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  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
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*/

/* sfileno.c */
/* File stream implementation using direct OS calls */
/******
 ****** NOTE: THIS FILE PROBABLY WILL NOT COMPILE ON NON-UNIX
 ****** PLATFORMS, AND IT MAY REQUIRE EDITING ON SOME UNIX PLATFORMS.
 ******/
#include "stdio_.h"		/* includes std.h */
#include "errno_.h"
#include "memory_.h"
/*
 * It's likely that you will have to edit the next line on some Unix
 * and most non-Unix platforms, since there is no standard (ANSI or
 * otherwise) for where to find these definitions.
 */
#include <unistd.h>		/* for read, write, fsync, lseek */
#include "gdebug.h"
#include "gpcheck.h"
#include "stream.h"
#include "strimpl.h"

/*
 * This is an alternate implementation of file streams.  It still uses
 * FILE * in the interface, but it uses direct OS calls for I/O.
 * It also includes workarounds for the nasty habit of System V Unix
 * of breaking out of read and write operations with EINTR, EAGAIN,
 * and/or EWOULDBLOCK "errors".
 *
 * The interface should be identical to that of sfile.c.  However,
 * in order to allow both implementations to exist in the same executable,
 * we use different names for sread_file, swrite_file, and sappend_file
 * (the public procedures).  If you want to use this implementation
 * instead of the one in sfile.c, uncomment the following #define.
 */
#define USE_SFILENO_FOR_SFILE

#ifdef USE_SFILENO_FOR_SFILE
#  define sread_fileno sread_file
#  define swrite_fileno swrite_file
#  define sappend_fileno sappend_file
#endif

/* Forward references for file stream procedures */
private int
  s_fileno_available(P2(stream *, long *)),
  s_fileno_read_seek(P2(stream *, long)),
  s_fileno_read_close(P1(stream *)),
  s_fileno_read_process(P4(stream_state *, stream_cursor_read *,
    stream_cursor_write *, bool));
private int
  s_fileno_write_seek(P2(stream *, long)),
  s_fileno_write_flush(P1(stream *)),
  s_fileno_write_close(P1(stream *)),
  s_fileno_write_process(P4(stream_state *, stream_cursor_read *,
    stream_cursor_write *, bool));
private int
  s_fileno_switch(P2(stream *, bool));

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

/* Get the file descriptor number of a stream. */
#define sfileno(s) fileno((s)->file)

/* Initialize a stream for reading an OS file. */
void
sread_fileno(register stream *s, FILE *file, byte *buf, uint len)
{	static const stream_procs p =
	   {	s_fileno_available, s_fileno_read_seek, s_std_read_reset,
		s_std_read_flush, s_fileno_read_close, s_fileno_read_process,
		s_fileno_switch
	   };
	/*
	 * There is no really portable way to test seekability,
	 * but this should work on most systems.
	 */
	int fd = fileno(file);
	long curpos = lseek(fd, 0L, SEEK_CUR);
	bool seekable = (curpos != -1L && lseek(fd, curpos, SEEK_SET) != -1L);

	s_std_init(s, buf, len, &p,
		   (seekable ? s_mode_read + s_mode_seek : s_mode_read));
	if_debug2('s', "[s]read file=0x%lx, fd=%d\n", (ulong)file,
		  fileno(file));
	s->file = file;
	s->file_modes = s->modes;
}
/* Procedures for reading from a file */
private int
s_fileno_available(register stream *s, long *pl)
{	int fd = sfileno(s);
	*pl = sbufavailable(s);
	if ( sseekable(s) )
	   {	long pos, end;
		pos = lseek(fd, 0L, SEEK_CUR);
		if ( pos < 0 )
		  return ERRC;
		end = lseek(fd, 0L, SEEK_END);
		if ( lseek(fd, pos, SEEK_SET) < 0 || end < 0 )
		  return ERRC;
		*pl += end - pos;
		if ( *pl == 0 ) *pl = -1;	/* EOF */
	   }
	else
	   {	if ( *pl == 0 ) *pl = -1;	/* EOF */
	   }
	return 0;
}
private int
s_fileno_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 ( lseek(sfileno(s), 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_fileno_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_fileno(register stream *s, FILE *file, byte *buf, uint len)
{	static const stream_procs p =
	   {	s_std_noavailable, s_fileno_write_seek, s_std_write_reset,
		s_fileno_write_flush, s_fileno_write_close, s_fileno_write_process,
		s_fileno_switch
	   };
	s_std_init(s, buf, len, &p,
		   (file == stdout ? s_mode_write : s_mode_write + s_mode_seek));
	if_debug2('s', "[s]write file=0x%lx, fd=%d\n", (ulong)file,
		  fileno(file));
	s->file = file;
	s->file_modes = s->modes;
}
/* Initialize for appending to an OS file. */
void
sappend_fileno(register stream *s, FILE *file, byte *buf, uint len)
{	swrite_fileno(s, file, buf, len);
	s->modes = s_mode_write + s_mode_append;	/* no seek */
	s->file_modes = s->modes;
	s->position = lseek(fileno(file), 0L, SEEK_END);
}
/* Procedures for writing on a file */
private int
s_fileno_write_seek(stream *s, long pos)
{	/* We must flush the buffer to reposition. */
	int code = sflush(s);
	if ( code < 0 )
	  return code;
	if ( lseek(sfileno(s), pos, SEEK_SET) < 0 )
	  return ERRC;
	s->position = pos;
	return 0;
}
private int
s_fileno_write_flush(register stream *s)
{	int result = s_process_write_buf(s, false);
	discard(fsync(sfileno(s)));
	return result;
}
private int
s_fileno_write_close(register stream *s)
{	s_process_write_buf(s, true);
	return s_fileno_read_close(s);
}

