/* Copyright (C) 1989, 1995, 1996, 1997 Aladdin Enterprises.  All rights reserved.
  
  This file is part of Aladdin Ghostscript.
  
  Aladdin Ghostscript is distributed with NO WARRANTY OF ANY KIND.  No author
  or distributor accepts any responsibility for the consequences of using it,
  or for whether it serves any particular purpose or works at all, unless he
  or she says so in writing.  Refer to the Aladdin Ghostscript Free Public
  License (the "License") for full details.
  
  Every copy of Aladdin Ghostscript must include a copy of the License,
  normally in a plain ASCII text file named PUBLIC.  The License grants you
  the right to copy, modify and redistribute Aladdin Ghostscript, but only
  under certain conditions described in the License.  Among other things, the
  License requires that the copyright notice and this notice be preserved on
  all copies.
*/

/* zfile.c */
/* Non-I/O file operators */
#include "memory_.h"
#include "string_.h"
#include "ghost.h"
#include "gp.h"
#include "gsstruct.h"			/* for registering root */
#include "errors.h"
#include "oper.h"
#include "estack.h"			/* for filenameforall, .execfile */
#include "ialloc.h"
#include "ilevel.h"			/* %names only work in Level 2 */
#include "interp.h"			/* gs_errorinfo_put_string prototype */
#include "isave.h"			/* for restore */
#include "iutil.h"
#include "stream.h"
#include "strimpl.h"
#include "sfilter.h"
#include "gxiodev.h"			/* must come after stream.h */
					/* and before files.h */
#include "files.h"			/* ditto */
#include "fname.h"			/* ditto */
#include "main.h"			/* for gs_lib_paths */
#include "store.h"

/* Import the file_open routine for %os%, which is the default. */
extern iodev_proc_open_file(iodev_os_open_file);

/* Forward references: file opening. */
int file_open(P6(const byte *, uint, const char *, uint, ref *, stream **));

/* Forward references: other. */
private int execfile_finish(P1(os_ptr));
private int execfile_cleanup(P1(os_ptr));
private stream_proc_report_error(filter_report_error);

/*
 * Since there can be many file objects referring to the same file/stream,
 * we can't simply free a stream when we close it.  On the other hand,
 * we don't want freed streams to clutter up memory needlessly.
 * Our solution is to retain the freed streams, and reuse them.
 * To prevent an old file object from being able to access a reused stream,
 * we keep a serial number in each stream, and check it against a serial
 * number stored in the file object (as the "size"); when we close a file,
 * we increment its serial number.  If the serial number ever overflows,
 * we leave it at zero, and do not reuse the stream.
 * (This will never happen.)
 *
 * Storage management for this scheme is a little tricky.
 * We maintain an invariant that says that a stream opened at a given
 * save level always uses a stream structure allocated at that level.
 * By doing this, we don't need to keep track separately of streams open
 * at a level vs. streams allocated at a level.  To make this interact
 * properly with save and restore, we maintain a list of all streams
 * currently allocated, both open and closed.  The save_count member
 * of a stream indicates the number of unmatched saves at which
 * the given stream was the head of the list.  Thus the streams
 * allocated at the current level are precisely those from the head of the
 * list up to and not including the first stream with non-zero save_count.
 *
 * We want to close streams freed by restore and by garbage collection.
 * We use the finalization procedure for this.  For restore, we don't
 * have to do anything special to make this happen; we only need to ensure
 * that we remove from the list of allocated streams any streams being freed,
 * as just described.  For garbage collection, we do something more drastic:
 * we simply clear the list of known streams (at all save levels).
 * Any streams open at the time of garbage collection will no longer
 * participate in the list of known streams, but this does no harm;
 * it simply means that they won't get reused, and can only be reclaimed
 * by a future garbage collection or restore.
 */
private stream *file_list;
private gs_gc_root_t file_list_root;

/* 
 * Define the default stream buffer sizes.  For file streams,
 * this is arbitrary, since the C library or operating system
 * does its own buffering in addition.
 * However, the buffer size for eexec decoding is NOT arbitrary:
 * it must be at most 512.
 */
#define default_buffer_size 512
const uint file_default_buffer_size = default_buffer_size;

/* An invalid file object */
stream *invalid_file_entry;		/* exported for zfileio.c */
private gs_gc_root_t invalid_file_root;

