/* Copyright (C) 1993, 1995 Aladdin Enterprises.  All rights reserved.
  
  This file is part of GNU Ghostscript.
  
  GNU Ghostscript is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY.  No author or distributor accepts responsibility to
  anyone for the consequences of using it or for whether it serves any
  particular purpose or works at all, unless he says so in writing.  Refer
  to the GNU Ghostscript General Public License for full details.
  
*/

/* sfile.c */
/* File stream implementation */
#include "stdio_.h"		/* includes std.h */
#include "memory_.h"
#include "gdebug.h"
#include "gpcheck.h"
#include "stream.h"
#include "strimpl.h"

/* Forward references for file stream procedures */
private int
  s_file_available(P2(stream *, long *)),
  s_file_read_seek(P2(stream *, long)),
  s_file_read_close(P1(stream *)),
  s_file_read_process(P4(stream_state *, stream_cursor_read *,
    stream_cursor_write *, bool));
private int
  s_file_write_seek(P2(stream *, long)),
  s_file_write_flush(P1(stream *)),
  s_file_write_close(P1(stream *)),
  s_file_write_process(P4(stream_state *, stream_cursor_read *,
    stream_cursor_write *, bool));
private int
  s_file_switch(P2(stream *, bool));

/* ------ File streams ------ */

/* Initialize a stream for reading an OS file. */
void
sread_file(register stream *s, FILE *file, byte *buf, uint len)
{	static const stream_procs p =
	   {	s_file_available, s_file_read_seek, s_std_read_reset,
		s_std_read_flush, s_file_read_close, s_file_read_process,
		s_file_switch
	   };
	s_std_init(s, buf, len, &p,
		   (file == stdin ? s_mode_read : s_mode_read + s_mode_seek));
	if_debug1('s', "[s]read file=0x%lx\n", (ulong)file);
	s->file = file;
	s->file_modes = s->modes;
	s->state = (stream_state *)s;	/* hack to avoid separate state */
}
/* Procedures for reading from a file */
private int
s_file_available(register stream *s, long *pl)
{	*pl = sbufavailable(s);
	if ( sseekable(s) )
	   {	long pos, end;
		pos = ftell(s->file);
		if ( fseek(s->file, 0L, SEEK_END) ) return ERRC;
		end = ftell(s->file);
		if ( fseek(s->file, pos, SEEK_SET) ) return ERRC;
		*pl += end - pos;
		if ( *pl == 0 ) *pl = -1;	/* EOF */
	   }
	else
	   {	if ( *pl == 0 && feof(s->file) ) *pl = -1;	/* EOF */
	   }
	return 0;
}
private int
s_file_read_seek(register stream *s, long pos)
{	uint end = s->srlimit - s->cbuf + 1;
	long offset = pos - s->position;
	if ( offset >= 0 && offset <= end )
	   {	/* Staying within the same buffer */
		s->srptr = s->cbuf + offset - 1;
		return 0;
	   }
	if ( fseek(s->file, pos, SEEK_SET) != 0 )
		return ERRC;
	s->srptr = s->srlimit = s->cbuf - 1;
	s->end_status = 0;
	s->position = pos;
	return 0;
}
private int
s_file_read_close(stream *s)
{	FILE *file = s->file;
	if ( file != 0 )
	  {	s->file = 0;
		return fclose(file);
	  }
	return 0;
}

/* Initialize a stream for writing an OS file. */
void
swrite_file(register stream *s, FILE *file, byte *buf, uint len)
{	static const stream_procs p =
	   {	s_std_noavailable, s_file_write_seek, s_std_write_reset,
		s_file_write_flush, s_file_write_close, s_file_write_process,
		s_file_switch
	   };
	s_std_init(s, buf, len, &p,
		   (file == stdout ? s_mode_write : s_mode_write + s_mode_seek));
	if_debug1('s', "[s]write file=0x%lx\n", (ulong)file);
	s->file = file;
	s->file_modes = s->modes;
	s->state = (stream_state *)s;	/* hack to avoid separate state */
}
/* Initialize for appending to an OS file. */
void
sappend_file(register stream *s, FILE *file, byte *buf, uint len)
{	swrite_file(s, file, buf, len);
	s->modes = s_mode_write + s_mode_append;	/* no seek */
	s->file_modes = s->modes;
	fseek(file, 0L, SEEK_END);
	s->position = ftell(file);
}
/* Procedures for writing on a file */
private int
s_file_write_seek(stream *s, long pos)
{	/* We must flush the buffer to reposition. */
	int code = sflush(s);
	if ( code < 0 )
		return code;
	if ( fseek(s->file, pos, SEEK_SET) != 0 )
		return ERRC;
	s->position = pos;
	return 0;
}
private int
s_file_write_flush(register stream *s)
{	int result = s_process_write_buf(s, false);
	fflush(s->file);
	return result;
}
private int
s_file_write_close(register stream *s)
{	s_process_write_buf(s, true);
	return s_file_read_close(s);
}

#define ss ((stream *)st)

/* Process a buffer for a file reading stream. */
/* This is the first stream in the pipeline, so pr is irrelevant. */
private int
s_file_read_process(stream_state *st, stream_cursor_read *ignore_pr,
  stream_cursor_write *pw, bool last)
{	FILE *file = ss->file;
	int count = fread(pw->ptr + 1, 1, (uint)(pw->limit - pw->ptr), file);
	if ( count < 0 )
		count = 0;
	pw->ptr += count;
	process_interrupts();
	return (ferror(file) ? ERRC : feof(file) ? EOFC : 1);
}

/* Process a buffer for a file writing stream. */
/* This is the last stream in the pipeline, so pw is irrelevant. */
private int
s_file_write_process(stream_state *st, stream_cursor_read *pr,
  stream_cursor_write *ignore_pw, bool last)
{	/* The DEC C library on AXP architectures gives an error on */
	/* fwrite if the count is zero! */
	uint count = pr->limit - pr->ptr;
	if ( count != 0 )
	  {	FILE *file = ss->file;
		int written = fwrite(pr->ptr + 1, 1, count, file);
		if ( written < 0 )
		  written = 0;
		pr->ptr += written;
		process_interrupts();
		return (ferror(file) ? ERRC : 0);
	  }
	else
	  {	process_interrupts();
		return 0;
	  }
}

#undef ss

/* Switch a file stream to reading or writing. */
private int
s_file_switch(stream *s, bool writing)
{	uint modes = s->file_modes;
	FILE *file = s->file;
	long pos;
	if ( writing )
	  {	if ( !(s->file_modes & s_mode_write) )
		  return ERRC;
		pos = stell(s);
		if_debug2('s', "[s]switch 0x%lx to write at %ld\n",
			  (ulong)s, pos);
		fseek(file, pos, SEEK_SET);
		if ( modes & s_mode_append )
		  {	sappend_file(s, file, s->cbuf, s->cbsize);	/* sets position */
		  }
		else
		  {	swrite_file(s, file, s->cbuf, s->cbsize);
			s->position = pos;
		  }
		s->modes = modes;
	  }
	else
	  {	if ( !(s->file_modes & s_mode_read) )
		  return ERRC;
		pos = stell(s);
		if_debug2('s', "[s]switch 0x%lx to read at %ld\n",
			  (ulong)s, pos);
		if ( sflush(s) < 0 )
		  return ERRC;
		fseek(file, 0L, SEEK_CUR);		/* pacify C library */
		sread_file(s, file, s->cbuf, s->cbsize);
		s->modes |= modes & s_mode_append;	/* don't lose append info */
		s->position = pos;
	  }
	s->file_modes = modes;
	return 0;
}