#define ss ((stream *)st)

/* Define the switch cases for System V interrupts. */
#define case_again(errn) case errn: goto again;
#ifdef EINTR
#  define handle_EINTR() case_again(EINTR)
#else
#  define handle_EINTR() /* */
#endif
#if defined(EAGAIN) && (!defined(EINTR) || EAGAIN != EINTR)
#  define handle_EAGAIN() case_again(EAGAIN)
#else
#  define handle_EAGAIN() /* */
#endif
#if defined(EWOULDBLOCK) && (!defined(EINTR) || EWOULDBLOCK != EINTR) && (!defined(EAGAIN) || EWOULDBLOCK != EAGAIN)
#  define handle_EWOULDBLOCK() case_again(EWOULDBLOCK)
#else
#  define handle_EWOULDBLOCK() /* */
#endif
#define handle_SYSV_errno()\
  handle_EINTR() handle_EAGAIN() handle_EWOULDBLOCK()

/* Process a buffer for a file reading stream. */
/* This is the first stream in the pipeline, so pr is irrelevant. */
private int
s_fileno_read_process(stream_state *st, stream_cursor_read *ignore_pr,
  stream_cursor_write *pw, bool last)
{	int nread, status;
again:	nread = read(sfileno(ss), pw->ptr + 1, (uint)(pw->limit - pw->ptr));
	if ( nread > 0 )
	  {	pw->ptr += nread;
		status = 0;
	  }
	else if ( nread == 0 )
	  status = EOFC;
	else switch ( errno )
	  {
	  handle_SYSV_errno() /* Handle System V interrupts */
	  default:
	    status = ERRC;
	  }
	process_interrupts();
	return status;
}

/* Process a buffer for a file writing stream. */
/* This is the last stream in the pipeline, so pw is irrelevant. */
private int
s_fileno_write_process(stream_state *st, stream_cursor_read *pr,
  stream_cursor_write *ignore_pw, bool last)
{	int nwrite, status;
	uint count;
again:	count = pr->limit - pr->ptr;
	/* Some versions of the DEC C library on AXP architectures */
	/* give an error on write if the count is zero! */
	if ( count == 0 )
	  {	process_interrupts();
		return 0;
	  }
	nwrite = write(sfileno(ss), pr->ptr + 1, count);
	if ( nwrite >= 0 )
	  {	pr->ptr += nwrite;
		status = 0;
	  }
	else switch ( errno )
	  {
	  handle_SYSV_errno() /* Handle System V interrupts */
	  default:
	    status = ERRC;
	  }
	process_interrupts();
	return status;
}

#undef ss

/* Switch a file stream to reading or writing. */
private int
s_fileno_switch(stream *s, bool writing)
{	uint modes = s->file_modes;
	int fd = sfileno(s);
	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);
		lseek(fd, pos, SEEK_SET);	/* pacify OS */
		if ( modes & s_mode_append )
		  {	sappend_file(s, s->file, s->cbuf, s->cbsize);	/* sets position */
		  }
		else
		  {	swrite_file(s, 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;
		lseek(fd, 0L, SEEK_CUR);	/* pacify OS */
		sread_file(s, 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;
}