/* Initialize the file table */
private void
zfile_init(void)
{
	/* Create and initialize an invalid (closed) stream. */
	/* Initialize the stream for the sake of the GC, */
	/* and so it can act as an empty input stream. */

	stream *s = s_alloc(imemory_system, "zfile_init");
	sread_string(s, NULL, 0);
	s->next = s->prev = 0;
	s->save_count = 0;
	s_init_no_id(s);
	invalid_file_entry = s;
	gs_register_struct_root(imemory, &invalid_file_root,
				(void **)&invalid_file_entry,
				"invalid_file_entry");

	/* Initialize the bookkeeping list. */
	
	file_list = 0;
	gs_register_struct_root(imemory, &file_list_root,
				(void **)&file_list, "file_list");
}

/* Make an invalid file object. */
void
make_invalid_file(ref *fp)
{	make_file(fp, avm_system, ~0, invalid_file_entry);
}

/* <name_string> <access_string> file <file> */
int
zfile(register os_ptr op)
{	char file_access[3];
	parsed_file_name pname;
	const byte *astr;
	int code;
	stream *s;
	check_read_type(*op, t_string);
	astr = op->value.const_bytes;
	switch ( r_size(op) )
	   {
	case 2:
		if ( astr[1] != '+' )
			return_error(e_invalidfileaccess);
		file_access[1] = '+';
		file_access[2] = 0;
		break;
	case 1:
		file_access[1] = 0;
		break;
	default:
		return_error(e_invalidfileaccess);
	   }
	switch ( astr[0] )
	   {
	case 'r': case 'w': case 'a':
		break;
	default:
		return_error(e_invalidfileaccess);
	   }
	file_access[0] = astr[0];
	code = parse_file_name(op - 1, &pname);
	if ( code < 0 )
		return code;
	if ( pname.iodev == NULL )
		pname.iodev = iodev_default;
	if ( pname.fname == NULL )		/* just a device */
		code = (*pname.iodev->procs.open_device)(pname.iodev,
					file_access, &s, imemory);
	else					/* file */
	{	iodev_proc_open_file((*open_file)) =
			pname.iodev->procs.open_file;
		if ( open_file == 0 )
			open_file = iodev_os_open_file;
		code = (*open_file)(pname.iodev, pname.fname, pname.len,
				    file_access, &s, imemory);
	}
	if ( code < 0 )
		return code;
	make_stream_file(op - 1, s, file_access);
	pop(1);
	return code;
}

/* ------ Level 2 extensions ------ */

/* <string> deletefile - */
private int
zdeletefile(register os_ptr op)
{	parsed_file_name pname;
	int code = parse_real_file_name(op, &pname, "deletefile");
	if ( code < 0 )
		return code;
	code = (*pname.iodev->procs.delete_file)(pname.iodev, pname.fname);
	free_file_name(&pname, "deletefile");
	if ( code < 0 )
		return code;
	pop(1);
	return 0;
}

/* <template> <proc> <scratch> filenameforall - */
/****** NOT CONVERTED FOR IODEVICES YET ******/
private int file_continue(P1(os_ptr));
private int file_cleanup(P1(os_ptr));
private int
zfilenameforall(register os_ptr op)
{	file_enum *pfen;
	int code;
	check_write_type(*op, t_string);
	check_proc(op[-1]);
	check_read_type(op[-2], t_string);
	/* Push a mark, the pattern, the scratch string, the enumerator, */
	/* and the procedure, and invoke the continuation. */
	check_estack(7);
	pfen = gp_enumerate_files_init((char *)op[-2].value.bytes, r_size(op - 2), imemory);
	if ( pfen == 0 )
	  return_error(e_VMerror);
	push_mark_estack(es_for, file_cleanup);
	*++esp = op[-2];
	*++esp = *op;
	++esp;
	make_istruct(esp, 0, pfen);
	*++esp = op[-1];
	pop(3);  op -= 3;
	code = file_continue(op);
	return (code == o_pop_estack ? o_push_estack : code);
}
/* Continuation operator for enumerating files */
private int
file_continue(register os_ptr op)
{	es_ptr pscratch = esp - 2;
	file_enum *pfen = r_ptr(esp - 1, file_enum);
	uint len = r_size(pscratch);
	uint code =
	  gp_enumerate_files_next(pfen, (char *)pscratch->value.bytes, len);
	if ( code == ~(uint)0 )		/* all done */
	   {	esp -= 4;		/* pop proc, pfen, scratch, mark */
		return o_pop_estack;
	   }
	else if ( code > len )		/* overran string */
		return_error(e_rangecheck);
	else
	   {	push(1);
		ref_assign(op, pscratch);
		r_set_size(op, code);
		push_op_estack(file_continue);	/* come again */
		*++esp = pscratch[2];	/* proc */
		return o_push_estack;
	   }
}
/* Cleanup procedure for enumerating files */
private int
file_cleanup(os_ptr op)
{	gp_enumerate_files_close(r_ptr(esp + 4, file_enum));
	return 0;
}

