequential access in a standard way, and a set of
 * procedures that handle things like buffer refilling.  See stream.h
 * for more information about streams.
 */
#ifndef stream_DEFINED
#  define stream_DEFINED
typedef struct stream_s stream;

#endif
/*
 * A stream_state records the state specific to a given variety of stream.
 * The buffer processing function of a stream maintains this state.
 */
typedef struct stream_state_s stream_state;

/*
 * A stream_template provides the information needed to create a stream.
 * The client must fill in any needed setup parameters in the appropriate
 * variety of stream_state, and then call the initialization function
 * provided by the template.  See strimpl.h for more information about
 * stream_templates.
 */
typedef struct stream_template_s stream_template;

/*
 * The stream package works with bytes, not chars.
 * This is to ensure unsigned representation on all systems.
 * A stream currently can only be read or written, not both.
 * Note also that the read procedure returns an int, not a char or a byte;
 * we use negative values to indicate exceptional conditions.
 * (We cast these values to int explicitly, because some compilers
 * don't do this if the other arm of a conditional is a byte.)
 */
/* End of data */
#define EOFC ((int)(-1))
/* Error */
#define ERRC ((int)(-2))
/* Interrupt */
#define INTC ((int)(-3))
/****** INTC IS NOT USED YET ******/
/* Callout */
#define CALLC ((int)(-4))
#define max_stream_exception 4
/* The following hack is needed for initializing scan_char_array in iscan.c. */
#define stream_exception_repeat(x) x, x, x, x

/*
 * Define cursors for reading from or writing into a buffer.
 * We lay them out this way so that we can alias
 * the write pointer and the read limit.
 */
typedef struct stream_cursor_read_s {
    const byte *ptr;
    const byte *limit;
    byte *_skip;
} stream_cursor_read;
typedef struct stream_cursor_write_s {
    const byte *_skip;
    byte *ptr;
    byte *limit;
} stream_cursor_write;
typedef union stream_cursor_s {
    stream_cursor_read r;
    stream_cursor_write w;
} stream_cursor;

/*
 * Define the prototype for the procedures known to both the generic
 * stream code and the stream implementations.
 */

/* Initialize the stream state (after the client parameters are set). */
#define stream_proc_init(proc)\
  int proc(P1(stream_state *))

/* Process a buffer.  See strimpl.h for details. */
#define stream_proc_process(proc)\
  int proc(P4(stream_state *, stream_cursor_read *,\
    stream_cursor_write *, bool))

/* Release the stream state when closing. */
#define stream_proc_release(proc)\
  void proc(P1(stream_state *))

/* Initialize the client parameters to default values. */
#define stream_proc_set_defaults(proc)\
  void proc(P1(stream_state *))

/* Reinitialize any internal stream state.  Note that this does not */
/* affect buffered data.  We declare this as returning an int so that */
/* it can be the same as the init procedure; however, reinit cannot fail. */
#define stream_proc_reinit(proc)\
  int proc(P1(stream_state *))

/* Report an error.  Note that this procedure is stored in the state, */
/* not in the main stream structure. */
#define stream_proc_report_error(proc)\
  int proc(P2(stream_state *, const char *))
stream_proc_report_error(s_no_report_error);

/*
 * Some types of streams have the ability to read their parameters from
 * a parameter list, and to write all (or only the non-default)
 * parameters to a parameter list.  Since these are not virtual
 * procedures for the stream (they operate on stream_state structures
 * even if no actual stream has been created), we name them differently.
 */
#define stream_state_proc_get_params(proc, state_type)\
  int proc(P3(gs_param_list *plist, const state_type *ss, bool all))
#define stream_state_proc_put_params(proc, state_type)\
  int proc(P2(gs_param_list *plist, state_type *ss))

/*
 * Define a generic stream state.  If a processing procedure has no
 * state of its own, it can use stream_state; otherwise, it must
 * create a "subclass".  There is a hack in stream.h to allow the stream
 * itself to serve as the "state" of a couple of heavily used stream types.
 *
 * In order to simplify the structure descriptors for concrete streams,
 * we require that the generic stream state not contain any pointers
 * to garbage-collectable storage.
 */
#define STREAM_MAX_ERROR_STRING 79
#define stream_state_common\
	const stream_template *template;\
	gs_memory_t *memory;\
	stream_proc_report_error((*report_error));\
        int min_left; /* required bytes for lookahead */ \
	char error_string[STREAM_MAX_ERROR_STRING + 1]
struct stream_state_s {
    stream_state_common;
};

extern_st(st_stream_state);
#define public_st_stream_state() /* in stream.c */\
  gs_public_st_simple(st_stream_state, stream_state, "stream_state")

#endif /* scommon_INCLUDED */