/* <string1> <string2> renamefile - */
private int
zrenamefile(register os_ptr op)
{	parsed_file_name pname1, pname2;
	int code = parse_real_file_name(op - 1, &pname1, "renamefile(from)");
	if ( code < 0 )
		return code;
	pname2.fname = 0;
	code = parse_real_file_name(op, &pname2, "renamefile(to)");
	if ( code < 0 || pname1.iodev != pname2.iodev ||
	     (code = (*pname1.iodev->procs.rename_file)(pname1.iodev,
				     pname1.fname, pname2.fname)) < 0
	   )
	{	if ( code >= 0 )
			code = gs_note_error(e_invalidfileaccess);
	}
	free_file_name(&pname2, "renamefile(to)");
	free_file_name(&pname1, "renamefile(from)");
	if ( code < 0 )
		return code;
	pop(2);
	return 0;
}	

/* <file> status <open_bool> */
/* <string> status <pages> <bytes> <ref_time> <creation_time> true */
/* <string> status false */
private int
zstatus(register os_ptr op)
{	switch ( r_type(op) )
	{
	case t_file:
	  {	stream *s;
		make_bool(op, (file_is_valid(s, op) ? 1 : 0));
	  }	return 0;
	case t_string:
	{	parsed_file_name pname;
		struct stat fstat;
		int code = parse_file_name(op, &pname);
		if ( code < 0 )
			return code;
		code = terminate_file_name(&pname, "status");
		if ( code < 0 )
			return code;
		code = (*pname.iodev->procs.file_status)(pname.iodev,
				pname.fname, &fstat);
		switch ( code )
		{
		case 0:
			push(4);
			make_int(op - 4, stat_blocks(&fstat));
			make_int(op - 3, fstat.st_size);
			make_int(op - 2, fstat.st_mtime);
			make_int(op - 1, fstat.st_ctime);
			make_bool(op, 1);
			break;
		case e_undefinedfilename:
			make_bool(op, 0);
			code = 0;
		}
		free_file_name(&pname, "status");
		return code;
	}
	default:
		return_op_typecheck(op);
	}
}

/* ------ Non-standard extensions ------ */

/* <executable_file> .execfile - */
private int
zexecfile(register os_ptr op)
{	check_type_access(*op, t_file, a_executable | a_read | a_execute);
	check_estack(4);	/* cleanup, file, finish, file */
	push_mark_estack(es_other, execfile_cleanup);
	*++esp = *op;
	push_op_estack(execfile_finish);
	return zexec(op);
}
/* Finish normally. */
private int
execfile_finish(os_ptr op)
{	check_ostack(1);
	esp -= 2;
	execfile_cleanup(op);
	return o_pop_estack;
}
/* Clean up by closing the file. */
private int
execfile_cleanup(os_ptr op)
{	check_ostack(1);
	*++osp = esp[2];
	return zclosefile(osp);
}

/* <dir> <name> .filenamedirseparator <string> */
int
zfilenamedirseparator(os_ptr op)
{	const char *sepr;

	check_read_type(*op, t_string);
	check_read_type(op[-1], t_string);
	sepr =
	  gp_file_name_concat_string((const char *)op[-1].value.const_bytes,
				     r_size(op - 1),
				     (const char *)op->value.const_bytes,
				     r_size(op));
	make_const_string(op - 1, avm_foreign | a_readonly,
			  strlen(sepr), (const byte *)sepr);
	pop(1);
	return 0;
}

/* - .filenamelistseparator <string> */
int
zfilenamelistseparator(os_ptr op)
{	push(1);
	make_const_string(op, avm_foreign | a_readonly, 1,
			  (const byte *)&gp_file_name_list_separator);
	return 0;
}

/* <name> .filenamesplit <dir> <base> <extension> */
int
zfilenamesplit(os_ptr op)
{	check_read_type(*op, t_string);
	/****** NOT IMPLEMENTED YET ******/
	return_error(e_undefined);
}

/* <string> findlibfile <found_string> <file> true */
/* <string> findlibfile <string> false */
int
zfindlibfile(register os_ptr op)
{	int code;
#define maxclen 200
	byte cname[maxclen];
	uint clen;
	parsed_file_name pname;
	stream *s;
	check_ostack(2);
	code = parse_file_name(op, &pname);
	if ( code < 0 )
		return code;
	if ( pname.iodev == NULL )
		pname.iodev = iodev_default;
	if ( pname.iodev != iodev_default )
	{	/* Non-OS devices don't have search paths (yet). */
		code =
		  (pname.fname == NULL ?
		   (*pname.iodev->procs.open_device)(pname.iodev, "r",
						     &s, imemory) :
		   (*pname.iodev->procs.open_file)(pname.iodev,
						   pname.fname, pname.len, "r",
						   &s, imemory));
		if ( code < 0 )
		{	push(1);
			make_false(op);
			return 0;
		}
		make_stream_file(op + 1, s, "r");
	}
	else
	{	byte *cstr;
		code = lib_file_open(pname.fname, pname.len, cname, maxclen,
				     &clen, op + 1);
		if ( code == e_VMerror )
		  return code;
		if ( code < 0 )
		{	push(1);
			make_false(op);
			return 0;
		}
		cstr = ialloc_string(clen, "findlibfile");
		if ( cstr == 0 )
			return_error(e_VMerror);
		memcpy(cstr, cname, clen);
		make_string(op, a_all | icurrent_space, clen, cstr);
	}
	push(2);
	make_true(op);
	return 0;
}

/* ------ Initialization procedure ------ */

BEGIN_OP_DEFS(zfile_op_defs) {
	{"1deletefile", zdeletefile},
	{"1.execfile", zexecfile},
	{"2file", zfile},
	{"3filenameforall", zfilenameforall},
	{"2.filenamedirseparator", zfilenamedirseparator},
	{"0.filenamelistseparator", zfilenamelistseparator},
	{"1.filenamesplit", zfilenamesplit},
	{"1findlibfile", zfindlibfile},
	{"2renamefile", zrenamefile},
	{"1status", zstatus},
		/* Internal operators */
	{"0%file_continue", file_continue},
	{"0%execfile_finish", execfile_finish},
END_OP_DEFS(zfile_init) }

/* ------ Stream opening ------ */

/* Make a t_file reference to a stream. */
void
make_stream_file(ref *pfile, stream *s, const char *access)
{	uint attrs =
		(access[1] == '+' ? a_write + a_read + a_execute : 0) |
		imemory_space((gs_ref_memory_t *)s->memory);
	if ( access[0] == 'r' )
	{	make_file(pfile, attrs | (a_read | a_execute), s->read_id, s);
		s->write_id = 0;
	}
	else
	{	make_file(pfile, attrs | a_write, s->write_id, s);
		s->read_id = 0;
	}
}

/* Open an OS-level file (like fopen), using the search paths if necessary. */
/* Note that it does not automatically look in the current */
/* directory first (or at all): this is like Unix, and unlike MS-DOS. */
private int
lib_file_fopen(gx_io_device *iodev, const char *bname,
  const char *ignore_access, FILE **pfile, char *rfname, uint rnamelen)
{	char fmode[3];			/* r, [b], null */
	int len = strlen(bname);
	const gs_file_path *pfpath = &gs_lib_path;
	uint pi;

	strcpy(fmode, "r");
	strcat(fmode, gp_fmode_binary_suffix);
	if ( gp_file_name_is_absolute(bname, len) )
	  return (*iodev->procs.fopen)(iodev, bname, fmode, pfile,
				       rfname, rnamelen);
	/* Go through the list of search paths */
	for ( pi = 0; pi < r_size(&pfpath->list); ++pi )
	   {	const ref *prdir = pfpath->list.value.refs + pi;
		const char *pstr = (const char *)prdir->value.const_bytes;
		uint plen = r_size(prdir);
		const char *cstr =
		  gp_file_name_concat_string(pstr, plen, bname, len);
		int up, i;
		int code;

		/* Concatenate the prefix, combiner, and file name. */
		/* Do this carefully in case rfname is the same */
		/* as fname.  (We don't worry about the case */
		/* where rfname only overlaps fname.) */
		up = plen + strlen(cstr);
		if ( up + len + 1 > rnamelen )
		  return_error(e_limitcheck);
		for ( i = len + 1; --i >= 0; )
		  rfname[i + up] = bname[i];
		memcpy(rfname, pstr, plen);
		memcpy(rfname + plen, cstr, strlen(cstr));
		code = (*iodev->procs.fopen)(iodev, rfname, fmode,
					     pfile, rfname, rnamelen);
		if ( code >= 0 )
		  return code;
		/* strcpy isn't guaranteed to work for overlapping */
		/* source and destination, so: */
		if ( rfname == bname )
		  for ( i = 0; (rfname[i] = rfname[i + up]) != 0; i++ )
		    ;
	   }
	return_error(e_undefinedfilename);
}
/* The startup code calls this to open @-files. */
FILE *
lib_fopen(const char *bname)
{	FILE *file = NULL;
	/* We need a buffer to hold the expanded file name. */
#define max_filename 129
	char buffer[max_filename];
	int code = lib_file_fopen(iodev_default, bname, "r", &file, 
				  buffer, max_filename);
#undef max_filename
	return (code < 0 ? NULL : file);
}

/* Open a file stream on an OS file and create a file object, */
/* using the search paths. */
/* The startup code calls this to open the initialization file gs_init.ps. */
int
lib_file_open(const char *fname, uint len, byte *cname, uint max_clen,
  uint *pclen, ref *pfile)
{	stream *s;
	int code = file_open_stream(fname, len, "r",
				    default_buffer_size, &s, lib_file_fopen);
	char *bname;
	uint blen;

	if ( code < 0 )
	  return code;
	/* Get the name from the stream buffer. */
	bname = (char *)s->cbuf;
	blen = strlen(bname);
	if ( blen > max_clen )
	{	sclose(s);
		return_error(e_limitcheck);
	}
	memcpy(cname, bname, blen);
	*pclen = blen;
	make_stream_file(pfile, s, "r");
	return 0;
}

/* Open a file stream that reads a string. */
/* (This is currently used only by the ccinit feature.) */
/* The string must be allocated in non-garbage-collectable (foreign) space. */
int
file_read_string(const byte *str, uint len, ref *pfile)
{	stream *s = file_alloc_stream(imemory, "file_read_string");
	int space;

	if ( s == 0 )
	  return_error(e_VMerror);
	space = icurrent_space;
	sread_string(s, str, len);
	s->foreign = 1;
	s->write_id = 0;
	make_file(pfile, a_readonly | space, s->read_id, s);
	s->save_close = s->procs.close;
	s->procs.close = file_close_disable;
	return 0;
}

/* Open a file stream, optionally on an OS file. */
/* Return 0 if successful, error code if not. */
/* On a successful return, the C file name is in the stream buffer. */
/* If fname==0, set up the file entry, stream, and buffer, */
/* but don't open an OS file or initialize the stream. */
int
file_open_stream(const char *fname, uint len, const char *file_access,
  uint buffer_size, stream **ps, iodev_proc_fopen_t fopen_proc)
{	byte *buffer;
	register stream *s;
	if ( buffer_size == 0 )
	  buffer_size = default_buffer_size;
	if ( len >= buffer_size )
	  return_error(e_limitcheck);	/* we copy the file name into the buffer */
	/* Allocate the stream first, since it persists */
	/* even after the file has been closed. */
  	s = file_alloc_stream(imemory, "file_open_stream");
	if ( s == 0 )
		return_error(e_VMerror);
	/* Allocate the buffer. */
	buffer = ialloc_bytes(buffer_size, "file_open(buffer)");
	if ( buffer == 0 )
		return_error(e_VMerror);
	if ( fname != 0 )
	   {	/* Copy the name (so we can terminate it with a zero byte.) */
		char *file_name = (char *)buffer;
		char fmode[4];		/* r/w/a, [+], [b], null */
		FILE *file;
		int code;
		memcpy(file_name, fname, len);
		file_name[len] = 0;		/* terminate string */
		/* Open the file, always in binary mode. */
		strcpy(fmode, file_access);
		strcat(fmode, gp_fmode_binary_suffix);
		/****** iodev_default IS QUESTIONABLE ******/
		code = (*fopen_proc)(iodev_default, file_name, fmode, &file,
				     (char *)buffer, buffer_size);
		if (code < 0 )
		{	ifree_object(buffer, "file_open(buffer)");
			return code;
		}
		/* Set up the stream. */
		switch ( fmode[0] )
		{
		case 'a':
			sappend_file(s, file, buffer, buffer_size);
			break;
		case 'r':
			sread_file(s, file, buffer, buffer_size);
			break;
		case 'w':
			swrite_file(s, file, buffer, buffer_size);
		}
		if ( fmode[1] == '+' )
		  s->file_modes |= s_mode_read | s_mode_write;
		s->save_close = s->procs.close;
		s->procs.close = file_close_file;
	   }
	else				/* save the buffer and size */
	   {	s->cbuf = buffer;
		s->bsize = s->cbsize = buffer_size;
	   }
	*ps = s;
	return 0;
}

/* Open a file stream for a filter. */
int
filter_open(const char *file_access, uint buffer_size, ref *pfile,
  const stream_procs _ds *procs, const stream_template *template,
  const stream_state *st)
{	stream *s;
	uint ssize = gs_struct_type_size(template->stype);
	stream_state *sst = 0;
	int code;

	if ( template->stype != &st_stream_state )
	{	sst = s_alloc_state(imemory, template->stype,
				    "filter_open(stream_state)");
		if ( sst == 0 )
		  return_error(e_VMerror);
	}
	code = file_open_stream((char *)0, 0, file_access,
				buffer_size, &s, (iodev_proc_fopen_t)0);
	if ( code < 0 )
	{	ifree_object(sst, "filter_open(stream_state)");
		return code;
	}
	s_std_init(s, s->cbuf, s->bsize, procs,
		   (*file_access == 'r' ? s_mode_read : s_mode_write));
	s->procs.process = template->process;
	s->save_close = s->procs.close;
	s->procs.close = file_close_file;
	if ( sst == 0 )
	{	/* This stream doesn't have any state of its own. */
		/* Hack: use the stream itself as the state. */
		sst = (stream_state *)s;
	}
	else if ( st != 0 )	/* might not have client parameters */
	  memcpy(sst, st, ssize);
	s->state = sst;
	sst->template = template;
	sst->memory = imemory;
	sst->report_error = filter_report_error;
	if ( template->init != 0 )
	{	code = (*template->init)(sst);
		if ( code < 0 )
		{	ifree_object(sst, "filter_open(stream_state)");
			ifree_object(s->cbuf, "filter_open(buffer)");
			return code;
		}
	}
	make_stream_file(pfile, s, file_access);
	return 0;
}

/* Report an error by storing it in $error.errorinfo. */
private int
filter_report_error(stream_state *st, const char *str)
{	if_debug1('s', "[s]stream error: %s\n", str);
	return gs_errorinfo_put_string(str);
}

/* Allocate and return a file stream. */
/* Return 0 if the allocation failed. */
/* The stream is initialized to an invalid state, so the caller need not */
/* worry about cleaning up if a later step in opening the stream fails. */
stream *
file_alloc_stream(gs_memory_t *mem, client_name_t cname)
{	stream *s;
	/* Look first for a free stream allocated at this level. */
	s = file_list;
	while ( s != 0 && s->save_count == 0 )
	{	if ( !s_is_valid(s) && s->read_id != 0 /* i.e. !overflowed */
		     && s->memory == mem
		   )
		{	s->is_temp = 0;		/* not a temp stream */
			return s;
		}
		s = s->next;
	}
	s = s_alloc(mem, cname);
	if ( s == 0 )
	  return 0;
	s_init_ids(s);
	s->is_temp = 0;			/* not a temp stream */
	/* Disable the stream now (in case we can't open the file, */
	/* or a filter init procedure fails) so that `restore' won't */
	/* crash when it tries to close open files. */
	s_disable(s);
	/* Add s to the list of files. */
	if ( file_list != 0 )
	  file_list->prev = s;
	s->next = file_list;
	s->prev = 0;
	s->save_count = 0;
	file_list = s;
	return s;
}

/* ------ Stream closing ------ */

/* Finish closing a file stream.  This used to check whether it was */
/* currentfile, but we don't have to do this any longer. */
/* This replaces the close procedure for the std* streams, */
/* which cannot actually be closed. */
/* This is exported for ziodev.c. */
int
file_close_finish(stream *s)
{	return 0;
}

/* Close a file stream, but don't deallocate the buffer. */
/* This replaces the close procedure for %lineedit and %statementedit. */
/* (This is WRONG: these streams should allocate a new buffer each time */
/* they are opened, but that would overstress the allocator right now.) */
/* This is exported for ziodev.c. */
/* This also replaces the close procedure for the string-reading */
/* stream created for gs_run_string. */
int
file_close_disable(stream *s)
{	int code = (*s->save_close)(s);
	if ( code )
	  return code;
	/* Increment the IDs to prevent further access. */
	s->read_id = s->write_id = (s->read_id | s->write_id) + 1;
	return file_close_finish(s);
}

/* Close a file stream.  This replaces the close procedure in the stream */
/* for normal (OS) files and for filters. */
int
file_close_file(stream *s)
{	stream *stemp = s->strm;
	gs_memory_t *mem;
	int code = file_close_disable(s);
	if ( code )
	  return code;
	/*
	 * Check for temporary streams created for filters.
	 * There may be more than one in the case of a procedure-based filter,
	 * or if we created an intermediate stream to ensure
	 * a large enough buffer.  Note that these streams may have been
	 * allocated by file_alloc_stream, so we mustn't free them.
	 */
	while ( stemp != 0 && stemp->is_temp != 0 )
	{	stream *snext = stemp->strm;
		mem = stemp->memory;
		if ( stemp->is_temp > 1 )
		 gs_free_object(mem, stemp->cbuf,
				"file_close(temp stream buffer)");
		s_disable(stemp);
		stemp = snext;
	}
	mem = s->memory;
	gs_free_object(mem, s->cbuf, "file_close(buffer)");
	return 0;
}

/* Close a file object. */
/* This is exported only for gsmain.c. */
int
file_close(ref *pfile)
{	stream *s;
	if ( file_is_valid(s, pfile) )	/* closing a closed file is a no-op */
	  {	if ( sclose(s) )
		  return_error(e_ioerror);
	  }
	return 0;
}

/* ------ Memory management ------ */

/* Mark the current file list at a save. */
void
file_save(void)
{	if_debug1('u', "[u]file_save 0x%lx\n",
		  (ulong)file_list);
	if ( file_list != 0 )
	  file_list->save_count++;
}

/* Update the file list before a restore. */
void
file_restore(const alloc_save_t *save, const gs_memory_t *mem)
{	stream *prev = 0;
	stream *s;
	stream **ps;
	/* We must be careful to unlink only those streams which */
	/* were allocated in the VM space being restored. */
	for ( ps = &file_list; (s = *ps) != 0 && s->save_count == 0; )
	  if ( s->memory == mem )
	    { if ( (*ps = s->next) != 0 )
		(*ps)->prev = prev;
	    }
	  else
	    prev = s, ps = &s->next;
	if ( s != 0 )			/* i.e., s->save_count != 0 */
	  s->save_count--;
	if_debug2('u', "[u]file_restore 0x%lx for 0x%lx\n",
		  (ulong)file_list, (ulong)save);
}

/* Note that a save has been forgotten. */
void
file_forget_save(const alloc_save_t *save)
{	stream *s;
	for ( s = file_list; s != 0 && s->save_count == 0; )
	  s = s->next;
	if ( s != 0 )
	  s->save_count--;
	if_debug2('u', "[u]file_forget_save 0x%lx for 0x%lx\n",
		  (ulong)file_list, (ulong)save);
}

/* Clear the file list for a GC. */
void
file_gc_prepare(void)
{	/* We have to unlink every stream from its neighbors, */
	/* so that referenced streams don't keep all streams around. */
	while ( file_list != 0 )
	  {	stream *s = file_list;
		file_list = s->next;
		s->prev = s->next = 0;
	  }
}
